Gotowe bibliografie tematyczne / Auroral plasma

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Gotowa bibliografia na temat „Auroral plasma”

Autor: Grafiati
Data publikacji: 6 września 2023

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Artykuły w czasopismach na temat "Auroral plasma"

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Titova, E. E., A. G. Yahnin, O. Santolík, D. A. Gurnett, F. Jirícek, J. L. Rauch, F. Lefeuvre, L. A. Frank, J. B. Sigwarth i M. M. Mogilevsky. "The relationship between auroral hiss at high altitudes over the polar caps and the substorm dynamics of aurora". Annales Geophysicae 23, nr 6 (15.09.2005): 2117–28. http://dx.doi.org/10.5194/angeo-23-2117-2005.

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Abstract. Strong variations of intensity and cutoff frequency of the auroral hiss were observed by INTERBALL-2 and POLAR satellites at high altitudes, poleward from the auroral oval. The hiss intensifications are correlated with the auroral activations during substorms and/or pseudo-breakups. The low cutoff frequency of auroral hiss increases with the distance between the aurora and the satellite footprint. Multicomponent wave measurements of the hiss emissions on board the POLAR spacecraft show that the horizontal component of the Poynting flux of auroral hiss changes its direction in good accordance with longitudinal displacements of the bright auroras. The vertical component of the Poynting flux is directed upward from the aurora region, indicating that hiss could be generated by upgoing electron beams. This relationship between hiss and the aurora dynamics means that the upgoing electron beams are closely related to downgoing electron beams which produce the aurora. During the auroral activations the upgoing and downgoing beams move and change their intensities simultaneously. Keywords. Magnetospheric physics (Auroral phenomena; Plasma waves and instabilities; Storms and substorms)
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Blomberg, L. G., J. A. Cumnock, I. I. Alexeev, E. S. Belenkaya, S. Yu Bobrovnikov i V. V. Kalegaev. "Transpolar aurora: time evolution, associated convection patterns, and a possible cause". Annales Geophysicae 23, nr 5 (28.07.2005): 1917–30. http://dx.doi.org/10.5194/angeo-23-1917-2005.

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Abstract. We present two event studies illustrating the detailed relationships between plasma convection, field-aligned currents, and polar auroral emissions, as well as illustrating the influence of the Interplanetary Magnetic Field's y-component on theta aurora development. The transpolar arc of the theta aurorae moves across the entire polar region and becomes part of the opposite side of the auroral oval. Electric and magnetic field and precipitating particle data are provided by DMSP, while the POLAR UVI instrument provides measurements of auroral emissions. Ionospheric electrostatic potential patterns are calculated at different times during the evolution of the theta aurora using the KTH model. These model patterns are compared to the convection predicted by mapping the magnetopause electric field to the ionosphere using the Paraboloid Model of the magnetosphere. The model predicts that parallel electric fields are set up along the magnetic field lines projecting to the transpolar aurora. Their possible role in the acceleration of the auroral electrons is discussed. Keywords. Ionosphere (Plasma convection; Polar ionosphere) – Magnetospheric physics (Magnetosphereionosphere interactions)
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Miyashita, Yukinaga, i Akimasa Ieda. "Revisiting substorm events with preonset aurora". Annales Geophysicae 36, nr 5 (19.10.2018): 1419–38. http://dx.doi.org/10.5194/angeo-36-1419-2018.

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Abstract. Nishimura et al. (2010) proposed a new plasma intrusion or preonset aurora scenario of substorm triggering. In this scenario, a substorm is triggered by a fast earthward flow generated at the distant neutral line which corresponds to a preonset auroral streamer or arc in the ionosphere propagating from the auroral poleward boundary to the initial auroral brightening site, i.e., “preonset aurora”. In the present paper, we revisited three substorm events reported as being triggered by such a mechanism related to preonset auroras, based on THEMIS ground-based all-sky imager data. Unlike previous studies, we examined the arrival timing of the preonset aurora relative to the three steps of auroral onset arc development (initial brightening, enhancement of the wave-like structure, and poleward expansion) to make the role of the preonset aurora in the auroral steps clearer. Our detailed timing analysis found that preonset auroral streamers reached the auroral onset arc but away from the initial brightening site after initial brightening for two events, while no preonset aurora reaching the initial brightening site could be identified for the other event. This result suggests that the processes associated with auroral streamers are unlikely to affect at least initial brightening, even if we consider not only the presence and arrival timing and location of the auroral streamers but also the scale of the corresponding flow and flow vortices. We list a series of open questions for testing the preonset aurora scenario further in future studies. Keywords. Magnetospheric physics (storms and substorms; auroral phenomena; magnetotail)
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Sandholt, P. E., i C. J. Farrugia. "Monitoring magnetosheath-magnetosphere interconnection topology from the aurora". Annales Geophysicae 20, nr 5 (31.05.2002): 629–37. http://dx.doi.org/10.5194/angeo-20-629-2002.

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Abstract. A strong southward rotation of the IMF (BZ from 5 to -6 nT in ~ 20 s) on 4 January 1995 caused an abrupt reconfiguration of midday aurorae and plasma convection consisting of the following: (1) the red-line aurora associated with magnetosheath plasma transfer at the low-latitude magnetopause appeared at the same time that (2) the green-line aurora from precipitating energetic plasma sheet particles equatorward of the cusp (near the open-closed field line boundary) weakened visibly and shifted equatorward, (3) the high-latitude aurora during the previous northward IMF, which is associated with lobe reconnection, persisted briefly (3 min) and brightened, before it disappeared from the field-of-view, (4) the activation of a strong convection bay (DPY current) at cusp and sub-cusp latitudes when the field turned strongly south, (5) a distinct wave motion of the plasma sheet outer boundary, as inferred from the aurora, which correlates closely with Pc 5 magnetic pulsations. Our interpretation of the dramatic reconfiguration is that reconnection poleward of the cusp coexisted briefly with reconnection at sub-cusp latitudes. The latter provided a magnetic field connection which enabled, on the one hand, magnetosheath particles to enter and cause the red-line cusp aurora, and on the other hand, allowed for magnetospheric energetic particles to escape and weaken the outer plasma sheet source of the green-line emission. The coexistence of the two cusp auroras reflects the time required for one field line topology to replace another, which, under the prevailing high speed wind ( ~ 650 km/s), lasts ~ 3–4 min. The motion of open flux tubes propagating from equator to pole during this transition is traced in the aurora by a poleward moving form. The waves on the outer boundary of the plasma sheet are most likely due to the Kelvin-Helmholtz instability. The study illustrates the ability of local auroral observations to monitor even a global change in magnetospheric magnetic topology.Key words. Magnetospheric Physics (auroral phenomena; magnetopause, cusp, and boundary layers; solar wind-magnethoshere interactions)
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Blixt, E. M., M. J. Kosch i J. Semeter. "Relative drift between black aurora and the ionospheric plasma". Annales Geophysicae 23, nr 5 (27.07.2005): 1611–21. http://dx.doi.org/10.5194/angeo-23-1611-2005.

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Abstract. Black auroras are recognized as spatially well-defined regions within uniform diffuse aurora where the optical emission is significantly reduced. Although a well studied phenomenon, there is no generally accepted theory for black auroras. One theory suggests that black regions are formed when energetic magnetospheric electrons no longer have access to the loss cone. If this blocking mechanism drifts with the source electron population in the magnetosphere, black auroras in the ionosphere should drift eastward with a velocity that increases with the energy of the precipitating electrons in the surrounding aurora, since the gradient-B curvature drift is energy dependent. It is the purpose of this paper to test this hypothesis. To do so we have used simultaneous measurements by the European Incoherent Scatter (EISCAT) radar and an auroral TV camera at Tromsø, Norway. We have analyzed 8 periods in which a black aurora occurred frequently to determine their relative drift with respect to the ionospheric plasma. The black aurora was found to drift eastward with a velocity of 1.5–4km/s, which is in accordance with earlier observations. However, one case was found where a black patch was moving westward, this being the first report of such behaviour in the literature. In general, the drift was parallel to the ionospheric flow but at a much higher velocity. This suggests that the generating mechanism is not of ionospheric origin. The characteristic energy of the precipitating electron population was estimated through inversion of E-region plasma density profiles. We show that the drift speed of the black patches increased with the energy of the precipitating electrons in a way consistent with the gradient-B curvature drift, suggesting a magnetospheric mechanism for the black aurora. As expected, a comparison of the drift speeds with a rudimentary dipole field model of the gradient-B curvature drift speed only yields order-of-magnitude agreement, which most likely is due to the nightside disturbed magnetosphere being significantly stretched. Keywords. Auroral ionosphere; MI interaction; Energetic particles, precipitating
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Yahnin, A. G., V. A. Sergeev, B. B. Gvozdevsky i S. Vennerstrøm. "Magnetospheric source region of discrete auroras inferred from their relationship with isotropy boundaries of energetic particles". Annales Geophysicae 15, nr 8 (31.08.1997): 943–58. http://dx.doi.org/10.1007/s00585-997-0943-z.

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Abstract. According to observations, the discrete auroral arcs can sometimes be found, either deep inside the auroral oval or at the poleward border of the wide (so-called double) auroral oval, which map to very different regions of the magnetotail. To find common physical conditions for the auroral-arc generation in these magnetotail regions, we study the spatial relationship between the diffuse and discrete auroras and the isotropic boundaries (IBs) of the precipitating energetic particles which can be used to characterise locally the equatorial magnetic field in the tail. From comparison of ground observation of auroral forms with meridional profiles of particle flux measured simultaneously by the low-altitude NOAA satellites above the ground observation region, we found that (1) discrete auroral arcs are always situated polewards from (or very close to) the IB of >30-keV electrons, whereas (2) the IB of the >30-keV protons is often seen inside the diffuse aurora. These relationships hold true for both quiet and active (substorm) conditions in the premidnight-nightside (18-01-h) MLT sector considered. In some events the auroral arcs occupy a wide latitudinal range. The most equatorial of these arcs was found at the poleward edge of the diffuse auroras (but anyway in the vicinity of the electron IB), the most poleward arcs were simultaneously observed on the closed field lines near the polar-cap boundary. These observations disagree with the notion that the discrete aurora originate exclusively in the near-Earth portion of plasma sheet or exclusively on the PSBL field lines. Result (1) may imply a fundamental feature of auroral-arc formation: they originate in the current-sheet regions having very curved and tailward-stretched magnetic field lines.
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De Keyser, J., i M. Echim. "Auroral and sub-auroral phenomena: an electrostatic picture". Annales Geophysicae 28, nr 2 (23.02.2010): 633–50. http://dx.doi.org/10.5194/angeo-28-633-2010.

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Abstract. Many auroral and sub-auroral phenomena are manifestations of an underlying magnetosphere-ionosphere coupling. In the electrostatic perspective the associated auroral current circuit describes how the generator (often in the magnetosphere) is connected to the load (often in the ionosphere) through field-aligned currents. The present paper examines the generic properties of the current continuity equation that characterizes the auroral circuit. The physical role of the various elements of the current circuit is illustrated by considering a number of magnetospheric configurations, various auroral current-voltage relations, and different types of behaviour of the ionospheric conductivity. Based on realistic assumptions concerning the current-voltage relation and the ionospheric conductivity, a comprehensive picture of auroral and sub-auroral phenomena is presented, including diffuse aurora, discrete auroral arcs, black aurora, and subauroral ion drift. The electrostatic picture of field-aligned potential differences, field-aligned currents, ionospheric electric fields and plasma drift, and spatial scales for all these phenomena is in qualitative agreement with observations.
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Borodkova, N. L., A. G. Yahnin, K. Liou, J. A. Sauvaud, A. O. Fedorov, V. N. Lutsenko, M. N. Nozdrachev i A. A. Lyubchich. "Plasma sheet fast flows and auroral dynamics during substorm: a case study". Annales Geophysicae 20, nr 3 (31.03.2002): 341–47. http://dx.doi.org/10.5194/angeo-20-341-2002.

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Abstract. Interball-1 observations of a substorm development in the mid-tail on 16 December 1998 are compared with the auroral dynamics obtained from the Polar UV imager. Using these data, the relationship between plasma flow directions in the tail and the location of the auroral activation is examined. Main attention is given to tailward and earth-ward plasma flows, interpreted as signatures of a Near Earth Neutral Line (NENL). It is unambiguously shown that in the mid-plasma sheet the flows were directed tailward when the auroral bulge developed equatorward of the spacecraft ionospheric footprint. On the contrary, when active auroras moved poleward of the Interball-1 projection, earthward fast flow bursts were observed. This confirms the concept that the NENL (or flow reversal region) is the source of auroras forming the poleward edge of the auroral bulge. The observed earthward flow bursts have all typical signatures of Bursty Bulk Flows (BBFs), described by Angelopolous et al. (1992). These BBFs are related to substorm activations starting at the poleward edge of the expanded auroral bulge. We interpret the BBFs as a result of reconnection pulses occurring tail-ward of Interball-1. In addition, some non-typically observed phenomena were detected in the plasma sheet during this substorm: (i) tailward/earthward flows were superimposed on a very strong duskward flow, and (ii) wavy structures of both magnetic field and plasma density were registered. The latter observation is probably linked to the filamentary structure of the current sheet.Key words. Magnetospheric physics (auroral phenomena; plasma sheet; storms and substorms)
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Cumnock, J. A., i L. G. Blomberg. "Transpolar arc evolution and associated potential patterns". Annales Geophysicae 22, nr 4 (2.04.2004): 1213–31. http://dx.doi.org/10.5194/angeo-22-1213-2004.

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Abstract. We present two event studies encompassing detailed relationships between plasma convection, field-aligned current, auroral emission, and particle precipitation boundaries. We illustrate the influence of the Interplanetary Magnetic Field By component on theta aurora development by showing two events during which the theta originates on both the dawn and dusk sides of the auroral oval. Both theta then move across the entire polar region and become part of the opposite side of the auroral oval. Electric and magnetic field and precipitating particle data are provided by DMSP, while the Polar UVI instrument provides measurements of auroral emissions. Utilizing satellite data as inputs, the Royal Institute of Technology model provides the high-latitude ionospheric electrostatic potential pattern calculated at different times during the evolution of the theta aurora, resulting from a variety of field-aligned current configurations associated with the changing global aurora. Key words. Ionosphere (auroral ionosphere; electric fields and currents). Magnetospheric physics (magnetosphereionosphere interactions)
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Rycroft, M. J. "Auroral plasma dynamics". Journal of Atmospheric and Terrestrial Physics 57, nr 13 (listopad 1995): 1668. http://dx.doi.org/10.1016/0021-9169(95)90035-7.

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Rozprawy doktorskie na temat "Auroral plasma"

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Liléo, Sónia. "Auroral electrodynamics of plasma boundary regions". Doctoral thesis, KTH, Rymd- och plasmafysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10446.

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The electrodynamic coupling between the auroral ionosphere and the magnetosphere is the main subject of this thesis. Satellite measurements of electric and magnetic fields and of charged particles are used to explore three distinct plasma boundaries, magnetically linked to the nightside auroral ionosphere. These boundaries are the inner edge of the plasma sheet (PS), and the inner and the outer edges of the plasma sheet boundary layer (PSBL). Strong ionospheric electric fields with amplitudes up to 400 mV/m may be observed in the subauroral ionosphere, in the vicinity of the ionospheric projection of the PS inner edge. Intense and dynamic auroral electric fields with local magnitudes up to 150 mV/m associated with upward ion beams and field-aligned currents are observed for the events treated here, at the inner and outer boundaries of the PSBL at an altitude of about 4-5 Earth radii, well above the acceleration region. Subauroral and auroral electric fields are the two main subjects of this thesis. Subauroral ion drifts (SAID) are associated with poleward electric fields, occurring predominantly in the premidnight region during the substorm recovery phase. The recently revealed abnormal subauroral ion drifts (ASAID) are associated with equatorward electric fields, occurring during extended periods of low auroral activity. The results indicate that the generation mechanism of SAID can neither be regarded as a pure voltage generator nor a pure current generator, but having certain characteristics of both generator types. Ionospheric feedback appears to play a major role for the development and maintenance of the SAID electric fields. The formation of ASAID is proposed to result from the proximity and interaction between different plasma boundaries of the innermost magnetosphere during extended periods of low auroral activity. The auroral electric fields observed in the upward current region at the PSBL inner and outer edges are associated with upward parallel electric fields, which partially decouple the high-altitude electric fields from the ionosphere. This is in contrast to the subauroral electric fields which are coupled. Multi-point measurements provided by the Cluster mission show that the observed electric fields are highly variable in space and time, revealing various types of acceleration processes. However, they appear to be tied to the boundary where they are originally formed. A case is  presented where they are associated with large electromagnetic energy fluxes directed upward away from the ionosphere. The interaction between the magnetosphere and ionosphere, being more pronounced at plasma boundary regions, is important for the understanding of the formation and regulation of the highly structured auroral electric fields observed in the upward current region.
QC 20100727
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Schlatter, Nicola. "Radar Signatures of Auroral Plasma Instability". Doctoral thesis, KTH, Rymd- och plasmafysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160894.

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Incoherent scatter radars are powerful ground based instruments for ionospheric measurements. By analysis of the Doppler shifted backscatter spectrum, containing the signature of electrostatic plasma waves, plasma bulk properties are estimated. At high latitudes the backscattered radar power is occasionally enhanced several orders of magnitude above the thermal backscatter level. These enhancements occur during geomagnetic disturbed conditions and are referred to as naturally enhanced ion acoustic echoes (NEIALs). NEIALs are linked to auroral activity with optical auroral emission observed in the vicinity of the radar measurement volume simultaneously to NEIALs. The backscatter enhancements are thought to be caused by wave activity above thermal level due to instability. A number of theories have been put forward including streaming instabilities and Langmuir turbulence to explain NEIAL observations. NEIALs occur in two classes distinct by their Doppler features. Observations of the first type, which has been studied more extensively, are generally modelled well by the Langmuir turbulence model. The difficulty in trying to understand the driving mechanism of the instability is the limited spatial resolution of the radar measurements. Observations of the second type, reported on more recently, have been interpreted as evidence for naturally occurring strong Langmuir turbulence by means of their Doppler features. Aperture synthesis is a technique to increase the spatial resolution of the radar measurements to below beam width of the single receiver antennas. The technique is employed to investigate the structure of NEIALs in the plane perpendicular to the magnetic field at sub-degree scale corresponding to hundreds of meters to a few kilometres at ionospheric altitudes. Calibration of the radar interferometer is necessary and a calibration technique is presented in paper I. Interferometry observations of a NEIAL event with receivers deployed at the EISCAT incoherent scatter radar on Svalbard are presented in paper II. The size of the enhanced backscatter region is found to be limited to 900 x 500m in the plane perpendicular to the geomagnetic field. These observations constitute the first unambiguous measurements giving evidence for the limited size of the enhanced backscatter region. In paper III observations of strong Langmuir turbulence signatures are presented. The apparent turbulent region in these observations is limited to two narrow altitude regions, 2km extent, and electron density irregularities caused by the turbulence are thought to reach down to decimeter scale length. The turbulence observations were obtained during energetic electron precipitation thereby differing from other observations during which a low energy component in the electron precipitation is reported. In paper IV a statistical study of strong Langmuir turbulence radar signatures is presented. The study reveals differing local time distributions for these signatures from type I NEIALs indicating di_ering driving conditions for the two types of NEIALs. It is found that strong Langmuir turbulence signatures are predominantly observed in the pre-midnight sector where auroral break-up aurora prevails.

QC 20150303

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Liléo, Sónia. "Auroral electrodynamics of plasma boundary regions /". Stockholm : Skolan för elektro- och systemteknik, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10446.

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Dreyer, Joshua. "A detailed study of auroral fragments". Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388546.

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Aurora occurs in various shapes, one of which is the hitherto unreported phenomenon of auroral fragments. For three periods of occurrence of these fragments their properties were studied in detail during this master’s thesis, using mainly ground-based instrumentation located near Longyearbyen on Svalbard, Norway. A base dataset was constructed from 103 all-sky camera images, manually marking 305 fragments for further analysis. This thesis reports and describes the fragment observations during the observed events, including the auroral and geomagnetic context. Fragments generally seem to fall into two categories, the first being singular, apparently randomly distributed fragments, and the second being periodic fragments that occur in groups with a regular spacing close to auroral arcs. A typical fragment has a small horizontal size below 20 km, a short lifetime of less than a minute and shows no field-aligned extent in the emission. The fragments appear mainly west of zenith (73%) during the three observation nights, whereas their north-south distribution is symmetric around the zenith. Almost all of them exhibit westward drift, the estimated speed for one of the fragments passing the field of view of ASK is ∼1 km/s. A spectral signature can be seen in the green auroral wavelength of O at 557.7 nm and red emission line of N2 at 673.0 nm, but no emission enhancement was observed in the blue wavelengths. One fragment passing the EISCAT Svalbard radar’s field of view shows a local ion temperature increase in a small altitude range of ∼15 km, whereas there is no visible increase in electron density. This could be explained by fragment generation due to locally strong horizontal electric fields. A potential mechanism for this might be electric fields of atmospheric waves superposing with the converging electric fields of auroral arcs created by particle precipitation and the corresponding field-aligned currents. The resulting field would be perpendicular to the magnetic field and the auroral arcs, leading to wave-like density variations of excited plasma close to the arcs. Further study is required to verify this hypothesis and improve the understanding of fragment properties determined from the limited dataset used for this thesis.
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Vedin, Jörgen. "Numerical modeling of auroral processes". Doctoral thesis, Umeå University, Physics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1117.

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One of the most conspicuous problems in space physics for the last decades has been to theoretically describe how the large parallel electric fields on auroral field lines can be generated. There is strong observational evidence of such electric fields, and stationary theory supports the need for electric fields accelerating electrons to the ionosphere where they generate auroras. However, dynamic models have not been able to reproduce these electric fields. This thesis sheds some light on this incompatibility and shows that the missing ingredient in previous dynamic models is a correct description of the electron temperature. As the electrons accelerate towards the ionosphere, their velocity along the magnetic field line will increase. In the converging magnetic field lines, the mirror force will convert much of the parallel velocity into perpendicular velocity. The result of the acceleration and mirroring will be a velocity distribution with a significantly higher temperature in the auroral acceleration region than above. The enhanced temperature corresponds to strong electron pressure gradients that balance the parallel electric fields. Thus, in regions with electron acceleration along converging magnetic field lines, the electron temperature increase is a fundamental process and must be included in any model that aims to describe the build up of parallel electric fields. The development of such a model has been hampered by the difficulty to describe the temperature variation. This thesis shows that a local equation of state cannot be used, but the electron temperature variations must be descibed as a nonlocal response to the state of the auroral flux tube. The nonlocal response can be accomplished by the particle-fluid model presented in this thesis. This new dynamic model is a combination of a fluid model and a Particle-In-Cell (PIC) model and results in large parallel electric fields consistent with in-situ observations.

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Schroeder, James William Ryan. "Exploring the Alfvén-wave acceleration of auroral electrons in the laboratory". Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5846.

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Inertial Alfvén waves occur in plasmas where the Alfvén speed is greater than the electron thermal speed and the scale of wave field structure across the background magnetic field is comparable to the electron skin depth. Such waves have an electric field aligned with the background magnetic field that can accelerate electrons. It is likely that electrons are accelerated by inertial Alfvén waves in the auroral magnetosphere and contribute to the generation of auroras. While rocket and satellite measurements show a high level of coincidence between inertial Alfvén waves and auroral activity, definitive measurements of electrons being accelerated by inertial Alfvén waves are lacking. Continued uncertainty stems from the difficulty of making a conclusive interpretation of measurements from spacecraft flying through a complex and transient process. A laboratory experiment can avoid some of the ambiguity contained in spacecraft measurements. Experiments have been performed in the Large Plasma Device (LAPD) at UCLA. Inertial Alfvén waves were produced while simultaneously measuring the suprathermal tails of the electron distribution function. Measurements of the distribution function use resonant absorption of whistler mode waves. During a burst of inertial Alfvén waves, the measured portion of the distribution function oscillates at the Alfvén wave frequency. The phase space response of the electrons is well-described by a linear solution to the Boltzmann equation. Experiments have been repeated using electrostatic and inductive Alfvén wave antennas. The oscillation of the distribution function is described by a purely Alfvénic model when the Alfvén wave is produced by the inductive antenna. However, when the electrostatic antenna is used, measured oscillations of the distribution function are described by a model combining Alfvénic and non-Alfvénic effects. Indications of a nonlinear interaction between electrons and inertial Alfvén waves are present in recent data.
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Eliasson, Lars. "Satellite observations of auroral acceleration processes". Doctoral thesis, Umeå universitet, Rymdfysik, 1994. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-102339.

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Measurements with satellite and sounding rocket borne instruments contain important information on remote and local processes in regions containing matter in the plasma state. The characteristic features of the particle distributions can be used to explain the morphology and dynamics of the different plasma populations. Charged particles are lost from a region due to precipitation into the atmosphere, charge exchange processes, or convection to open magnetic field lines. The sources of the Earth’s magnetospheric plasma are mainly ionization and extraction of upper atmosphere constituents, and entry of solar wind plasma. The intensity and distribution of auroral precipitation is controlled in part by the conditions of the interplanetary magnetic field causing different levels of auroral activity. Acceleration of electrons and positive ions along auroral field lines play an important role in magnetospheric physics. Electric fields that are quasi-steady during particle transit times, as well as fluctuating fields, are important for our understanding of the behaviour of the plasma in the auroral region. High-resolution data from the Swedish Viking and the Swedish/German Freja satellites have increased our knowledge considerably about the interaction processes between different particle populations and between particles and wave fields. This thesis describes acceleration processes influencing both ions and electrons and is based on in-situ measurements in the auroral acceleration/heating region, with special emphasis on; processes at very high latitudes, the role of fluctuating electric fields in producing so called electron conics, and positive ion heating transverse to the geomagnetic field lines.

Diss. (sammanfattning) Umeå : Umeå universitet, 1994, härtill 6 uppsatser.


digitalisering@umu.se
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Fillingim, Matthew Owen. "Kinetic processes in the plasma sheet observed during auroral activity /". Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/6824.

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Kalmoni, N. M. E. "The role of magnetospheric plasma instabilities in auroral and substorm dynamics". Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1546163/.

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The auroral substorm is the manifestation of explosive energy release from the rapid and global reconfiguration of the magnetotail. The auroral substorm is marked by a sudden brightening and poleward expansion of the most equatorward auroral arc in the midnight sector of the ionosphere. The temporal sequence of magnetospheric processes which lead to the dynamic auroral substorm display remain disputed to this day. This thesis contains original research on the development and exploitation of novel data analysis techniques in order to analyse ground-based all sky imager data of the aurora, enabling the study of substorm processes in remarkable detail. Fourier analysis techniques are used to find the spatial scales of wave-like signatures (otherwise known as auroral beads/rays), which form along substorm onset arcs. Growth rates of ∼0.05 s−1 are found from the exponential growth of the power spectral density of individual spatial scales. By analysing the dataset in this way, comparisons are made between observations and theoretical predictions of plasma instabilities at the near-Earth edge of the plasma-sheet which have been proposed to play a critical part in the substorm onset process. Auroral arc tracking techniques are developed to automate and increase the size of the database of events analysed. The vast majority of independently identified substorm onsets are preceded by azimuthal structuring along the onset arc with median wavelengths of ∼80 km. These beads grow and develop into a magnetospheric instability around 2 minutes prior to auroral substorm onset. Showing that beads are a common feature along the substorm onset arc provides unprecedented quantitative evidence that a near-Earth instability is a fundamental component of the substorm onset process. Finally, analysis techniques are extended to state-of-the-art high resolution multi-spectral auroral data to investigate the processes driving auroral beads. Beads can be resolved in the green-, blue- and red-line aurora with spatial scales as small as 30 km, which later develop into larger structures of ∼80 km. These observations are consistent with Alfvén wave accelerated auroral particle precipitation and therefore imply that the substorm onset arc and auroral beads are driven unstable by waves.
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Kopf, Andrew James. "A multi-instrument study of auroral hiss at Saturn". Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/692.

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Over the last fifty years, a multitude of spacecraft and rocket experiments have studied plasma wave emissions from Earth's auroral regions. One such emission is auroral hiss, a low-frequency whistler-mode wave that is produced in the auroral zone. Observations from Earth-orbiting spacecraft show that auroral hiss is generated by field-aligned electron beams, with the resulting plasma wave emission propagating along the resonance cone. This propagation results in auroral hiss appearing as a V-shaped funnel when observed on a frequency-time spectrogram. This thesis presents the first comprehensive study of auroral hiss at a planet other than Earth, using the Cassini spacecraft to study auroral hiss at Saturn. NASA's Cassini spacecraft, currently in orbit around Saturn, has allowed for the first opportunity to study this emission in detail at another planet. Since 2006, the Cassini spacecraft has twice been in a series of high inclination orbits, allowing investigation and measurements of Saturnian auroral phenomena. During this time, the Radio and Plasma Wave Science (RPWS) Investigation on Cassini detected low frequency whistler mode emissions propagating upward along the auroral field lines, much like terrestrial auroral hiss. Comparisons of RPWS data with observations from several other Cassini instruments, including the Dual-Technique Magnetometer (MAG), Magnetospheric Imaging Instrument (MIMI), and the Cassini Plasma Spectrometer (CAPS), have revealed a complete picture of this emission at Saturn. Observations from these instruments have been used to make a variety of determinations about auroral hiss at Saturn. RPWS has only observed this emission when Cassini was at high-latitudes, although these observations have shown no preference for local time. Tracking the times this emission has been observed revealed a clear periodicity in the emission. Further study later revealed not one but two rotational modulations, one in each hemisphere, rotating at rates of 813.9 and 800.7 degrees per day in the northern and southern hemispheres, respectively. These rates match with observations of the clock-like Saturn Kilometric Radiation. Study of the field-aligned current structures in the auroral regions revealed a strong upward-directed current in both hemispheres on the lower-latitude side of the auroral hiss emission. Along with correlating particle densities, these observations were used to infer the presence of a high-density plasmasphere at low latitudes, with the series of field-aligned current structures lining up with the outer boundary at L-shell values of around 12-15. Analysis of electron beams observed in conjunction with auroral hiss shows that these beams produce large growth rates for whistler-mode waves propagating along the resonance cone, similar to terrestrial auroral hiss. Analytical calculation of the normalized growth rates of ten electron beam events on Day 291, 2008, yielded a wide range of growth rates, from 0.004 to over 6.85 times the real frequency. The latter, a non-physical result, came from a violation of the weak growth approximation, suggesting there was so much growth that the analytical calculation was not valid in this instance. Numerical calculation using a plasma dispersion-solving code called WHAMP produced a growth rate of about 0.3, a still very large number, suggesting the detected beams may be the source of the observed auroral hiss plasma wave emission.
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Książki na temat "Auroral plasma"

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Götz, Paschmann, Haaland Stein i Treumann Rudolf A, red. Auroral plasma physics. Boston: Kluwer Academic Publishers, 2003.

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L, Lysak Robert, red. Auroral plasma dynamics. Washington, D.C: American Geophysical Union, 1993.

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Lysak, Robert L., red. Auroral Plasma Dynamics. Washington, D. C.: American Geophysical Union, 1993. http://dx.doi.org/10.1029/gm080.

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Paschmann, Götz, Stein Haaland i Rudolf Treumann, red. Auroral Plasma Physics. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-007-1086-3.

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University of Iowa. Dept. of Physics and Astronomy. i United States. National Aeronautics and Space Administration., red. Auroral plasma waves. Iowa City, Iowa: Dept. of Physics and Astronomy, University of Iowa, 1989.

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Moore, T. E. Plasma heating and flow in an auroral arc. [Washington, D.C: National Aeronautics and Space Administration, 1997.

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COSPAR. Scientific Commission D. D0.3 Symposium. Advances in auroral plasma physics: Proceedings of the D0.3 Symposium of COSPAR Scientific Commission D which was held during the Thirty-second COSPAR Scientific Assembly, Nagoya, Japan, 12-19 July, 1998. Oxford: Published for The Committee on Space Research [by] Pergamon, 1999.

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United States. National Aeronautics and Space Administration., red. A mathematical model of the structure and evolution of small scale discrete auroral arcs. Ithaca, N.Y: School of Electrical Engineering and Laboratory of Plasma Studies, Cornell University, 1990.

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Meeting, COSPAR Plenary. Auroral and related phenomena: Proceedings of Symposia D3 and D4 of the COSPAR twenty-ninth Plenary Meeting held in Washington, DC, U.S.A., 28th August-5 September, 1992. Oxford [England]: Published for the Committee on Space Research by Pergamon Press, 1993.

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United States. National Aeronautics and Space Administration., red. Spatial relationships of auroral particle acceleration relative to high latitude plasma boundaries: Final report for 1994 - 1997, NASA research grant no. NAGW-4160. Palo Alto, CA: Lockheed Martin Missiles and Space, Advanced Technology Center, 1997.

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Części książek na temat "Auroral plasma"

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Paschmann, Götz, Stein Haaland i Rudolf Treumann. "Introduction". W Auroral Plasma Physics, 1–19. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-007-1086-3_1.

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Paschmann, Götz, Stein Haaland i Rudolf Treumann. "Remote Sensing of Auroral Arcs". W Auroral Plasma Physics, 21–40. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-007-1086-3_2.

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Paschmann, Götz, Stein Haaland i Rudolf Treumann. "Theoretical Building Blocks". W Auroral Plasma Physics, 41–92. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-007-1086-3_3.

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Paschmann, Götz, Stein Haaland i Rudolf Treumann. "In Situ Measurements in the Auroral Plasma". W Auroral Plasma Physics, 93–208. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-007-1086-3_4.

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Paschmann, Götz, Stein Haaland i Rudolf Treumann. "Statistics and Mapping of Auroral Features". W Auroral Plasma Physics, 209–50. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-007-1086-3_5.

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Paschmann, Götz, Stein Haaland i Rudolf Treumann. "Electrodynamics of Auroral Forms". W Auroral Plasma Physics, 251–309. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-007-1086-3_6.

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Paschmann, Götz, Stein Haaland i Rudolf Treumann. "Theoretical Models". W Auroral Plasma Physics, 311–76. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-007-1086-3_7.

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Paschmann, Götz, Stein Haaland i Rudolf Treumann. "Dynamic Coupling to the Magnetosphere". W Auroral Plasma Physics, 377–414. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-007-1086-3_8.

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Paschmann, Götz, Stein Haaland i Rudolf Treumann. "The Aurora as a Universal Phenomenon". W Auroral Plasma Physics, 415–34. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-007-1086-3_9.

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Winckler, John R., i Robert J. Nemzek. "Observations of the Pulsation Phase of Auroras Observed at Minneapolis During the Peak of Solar Cycle 22". W Auroral Plasma Dynamics, 1–15. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm080p0001.

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Streszczenia konferencji na temat "Auroral plasma"

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Schukla, P. K. "Theory of auroral arcs". W International conference on plasma physics ICPP 1994. AIP, 1995. http://dx.doi.org/10.1063/1.49054.

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Souza de Assis, Altair. "Turbulence-Double-Layer Synergetic Auroral Electron Acceleration". W PLASMA PHYSICS: 11th International Congress on Plasma Physics: ICPP2002. AIP, 2003. http://dx.doi.org/10.1063/1.1594022.

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Murphree, J. S. "Auroral optical observations of plasma processes". W 1990 Plasma Science IEEE Conference Record - Abstracts. IEEE, 1990. http://dx.doi.org/10.1109/plasma.1990.110518.

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Sakanaka, Paulo H. "Evolution of Electron-Acoustic Wave in Auroral Region". W PLASMA PHYSICS: 11th International Congress on Plasma Physics: ICPP2002. AIP, 2003. http://dx.doi.org/10.1063/1.1593981.

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McConville, S. L., A. W. Cross, K. Ronald, D. C. Speirs, K. M. Gillespie, A. D. R. Phelps, C. W. Robertson i in. "Laboratory Experimental Investigations of Auroral Cyclotron Emissions". W 2007 IEEE Pulsed Power Plasma Science Conference. IEEE, 2007. http://dx.doi.org/10.1109/ppps.2007.4346236.

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Speirs, D. C., K. M. Gillespie, S. L. McConville, A. D. R. Phelps, A. W. Cross, K. Ronald, R. Bingham, B. J. Kellett, R. A. Cairns i I. Vorgul. "Numerical investigation of auroral magnetospheric radio emission". W 2012 IEEE 39th International Conference on Plasma Sciences (ICOPS). IEEE, 2012. http://dx.doi.org/10.1109/plasma.2012.6383593.

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Ronald, K., D. C. Speirs, S. L. McConville, K. M. Gillespie, A. D. R. Phelps, A. W. Cross, R. Bingham i in. "Laboratory Reproduction of Auroral Magnetospheric Radio Wave Sources". W FRONTIERS IN MODERN PLASMA PHYSICS: 2008 ICTP International Workshop on the Frontiers of Modern Plasma Physics. AIP, 2008. http://dx.doi.org/10.1063/1.3013767.

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Podgorny, A. I., I. M. Podgorny i A. V. Borisenko. "MHD simulation of flare situation above the active region AR 10365 in the real time scale." W Physics of Auroral Phenomena. FRC KSC RAS, 2020. http://dx.doi.org/10.37614/2588-0039.2020.43.013.

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Since the configuration of the magnetic field in the corona, where solar flares appear, cannot be determined from observations, to study the flare situation, a numerical magnetohydrodynamic (MHD) simulation is carried out above the active region. MHD simulation performed in a greatly reduced (10 000 times) time scale permit to obtain results on the study of the solar flare mechanism, but the magnetic field configuration was distorted, especially near the photospheric boundary, due to the unnaturally rapid change in the field on the photosphere. For a more accurate study of the flare situation, MHD simulation in the real time scale was performed above the active region of AR 10365, which was made possible through the use of parallel calculations. The MHD simulation in the real scale of time above the AR 10365 during the first day of evolution showed the appearance of current density maxima with singular X-type line and plasma flow, which have to cause to the formation of a current sheet.
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Gelinas, L. J. "Auroral emissions due to a dusty plasma instability". W Waves in dusty, solar and space plasmas. AIP, 2000. http://dx.doi.org/10.1063/1.1324922.

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Panchenko, M., Ivan Zhelyazkov i Todor Mishonov. "Auroral Radio Emission from the Solar System Planets". W 3RD SCHOOL AND WORKSHOP ON SPACE PLASMA PHYSICS. AIP, 2011. http://dx.doi.org/10.1063/1.3598106.

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Raporty organizacyjne na temat "Auroral plasma"

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Fennell, Joseph F. Plasma Observations in the Auroral and Polar Cap Region. Fort Belvoir, VA: Defense Technical Information Center, grudzień 1985. http://dx.doi.org/10.21236/ada163654.

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Branduardi-Raymont, Graziella, i et al. SMILE Definition Study Report. ESA SCI, grudzień 2018. http://dx.doi.org/10.5270/esa.smile.definition_study_report-2018-12.

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The SMILE definition study report describes a novel self-standing mission dedicated to observing solar wind-magnetosphere coupling via simultaneous in situ solar wind/magnetosheath plasma and magnetic field measurements, X-Ray images of the magnetosheath and magnetic cusps, and UV images of global auroral distributions defining system-level consequences. The Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) will complement all solar, solar wind and in situ magnetospheric observations, including both space- and ground-based observatories, to enable the first-ever observations of the full chain of events that drive the Sun-Earth connection.
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Semeter, Joshua. High-Speed Intensified Camera System for Investigation of Plasma Turbulence Induced by the Aurora. Fort Belvoir, VA: Defense Technical Information Center, luty 2013. http://dx.doi.org/10.21236/ada578221.

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Meeks, E., J. F. Grcar, R. J. Kee i H. K. Moffat. AURORA: A FORTRAN program for modeling well stirred plasma and thermal reactors with gas and surface reactions. Office of Scientific and Technical Information (OSTI), luty 1996. http://dx.doi.org/10.2172/206570.

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