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Found 6 entries in the Bibliography.
Showing entries from 1 through 6
| 2019 |
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A Pc5 wave was simultaneously observed in the ionosphere by EKB radar and in the magnetosphere by both Van Allen Probe spacecraft within a substorm activity. The wave was located in the nightside, in 1.5- to 3-hr magnetic local time sector, and in the region corresponding to the magnetic shells with maximal distances 4.6\textendash7.8 Earth\textquoterights radii. As it was found using both the radar and spacecraft data, the wave had frequency of about 1.8 mHz and azimuthal wave number m≈-10; that is, the wave was westward propagating. The EKB radar data revealed the equatorward wave propagating in the ionosphere, which corresponded to the earthward propagation in the magnetosphere. Furthermore, the field-aligned magnetic component was approximately 2 times larger than both transverse components and accompanied by antiphase pressure oscillations; that is, the wave is compressional and diamagnetic. According to both radar and spacecraft measurements, among two transverse magnetic components, the dominant one was the poloidal. The wave was possibly driven by substorm-injected energetic protons registered by the spacecraft: the proton fluxes were modulated with the wave frequency at energies of about 90 keV, which corresponded to the energy of the drift wave-particle resonance. The wave frequency was much lower than the minimal frequency of the field line resonance calculated using the spacecraft data. We conclude that the wave is not the Alfv\ en mode, but some kind of compressional wave, for example, the drift-compressional mode. Mager, Olga; Chelpanov, Maksim; Mager, Pavel; Klimushkin, Dmitri; Berngardt, Oleg; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2019 YEAR: 2019 DOI: 10.1029/2019JA026541 compressional waves; Pc5; poloidal waves; SUPERDARN; ULF waves; Van Allen Probes |
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A Pc5 wave was simultaneously observed in the ionosphere by EKB radar and in the magnetosphere by both Van Allen Probe spacecraft within a substorm activity. The wave was located in the nightside, in 1.5- to 3-hr magnetic local time sector, and in the region corresponding to the magnetic shells with maximal distances 4.6\textendash7.8 Earth\textquoterights radii. As it was found using both the radar and spacecraft data, the wave had frequency of about 1.8 mHz and azimuthal wave number m≈-10; that is, the wave was westward propagating. The EKB radar data revealed the equatorward wave propagating in the ionosphere, which corresponded to the earthward propagation in the magnetosphere. Furthermore, the field-aligned magnetic component was approximately 2 times larger than both transverse components and accompanied by antiphase pressure oscillations; that is, the wave is compressional and diamagnetic. According to both radar and spacecraft measurements, among two transverse magnetic components, the dominant one was the poloidal. The wave was possibly driven by substorm-injected energetic protons registered by the spacecraft: the proton fluxes were modulated with the wave frequency at energies of about 90 keV, which corresponded to the energy of the drift wave-particle resonance. The wave frequency was much lower than the minimal frequency of the field line resonance calculated using the spacecraft data. We conclude that the wave is not the Alfv\ en mode, but some kind of compressional wave, for example, the drift-compressional mode. Mager, Olga; Chelpanov, Maksim; Mager, Pavel; Klimushkin, Dmitri; Berngardt, Oleg; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2019 YEAR: 2019 DOI: 10.1029/2019JA026541 compressional waves; Pc5; poloidal waves; SUPERDARN; ULF waves; Van Allen Probes |
| 2018 |
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Eigenmodes of the transverse Alfv\ enic resonator at the plasmapause: a Van Allen Probes case study A Pc4 ULF wave was detected at spacecraft B of the Van Allen Probes at the plasmapause. A distinctive feature of this wave is the strong periodical modulation of the wave. It is assumed that this modulation is a beating of oscillations close in frequency: at least two harmonics with frequencies of 15.3 and 13.6 MHz are found. It is shown that these harmonics can be the eigenmodes of the transverse resonator at the local maximum of the Alfv\ en velocity. In addition, the observed wave was in a drift resonance with energetic 80 keV protons and could be generated by an unstable \textquotedblleftbump on tail\textquotedblright distribution of protons simultaneously observed with the wave. The estimate of the azimuthal wave number m made from the drift resonance condition gives a value of about -100, i.e., it is a westward propagating azimuthally small-scale wave. Mager, Pavel; Mikhailova, Olga; Mager, Olga; Klimushkin, Dmitri; Published by: Geophysical Research Letters Published on: 09/2018 YEAR: 2018 DOI: 10.1029/2018GL079596 Magnetosphere; Plasmapause; poloidal Alfven waves; transverse resonator; ULF waves; Van Allen Probes; Wave-particle interaction |
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Eigenmodes of the transverse Alfv\ enic resonator at the plasmapause: a Van Allen Probes case study A Pc4 ULF wave was detected at spacecraft B of the Van Allen Probes at the plasmapause. A distinctive feature of this wave is the strong periodical modulation of the wave. It is assumed that this modulation is a beating of oscillations close in frequency: at least two harmonics with frequencies of 15.3 and 13.6 MHz are found. It is shown that these harmonics can be the eigenmodes of the transverse resonator at the local maximum of the Alfv\ en velocity. In addition, the observed wave was in a drift resonance with energetic 80 keV protons and could be generated by an unstable \textquotedblleftbump on tail\textquotedblright distribution of protons simultaneously observed with the wave. The estimate of the azimuthal wave number m made from the drift resonance condition gives a value of about -100, i.e., it is a westward propagating azimuthally small-scale wave. Mager, Pavel; Mikhailova, Olga; Mager, Olga; Klimushkin, Dmitri; Published by: Geophysical Research Letters Published on: 09/2018 YEAR: 2018 DOI: 10.1029/2018GL079596 Magnetosphere; Plasmapause; poloidal Alfven waves; transverse resonator; ULF waves; Van Allen Probes; Wave-particle interaction |
| 2016 |
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A case study of shortwave radar observations of magnetospheric Pc5 ULF waves (wave periods of 150\textendash600 s) that occurred on 26 December 2014 in the nightside magnetosphere during substorm activity is presented. The radar study of waves in the magnetosphere is based on analysis of scattering from field-aligned irregularities of the ionospheric F layer. Variations of their inline image drift velocity at F layer heights are associated with the wave electric field. Analysis of the observations from the Ekaterinburg (EKB) radar shows that the frequency f of the observed wave depends on the azimuthal wave number m (positive correlation of about 0.90): an increase in frequency from 2.5 to 5 mHz corresponds to increased m number from 20 to 80. Of the known types of waves in the magnetosphere corresponding to the Pc5 range, only drift compressional waves have such azimuthal dispersion: the frequency of the drift compressional mode is directly proportional to the azimuthal wave number and the gradient-curvature drift velocity of energetic particles in the magnetic field. This wave has a kinetic nature and represents the most common kind of the compressional modes, demanding for its existence only finite pressure and plasma inhomogeneity across magnetic shells. Chelpanov, Maksim; Mager, Pavel; Klimushkin, Dmitri; Berngardt, Oleg; Mager, Olga; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2016 YEAR: 2016 DOI: 10.1002/2015JA022155 |
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A case study of shortwave radar observations of magnetospheric Pc5 ULF waves (wave periods of 150\textendash600 s) that occurred on 26 December 2014 in the nightside magnetosphere during substorm activity is presented. The radar study of waves in the magnetosphere is based on analysis of scattering from field-aligned irregularities of the ionospheric F layer. Variations of their inline image drift velocity at F layer heights are associated with the wave electric field. Analysis of the observations from the Ekaterinburg (EKB) radar shows that the frequency f of the observed wave depends on the azimuthal wave number m (positive correlation of about 0.90): an increase in frequency from 2.5 to 5 mHz corresponds to increased m number from 20 to 80. Of the known types of waves in the magnetosphere corresponding to the Pc5 range, only drift compressional waves have such azimuthal dispersion: the frequency of the drift compressional mode is directly proportional to the azimuthal wave number and the gradient-curvature drift velocity of energetic particles in the magnetic field. This wave has a kinetic nature and represents the most common kind of the compressional modes, demanding for its existence only finite pressure and plasma inhomogeneity across magnetic shells. Chelpanov, Maksim; Mager, Pavel; Klimushkin, Dmitri; Berngardt, Oleg; Mager, Olga; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2016 YEAR: 2016 DOI: 10.1002/2015JA022155 |
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