Journal articles on the topic 'Planetary science (excl. solar system and planetary geology)'
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Sun, Wei, Jian Wang, JinRu Chen, Ying Wang, GuangMing Yu, and XianHai Xu. "Contrast analysis between the trajectory of the planetary system and the periodicity of solar activity." Annales Geophysicae 35, no. 3 (May 17, 2017): 659–69. http://dx.doi.org/10.5194/angeo-35-659-2017.
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Abstract. The relationship between the periodic movement of the planetary system and its influence on solar activity is currently a serious topic in research. The kinematic index of the planet juncture index has been developed to find the track and variation of the Sun around the centroid of the solar system and the periodicity of solar activity. In the present study, the kinematic index of the planetary system's heliocentric longitude, developed based on the orbital elements of planets in the solar system, and it is used to investigate the periodic movement of the planetary system. The kinematic index of the planetary system's heliocentric longitude and that of the planet juncture index are simulated and analyzed. The numerical simulation of the two kinematic indexes shows orderly orbits and disorderly orbits of 49.9 and 129.6 years, respectively. Two orderly orbits or two disorderly orbits show a period change rule of 179.5 years. The contrast analysis between the periodic movement of the planetary system and the periodicity of solar activity shows that the two phenomena exhibit a period change rule of 179.5 years. Moreover, orderly orbits correspond to high periods of solar activity and disorderly orbits correspond to low periods of solar activity. Therefore, the relative movement of the planetary system affects solar activity to some extent. The relationship provides a basis for discussing the movement of the planetary system and solar activity.
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Kobayashi, Hiroshi, Hiroshi Kimura, Satoru Yamamoto, Sei-ichiro Watanabe, and Tetsuo Yamamoto. "Ice sublimation of dust particles and their detection in the outer solar system." Earth, Planets and Space 62, no. 1 (January 2010): 57–61. http://dx.doi.org/10.5047/eps.2009.03.001.
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Uchida, Tomohisa, Hiroyuki K. M. Tanaka, and Manobu Tanaka. "Development of a muon radiographic imaging electronic board system for a stable solar power operation." Earth, Planets and Space 62, no. 2 (February 2010): 167–72. http://dx.doi.org/10.5047/eps.2009.03.002.
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Yeghikyan, A. G., and H. J. Fahr. "Consequences of the Solar System passage through dense interstellar clouds." Annales Geophysicae 21, no. 6 (June 30, 2003): 1263–73. http://dx.doi.org/10.5194/angeo-21-1263-2003.
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Abstract. Several consequences of the passage of the solar system through dense interstellar molecular clouds are discussed. These clouds, dense (more than 100 cm-3), cold (10–50 K) and extended (larger than 1 pc), are characterized by a gas-to-dust mass ratio of about 100, by a specific power grain size spectrum (grain radii usually cover the range 0.001–3 micron) and by an average dust-to-gas number density ratio of about 10-12. Frequently these clouds contain small-scale (10–100 AU) condensations with gas concentrations ranging up to 10 5 cm-3. At their casual passage over the solar system they exert pressures very much enhanced with respect to today’s standards. Under these conditions it will occur that the Earth is exposed directly to the interstellar flow. It is shown first that even close to the Sun, at 1 AU, the cloud’s matter is only partly ionized and should mainly interact with the solar wind by charge exchange processes. Dust particles of the cloud serve as a source of neutrals, generated by the solar UV irradiation of dust grains, causing the evaporation of icy materials. The release of neutral atoms from dust grains is then followed by strong influences on the solar wind plasma flow. The behavior of the neutral gas inflow parameters is investigated by a 2-D hydrodynamic approach to model the interaction processes. Because of a reduction of the heliospheric dimension down to 1 AU, direct influence of the cloud’s matter to the terrestrial environment and atmosphere could be envisaged.Key words. Interplanetary physics (heliopause and solar wind termination; interplanetary dust; interstellar gas)
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Tveito, Torbjørn, Juha Vierinen, Björn Gustavsson, and Viswanathan Lakshmi Narayanan. "Planetary radar science case for EISCAT 3D." Annales Geophysicae 39, no. 3 (May 12, 2021): 427–38. http://dx.doi.org/10.5194/angeo-39-427-2021.
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Abstract. Ground-based inverse synthetic aperture radar is a tool that can provide insights into the early history and formative processes of planetary bodies in the inner solar system. This information is gathered by measuring the scattering matrix of the target body, providing composite information about the physical structure and chemical makeup of its surface and subsurface down to the penetration depth of the radio wave. This work describes the technical capabilities of the upcoming 233 MHz European Incoherent Scatter Scientific Association (EISCAT) 3D radar facility for measuring planetary surfaces. Estimates of the achievable signal-to-noise ratios for terrestrial target bodies are provided. While Venus and Mars can possibly be detected, only the Moon is found to have sufficient signal-to-noise ratio to allow high-resolution mapping to be performed. The performance of the EISCAT 3D antenna layout is evaluated for interferometric range–Doppler disambiguation, and it is found to be well suited for this task, providing up to 20 dB of separation between Doppler northern and southern hemispheres in our case study. The low frequency used by EISCAT 3D is more affected by the ionosphere than higher-frequency radars. The magnitude of the Doppler broadening due to ionospheric propagation effects associated with traveling ionospheric disturbances has been estimated. The effect is found to be significant but not severe enough to prevent high-resolution imaging. A survey of lunar observing opportunities between 2022 and 2040 is evaluated by investigating the path of the sub-radar point when the Moon is above the local radar horizon. During this time, a good variety of look directions and Doppler equator directions are found, with observations opportunities available for approximately 10 d every lunar month. EISCAT 3D will be able to provide new, high-quality polarimetric scattering maps of the nearside of the Moon with the previously unused wavelength of 1.3 m, which provides a good compromise between radio wave penetration depth and Doppler resolution.
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Jakowski, N., and H. D. Bettac. "Proposal for an ionosphere/plasmasphere monitoring system." Annales Geophysicae 12, no. 5 (April 30, 1994): 431–37. http://dx.doi.org/10.1007/s00585-994-0431-7.
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Abstract. A space-based satellite system suited for long-term monitoring of the Earth's ionosphere/plasmasphere systems is proposed. The monitoring system consists of a network of radio beacon satellites capable of measuring the ionospheric and plasmaspheric electron content on a continuous base with high time resolution. It takes advantage of the geometrical relationship between the orbit of geostationary satellites and the position of the plasmapause region characterized by a steep electron density gradient. A combination of geostationary and nongeostationary satellites may explore the three-dimensional structure of the plasmasphere. Taking into account plasmaspheric characteristics some criteria for an effective arrangement of the satellites are derived and discussed. Since the plasmapause position is very sensitive to changes or distortions in the solar wind and the related geomagnetic activity, a continuous monitoring of the position of the plasmapause would be helpful in understanding solar-terrestrial relationships.
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Prikryl, Paul, Vojto Rušin, Emil A. Prikryl, Pavel Šťastný, Maroš Turňa, and Martina Zeleňáková. "Heavy rainfall, floods, and flash floods influenced by high-speed solar wind coupling to the magnetosphere–ionosphere–atmosphere system." Annales Geophysicae 39, no. 4 (August 27, 2021): 769–93. http://dx.doi.org/10.5194/angeo-39-769-2021.
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Abstract. Heavy rainfall events causing floods and flash floods are examined in the context of solar wind coupling to the magnetosphere–ionosphere–atmosphere system. The superposed epoch (SPE) analyses of solar wind variables have shown the tendency of severe weather to follow arrivals of high-speed streams from solar coronal holes. Precipitation data sets based on rain gauge and satellite sensor measurements are used to examine the relationship between the solar wind high-speed streams and daily precipitation rates over several midlatitude regions. The SPE analysis results show an increase in the occurrence of high precipitation rates following arrivals of high-speed streams, including recurrence with a solar rotation period of 27 d. The cross-correlation analysis applied to the SPE averages of the green (Fe XIV; 530.3 nm) corona intensity observed by ground-based coronagraphs, solar wind parameters, and daily precipitation rates show correlation peaks at lags spaced by solar rotation period. When the SPE analysis is limited to years around the solar minimum (2008–2009), which was dominated by recurrent coronal holes separated by ∼ 120∘ in heliographic longitude, significant cross-correlation peaks are found at lags spaced by 9 d. These results are further demonstrated by cases of heavy rainfall, floods and flash floods in Europe, Japan, and the USA, highlighting the role of solar wind coupling to the magnetosphere–ionosphere–atmosphere system in severe weather, mediated by aurorally excited atmospheric gravity waves.
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Gallagher, P. T., C. Denker, V. Yurchyshyn, T. Spirock, J. Qiu, H. Wang, and P. R. Goode. "Solar activity monitoring and forecasting capabilities at Big Bear Solar Observatory." Annales Geophysicae 20, no. 7 (July 31, 2002): 1105–15. http://dx.doi.org/10.5194/angeo-20-1105-2002.
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Abstract. The availability of full-disk, high-resolution Ha images from Big Bear Solar Observatory (USA), Kanzelhöhe Solar Observatory (Austria), and Yunnan Astronomical Observatory (China) allows for the continual monitoring of solar activity with unprecedented spatial and temporal resolution. Typically, this Global Ha Network (GHN) provides almost uninterrupted Ha images with a cadence of 1 min and an image scale of 1'' per pixel. Every hour, GHN images are transferred to the web-based BBSO Active Region Monitor (ARM; www.bbso.njit.edu/arm), which includes the most recent EUV, continuum, and magnetogram data from the Solar and Heliospheric Observatory, together with magnetograms from the Global Oscillation Network Group. ARM also includes a variety of active region properties from the National Oceanic and Atmospheric Administration’s Space Environment Center, such as up-to-date active region positions, GOES 5-min X-ray data, and flare identification. Stokes I, V, Q, and U images are available from the recently operational BBSO Digital Vector Magnetograph and the Vector Magnetograph at the Huairou Solar Observing Station of Beijing Observatory. Vector magnetograms provide complete information on the photospheric magnetic field, and allow for magnetic flux gradients, electric currents, and shear forces to be calculated: these measurements are extremely sensitive to conditions resulting in flaring activity. Furthermore, we have developed a Flare Prediction System which estimates the probability for each region to produce C-, M-, or X-class flares based on nearly eight years of NOAA data from cycle 22. This, in addition to BBSO’s daily solar activity reports, has proven a useful resource for activity forecasting.Key words. Solar physics, astronomy and astrophysics (flares and mass ejections; instruments and techniques; photosphere and chromosphere)
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TSUCHIYAMA, Akira, and Junya MATSUNO. "Using Mineral Science to Elucidate Mysteries of the Early Solar System." Journal of Geography (Chigaku Zasshi) 131, no. 2 (April 25, 2022): 193–211. http://dx.doi.org/10.5026/jgeography.131.193.
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Lopez, R. E., V. G. Merkin, and J. G. Lyon. "The role of the bow shock in solar wind-magnetosphere coupling." Annales Geophysicae 29, no. 6 (June 25, 2011): 1129–35. http://dx.doi.org/10.5194/angeo-29-1129-2011.
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Abstract. In this paper we examine the role of the bow shock in coupling solar wind energy to the magnetosphere using global magnetohydrodynamic simulations of the solar wind-magnetosphere interaction with southward IMF. During typical solar wind conditions, there are two significant dynamo currents in the magnetospheric system, one in the high-latitude mantle region tailward of the cusp and the other in the bow shock. As the magnitude of the (southward) IMF increases and the solar wind becomes a low Mach number flow, there is a significant change in solar wind-magnetosphere coupling. The high-latitude magnetopause dynamo becomes insignificant compared to the bow shock and a large load appears right outside the magnetopause. This leaves the bow shock current as the only substantial dynamo current in the system, and the only place where a significant amount of mechanical energy is extracted from the solar wind. That energy appears primarily as electromagnetic energy, and the Poynting flux generated at the bow shock feeds energy back into the plasma, reaccelerating it to solar wind speeds. Some small fraction of that Poynting flux is directed into the magnetosphere, supplying the energy needed for magnetospheric dynamics. Thus during periods when the solar wind flow has a low Mach number, the main dynamo in the solar wind-magnetosphere system is the bow shock.
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Soon, W., E. Posmentier, and S. Baliunas. "Climate hypersensitivity to solar forcing?" Annales Geophysicae 18, no. 5 (May 31, 2000): 583–88. http://dx.doi.org/10.1007/s00585-000-0583-z.
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Abstract. We compare the equilibrium climate responses of a quasi-dynamical energy balance model to radiative forcing by equivalent changes in CO2, solar total irradiance (Stot) and solar UV (SUV). The response is largest in the SUV case, in which the imposed UV radiative forcing is preferentially absorbed in the layer above 250 mb, in contrast to the weak response from global-columnar radiative loading by increases in CO2 or Stot. The hypersensitive response of the climate system to solar UV forcing is caused by strongly coupled feedback involving vertical static stability, tropical thick cirrus ice clouds and stratospheric ozone. This mechanism offers a plausible explanation of the apparent hypersensitivity of climate to solar forcing, as suggested by analyses of recent climatic records. The model hypersensitivity strongly depends on climate parameters, especially cloud radiative properties, but is effective for arguably realistic values of these parameters. The proposed solar forcing mechanism should be further confirmed using other models (e.g., general circulation models) that may better capture radiative and dynamical couplings of the troposphere and stratosphere.Key words: Meteorology and atmospheric dynamics (climatology · general or miscellaneous) · Solar physics · astrophysics · and astronomy (ultraviolet emissions)
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Daglis, Ioannis A., Loren C. Chang, Sergio Dasso, Nat Gopalswamy, Olga V. Khabarova, Emilia Kilpua, Ramon Lopez, et al. "Predictability of variable solar–terrestrial coupling." Annales Geophysicae 39, no. 6 (December 10, 2021): 1013–35. http://dx.doi.org/10.5194/angeo-39-1013-2021.
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Abstract. In October 2017, the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) Bureau established a committee for the design of SCOSTEP's Next Scientific Programme (NSP). The NSP committee members and authors of this paper decided from the very beginning of their deliberations that the predictability of the Sun–Earth System from a few hours to centuries is a timely scientific topic, combining the interests of different topical communities in a relevant way. Accordingly, the NSP was christened PRESTO – PREdictability of the variable Solar–Terrestrial cOupling. This paper presents a detailed account of PRESTO; we show the key milestones of the PRESTO roadmap for the next 5 years, review the current state of the art and discuss future studies required for the most effective development of solar–terrestrial physics.
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Walsh, A. P., S. Haaland, C. Forsyth, A. M. Keesee, J. Kissinger, K. Li, A. Runov, et al. "Dawn–dusk asymmetries in the coupled solar wind–magnetosphere–ionosphere system: a review." Annales Geophysicae 32, no. 7 (July 1, 2014): 705–37. http://dx.doi.org/10.5194/angeo-32-705-2014.
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Abstract. Dawn–dusk asymmetries are ubiquitous features of the coupled solar-wind–magnetosphere–ionosphere system. During the last decades, increasing availability of satellite and ground-based measurements has made it possible to study these phenomena in more detail. Numerous publications have documented the existence of persistent asymmetries in processes, properties and topology of plasma structures in various regions of geospace. In this paper, we present a review of our present knowledge of some of the most pronounced dawn–dusk asymmetries. We focus on four key aspects: (1) the role of external influences such as the solar wind and its interaction with the Earth's magnetosphere; (2) properties of the magnetosphere itself; (3) the role of the ionosphere and (4) feedback and coupling between regions. We have also identified potential inconsistencies and gaps in our understanding of dawn–dusk asymmetries in the Earth's magnetosphere and ionosphere.
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Asayama, Shinichiro, Masahiro Sugiyama, Atsushi Ishii, and Takanobu Kosugi. "Beyond solutionist science for the Anthropocene: To navigate the contentious atmosphere of solar geoengineering." Anthropocene Review 6, no. 1-2 (April 2019): 19–37. http://dx.doi.org/10.1177/2053019619843678.
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The emerging narrative of the Anthropocene has created a new space for changes in global environmental change (GEC) science. On the one hand, there is a mounting call for changing scientific practices towards a solution-oriented transdisciplinary mode that can help achieve global sustainability. On the other hand, the scientists’ desire to avoid exceeding planetary boundaries has broken a taboo on researching solar geoengineering, a dangerous idea of deliberately cooling the Earth’s climate. Whilst to date the two features have been discussed separately, there is a possible confluence in the future. This paper explores this close yet precarious relationship between transdisciplinary GEC science and solar geoengineering in the context of Future Earth, a new international platform of Earth system science. Our aim is to understand how a transdisciplinary mode of science can navigate the contention over solar geoengineering and its course of research without breeding polarization. By seeking the immediacy of ‘problem-solving’, Future Earth is drawn into the solutionist thinking that orders the mode of engagement in pursuing consensus. However, because conflict is inescapable on the solar geoengineering debate, transdisciplinary engagement might as well aim at mapping out plural viewpoints and allowing people to disagree. In transdisciplinary engagement, as co-design signifies the engagement of stakeholders with decision-making in science, a fair and transparent procedure of making decisions is also needed. From our own experience of co-designing research priorities, we suggest that, if carefully designed, voting can be a useful tool to mediate the contentious process of transdisciplinary decision-making with three different benefits for collective decision-making, namely, efficiency, inclusivity and learning. For the future directions of transdisciplinary GEC science, since the Anthropocene challenges are truly uncertain and contentious, it is argued that the science for the Anthropocene should move away from a solutionist paradigm towards an experimentalist turn.
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Mann, Ingrid, Libor Nouzák, Jakub Vaverka, Tarjei Antonsen, Åshild Fredriksen, Karine Issautier, David Malaspina, et al. "Dust observations with antenna measurements and its prospects for observations with Parker Solar Probe and Solar Orbiter." Annales Geophysicae 37, no. 6 (December 10, 2019): 1121–40. http://dx.doi.org/10.5194/angeo-37-1121-2019.
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Abstract. The electric and magnetic field instrument suite FIELDS on board the NASA Parker Solar Probe and the radio and plasma waves instrument RPW on the ESA Solar Orbiter mission that explore the inner heliosphere are sensitive to signals generated by dust impacts. Dust impacts have been observed using electric field antennas on spacecraft since the 1980s and the method was recently used with a number of space missions to derive dust fluxes. Here, we consider the details of dust impacts, subsequent development of the impact generated plasma and how it produces the measured signals. We describe empirical approaches to characterise the signals and compare these in a qualitative discussion of laboratory simulations to predict signal shapes for spacecraft measurements in the inner solar system. While the amount of charge production from a dust impact will be higher near the Sun than observed in the interplanetary medium before, the amplitude of pulses is determined by the recovery behaviour that is different near the Sun since it varies with the plasma environment.
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Vasyliūnas, V. M. "The mechanical advantage of the magnetosphere: solar-wind-related forces in the magnetosphere-ionosphere-Earth system." Annales Geophysicae 25, no. 1 (February 1, 2007): 255–69. http://dx.doi.org/10.5194/angeo-25-255-2007.
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Abstract. Magnetosphere-ionosphere interactions involve electric currents that circulate between the two regions; the associated Lorentz forces, existing in both regions as matched opposite pairs, are generally viewed as the primary mechanism by which linear momentum, derived ultimately from solar wind flow, is transferred from the magnetosphere to the ionosphere, where it is further transferred by collisions to the neutral atmosphere. For a given total amount of current, however, the total force is proportional to ℒB and in general, since ℒ2B~ constant by flux conservation, is much larger in the ionosphere than in the magnetosphere (ℒ = effective length, B = magnetic field). The magnetosphere may be described as possesing a mechanical advantage: the Lorentz force in it is coupled with a Lorentz force in the ionosphere that has been amplified by a factor given approximately by the square root of magnetic field magnitude ratio (~20 to 40 on field lines connected to the outer magnetosphere). The linear momentum transferred to the ionosphere (and thence to the atmosphere) as the result of magnetic stresses applied by the magnetosphere can thus be much larger than the momentum supplied by the solar wind through tangential stress. The added linear momentum comes from within the Earth, extracted by the Lorentz force on currents that arise as a consequence of magnetic perturbation fields from the ionosphere (specifically, the shielding currents within the Earth that keep out the time-varying external fields). This implies at once that Fukushima's theorem on the vanishing of ground-level magnetic perturbations cannot be fully applicable, a conclusion confirmed by re-examining the assumptions from which the theorem is derived. To balance the inferred Lorentz force within the Earth's interior, there must exist an antisunward mechanical stress there, only a small part of which is the acceleration of the entire Earth system by the net force exerted on it by the solar wind. The solar-wind interaction can thus give rise to internal forces, significantly larger than the force exerted by the solar wind itself, between the ionosphere and the neutral atmosphere as well as within the current-carrying regions of the Earth's interior.
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Behar, Etienne, Shahab Fatemi, Pierre Henri, and Mats Holmström. "<i>Menura</i>: a code for simulating the interaction between a turbulent solar wind and solar system bodies." Annales Geophysicae 40, no. 3 (May 9, 2022): 281–97. http://dx.doi.org/10.5194/angeo-40-281-2022.
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Abstract. Despite the close relationship between planetary science and plasma physics, few advanced numerical tools allow bridging the two topics. The code Menura proposes a breakthrough towards the self-consistent modelling of these overlapping fields, in a novel two-step approach allowing for the global simulation of the interaction between a fully turbulent solar wind and various bodies of the solar system. This article introduces the new code and its two-step global algorithm, illustrated by a first example: the interaction between a turbulent solar wind and a comet.
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McKenzie, J. F. "Instability of coupled gravity-inertial-Rossby waves on a β-plane in solar system atmospheres." Annales Geophysicae 27, no. 11 (November 9, 2009): 4221–27. http://dx.doi.org/10.5194/angeo-27-4221-2009.
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Abstract. This paper provides an analysis of the combined theory of gravity-inertial-Rossby waves on a β-plane in the Boussinesq approximation. The wave equation for the system is fifth order in space and time and demonstrates how gravity-inertial waves on the one hand are coupled to Rossby waves on the other through the combined effects of β, the stratification characterized by the Väisälä-Brunt frequency N, the Coriolis frequency f at a given latitude, and vertical propagation which permits buoyancy modes to interact with westward propagating Rossby waves. The corresponding dispersion equation shows that the frequency of a westward propagating gravity-inertial wave is reduced by the coupling, whereas the frequency of a Rossby wave is increased. If the coupling is sufficiently strong these two modes coalesce giving rise to an instability. The instability condition translates into a curve of critical latitude Θc versus effective equatorial rotational Mach number M, with the region below this curve exhibiting instability. "Supersonic" fast rotators are unstable in a narrow band of latitudes around the equator. For example Θc~12° for Jupiter. On the other hand slow "subsonic" rotators (e.g. Mercury, Venus and the Sun's Corona) are unstable at all latitudes except very close to the poles where the β effect vanishes. "Transonic" rotators, such as the Earth and Mars, exhibit instability within latitudes of 34° and 39°, respectively, around the Equator. Similar results pertain to Oceans. In the case of an Earth's Ocean of depth 4km say, purely westward propagating waves are unstable up to 26° about the Equator. The nonlinear evolution of this instability which feeds off rotational energy and gravitational buoyancy may play an important role in atmospheric dynamics.
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Prikryl, P., R. Ghoddousi-Fard, E. G. Thomas, J. M. Ruohoniemi, S. G. Shepherd, P. T. Jayachandran, D. W. Danskin, et al. "GPS phase scintillation at high latitudes during geomagnetic storms of 7–17 March 2012 – Part 1: The North American sector." Annales Geophysicae 33, no. 6 (June 2, 2015): 637–56. http://dx.doi.org/10.5194/angeo-33-637-2015.
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Abstract. The interval of geomagnetic storms of 7–17 March 2012 was selected at the Climate and Weather of the Sun-Earth System (CAWSES) II Workshop for group study of space weather effects during the ascending phase of solar cycle 24 (Tsurutani et al., 2014). The high-latitude ionospheric response to a series of storms is studied using arrays of GPS receivers, HF radars, ionosondes, riometers, magnetometers, and auroral imagers focusing on GPS phase scintillation. Four geomagnetic storms showed varied responses to solar wind conditions characterized by the interplanetary magnetic field (IMF) and solar wind dynamic pressure. As a function of magnetic latitude and magnetic local time, regions of enhanced scintillation are identified in the context of coupling processes between the solar wind and the magnetosphere–ionosphere system. Large southward IMF and high solar wind dynamic pressure resulted in the strongest scintillation in the nightside auroral oval. Scintillation occurrence was correlated with ground magnetic field perturbations and riometer absorption enhancements, and collocated with mapped auroral emission. During periods of southward IMF, scintillation was also collocated with ionospheric convection in the expanded dawn and dusk cells, with the antisunward convection in the polar cap and with a tongue of ionization fractured into patches. In contrast, large northward IMF combined with a strong solar wind dynamic pressure pulse was followed by scintillation caused by transpolar arcs in the polar cap.
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Roth, I. "Terrestrial aurora: astrophysical laboratory for anomalous abundances in stellar systems." Annales Geophysicae 32, no. 2 (February 11, 2014): 77–82. http://dx.doi.org/10.5194/angeo-32-77-2014.
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Abstract. The unique magnetic structure of the terrestrial aurora as a conduit of information between the ionosphere and magnetosphere can be utilized as a laboratory for physical processes at similar magnetic configurations and applied to various evolutionary phases of the solar (stellar) system. The most spectacular heliospheric abundance enhancement involves the 3He isotope and selective heavy elements in impulsive solar flares. In situ observations of electromagnetic waves on active aurora are extrapolated to flaring corona in an analysis of solar acceleration processes of 3He, the only element that may resonate strongly with the waves, as well as heavy ions with specific charge-to-mass ratios, which may resonate weaker via their higher gyroharmonics. These results are applied to two observed anomalous astrophysical abundances: (1) enhanced abundance of 3He and possibly 13C in the late stellar evolutionary stages of planetary nebulae; and (2) enhanced abundance of the observed fossil element 26Mg in meteorites as a decay product of radioactive 26Al isotope due to interaction with the flare-energized 3He in the early solar system.
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Moran, P. J., S. Ananthakrishnan, V. Balasubramanian, A. R. Breen, A. Canals, R. A. Fallows, P. Janardhan, M. Tokumaru, and P. J. S. Williams. "Observations of interplanetary scintillation during the 1998 Whole Sun Month: a comparison between EISCAT, ORT and Nagoya data." Annales Geophysicae 18, no. 9 (September 30, 2000): 1003–8. http://dx.doi.org/10.1007/s00585-000-1003-0.
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Abstract. Observations of interplanetary scintillation (IPS) allow accurate solar wind velocity measurements to be made at all heliographic latitudes and at a range of distances from the Sun. The data may be obtained with either single, double or multiple antennas, each requiring a different method of analysis. IPS data taken during the 1998 whole sun month (30th July-31st August 1998) by EISCAT, the ORT (Ooty Radio Telescope), India, and the Nagoya IPS system, Japan, allow the results of individual methods of analysis to be compared. Good agreement is found between the velocity measurements using each method, and when combined an improved understanding of the structure of the solar wind can be obtained.Key words: Interplanetary physics (solar wind plasma; sources of the solar wind) - Solar physics, astrophysics and astronomy (instruments and techniques)
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Francia, P., U. Villante, and A. Meloni. "An analysis of geomagnetic field variations (3 min-2 h) at a low-latitude observatory (L=1.6)." Annales Geophysicae 13, no. 5 (May 31, 1995): 522–31. http://dx.doi.org/10.1007/s00585-995-0522-0.
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Abstract. An analysis of the geomagnetic field variations between 3 min and 2 h at L'Aquila (L=1.6) shows that the power level in the low-frequency range (i.e. for periods longer than approximately 10 min) at solar maximum (1989/90) is much higher than at solar minimum (1985/86). Conversely, at solar minimum, it emerges that there is a greater relative importance of fluctuations with periods smaller than 10 min which might be related to the greater percentage of solar wind speeds greater than approximately 540 km s–1. Diurnal, seasonal and solar cycle variations of both the high- and the low-frequency power are also discussed. We found that several aspects of these variations might be correlated with ionospheric features such as the ionisation of the F2 layer and the location and the intensity of the S current system.
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Cowley, S. W. H., J. D. Nichols, and D. J. Andrews. "Modulation of Jupiter's plasma flow, polar currents, and auroral precipitation by solar wind-induced compressions and expansions of the magnetosphere: a simple theoretical model." Annales Geophysicae 25, no. 6 (June 29, 2007): 1433–63. http://dx.doi.org/10.5194/angeo-25-1433-2007.
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Abstract. We construct a simple model of the plasma flow, magnetosphere-ionosphere coupling currents, and auroral precipitation in Jupiter's magnetosphere, and examine how they respond to compressions and expansions of the system induced by changes in solar wind dynamic pressure. The main simplifying assumption is axi-symmetry, the system being modelled principally to reflect dayside conditions. The model thus describes three magnetospheric regions, namely the middle and outer magnetosphere on closed magnetic field lines bounded by the magnetopause, together with a region of open field lines mapping to the tail. The calculations assume that the system is initially in a state of steady diffusive outflow of iogenic plasma with a particular equatorial magnetopause radius, and that the magnetopause then moves rapidly in or out due to a change in the solar wind dynamic pressure. If the change is sufficiently rapid (~2–3 h or less) the plasma angular momentum is conserved during the excursion, allowing the modified plasma angular velocity to be calculated from the radial displacement of the field lines, together with the modified magnetosphere-ionosphere coupling currents and auroral precipitation. The properties of these transient states are compared with those of the steady states to which they revert over intervals of ~1–2 days. Results are shown for rapid compressions of the system from an initially expanded state typical of a solar wind rarefaction region, illustrating the reduction in total precipitating electron power that occurs for modest compressions, followed by partial recovery in the emergent steady state. For major compressions, however, typical of the onset of a solar wind compression region, a brightened transient state occurs in which super-rotation is induced on closed field lines, resulting in a reversal in sense of the usual magnetosphere-ionosphere coupling current system. Current system reversal results in accelerated auroral electron precipitation occurring in the outer magnetosphere region rather than in the middle magnetosphere as is usual, with peak energy fluxes occurring just poleward of the boundary between the outer and middle magnetosphere. Plasma sub-corotation is then re-established as steady-state conditions re-emerge, together with the usual sense of flow of the closed field current system and renewed but weakened accelerated electron precipitation in the middle magnetosphere. Results for rapid expansions of the system from an initially compressed state typical of a solar wind compression region are also shown, illustrating the enhancement in precipitating electron power that occurs in the transient state, followed by partial reduction as steady conditions re-emerge.
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Boynton, R. J., S. A. Billings, O. A. Amariutei, and I. Moiseenko. "The coupling between the solar wind and proton fluxes at GEO." Annales Geophysicae 31, no. 10 (October 2, 2013): 1631–36. http://dx.doi.org/10.5194/angeo-31-1631-2013.
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Abstract. The relationship between the solar wind and the proton flux at geosynchronous Earth orbit (GEO) is investigated using the error reduction ratio (ERR) analysis. The ERR analysis is able to search for the most appropriate inputs that control the evolution of the system. This approach is a black box method and is able to derive a mathematical model of a system from input-output data. This method is used to analyse eight energy ranges of the proton flux at GEO from 80 keV to 14.5 MeV. The inputs to the algorithm were solar wind velocity, density and pressure; the Dst index; the solar energetic proton (SEP) flux; and a function of the interplanetary magnetic field (IMF) tangential magnitude and clock angle. The results show that for lowest five energy channels (80 to 800 keV) the GEO proton fluxes are controlled by the solar wind velocity with a lag of two to three days. However, above 350 keV, the SEP fluxes, accounts for a significant portion of the GEO proton flux variance. For the highest three energy channels (0.74 to 14.5 MeV), the SEPs account for the majority of the ERR. The results also show an anisotropy of protons with gyrocenters inside GEO and outside GEO, where the protons inside GEO are controlled partly by the Dst index and also an IMF-clock angle function.
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Davies, J. A., M. Lester, and I. W. McCrea. "Solar and seasonal dependence of ion frictional heating." Annales Geophysicae 17, no. 5 (May 31, 1999): 682–91. http://dx.doi.org/10.1007/s00585-999-0682-4.
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Abstract. Ion frictional heating constitutes one of the principal mechanisms whereby energy, originating in the solar wind, is deposited into the Earth's ionosphere and ultimately the neutral atmosphere. Common programme observations by the EISCAT UHF radar system, spanning the years 1984 to 1995, provide the basis for a comprehensive statistical study of ion frictional heating, results of which are documented in this and a previous paper by the authors. In the present work, the authors demonstrate the solar and seasonal dependence of the universal time distribution of frictional heating, and explain these results with reference to corresponding dependences of the ion velocity. Although EISCAT observes a significant increase in the occurrence of enhanced ion velocities associated with increased solar activity, the latter characterised according to the prevailing 10.7 cm solar flux, this is not reflected to such an extent in the occurrence of frictional heating. It is suggested that this is a consequence of the decreased neutral atmosphere response times associated with active solar conditions, resulting from the higher ionospheric plasma densities present. Seasonal effects on the diurnal distribution of ion frictional heating are well explained by corresponding variations in ionospheric convection, the latter principally a result of geometrical factors. It is noted that, over the entire dataset, the variations in the unperturbed F-region ion temperature, required to implement the identification criterion for ion heating, are highly correlated with model values of thermospheric temperature.Keywords. Ionosphere (auroral ionosphere; ionosphere-atmosphere interactions; plasma temperature and density)
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Holmstrom, Mats. "Estimating ion escape from unmagnetized planets." Annales Geophysicae 40, no. 1 (January 31, 2022): 83–89. http://dx.doi.org/10.5194/angeo-40-83-2022.
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Abstract. We propose a new method to estimate ion escape from unmagnetized planets that combines observations and models. Assuming that upstream solar wind conditions are known, a computer model of the interaction between the solar wind and the planet is executed for different ionospheric ion production rates. This results in different amounts of mass loading of the solar wind. We then obtain the ion escape rate from the model run that best fits observations of the bow shock location. As an example of the method, we estimate the heavy-ion escape from Mars on 1 March 2015 to be 2×1024 ions s−1, using a hybrid plasma model and observations by the Mars Atmosphere and Volatile Evolution (MAVEN) and Mars Express (MEX) missions. This method enables studies on how escape depends on different parameters as well as studies on escape rates during extreme solar wind conditions; moreover, the technique is applicable to studies of escape in the early solar system and at exoplanets.
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Berghmans, D., R. A. M. Van der Linden, P. Vanlommel, R. Warnant, A. Zhukov, E. Robbrecht, F. Clette, et al. "Solar activity: nowcasting and forecasting at the SIDC." Annales Geophysicae 23, no. 9 (November 22, 2005): 3115–28. http://dx.doi.org/10.5194/angeo-23-3115-2005.
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Abstract. The Solar Influences Data analysis Center (SIDC) is the World Data Center for the production and the distribution of the International Sunspot Index, coordinating a network of about 80 stations worldwide. From this core activity, the SIDC has grown in recent years to a European center for nowcasting and forecasting of solar activity on all timescales. This paper reviews the services (data, forecasts, alerts, software) that the SIDC currently offers to the scientific community. The SIDC operates instruments both on the ground and in space. The USET telescope in Brussels produces daily white light and Hα images. Several members of the SIDC are co-investigators of the EIT instrument onboard SOHO and are involved in the development of the next generation of Europe's solar weather monitoring capabilities. While the SIDC is staffed only during day-time (7 days/week), the monitoring service is a 24 h activity thanks to the implementation of autonomous software for data handling and analysis and the sending of automated alerts. We will give an overview of recently developed techniques for visualization and automated analysis of solar images and detection of events significant for space weather (e.g. CMEs or EIT waves). As part of the involvement of the SIDC in the ESA Pilot Project for Space Weather Applications we have developed services dedicated to the users of the Global Positioning System (GPS). As a Regional Warning Center (RWC) of the International Space Environment Service (ISES), the SIDC produces daily forecasts of flaring probability, geomagnetic activity and 10.7 cm radio flux. The accuracy of these forecasts will be investigated through an in-depth quality analysis.
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Kockarts, G. "Aeronomy, a 20th Century emergent science: the role of solar Lyman series." Annales Geophysicae 20, no. 5 (May 31, 2002): 585–98. http://dx.doi.org/10.5194/angeo-20-585-2002.
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Abstract. Aeronomy is, by definition, a multidisciplinary science which can be used to study the terrestrial atmosphere, as well as any planetary atmosphere and even the interplanetary space. It was officially recognized in 1954 by the International Union of Geodesy and Geophysics. The major objective of the present paper is to show how aeronomy developed since its infancy. The subject is so large that a guide-line has been chosen to see how aeronomy affects our atmospheric knowledge. This guideline is the solar Lyman alpha radiation which has different effects in the solar system. After a short description of the origins of aeronomy the first observations of this line are summarized since the beginning of the space age. Then the consequences of these observations are analyzed for the physics and chemistry of the neutral terrestrial atmosphere. New chemical processes had to be introduced, as well as new transport phenomena. Solar Lyman alpha also influences the structure of the Earth’s ionosphere, particularly the D-region. In the terrestrial exosphere, solar Lyman alpha scattered resonantly by atomic hydrogen is at present the only way to estimate this constituent in an almost collisionless medium. Since planetary atmospheres also contain atomic hydrogen, the Lyman alpha line has been used to deduce the abundance of this constituent. The same is true for the interplanetary space where Lyman alpha observations can be a good tool to determine the concentration. The last section of the paper presents a question which is intended to stimulate further research in aeronomy.Key words. Atmospheric composition and structure (middle atmosphere – composition and chemistry; thermosphere – composition and chemistry) – history of geophysics (atmospheric sciences)
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Aboudarham, J., I. Scholl, N. Fuller, M. Fouesneau, M. Galametz, F. Gonon, A. Maire, and Y. Leroy. "Automatic detection and tracking of filaments for a solar feature database." Annales Geophysicae 26, no. 2 (February 26, 2008): 243–48. http://dx.doi.org/10.5194/angeo-26-243-2008.
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Abstract. A new method for the automatic detection and tracking of solar filaments is presented. The method addresses the problems facing existing catalogs, such as the one developed recently in the frame of the European Grid of Solar Observations (EGSO) project. In particular, it takes into account the structural and temporal evolution of filaments, differences in intensity as seen from one observation to the next, and the possibility of sudden disappearance followed by reappearance. In this study, the problem of tracking is solved by plotting all detected filaments during each solar rotation on a Carrington map and then by applying region growing techniques on those plots. Using this approach, the "fixed" positions of the envelopes in the Carrington system can be deduced. This is followed by a backward tracking of each filament by considering one full solar rotation. The resulting shifted Carrington map then enables one to follow any filament from one rotation to the next. Such maps should prove valuable for studies of the role of filaments in solar activity, notably coronal mass ejections (CMEs).
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Ernst, Carolyn M., Nancy L. Chabot, Rachel L. Klima, Sanae Kubota, Gabe Rogers, Paul K. Byrne, Steven A. Hauck, et al. "Science Goals and Mission Concept for a Landed Investigation of Mercury." Planetary Science Journal 3, no. 3 (March 1, 2022): 68. http://dx.doi.org/10.3847/psj/ac1c0f.
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Abstract Mercury holds valuable clues to the distribution of elements at the birth of the solar system and how planets form and evolve in close proximity to their host stars. This Mercury Lander mission concept returns in situ measurements that address fundamental science questions raised by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission’s pioneering exploration of Mercury. Such measurements are needed to understand Mercury's unique mineralogy and geochemistry, characterize the proportionally massive core's structure, measure the planet's active and ancient magnetic fields at the surface, investigate the processes that alter the surface and produce the exosphere, and provide ground truth for remote data sets. The mission concept achieves one full Mercury year (∼88 Earth days) of surface operations with an 11-instrument, high-heritage payload delivered to a landing site within Mercury's widely distributed low-reflectance material, and it addresses science goals encompassing geochemistry, geophysics, the Mercury space environment, and geology. The spacecraft launches in 2035, and the four-stage flight system uses a solar electric propulsion cruise stage to reach Mercury in 2045. Landing is at dusk to meet thermal requirements, permitting ∼30 hr of sunlight for initial observations. The radioisotope-powered lander continues operations through the Mercury night. Direct-to-Earth communication is possible for the initial 3 weeks of landed operations, drops out for 6 weeks, and resumes for the final month. Thermal conditions exceed lander operating temperatures shortly after sunrise, ending operations. Approximately 11 GB of data are returned to Earth. The cost estimate demonstrates that a Mercury Lander mission is feasible and compelling as a New Frontiers–class mission.
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Burston, R., K. Hodges, I. Astin, and P. T. Jayachandran. "Automated identification and tracking of polar-cap plasma patches at solar minimum." Annales Geophysicae 32, no. 3 (March 11, 2014): 197–206. http://dx.doi.org/10.5194/angeo-32-197-2014.
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Abstract. A method of automatically identifying and tracking polar-cap plasma patches, utilising data inversion and feature-tracking methods, is presented. A well-established and widely used 4-D ionospheric imaging algorithm, the Multi-Instrument Data Assimilation System (MIDAS), inverts slant total electron content (TEC) data from ground-based Global Navigation Satellite System (GNSS) receivers to produce images of the free electron distribution in the polar-cap ionosphere. These are integrated to form vertical TEC maps. A flexible feature-tracking algorithm, TRACK, previously used extensively in meteorological storm-tracking studies is used to identify and track maxima in the resulting 2-D data fields. Various criteria are used to discriminate between genuine patches and "false-positive" maxima such as the continuously moving day-side maximum, which results from the Earth's rotation rather than plasma motion. Results for a 12-month period at solar minimum, when extensive validation data are available, are presented. The method identifies 71 separate structures consistent with patch motion during this time. The limitations of solar minimum and the consequent small number of patches make climatological inferences difficult, but the feasibility of the method for patches larger than approximately 500 km in scale is demonstrated and a larger study incorporating other parts of the solar cycle is warranted. Possible further optimisation of discrimination criteria, particularly regarding the definition of a patch in terms of its plasma concentration enhancement over the surrounding background, may improve results.
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McPherron, R. L., L. Kepko, T. I. Pulkkinen, T. S. Hsu, J. W. Weygand, and L. F. Bargatze. "Changes in the response of the AL Index with solar cycle and epoch within a corotating interaction region." Annales Geophysicae 27, no. 8 (August 14, 2009): 3165–78. http://dx.doi.org/10.5194/angeo-27-3165-2009.
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Abstract. We use observations in the solar wind and on the ground to study the interaction of the solar wind and interplanetary magnetic field with Earth's magnetosphere. We find that the type of response depends on the state of the solar wind. Coupling functions change as the properties of the solar wind change. We examine this behavior quantitatively with time dependent linear prediction filters. These filters are determined from ensemble arrays of representative events organized by some characteristic time in the event time series. In our study we have chosen the stream interface at the center of a corotating interaction region as the reference time. To carry out our analysis we have identified 394 stream interfaces in the years 1995–2007. For each interface we have selected ten-day intervals centered on the interface and placed data for the interval in rows of an ensemble array. In this study we use Es the rectified dawn-dusk electric field in gsm coordinates as input and the AL index as output. A selection window of width one day is stepped across the ensemble and for each of the nine available windows all events in a given year (~30) are used to calculate a system impulse response function. A change in the properties of the system as a consequence of changes in the solar wind relative to the reference time will appear as a change in the shape and/or the area of the response function. The analysis shows that typically only 45% of the AL variance is predictable in this manner when filters are constructed from a full year of data. We find that the weakest coupling occurs around the stream interface and the strongest well away from the interface. The interface is the time of peak dynamic pressure and strength of the electric field. We also find that coupling appears to be stronger during recurrent high-speed streams in the declining phase of the solar cycle than it is around solar maximum. These results are consistent with the previous report that both strong driving (Es) and high dynamic pressure (Pdyn) reduce the coupling efficiency. Although the changes appear to be statistically significant their physical cause cannot be uniquely identified because various properties of the solar wind vary systematically through a corotating interaction region. It is also possible that the quality of the propagated solar wind data depends on the state of the solar wind. Finally it is likely that the quality of the AL index during the last solar cycle may affect the results. Despite these limitations our results indicate that the Es-AL coupling function is 50% stronger outside a corotating interaction region than inside.
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Costa, E., P. A. Roddy, and J. O. Ballenthin. "Statistical analysis of C/NOFS planar Langmuir probe data." Annales Geophysicae 32, no. 7 (July 14, 2014): 773–91. http://dx.doi.org/10.5194/angeo-32-773-2014.
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Abstract. The planar Langmuir probe (PLP) onboard the Communication/Navigation Outage Forecasting System (C/NOFS) satellite has been monitoring ionospheric plasma densities and their irregularities with high resolution almost seamlessly since May 2008. Considering the recent changes in status of the C/NOFS mission, it may be interesting to summarize some statistical results from these measurements. PLP data from 2 different years (1 October 2008–30 September 2009 and 1 January 2012–31 December 2012) were selected for analysis. The first data set corresponds to solar minimum conditions and the second one is as close to solar maximum conditions of solar cycle 24 as possible at the time of the analysis. The results from the analysis show how the values of the standard deviation of the ion density which are greater than specified thresholds are statistically distributed as functions of several combinations of the following geophysical parameters: (i) solar activity, (ii) altitude range, (iii) longitude sector, (iv) local time interval, (v) geomagnetic latitude interval, and (vi) season.
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Ukhorskiy, A. Y., M. I. Sitnov, A. S. Sharma, and K. Papadopoulos. "Combining global and multi-scale features in a description of the solar wind-magnetosphere coupling." Annales Geophysicae 21, no. 9 (September 30, 2003): 1913–29. http://dx.doi.org/10.5194/angeo-21-1913-2003.
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Abstract. The solar wind-magnetosphere coupling during substorms exhibits dynamical features in a wide range of spatial and temporal scales. The goal of our work is to combine the global and multi-scale description of magnetospheric dynamics in a unified data-derived model. For this purpose we use deterministic methods of nonlinear dynamics, together with a probabilistic approach of statistical physics. In this paper we discuss the mathematical aspects of such a combined analysis. In particular we introduce a new method of embedding analysis based on the notion of a mean-field dimension. For a given level of averaging in the system the mean-filed dimension determines the minimum dimension of the embedding space in which the averaged dynamical system approximates the actual dynamics with the given accuracy. This new technique is first tested on a number of well-known autonomous and open dynamical systems with and without noise contamination. Then, the dimension analysis is carried out for the correlated solar wind-magnetosphere database using vBS time series as the input and AL index as the output of the system. It is found that the minimum embedding dimension of vBS - AL time series is a function of the level of ensemble averaging and the specified accuracy of the method. To extract the global component from the observed time series the ensemble averaging is carried out over the range of scales populated by a high dimensional multi-scale constituent. The wider the range of scales which are smoothed away, the smaller the mean-field dimension of the system. The method also yields a probability density function in the reconstructed phase space which provides the basis for the probabilistic modeling of the multi-scale dynamical features, and is also used to visualize the global portion of the solar wind-magnetosphere coupling. The structure of its input-output phase portrait reveals the existence of two energy levels in the system with non-equilibrium dynamical features such as hysteresis which are typical for non-equilibrium phase transitions. Further improvements in space weather forecasting tools may be achieved by a combination of the dynamical description for the global component and a statistical approach for the multi-scale component.Key words. Magnetospheric physics (solar wind– magnetosphere interactions; storms and substorms) – Space plasma physics (nonlinear phenomena)
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Leonovich, L. A., E. L. Afraimovich, E. B. Romanova, and A. V. Taschilin. "Estimating the contribution from different ionospheric regions to the TEC response to the solar flares using data from the international GPS network." Annales Geophysicae 20, no. 12 (December 31, 2002): 1935–41. http://dx.doi.org/10.5194/angeo-20-1935-2002.
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Abstract. This paper proposes a new method for estimating the contribution from different ionospheric regions to the response of total electron content variations to the solar flare, based on data from the international network of two-frequency multichannel receivers of the navigation GPS system. The method uses the effect of partial "shadowing" of the atmosphere by the terrestrial globe. The study of the solar flare influence on the atmosphere uses GPS stations located near the boundary of the shadow on the ground in the nightside hemisphere. The beams between the satellite-borne transmitter and the receiver on the ground for these stations pass partially through the atmosphere lying in the region of total shadow, and partially through the illuminated atmosphere. The analysis of the ionospheric effect of a powerful solar flare of class X5.7/3B that was recorded on 14 July 2000 (10:24 UT, N22 W07) in quiet geomagnetic conditions (Dst = -10 nT) has shown that about 75% of the TEC increase corresponds to the ionospheric region lying below 300 km and about 25% to regions lying above 300 km.Key words. Ionosphere (solar radiation and cosmic ray effects; instruments and techniques) – Solar physics, astrophysics and astronomy (ultraviolet emissions)
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Korth, H., B. J. Anderson, and C. L. Waters. "Statistical analysis of the dependence of large-scale Birkeland currents on solar wind parameters." Annales Geophysicae 28, no. 2 (February 10, 2010): 515–30. http://dx.doi.org/10.5194/angeo-28-515-2010.
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Abstract. The spatial distributions of large-scale field-aligned Birkeland currents have been derived using magnetic field data obtained from the Iridium constellation of satellites from February 1999 to December 2007. From this database, we selected intervals that had at least 45% overlap in the large-scale currents between successive hours. The consistency in the current distributions is taken to indicate stability of the large-scale magnetosphere–ionosphere system to within the spatial and temporal resolution of the Iridium observations. The resulting data set of about 1500 two-hour intervals (4% of the data) was sorted first by the interplanetary magnetic field (IMF) GSM clock angle (arctan(By/Bz)) since this governs the spatial morphology of the currents. The Birkeland current densities were then corrected for variations in EUV-produced ionospheric conductance by normalizing the current densities to those occurring for 0° dipole tilt. To determine the dependence of the currents on other solar wind variables for a given IMF clock angle, the data were then sorted sequentially by the following parameters: the solar wind electric field in the plane normal to the Earth–Sun line, Eyz; the solar wind ram pressure; and the solar wind Alfvén Mach number. The solar wind electric field is the dominant factor determining the Birkeland current intensities. The currents shift toward noon and expand equatorward with increasing solar wind electric field. The total current increases by 0.8 MA per mV m−1 increase in Eyz for southward IMF, while for northward IMF it is nearly independent of the electric field, increasing by only 0.1 MA per mV m−1 increase in Eyz. The dependence on solar wind pressure is comparatively modest. After correcting for the solar dynamo dependencies in intensity and distribution, the total current intensity increases with solar wind dynamic pressure by 0.4 MA/nPa for southward IMF. Normalizing the Birkeland current densities to both the median solar wind electric field and dynamic pressure effects, we find no significant dependence of the Birkeland currents on solar wind Alfvén Mach number.
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Rucinski, D., M. Bzowski, and H. J. Fahr. "Imprints from the solar cycle on the helium atom and helium pickup ion distributions." Annales Geophysicae 21, no. 6 (June 30, 2003): 1315–30. http://dx.doi.org/10.5194/angeo-21-1315-2003.
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Abstract. Neutral interstellar helium atoms penetrate into the solar system almost unaffected by gas–plasma interactions in the heliospheric interface region, and thus can be considered as carriers of original information on the basic parameters (like density, temperature, bulk velocity) of the Very Local Interstellar Medium (VLISM). Such information can nowadays be derived from analysis of data obtained from different experimental methods: in situ measurements of He atoms (Ulysses), observations of the solar backscattered He 584 A radiation (EUVE), in situ measurements of He + pickup ions (AMPTE, Ulysses, Wind, SOHO, ACE). In view of the current coordinated international ISSI campaign devoted to the study of the helium focusing cone structure and its evolution, we analyze expected variations of neutral He density, of He + pickup fluxes and of their phase space distributions at various phases of the solar activity cycle based on a realistic time-dependent modelling of the neutral helium and He + pickup ion distributions, which reflect solar cycle-induced variations of the photoionization rate. We show that the neutral helium density values are generally anticorrelated with the solar activity phase and in extreme cases (near the downwind axis) the maximum-to-minimum density ratio may even exceed factors of ~ 3 at 1 AU. We also demonstrate that in the upwind hemisphere (at 1 AU and beyond) the He + fluxes are correlated with the solar cycle activity, whereas on the downwind side the maximum of the expected flux up to distances of ~ 3 AU occurs around solar minimum epoch, and only further away does the correlation with solar activity become positive. Finally, we present the response of the phase space distribution spectra of He + pickup ions (in the solar wind frame) for different epochs of the solar cycle and heliocentric distances from 1 to 5 AU covering the range of Ulysses, Wind and ACE observations.Key words. Solar physics, astrophysics and astronomy (ultraviolet emissions) – Space plasma physics (ionization processes; numerical simulation studies)
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Kepkar, Ankur, Christina Arras, Jens Wickert, Harald Schuh, Mahdi Alizadeh, and Lung-Chih Tsai. "Occurrence climatology of equatorial plasma bubbles derived using FormoSat-3 ∕ COSMIC GPS radio occultation data." Annales Geophysicae 38, no. 3 (May 13, 2020): 611–23. http://dx.doi.org/10.5194/angeo-38-611-2020.
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Abstract. The Global Positioning System – Radio Occultation (GPS-RO) observations from FormoSat-3 ∕ COSMIC are used to comprehend the global distribution of equatorial plasma bubbles which are characterized by depletion regions of plasma in the F region of the ionosphere. Plasma bubbles that cause intense scintillation of the radio signals are identified based on the S4 index derived from the 1 Hz raw signal-to-noise ratio measurements between 2007 and 2017. The analyses revealed that bubbles influenced by background plasma density occurred along the geomagnetic equator and had an occurrence peak around the dip equator during high solar activity. The peak shifted between the African and American sectors, depending on different solar conditions. Plasma bubbles usually developed around 19:00 local time (LT), with maximum occurrence around 21:00 LT during solar maximum and ∼22:00 LT during solar minimum. The occurrence of bubbles showed a strong dependence on longitudes, seasons, and solar cycle with the peak occurrence rate in the African sector around the March equinox during high solar activity, which is consistent with previous studies. The GPS-RO technique allows an extended analysis of the altitudinal distribution of global equatorial plasma bubbles obtained from high vertical resolution profiles, thus making it a convenient tool which could be further used with other techniques to provide a comprehensive view of such ionospheric irregularities.
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Dorman, L. I. "Cosmic rays and space weather: effects on global climate change." Annales Geophysicae 30, no. 1 (January 4, 2012): 9–19. http://dx.doi.org/10.5194/angeo-30-9-2012.
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Abstract. We consider possible effects of cosmic rays and some other space factors on the Earth's climate change. It is well known that the system of internal and external factors formatting the climate is very unstable; decreasing planetary temperature leads to an increase of snow surface, and decrease of the total solar energy input into the system decreases the planetary temperature even more, etc. From this it follows that even energetically small factors may have a big influence on climate change. In our opinion, the most important of these factors are cosmic rays and cosmic dust through their influence on clouds, and thus, on climate.
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Amariutei, O. A., S. N. Walker, and T. L. Zhang. "Occurrence rate of magnetic holes between 0.72 and 1 AU: comparative study of Cluster and VEX data." Annales Geophysicae 29, no. 5 (May 2, 2011): 717–22. http://dx.doi.org/10.5194/angeo-29-717-2011.
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Abstract. Localised depressions in the magnetic field magnitude, or magnetic holes, are common features in many regions of solar system plasma. Two distinct mechanisms for their generation have been proposed. The first proposed that the structures are generated locally, close to the point of observation. The alternative has been proposed by Russell et al. (2008), who suggest that the observed magnetic holes represent nonlinear mirror structures that can be carried by the solar wind over vast distances of mirror stable plasma. According to Russell et al. (2008), magnetic holes are created in the vicinity of the sun and are convected by the solar wind outward. Periods of Cluster 1 and VEX data when both spacecraft were connected by the solar wind flow have been considered in this study, in order to determine the evolution of the magnetic holes occurrence rate. The comparison of the magnetic holes occurrence near the Venus and the Earth supports the Russell et al. (2008) premise that they are generated closer to the Sun most likely somewhere within the orbit of Mercury.
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Anderson, Anja C., and Axel Brandenburg. "Editorial." International Journal of Astrobiology 4, no. 1 (January 2005): 1–2. http://dx.doi.org/10.1017/s1473550405002508.
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Astrobiology harbours a number of rather diverse disciplines combining expertise in astronomy and astrophysics, biophysics and biology, chemistry and biochemistry, geophysics and geology, as well as mathematics. The need to foster advances in astrobiology are two-fold. On the one hand, there are many scientific reasons: the discoveries of extra-solar planets which contribute to our understanding of the Solar System and the formation of Earth-like planets, the realization that life can thrive under rather extreme conditions making it more probable for life to exist elsewhere in the Solar System and beyond, and the fact that major resources are being spent in developing the technology to produce artificial life, which helps us to appreciate the range of possibilities that nature may have utilized on Earth or elsewhere. On the other hand, astrobiology touches upon some fundamental questions regarding our very existence, and it is perhaps this that attracts the broad interest of scientists and the public alike. As a result, astrobiology networks and astrobiology centres have been emerging all over the world.
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Meyer, Stefan, Marek Tulej, and Peter Wurz. "Mass spectrometry of planetary exospheres at high relative velocity: direct comparison of open- and closed-source measurements." Geoscientific Instrumentation, Methods and Data Systems 6, no. 1 (January 10, 2017): 1–8. http://dx.doi.org/10.5194/gi-6-1-2017.
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Abstract. The exploration of habitable environments on or inside icy moons around the gas giants in the solar system is of major interest in upcoming planetary missions. Exactly this theme is addressed by the JUpiter ICy moons Explorer (JUICE) mission of ESA, which will characterise Ganymede, Europa and Callisto as planetary objects and potential habitats. We developed a prototype of the Neutral Gas and Ion Mass spectrometer (NIM) of the Particle Environment Package (PEP) for the JUICE mission intended for composition measurements of neutral gas and thermal plasma. NIM/PEP will be used to measure the chemical composition of the exospheres of the icy Jovian moons. Besides direct ion measurement, the NIM instrument is able to measure the inflowing neutral gas in two different modes: in neutral mode, where the gas enters directly the ion source (open source), and in thermal mode, where the gas gets thermally accommodated to the wall temperature by several collisions inside an equilibrium sphere, called antechamber, before entering the ion source (closed source). We performed measurements with the prototype NIM using a neutral gas beam of 1 up to 4.5 km s−1 velocity in the neutral and thermal mode. The current trajectory of JUICE foresees a flyby velocity of 4 km s−1 at Europa; other flybys are in the range of 1 up to 7 km s−1 and orbital velocity in Ganymede orbits is around 2 km s−1. Different species are used for the gas beam, such as noble gases Ne, Ar, Kr as well as molecules like H2, methane, ethane, propane and more complex ones. The NIM prototype was successfully tested under realistic JUICE mission conditions. In addition, we find that the antechamber (closed source) behaves as expected with predictable density enhancement over the specified mass range and within the JUICE mission phase velocities. Furthermore, with the open source and the closed source we measure almost the same composition for noble gases, as well as for molecules, indicating no additional fragmentation of the species recorded with the antechamber for the investigated parameter range.
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Klenzing, J., A. G. Burrell, R. A. Heelis, J. D. Huba, R. Pfaff, and F. Simões. "Exploring the role of ionospheric drivers during the extreme solar minimum of 2008." Annales Geophysicae 31, no. 12 (December 4, 2013): 2147–56. http://dx.doi.org/10.5194/angeo-31-2147-2013.
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Abstract. During the recent solar minimum, solar activity reached the lowest levels observed during the space age, resulting in a contracted atmosphere. This extremely low solar activity provides an unprecedented opportunity to understand the variability of the Earth's ambient ionosphere. The average E × B drifts measured by the Vector Electric Field Instrument (VEFI) on the Communications/Navigation Outage Forecasting System (C/NOFS) satellite during this period are found to have several differences from the expected climatology based on previous solar minima, including downward drifts in the early afternoon and a weak to non-existent pre-reversal enhancement. Using SAMI2 (Sami2 is Another Model of the Ionosphere) as a computational engine, we investigate the effects of these electrodynamical changes as well as the contraction of the thermosphere and reduced EUV ionization on the ionosphere. The sensitivity of the simulations to wind models is also discussed. These modeled ionospheres are compared to the C/NOFS average topside ion density and composition and Formosa Satellite-3/Constellation Observing System for Meteorology, Ionosphere, and Climate average NmF2 and hmF2. In all cases, incorporating the VEFI drift data significantly improves the model results when compared to both the C/NOFS density data and the F3/C GOX data. Changing the MSIS and EUVAC models produced changes in magnitude, but not morphology with respect to local time. The choice of wind model modulates the resulting topside density and composition, but only the use of the VEFI E × B drifts produces the observed post-sunset drop in the F peak.
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Kvammen, Andreas, Kristoffer Wickstrøm, Samuel Kociscak, Jakub Vaverka, Libor Nouzak, Arnaud Zaslavsky, Kristina Rackovic Babic, et al. "Machine learning detection of dust impact signals observed by the Solar Orbiter." Annales Geophysicae 41, no. 1 (January 24, 2023): 69–86. http://dx.doi.org/10.5194/angeo-41-69-2023.
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Abstract. This article presents the results of automatic detection of dust impact signals observed by the Solar Orbiter – Radio and Plasma Waves instrument. A sharp and characteristic electric field signal is observed by the Radio and Plasma Waves instrument when a dust particle impacts the spacecraft at high velocity. In this way, ∼ 5–20 dust impacts are daily detected as the Solar Orbiter travels through the interplanetary medium. The dust distribution in the inner solar system is largely uncharted and statistical studies of the detected dust impacts will enhance our understanding of the role of dust in the solar system. It is however challenging to automatically detect and separate dust signals from the plural of other signal shapes for two main reasons. Firstly, since the spacecraft charging causes variable shapes of the impact signals, and secondly because electromagnetic waves (such as solitary waves) may induce resembling electric field signals. In this article, we propose a novel machine learning-based framework for detection of dust impacts. We consider two different supervised machine learning approaches: the support vector machine classifier and the convolutional neural network classifier. Furthermore, we compare the performance of the machine learning classifiers to the currently used on-board classification algorithm and analyze 2 years of Radio and Plasma Waves instrument data. Overall, we conclude that detection of dust impact signals is a suitable task for supervised machine learning techniques. The convolutional neural network achieves the highest performance with 96 % ± 1 % overall classification accuracy and 94 % ± 2 % dust detection precision, a significant improvement to the currently used on-board classifier with 85 % overall classification accuracy and 75 % dust detection precision. In addition, both the support vector machine and the convolutional neural network classifiers detect more dust particles (on average) than the on-board classification algorithm, with 16 % ± 1 % and 18 % ± 8 % detection enhancement, respectively. The proposed convolutional neural network classifier (or similar tools) should therefore be considered for post-processing of the electric field signals observed by the Solar Orbiter.
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Rao, Yamini K., Abhishek K. Srivastava, Pradeep Kayshap, and Bhola N. Dwivedi. "Signatures of red-shifted foot points in the quiescent coronal loop system." Annales Geophysicae 37, no. 4 (August 30, 2019): 765–73. http://dx.doi.org/10.5194/angeo-37-765-2019.
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Abstract. We observed quiescent coronal loops using multi-wavelength observations from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) on 13 April 2016. The flows at the foot points of such loop systems are studied using spectral data from the Interface Region Imaging Spectrograph (IRIS). The Doppler velocity distributions at the foot points lying in the moss region show the negligible or small flows at the Ni I, Mg II k3, and C II line corresponding to upper photospheric and chromospheric emissions. Significant red shifts (downflows) ranging from 1 to 7 km s−1 are observed at Si IV (1393.78 Å; log(T/K)=4.8), which is found to be consistent with the existing results regarding dynamical loop systems and moss regions. Such downflows agree well with the impulsive heating mechanism reported earlier.
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Marques de Souza, Adriane, Ezequiel Echer, Mauricio José Alves Bolzan, and Rajkumar Hajra. "Cross-correlation and cross-wavelet analyses of the solar wind IMF <i>B</i><sub><i>z</i></sub> and auroral electrojet index AE coupling during HILDCAAs." Annales Geophysicae 36, no. 1 (February 9, 2018): 205–11. http://dx.doi.org/10.5194/angeo-36-205-2018.
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Abstract. Solar-wind–geomagnetic activity coupling during high-intensity long-duration continuous AE (auroral electrojet) activities (HILDCAAs) is investigated in this work. The 1 min AE index and the interplanetary magnetic field (IMF) Bz component in the geocentric solar magnetospheric (GSM) coordinate system were used in this study. We have considered HILDCAA events occurring between 1995 and 2011. Cross-wavelet and cross-correlation analyses results show that the coupling between the solar wind and the magnetosphere during HILDCAAs occurs mainly in the period ≤ 8 h. These periods are similar to the periods observed in the interplanetary Alfvén waves embedded in the high-speed solar wind streams (HSSs). This result is consistent with the fact that most of the HILDCAA events under present study are related to HSSs. Furthermore, the classical correlation analysis indicates that the correlation between IMF Bz and AE may be classified as moderate (0.4–0.7) and that more than 80 % of the HILDCAAs exhibit a lag of 20–30 min between IMF Bz and AE. This result corroborates with Tsurutani et al. (1990) where the lag was found to be close to 20–25 min. These results enable us to conclude that the main mechanism for solar-wind–magnetosphere coupling during HILDCAAs is the magnetic reconnection between the fluctuating, negative component of IMF Bz and Earth's magnetopause fields at periods lower than 8 h and with a lag of about 20–30 min. Keywords. Magnetospheric physics (solar-wind–magnetosphere interactions)
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Mengistu Tsidu, Gizaw, and Mulugeta Melaku Zegeye. "Comparison of quiet-time ionospheric total electron content from the IRI-2016 model and from gridded and station-level GPS observations." Annales Geophysicae 38, no. 3 (June 16, 2020): 725–48. http://dx.doi.org/10.5194/angeo-38-725-2020.
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Abstract. Earth's ionosphere is an important medium of radio wave propagation in modern times. However, the effective use of the ionosphere depends on the understanding of its spatiotemporal variability. Towards this end, a number of ground- and space-based monitoring facilities have been set up over the years. The information from these stations has also been complemented by model-based studies. However, assessment of the performance of ionospheric models in capturing observations needs to be conducted. In this work, the performance of the IRI-2016 model in simulating the total electron content (TEC) observed by a network of Global Positioning System (GPS) receivers is evaluated based on the RMSE, the bias, the mean absolute error (MAE) and skill score, the normalized mean bias factor (NMBF), the normalized mean absolute error factor (NMAEF), the correlation, and categorical metrics such as the quantile probability of detection (QPOD), the quantile categorical miss (QCM), and the quantile critical success index (QCSI). The IRI-2016 model simulations are evaluated against gridded International Global Navigation Satellite System (GNSS) Service (IGS) GPS-TEC and TEC observations at a network of GPS receiver stations during the solar minima in 2008 and solar maxima in 2013. The phases of modeled and simulated TEC time series agree strongly over most of the globe, as indicated by a high correlations during all solar activities with the exception of the polar regions. In addition, lower RMSE, MAE, and bias values are observed between the modeled and measured TEC values during the solar minima than during the solar maxima from both sets of observations. The model performance is also found to vary with season, longitude, solar zenith angle, and magnetic local time. These variations in the model skill arise from differences between seasons with respect to solar irradiance, the direction of neutral meridional winds, neutral composition, and the longitudinal dependence of tidally induced wave number four structures. Moreover, the variation in model performance as a function of solar zenith angle and magnetic local time might be linked to the accuracy of the ionospheric parameters used to characterize both the bottom- and topside ionospheres. However, when the NMBF and NMAEF are applied to the data sets from the two distinct solar activity periods, the difference in the skill of the model during the two periods decreases, suggesting that the traditional model evaluation metrics exaggerate the difference in model skill. Moreover, the performance of the model in capturing the highest ends of extreme values over the geomagnetic equator, midlatitudes, and high latitudes is poor, as noted from the decrease in the QPOD and QCSI as well as an increase in the QCM over most of the globe with an increase in the threshold percentile TEC values from 10 % to 90 % during both the solar minimum and the solar maximum periods. The performance of IRI-2016 in simulating observed low (as low as the 10th percentile) and high (higher than the 90th percentile) TEC correctly over equatorial ionization anomaly (EIA) crest regions is reasonably good given that IRI-2016 is a climatological model. However, it is worth noting that the performance of the IRI-2016 model is relatively poor in 2013 compared with 2008 at the highest ends of the TEC distribution. Therefore, this study reveals the strengths and weaknesses of the IRI-2016 model in simulating the observed TEC distribution correctly during all seasons and solar activities for the first time.
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Maruyama, T. "Regional reference total electron content model over Japan based on neural network mapping techniques." Annales Geophysicae 25, no. 12 (January 2, 2007): 2609–14. http://dx.doi.org/10.5194/angeo-25-2609-2007.
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Abstract. A regional reference model of total electron content (TEC) was constructed using data from the GPS Earth Observation Network (GEONET), which consists of more than 1000 Global Positioning System (GPS) satellite receivers distributed over Japan. The data covered almost one solar activity period from April 1997 to June 2007. First, TECs were determined for 32 grid points, expanding from 27 to 45° N in latitude and from 127 to 145° E in longitude at 15-min intervals. Secondly, the time-latitude variation averaged over three days was determined by using the surface harmonic functional expansion. The coefficients of the expansion were then modeled by using a neural network technique with input parameters of the season (day of the year) and solar activity (F10.7 index and sunspot number). Thus, two-dimensional TEC maps (time vs. latitude) can be obtained for any given set of solar activity and day of the year.
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Coley, W. R., R. A. Stoneback, R. A. Heelis, and M. R. Hairston. "Topside equatorial zonal ion velocities measured by C/NOFS during rising solar activity." Annales Geophysicae 32, no. 2 (February 4, 2014): 69–75. http://dx.doi.org/10.5194/angeo-32-69-2014.
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Abstract. The Ion Velocity Meter (IVM), a part of the Coupled Ion Neutral Dynamic Investigation (CINDI) instrument package on the Communication/Navigation Outage Forecast System (C/NOFS) spacecraft, has made over 5 yr of in situ measurements of plasma temperatures, composition, densities, and velocities in the 400–850 km altitude range of the equatorial ionosphere. These measured ion velocities are then transformed into a coordinate system with components parallel and perpendicular to the geomagnetic field allowing us to examine the zonal (horizontal and perpendicular to the geomagnetic field) component of plasma motion over the 2009–2012 interval. The general pattern of local time variation of the equatorial zonal ion velocity is well established as westward during the day and eastward during the night, with the larger nighttime velocities leading to a net ionospheric superrotation. Since the C/NOFS launch in April 2008, F10.7 cm radio fluxes have gradually increased from around 70 sfu to levels in the 130–150 sfu range. The comprehensive coverage of C/NOFS over the low-latitude ionosphere allows us to examine variations of the topside zonal ion velocity over a wide level of solar activity as well as the dependence of the zonal velocity on apex altitude (magnetic latitude), longitude, and solar local time. It was found that the zonal ion drifts show longitude dependence with the largest net eastward values in the American sector. The pre-midnight zonal drifts show definite solar activity (F10.7) dependence. The daytime drifts have a lower dependence on F10.7. The apex altitude (magnetic latitude) variations indicate a more westerly flow at higher altitudes. There is often a net topside subrotation at low F10.7 levels, perhaps indicative of a suppressed F region dynamo due to low field line-integrated conductivity and a low F region altitude at solar minimum.
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Chernogor, Leonid F., Kostyantyn P. Garmash, Qiang Guo, Victor T. Rozumenko, and Yu Zheng. "Ionospheric effects of the 5–6 January 2019 eclipse over the People's Republic of China: results from oblique sounding." Annales Geophysicae 40, no. 5 (October 6, 2022): 585–603. http://dx.doi.org/10.5194/angeo-40-585-2022.
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Abstract. This paper deals with the variations in the Doppler spectra and in the relative amplitudes of the signals observed at oblique incidence over the People's Republic of China (PRC) during the partial solar eclipse of 5–6 January 2019 and on reference days. The observations were made using the multifrequency multipath radio system for sounding the ionosphere at oblique incidence. The receiver system is located at the Harbin Engineering University, PRC, and 14 HF broadcasting station transmitters are used for taking measurements along the following radio-wave propagation paths: Lintong/Pucheng to Harbin, Hwaseong to Harbin, Chiba/Nagara to Harbin, Hailar/Nanmen to Harbin, Beijing to Harbin (three paths), Goyang to Harbin, Ulaanbaatar/Khonkhor to Harbin, Yakutsk to Harbin (two paths), Shijiazhuang to Harbin, Hohhot to Harbin, and Yamata to Harbin. The specific feature of this partial solar eclipse was that it occurred during the local morning with a geomagnetic disturbance (Kp ≈ 3−) in the background. The response of the ionosphere to the solar eclipse has been inferred from temporal variations in the Doppler spectra, the Doppler shift, and the signal relative amplitude. The partial solar eclipse was found to be associated with broadening of the Doppler spectrum, up to ± 1.5 Hz, alternating sign Doppler-shift variations, up to ± 0.5 Hz, in the main ray, and quasi-periodic Doppler-shift changes. The relative amplitude of electron density disturbances in the 15 min period of atmospheric gravity wave field and in the 4–5 min period of infrasound wave field is estimated to be 1.6 %–2.4 % and 0.2 %–0.3 %, respectively. The estimates of a maximum decrease in the electron density are in agreement with the observations.