Intermediate-&amp;lt;I&amp;gt;m&amp;lt;/I&amp;gt; ULF waves generated by substorm injection: a case study

Yeoman, T. K.; Klimushkin, D. Yu.; Mager, P. N.

doi:10.5194/angeo-28-1499-2010

Cited by 30 publications

(72 citation statements)

References 59 publications

(69 reference statements)

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“…It should be noted that 1.5–3 hr MLT sector, where the wave was observed by the radar and spacecraft, is smaller than the azimuthal wave length, which equals approximately 2.4 hr in MLT. The value | m |≈10 is close to that found at intermediate‐ m ULF waves earlier (Hao et al, ; Yeoman et al, ).…”

Section: Discussionsupporting

confidence: 87%

Conjugate Ionosphere‐Magnetosphere Observations of a Sub‐Alfvénic Compressional Intermediate‐m Wave: A Case Study Using EKB Radar and Van Allen Probes

et al. 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 4.6–7.8 Earth's 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 Alfvén mode, but some kind of compressional wave, for example, the drift‐compressional mode.

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Section: Discussionsupporting

confidence: 87%

Conjugate Ionosphere‐Magnetosphere Observations of a Sub‐Alfvénic Compressional Intermediate‐m Wave: A Case Study Using EKB Radar and Van Allen Probes

et al. 2019

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“…Earlier, Pilipenko et al [2001] were able to select analogous intermediate‐ m waves in ground data. They explained them as a result of non‐resonant generation by transverse non‐steady current, which agrees with the interpretation of Yeoman et al [2010].…”

Section: Introductionsupporting

confidence: 79%

SuperDARN observations of high‐m ULF waves with curved phase fronts and their interpretation in terms of transverse resonator theory

Yeoman¹,

James²,

Mager³

et al. 2012

J. Geophys. Res.

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[1] The Hankasalmi SuperDARN radar in Finland, while operating in a high spatial and temporal resolution mode, has measured the ionospheric signature of a naturally occurring ULF wave in scatter artificially induced by the Tromsø Heater. The wave had a period of 100 s and exhibited curved phase fronts across the heated volume (about 180 km along a single radar beam). Spatial information provided by the radar has enabled an m-number for the wave of about 38 to be determined. It is demonstrated here that the curved phase fronts are a generic feature of nonstationary poloidal waves in a transverse resonator, caused by the common action of the field line curvature, the plasma pressure, and the equilibrium current. Some features of the observed event agree with the resonator in the vicinity of the ring current, where it is proposed that the wave is excited by a moving source in the form of a proton cloud drifting in the magnetosphere in the azimuthal direction.

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“…The energy of these electrons was estimated at 25–70 keV between L shells of 7.5 and 15. The 580s period of the wave observed by Yeoman et al [] was somewhat longer than in previous observations. Yeoman et al [], in agreement with the theory developed by Mager and Klimushkin [, ], attributed this long period to the wave occurring close to midnight shortly after substorm onset, where the field lines would have been stretched, resulting in lower eigenfrequencies.…”

Section: Introductionmentioning

confidence: 54%

Multiradar observations of substorm‐driven ULF waves

et al. 2016

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A recent statistical study of ULF waves driven by substorm‐injected particles observed using Super Dual Auroral Radar Network (SuperDARN) found that the phase characteristics of these waves varied depending on where the wave was observed relative to the substorm. Typically, positive azimuthal wave numbers, m, were observed in waves generated to the east of the substorms and negative m to the west. The magnitude of m typically increased with the azimuthal separation between the wave observation and the substorm location. The energies estimated for the driving particles for these 83 wave events were found to be highest when the waves were observed closer to the substorm and lowest farther away. Each of the 83 events studied by James et al. (2013) involved just a single wave observation per substorm. Here a study of three individual substorm events are presented, with associated observations of multiple ULF waves using various different SuperDARN radars. We demonstrate that a single substorm is capable of driving a number of wave events characterized by different azimuthal scale lengths and wave periods, associated with different energies, W, in the driving particle population. We find that similar trends in m and W exist for multiple wave events with a single substorm as was seen in the single wave events of James et al. (2013). The variety of wave periods present on similar L shells in this study may also be evidence for the detection of both poloidal Alfvén and drift compressional mode waves driven by substorm‐injected particles.

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Intermediate-<I>m</I> ULF waves generated by substorm injection: a case study

Cited by 30 publications

References 59 publications

Conjugate Ionosphere‐Magnetosphere Observations of a Sub‐Alfvénic Compressional Intermediate‐m Wave: A Case Study Using EKB Radar and Van Allen Probes

Conjugate Ionosphere‐Magnetosphere Observations of a Sub‐Alfvénic Compressional Intermediate‐m Wave: A Case Study Using EKB Radar and Van Allen Probes

SuperDARN observations of high‐m ULF waves with curved phase fronts and their interpretation in terms of transverse resonator theory

Multiradar observations of substorm‐driven ULF waves

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