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Academic literature on the topic 'Ionospheric Signatures'

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Published: 6 September 2023

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Journal articles on the topic "Ionospheric Signatures"

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Wright, D. M., T. K. Yeoman, and J. A. Davies. "A comparison of EISCAT and HF Doppler observations of a ULF wave." Annales Geophysicae 16, no. 10 (October 31, 1998): 1190–99. http://dx.doi.org/10.1007/s00585-998-1190-7.

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Abstract. Since the middle of 1995, an HF Doppler sounder has been running almost continuously in northern Norway, with the receiver at Ramfjordmoen and the transmitter at Seljelvnes. Concurrent operation of the EISCAT UHF radar in common programme (CP-1) mode has made it possible to study the ionospheric signature of a magnetospheric ULF wave. These are the first results of such wave signatures observed simultaneously in both instruments. It has been demonstrated that the observed Doppler signature was mainly due to the vertical bulk motion of the ionosphere caused by the electric field perturbation of the ULF wave and the first direct observational confirmation of a numerical simulation has been achieved. The wave, which was Alfvénic in nature, was detected by the instruments 8° equatorward of the broad resonance region. The implications for the deduced wave modes in the ionosphere and the mechanism producing the HF Doppler variations are discussed.Key words. Magnetosphere-ionosphere interactions · MHD waves and instabilities · Radio science · Ionospheric physics
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Lockwood, M., and S. K. Morley. "A numerical model of the ionospheric signatures of time-varying magneticreconnection: I. ionospheric convection." Annales Geophysicae 22, no. 1 (January 1, 2004): 73–91. http://dx.doi.org/10.5194/angeo-22-73-2004.

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Abstract. This paper presents a numerical model for predicting the evolution of the pattern of ionospheric convection in response to general time-dependent magnetic reconnection at the dayside magnetopause and in the cross-tail current sheet of the geomagnetic tail. The model quantifies the concepts of ionospheric flow excitation by Cowley and Lockwood (1992), assuming a uniform spatial distribution of ionospheric conductivity. The model is demonstrated using an example in which travelling reconnection pulses commence near noon and then move across the dayside magnetopause towards both dawn and dusk. Two such pulses, 8min apart, are used and each causes the reconnection to be active for 1min at every MLT that they pass over. This example demonstrates how the convection response to a given change in the interplanetary magnetic field (via the reconnection rate) depends on the previous reconnection history. The causes of this effect are explained. The inherent assumptions and the potential applications of the model are discussed. Key words. Ionosphere (ionosphere-magnetosphere interactions; plasma convection) – Magnetospheric physics (magnetosphere-ionosphere interactions; solar wind-magnetosphere interactions)
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Wright, D. M., T. K. Yeoman, and P. J. Chapman. "High-latitude HF Doppler observations of ULF waves. 1. Waves with large spatial scale sizes." Annales Geophysicae 15, no. 12 (December 31, 1997): 1548–56. http://dx.doi.org/10.1007/s00585-997-1548-2.

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Abstract. A quantitative study of observations of the ionospheric signatures of magnetospheric ultra low frequency (ULF) waves by a high-latitude (geographic: 69.6°N 19.2°E) high-frequency Doppler sounder has been undertaken. The signatures, which are clearly correlated with pulsations in ground magnetometer data, exhibit periods in the range 100–400 s and have azimuthal wave numbers in the range 3–8. They are interpreted here as local field line resonances. Phase information provided by O- and X-mode Doppler data support the view that these are associated with field line resonances having large azimuthal scale sizes. The relative phases and amplitudes of the signatures in the Doppler and ground magnetometer data are compared with a model for the generation of Doppler signatures from incident ULF waves. The outcome suggests that the dominant mechanism involved in producing the Doppler signature is the vertical component of an E × B bulk motion of the local plasma caused by the electric field perturbation of the ULF wave.Key words. Auroral ionosphere · Magnetosphere-ionosphere interactions · MHD waves and instabilities HF Doppler · ULF Waves
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Wild, J. A., S. E. Milan, S. W. H. Cowley, M. W. Dunlop, C. J. Owen, J. M. Bosqued, M. G. G. T. Taylor, et al. "Coordinated interhemispheric SuperDARN radar observations of the ionospheric response to flux transfer events observed by the Cluster spacecraft at the high-latitude magnetopause." Annales Geophysicae 21, no. 8 (August 31, 2003): 1807–26. http://dx.doi.org/10.5194/angeo-21-1807-2003.

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Abstract. At 10:00 UT on 14 February 2001, the quartet of ESA Cluster spacecraft were approaching the Northern Hemisphere high-latitude magnetopause in the post-noon sector on an outbound trajectory. At this time, the interplanetary magnetic field incident upon the dayside magnetopause was oriented southward and duskward (BZ negative, BY positive), having turned from a northward orientation just over 1 hour earlier. As they neared the magnetopause the magnetic field, electron, and ion sensors on board the Cluster spacecraft observed characteristic field and particle signatures of magnetospheric flux transfer events (FTEs). Following the traversal of a boundary layer and the magnetopause, the spacecraft went on to observe further signatures of FTEs in the magnetosheath. During this interval of ongoing pulsed reconnection at the high-latitude post-noon magnetopause, the footprints of the Cluster spacecraft were located in the fields-of-view of the SuperDARN Finland and Syowa East radars located in the Northern and Southern Hemispheres, respectively. This study extends upon the initial survey of Wild et al. (2001) by comparing for the first time in situ magnetic field and plasma signatures of FTEs (here observed by the Cluster 1 spacecraft) with the simultaneous flow modulations in the conjugate ionospheres in the two hemispheres. During the period under scrutiny, the flow disturbances in the conjugate ionospheres are manifest as classic "pulsed ionospheric flows" (PIFs) and "poleward moving radar auroral forms" (PMRAFs). We demonstrate that the ionospheric flows excited in response to FTEs at the magnetopause are not those expected for a spatially limited reconnection region, somewhere in the vicinity of the Cluster 1 spacecraft. By examining the large- and small-scale flows in the high-latitude ionosphere, and the inter-hemispheric correspondence exhibited during this interval, we conclude that the reconnection processes that result in the generation of PIFs/PMRAFs must extend over many (at least 4) hours of magnetic local time on the pre- and post-noon magnetopause.Key words. Ionosphere (plasma convection) – Magnetospheric physics (magnetosphere-ionosphere interactions; magnetospheric configuration and dynamics)
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Pryse, S. E., A. M. Smith, I. K. Walker, and L. Kersley. "Multi-instrument study of footprints of magnetopause reconnection in the summer ionosphere." Annales Geophysicae 18, no. 9 (September 30, 2000): 1118–27. http://dx.doi.org/10.1007/s00585-000-1118-3.

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Abstract. Results are presented from a multi-instrument investigation of the signatures of equatorial reconnection in the summer, sunlit ionosphere. Well-established ion dispersion signatures measured during three DMSP satellite passes were used to identify footprints in ionospheric observations made by radio tomography, and both the EISCAT ESR and mainland radars. Under the prevalent conditions of southward IMF with the Bz component increasing in magnitude, the reconnection footprint was seen to move equatorward through the ESR field-of-view. The most striking signature was in the electron temperatures of the F2 region measured by the EISCAT mainland radar that revealed significantly enhanced temperatures with a steep equatorward edge, in general agreement with the leading edge of the ion dispersion. It is suggested that this sharp transition in the electron temperature may be an indicator of the boundary, mapping from the reconnection site, between closed geomagnetic field lines and those opened along which magnetosheath ions precipitate.Key words: Ionosphere (ionosphere-magnetosphere interactions; particle precipitation; plasma temperature and density)
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Neudegg, D. A., S. W. H. Cowley, S. E. Milan, T. K. Yeoman, M. Lester, G. Provan, G. Haerendel, et al. "A survey of magnetopause FTEs and associated flow bursts in the polar ionosphere." Annales Geophysicae 18, no. 4 (April 30, 2000): 416–35. http://dx.doi.org/10.1007/s00585-000-0416-0.

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Abstract. Using the Equator-S spacecraft and SuperDARN HF radars an extensive survey of bursty reconnection at the magnetopause and associated flows in the polar ionosphere has been conducted. Flux transfer event (FTE) signatures were identified in the Equator-S magnetometer data during periods of magnetopause contact in January and February 1998. Assuming the effects of the FTEs propagate to the polar ionosphere as geomagnetic field-aligned-currents and associated Alfvén-waves, appropriate field mappings to the fields-of-view of SuperDARN radars were performed. The radars observed discrete ionospheric flow channel events (FCEs) of the type previously assumed to be related to pulse reconnection. Such FCEs were associated with \\sim80% of the FTEs and the two signatures are shown to be statistically associated with greater than 99% confidence. Exemplary case studies highlight the nature of the ionospheric flows and their relation to the high latitude convection pattern, the association methodology, and the problems caused by instrument limitations.Key words: Ionosphere (polar ionosphere) · Magnetospheric physics (magnetosphere-ionosphere interaction; solar wind-magnetosphere interactions)
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Stocker, A. J., N. F. Arnold, and T. B. Jones. "The synthesis of travelling ionospheric disturbance (TID) signatures in HF radar observations using ray tracing." Annales Geophysicae 18, no. 1 (January 31, 2000): 56–64. http://dx.doi.org/10.1007/s00585-000-0056-4.

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Abstract. Characteristic signatures are often observed in HF radar range-time-intensity plots when travelling ionospheric disturbances (TIDs) are present. These signatures, in particular the variation of the F-region skip distance, have been synthesised using a ray tracing model. The magnitude of the skip variation is found to be a function of the peak electron density perturbation associated with the TID and radar frequency. Examination of experimental observations leads to an estimate of the peak electron density perturbation amplitude of around 25% for those TIDs observed by the CUTLASS radar system. The advantage of using the skip variation over the radar return amplitude as an indicator of density perturbation is also discussed. An example of a dual radar frequency experiment has been given. The investigation of the effect of radar frequency on the observations will aid the optimisation of future experiments..Key words. Ionosphere (auroral ionosphere; ionosphere -atmosphere interactions; ionospheric disturbances)
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Thorolfsson, A., J. C. Cerisier, M. Lockwood, P. E. Sandholt, C. Senior, and M. Lester. "Simultaneous optical and radar signatures of poleward-moving auroral forms." Annales Geophysicae 18, no. 9 (September 30, 2000): 1054–66. http://dx.doi.org/10.1007/s00585-000-1054-2.

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Abstract. Dayside poleward moving auroral forms (PMAFs) were detected between 06:30 and 07:00 UT on December 16, 1998, by the meridian scanning photometer and the all-sky camera at Ny Ålesund, Svalbard. Simultaneous SuperDARN HF radar measurements permitted the study of the associated ionospheric velocity pattern. A good general agreement is observed between the location and movement of velocity enhancements (flow channels) and the PMAFs. Clear signatures of equatorward flow were detected in the vicinity of PMAFs. This flow is believed to be the signature of a return flow outside the reconnected flux tube, as predicted by the Southwood model. The simulated signatures of this model reproduce globally the measured signatures, and differences with the experimental data can be explained by the simplifications of the model. Proposed schemes of the flow modification due to the presence of several flow channels and the modification of cusp and region 1 field-aligned currents at the time of sporadic reconnection events are shown to fit well with the observations.Key words: Ionosphere (auroral ionosphere; plasma convection) - Magnetospheric physics (magnetopause; cusp and boundary layers)
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Berry, S. T., L. Kersley, J. Moen, and W. F. Denig. "Ionospheric signatures of magnetospheric boundaries in the post-noon sector." Annales Geophysicae 18, no. 1 (January 31, 2000): 74–80. http://dx.doi.org/10.1007/s00585-000-0074-2.

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Abstract. Spatial structures in ionospheric electron density revealed in a tomographic image have been identified with auroral forms and related to their sources in precipitating particles observed by DMSP satellites. The observations of plasma enhancements relate to discrete auroral arcs seen in the post-noon sector, identified by both red- and green-line emissions measured by a meridional scanning photometer. The features lie within a very narrow latitudinal band on L-shells where the satellite detectors observed electron precipitation classified as from the boundary plasma sheet (BPS). The harder particles are identified with an E-region structure, while further north the precipitation is softer, resulting in a localised F-layer blob and 630.0 nm emissions. A steep gradient in plasma density represent a signature in the ionosphere of the central plasma sheet (CPS)/BPS boundary. A transition to a less-structured F-layer is found on crossing the convection reversal boundary..Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; polar ionosphere)
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Provan, G., and T. K. Yeoman. "Statistical observations of the MLT, latitude and size of pulsed ionospheric flows with the CUTLASS Finland radar." Annales Geophysicae 17, no. 7 (July 31, 1999): 855–67. http://dx.doi.org/10.1007/s00585-999-0855-1.

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Abstract. A study has been performed on the occurrence of pulsed ionospheric flows as detected by the CUTLASS Finland HF radar. These flows have been suggested as being created at the ionospheric footprint of newly-reconnected field lines, during episodes of magnetic flux transfer into the terrestrial magnetosphere (flux transfer events or FTEs). Two years of both high-time resolution and normal scan data from the CUTLASS Finland radar have been analysed in order to perform a statistical study of the extent and location of the pulsed ionospheric flows. We note a great similarity between the statistical pattern of the coherent radar observations of pulsed ionospheric flows and the traditional low-altitude satellite identification of the particle signature associated with the cusp/cleft region. However, the coherent scatter radar observations suggest that the merging gap is far wider than that proposed by the Newell and Meng model. The new model for cusp low-altitude particle signatures, proposed by Lockwood and Onsager and Lockwood provides a unified framework to explain the dayside precipitation regimes observed both by the low-altitude satellites and by coherent scatter radar detection.Key words. Magnetospheric physics (magnetosphere · ionosphere interactions; plasma convection; solar wind-magnetosphere interactions)
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Dissertations / Theses on the topic "Ionospheric Signatures"

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McWilliams, Kathryn Anne. "Ionospheric signatures of dayside reconnection processes." Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/30652.

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This thesis presents a study of the ionospheric response to dayside magnetopause reconnection. The principal data set employed is the ionospheric convection velocities from the CUTLASS HF radars. In addition to this, images of the ultraviolet aurora from the VIS Earth Camera and the Far Ultraviolet Imager aboard the Polar spacecraft were examined. In situ measurements have shown that there is a time-dependent, periodic nature to magnetic reconnection, with time scales of the order of minutes; the transient nature of magnetopause reconnection is reflected in the ionospheres. In this thesis the plasma velocity fluctuations in the dayside ionosphere were found to be in full agreement with the repetition rates of bursts of reconnection at the magnetopause, as well as with the repetition rates of polarised moving visible auroral forms seen from Earth. The first-ever full vector measurements of ionospheric convection velocity within the footprint of the reconnecting flux tubes revealed that, despite being transient, magnetic reconnection was a large scale process during which layers of magnetic flux were successively peeled from the magnetopause. Directly measured particle precipitation revealed that particles originating the reconnection region was found to be present on the same magnetic field lines as the HF radar signature of the reconnected field lines. The multi-instrument study of the ionospheric responses to reconnection demonstrated that the measured ionospheric convection velocities are inextricably linked to measured ultraviolet aurora. Energetic particle precipitation from the magnetosphere into the atmosphere via field-aligned currents excites auroral emissions, and field-aligned current estimates from measured ionospheric convection velocities were found to be in excellent agreement with the aurora.
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Borderick, James David. "Ionospheric signatures of ultra low frequency waves." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/9170.

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Ultra Low Frequency (ULF) waves have been studied for many years and the observation and modelling of such phenomena reveals important information about the solar-terrestrial interaction. Being ubiquitous in the collisionless terrestrial space plasma environment, ULF waves represent important physical processes in the transfer of energy and momentum. This thesis comprises three distinct studies to observe, model and analyse ULF phenomena. The first two studies focus on ULF wave observations at high-latitudes in the terrestrial ionosphere using a collection of both space- and ground-based instruments. The first study provides a detailed analysis of the time evolution of a ULF wave using the characteristics of the observed ULF wave as input-parameters to a 1-D numerical model. As the wave signature evolves towards a Field Line Resonance (FLR) a change in the incident wave mode from a partially Alfvénic wave to a purely shear Alfvénic wave is observed. The second study presents statistics of 25 large spatial-scale ULF waves with observations from a high-latitude Doppler sounder and ground-based magnetometers, complemented by model results. The third and final study describes the implementation of a well established radar technique ("double-pulse"), which is new for the Super Dual Auroral Radar Network (SuperDARN), which aims to provide an unprecedented temporal resolution for ULF wave studies. The new pulse sequence increases the temporal resolution of SuperDARN by a factor of three. Preliminary findings suggest this technique yields impressive results for ionospheric scatter with steady phase values but that the method cannot be used for data when the phase is rapidly changing or if the data originates from slowly decorrelating plasma irregularities. The running of two independent pulse sequences on the stereo channels of the Hankasalmi radar has also enabled, for the first time, the observation of cross-contamination between the radar channels.
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Norton, Andrew David. "Analysis of Ionospheric Data Sets to Identify Periodic Signatures Matching Atmospheric Planetary Waves." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/101791.

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Atmospheric planetary waves play a role in introducing variability to the low-latitude ionosphere. To better understand this coupling, this study investigates times when oscillations seen in both atmospheric planetary waves and ionospheric data-sets have similar periodicity. The planetary wave data-set used are temperature observations made by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). These highlight periods during which 2-Day westward propagating wave-number 3 waves are evident in the mesosphere and lower thermosphere. The ionospheric data-set is Total Electron Content (TEC), which is used to identify periods during which the ionosphere appears to respond to the planetary waves. Data from KP and F10.7 indices are used to determine events that may be of external origin. A 17-year time-span from 2002 to 2018 is used for this analysis so that both times of solar minimum and maximum can be studied. To extract the periods of this collection of data a Morlet Wavelet analysis is used, along with thresholding to indicate events when similar periods are seen in each data-set. Trends are then determined, which can lead to verification of previous assumptions and new discoveries.
Master of Science
The thermosphere and ionosphere are impacted by many sources. The sun and the magnetosphere externally impact this system. Planetary waves, which originate in the lower atmosphere, internally impact this system. This interaction leads to periodic signatures in the ionosphere that reflect periodic signatures seen in the lower atmosphere, the sun and the magnetosphere. This study identifies these times of similar oscillations in the neutral atmosphere, the ionosphere, and the sun, in order to characterize these interactions. Events are cataloged through wavelet analysis and thresholding techniques. Using a time-span of 17 years, trends are identified using histograms and percentages. From these trends, the characteristics of this coupling can be concluded. This study is meant to confirm the theory and provide new insights that will hopefully lead to further investigation through modeling. The goal of this study is to gain a better understanding of the role that planetary waves have on the interaction of the atmosphere and the ionosphere.
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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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Aminaei, Amin. "Characteristics of night time absorption spike events as signatures of magnetosphere ionosphere (M-I) coupling." Thesis, Lancaster University, 2007. http://eprints.lancs.ac.uk/6764/.

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Night time absorption spike events (NASE) are common signatures of magnetospheric substorms. Their occurrence in the ionosphere can be easily detected by riometers located at ground based stations. This unique feature is used to achieve a comprehensive study based on 500 NASE occurred during the period 1994-2003 in the IRIS (imaging riometer for ionospheric studies) field of view at Kilpisjarvi, Finland centred at 69.05° N, 20.79° E (L-shell 6.1). NASE generally had similar behaviour which has been mentioned for substorms in the literature. Occurrence of NASE dominates around magnetic local midnight (MLM) with majority of events in the pre-midnight sector. NASE seem to occur more often during high geomagnetic activity according to Kp index variation. Their occurrence during geomagnetic equinoxes is slightly more than that of s~lstices with the peak in the autumn and minimum in the summer time. They also tend to be solar cycle dependent as their appear3?ces during solar minimum dominate in agreement with occurrence of substorms. Our study confIrms most results of previous NASE studies. . . North/westward motion of spike events was dominant with speed in a range of few hundreds to few kms per second. Pi2 pulsations and auroral breakup (found from PIXIE, polar ionospheric X-ray imaging experiment images) are a common feature of NASE. The signifIcant frequency modulation of NASE is in the order of 50 mHz -200 mHz based on wavelet analysis. Apart from these new findings are also discussed in this thesis: Considering the temporal structure and variation of IT.- index, NASE are categorized into 4 classes. Classifications of spike events allow the identification of phenomena such as pseudobreakups from substorms. Another important finding of this study is the location of mapped points of NASE which is in the range of near Earth magnetotail rather than midtail region in favour of current disruption (CD) substorm model as opposed to near Earth neutral line (NENL) model. This yields using geomagnetic field model T-96 and NASE of IRIS and SGO (SodankyHi geophysical observatory) riometers where together covers auroral zone latitudes between 62.42° Nand 77.00 N (L- shell between 3.8-13.6).
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Koen, Etienne Johannes. "Ionospheric signatures of solar flares." Thesis, 2009. http://hdl.handle.net/10413/8339.

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VLF waves propagate in the Earth-ionosphere waveguide (EIW). The EIW is bounded below by the surface of the Earth and above by the ionospheric D-region (50–90 km altitude). The conditions for wave propagation in the EIW are studied and derived specifically for VLF propagation. The D-region is maintained by shortwave solar radiation that ionises the neutral atmosphere. The Wait parameters, H′ (reflection height) and (sharpness), describe the lower boundary of the D-region. Any enhancement in solar X-rays modifies these parameters, leading to a change in the propagation conditions for VLF signals. The effect of the terminator is presented where, it is found to narrow the depression of the monthly averaged diurnal amplitude profile from summer to winter. A series of solar flares were identified of which two case studies are presented. H′ and are calculated from the VLF signals by the Long Wave Propagation Code (LWPC). It is found that H′ decreased and increased at the time of flare. Once H′ and are obtained, the electron density profile can be constructed which is of crucial importance for VLF waves propagating in the EIW. The gradient of the electron density profile is found to increase as increases. It’s found that all the modal interference minima are moved towards the transmitter at the time of the flare. For flares of great magnitude, extrapolation is required to classify the flare in a magnitude class using VLF data. The change in the phase of the VLF signal is found to be linearly proportional to the change in the X-ray flux.
Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.
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FU-YUAN, CHANG, and 張富淵. "A Study on Ionospheric Neutral Wind Signatures by Using FORMOSAT-3/COSMIC." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/76chw3.

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博士
國立中央大學
太空科學研究所
105
The Earth’s upper atmosphere, comprised of the thermosphere and ionosphere, is where neutral and charged particles interact causing complicated physical processes. The ionospheric electron density is highly variable with the altitude, latitude, longitude, local time, season, solar cycle. This dissertation shows the investigation of the nighttime features from the coupling between the ionosphere and thermospheric neutral wind. Two interesting phenomena associated with the electrodynamic processes are examined, which include (1) The Weddell Sea Anomaly (WSA) in southern mid to high-latitude and Siberia-Yakutsk Anomaly (SYA) in northern mid-latitude. The increasing anomalies of electron density are most prominent over the Weddell Sea region in the southern hemisphere and Siberia and Yakutsk areas in the northern hemisphere during local summer nighttime; and (2) The Plasma Depletion Bays (PDBs) at equatorial/low-latitude. These features of the electron density and TIMED/GUVI 135.6nm airglow emission are observed at the evening/night hours near magnetic equator in three longitude regions, North Atlantic, India Ocean, and Southeast Asia during May. Six microsatellites of the joint Taiwan-US satellite constellation mission, termed FORMOSAT-3/COSMIC (F3/C), were successfully launched in to a circle low Earth orbit at 01:40 UTC on 15 April 2006. Each satellite houses a GPS occultation experiment payload globally deriving the vertical electron density profile in the ionosphere. This constellation daily provides instantly more than 2000 profiles from 90 to 800 km altitude. Dense global electron density probing brings a new era of studying the space weather in the ionosphere. In this dissertation work, the three-dimensional (3-D) plasma density structure constructed by electron density profiles from F3/C satellites are employed to study the diurnal, seasonal, latitudinal, and altitudinal variations of these anomalies and bay features. The results show that the WSA and SYA features occur prominently at about 300 km altitude, as well as yield the eastward shift of a single-peak plasma density along the WSA latitudes and a double-peak along the SYA latitudes during the period of 2007-2016. The thermospheric meridional and zonal winds simulated by Horizontal Wind Model 1993 (HWM93) is applied to interpret the plasma motions along the magnetic field lines associated with the WSA and SYA anomaly features. Results indicate that the meridional and vertical components of magnetic meridional wind can be responsible for the eastward shift of WSA single-peak and SYA double-peak plasma density. In fact, the WSA and SYA features constantly appear in whole day and all year round. The PDB structures in the F3/C electron density prominently appear at 275 km altitude in the equatorial/low ionosphere. Three PDBs curving in the northern hemisphere around the magnetic equator situate in regions 30°–60°W (North Atlantic), 30°–110°E (India Ocean), and 120°–160°E (Southeast Asia) from April-September, while one PDB curving in the southern hemisphere appears in 80°–150°W (Southwest America) from October-March. A detailed study on the F3/C 3-D electron density structure shows that the four PDBs are intense mainly below the ionospheric peak density layer (~350 km altitude) in whole day and all seasons. A simulation of HWM93 suggests that the trans-equatorial plasma transports induced by the zonal wind result in the PDB features in the nighttime equatorial/low-latitude ionosphere. Blowing of the thermospheric neutral winds play an important role in the formation of the two anomalies and bay features.
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Law, Colin Christian. "Observations of magnetic signatures and structure in the dayside ionosphere of Venus." Thesis, 1993. http://hdl.handle.net/1911/13753.

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Present models of the Venus solar wind interaction do not allow for changes in the orientation of the field as you approach the planet. Analysis of high resolution magnetic field data from the Pioneer Venus Orbiter spacecraft has revealed two distinct field rotations that are observed to occur in conjunction with the dayside ionosphere and ionopause. These rotations are a result of the velocity shear at the ionopause and indicate an alignment of the magnetic field with the day to night ionospheric plasma flow. From these results a new configuration of the dayside field draping has been determined. In addition, the field diagnostics discovered here can be used to probe the ionosphere of Mars which may otherwise go unobserved due to a lack of ion instrumentation onboard the Mars Observer spacecraft.
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Books on the topic "Ionospheric Signatures"

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Rice University. Space Physics and Astronomy Dept. and United States. National Aeronautics and Space Administration., eds. Final report, entitled, Data reduction and analysis of Pioneer Venus Orbital Ion Mass Spectrometer: NASA grant NAG 2-566, covering the period October 1998 - March 1996. Houston, Tex: Space Physics and Astronomy Dept., Rice University, 1996.

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Book chapters on the topic "Ionospheric Signatures"

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Newell, Patrick T., and David G. Sibeck. "Magnetosheath Fluctuations, Ionospheric Convection and Dayside Ionospheric Transients." In Physical Signatures of Magnetospheric Boundary Layer Processes, 245–61. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1052-5_17.

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Rodger, A. S. "Ionospheric Signatures of Magnetopause Processes." In Polar Cap Boundary Phenomena, 115–25. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5214-3_10.

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Lockwood, M. "Ionospheric Signatures of Pulsed Magnetopause Reconnection." In Physical Signatures of Magnetospheric Boundary Layer Processes, 229–43. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1052-5_16.

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Friis-Christensen, E. "Terrestrial ionospheric signatures of field-aligned currents." In Physics of Magnetic Flux Ropes, 605–10. Washington, D. C.: American Geophysical Union, 1990. http://dx.doi.org/10.1029/gm058p0605.

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Fenrich, F. R., C. L. Waters, M. Connors, and C. Bredeson. "Ionospheric signatures of ULF waves: Passive radar techniques." In Magnetospheric ULF Waves: Synthesis and New Directions, 259–71. Washington, D. C.: American Geophysical Union, 2006. http://dx.doi.org/10.1029/169gm17.

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Yeoman, T. K., D. M. Wright, and L. J. Baddeley. "Ionospheric signatures of ULF waves: Active radar techniques." In Magnetospheric ULF Waves: Synthesis and New Directions, 273–88. Washington, D. C.: American Geophysical Union, 2006. http://dx.doi.org/10.1029/169gm18.

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Knipp, D. J., B. A. Emery, and G. Lu. "Application of the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) Procedure to CUSP Identification." In Physical Signatures of Magnetospheric Boundary Layer Processes, 401–20. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1052-5_28.

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Watanabe, Masakazu, Michael Pinnock, Alan S. Rodger, Natsuo Sato, Hisao Yamagishi, A. Sessai Yukimatu, Raymond A. Greenwald, Jean-Paul Villain, and Marc R. Hairston. "Ionospheric Signatures of Distant Tail Reconnection Observed Just Before Substorm Onsets." In Substorms-4, 719–22. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-4798-9_150.

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Lognonné, P. "Seismic Waves from Atmospheric Sources and Atmospheric/Ionospheric Signatures of Seismic Waves." In Infrasound Monitoring for Atmospheric Studies, 281–304. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-1-4020-9508-5_10.

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Olsen, Nils, and Claudia Stolle. "Magnetic Signatures of Ionospheric and Magnetospheric Current Systems During Geomagnetic Quiet Conditions—An Overview." In Earth's Magnetic Field, 7–27. Dordrecht: Springer Netherlands, 2017. http://dx.doi.org/10.1007/978-94-024-1225-3_2.

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Conference papers on the topic "Ionospheric Signatures"

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Maheswaran, Veera Kumar, James A. Baskaradas, and Sriram Subramanian. "GNSS/GPS Spoofing Detection using Ionospheric Signatures." In 2021 IEEE Indian Conference on Antennas and Propagation (InCAP). IEEE, 2021. http://dx.doi.org/10.1109/incap52216.2021.9726378.

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Vorobjev, Vyacheslav, and Vladimir Zverev. "Dayside aurora signatures associated with ionospheric travelling twin vortices." In High Latitude Optics, edited by Sergej Leontyev. SPIE, 1993. http://dx.doi.org/10.1117/12.164828.

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Fasel, G. J., Joseph I. Minow, Roger W. Smith, C. S. Deehr, and Lou-Chuang Lee. "Ionospheric signatures of solar-wind magnetosphere interaction in dayside aurora." In High Latitude Optics, edited by Sergej Leontyev. SPIE, 1993. http://dx.doi.org/10.1117/12.164827.

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Almeida, P. D. S. C., C. M. Denardini, H. C. Aveiro, L. C. A. Resende, and L. M. Guizelli. "ANALYSIS OF SOLAR TIDAL SIGNATURES IN IONOSPHERIC ELECTRIC CURRENTS OBSERVED BY MAGNETOMETERS." In 11th International Congress of the Brazilian Geophysical Society & EXPOGEF 2009, Salvador, Bahia, Brazil, 24-28 August 2009. Society of Exploration Geophysicists and Brazilian Geophysical Society, 2009. http://dx.doi.org/10.1190/sbgf2009-030.

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Almeida, P. D. S. C., C. M. Denardini, H. C. Aveiro, L. C. A. Resende, and L. M. Guizelli. "Analysis Of Solar Tidal Signatures In Ionospheric Electric Currents Observed By Magnetometers." In 11th International Congress of the Brazilian Geophysical Society. European Association of Geoscientists & Engineers, 2009. http://dx.doi.org/10.3997/2214-4609-pdb.195.1841_evt_6year_2009.

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Hughes, David H. "Modeling the diurnal variation of ionospheric layers via Thom canonical potentials: time-frequency signatures." In International Symposium on Optical Science and Technology, edited by Franklin T. Luk. SPIE, 2002. http://dx.doi.org/10.1117/12.447888.

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Jansky, Jaroslav, and Victor Pasko. "Charge balance, electric field and ionospheric potential signatures in time dependent global electric circuit model." In 2014 XXXIth URSI General Assembly and Scientific Symposium (URSI GASS). IEEE, 2014. http://dx.doi.org/10.1109/ursigass.2014.6929973.

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Heitmann, Andrew J., Manuel A. Cervera, Robert S. Gardiner-Garden, David A. Holdsworth, Andrew D. MacKinnon, Iain M. Reid, and Bruce D. Ward. "Observations and modeling of traveling ionospheric disturbance signatures from an Australian network of oblique angle-of-arrival sounders." In 2017 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS). IEEE, 2017. http://dx.doi.org/10.23919/ursigass.2017.8105329.

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Maurya, Ajeet K., Rajesh Singh, Sushil Kumar, D. V. Phani Kumar, and B. Veenadhari. "Waves-like signatures in the D-region ionosphere generated by solar flares." In 2014 XXXIth URSI General Assembly and Scientific Symposium (URSI GASS). IEEE, 2014. http://dx.doi.org/10.1109/ursigass.2014.6929796.

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Yue, Wenjue, Bo Peng, Xizhang Wei, and Xiang Li. "Ionosphere effect estimation in micro-Doppler signature extraction for P-band radar targets." In 2017 Progress In Electromagnetics Research Symposium - Spring (PIERS). IEEE, 2017. http://dx.doi.org/10.1109/piers.2017.8262052.

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Reports on the topic "Ionospheric Signatures"

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Fox, Matthew W., Xiaoqing Pi, and Jeffrey M. Forbes. First Principles and Applications-Oriented Ionospheric Modeling Studies, and Wave Signatures in Upper Atmosphere Density,. Fort Belvoir, VA: Defense Technical Information Center, January 1997. http://dx.doi.org/10.21236/ada325072.

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Dea, J. Y., W. Van Bise, E. A. Rauscher, and W. M. Boerner. Observations of ELF Signatures Arising from Space Vehicle Disturbances of the Ionosphere. Fort Belvoir, VA: Defense Technical Information Center, May 1991. http://dx.doi.org/10.21236/ada236563.

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