East‐west type precursor activity prior to the auroral onset: Ground‐based and THEMIS observations

Golovchanskaya, I. V.; Kornilov, I. A.; Корнилова, Т. А.

doi:10.1002/2014ja020081

Cited by 9 publications

(3 citation statements)

References 38 publications

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“…The constellation of the five satellites of Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission provides a unique possibility to investigate the spatial and temporal structure of the ULF waves observed in situ. For example, high-m Pc5 pulsations are often studied with THEMIS Du et al, 2011;Golovchanskaya et al, 2015;Le et al, 2017;Liu et al, 2011Liu et al, , 2013Melikyan et al, 2013;Sarris et al, 2009;Sibeck et al, 2012;Takahashi et al, 2013). However, those studies did not reach an unambiguous conclusion on the nature of the compressional Pc5 waves: Some authors concluded that they represent drift mirror modes, other authors insist on their Alfvénic nature, and several authors suppose that they can represent the slow magnetosonic modes.…”

Section: Introductionmentioning

confidence: 99%

Drift Resonance of Compressional ULF Waves and Substorm‐Injected Protons From Multipoint THEMIS Measurements

et al. 2018

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A compressional Pc5 wave associated with localized hot proton injection was observed by the five THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft in the dusk sector of the Earth's magnetosphere at L ∼ 10R E on 21 May 2007. The wave magnetic field perturbation transverse to the background magnetic field was primarily poloidal, in agreement with the predominately azimuthal wave vector direction (with westward phase velocity). The observation followed two consecutive substorms, when the cloud of energetic particles comprised of the lower-energy protons from the earlier substorm was mixed with higher-energy protons from the subsequent one. The clear signatures of the wave-particle drift resonance of protons modulated by the wave were observed. The wave period was found to be about 2 times longer than the corresponding Alfvén wave eigenmode period on the same L-shells calculated with the THEMIS data. The increase of the particle energy with the distance from the Earth and the observed strong dependence of the wave frequency on the azimuthal wave number constitutes conditions for the gradient instability of the drift compressional mode (for the Alfvén mode one supposes the particle energy decrease with radial distance). Based on these results, we conclude that the observed wave was the drift compressional mode generated by the gradient instability.

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Section: Introductionmentioning

confidence: 99%

Drift Resonance of Compressional ULF Waves and Substorm‐Injected Protons From Multipoint THEMIS Measurements

et al. 2018

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“…Much attention was paid to the nearly northsouth aligned auroral structures originating at the poleward auroral boundary and progressing to lower latitudes, which were considered as substorm precursors (e.g., Rostoker et al, 1987). Golovchanskaya et al (2015) focused on the wavelike signatures of the east-west type of auroral activities, which appear before the breakup and may be related to ballooning waves propagating in the plasma sheet. In fact, any form of optical presubstorm activity could be considered as a precursor of the onset, so such investigations need to continue to clarify the situation.…”

Section: Preonset Phenomenamentioning

confidence: 99%

“…vection velocity. A detail description of the system was given by Greenwald et al (1995) and Chisham et al (2007).…”

Section: Instrumentationmentioning

confidence: 99%

Polar substorm on 7 December 2015: preonset phenomena and features of auroral breakup

Safargaleev

Kozlovsky²,

Mitrofanov

2020

Ann. Geophys.

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Abstract. Comprehensive analysis of a moderate 600 nT substorm was performed using simultaneous optical observations inside the auroral oval and in the polar cap, combined with data from satellites, radars, and ground magnetometers. The onset took place near the poleward boundary of the auroral oval that is not typical for classical substorms. The substorm onset was preceded by two negative excursions of the interplanetary magnetic field (IMF) Bz component, with a 1 min interval between them, two enhancements of the antisunward convection in the polar cap with the same time interval, and 15 min oscillations in the geomagnetic H component in the auroral zone. The distribution of the pulsation intensity along meridian has two local maxima, namely at the equatorial and poleward boundaries of the auroral oval, where pulsations occurred in the out-of-phase mode resembling the field line resonance. At the initial stage, the auroral breakup developed as the auroral torch stretched and expanded poleward along the meridian. Later it took the form of the large-scale coiling structure that also distinguishes the considered substorm from the classical one. Magnetic, radar, and the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) satellite data show that, before the collapse, the coiling structure was located between two field-aligned currents, namely downward at the poleward boundary of structure and upward at the equatorial boundary. The set of GEOTAIL satellites and ground data fit to the near-tail current disruption scenario of the substorm onset. We suggest that the 15 min oscillations might play a role in the substorm initiation.

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The Active Magnetosphere

Nishimura

Lyons

2021

Magnetospheres in the Solar System

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East‐west type precursor activity prior to the auroral onset: Ground‐based and THEMIS observations

Cited by 9 publications

References 38 publications

Drift Resonance of Compressional ULF Waves and Substorm‐Injected Protons From Multipoint THEMIS Measurements

Drift Resonance of Compressional ULF Waves and Substorm‐Injected Protons From Multipoint THEMIS Measurements

Polar substorm on 7 December 2015: preonset phenomena and features of auroral breakup

The Active Magnetosphere

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