Substorm‐associated explosive magnetic field stretching near the earthward edge of the plasma sheet

Kozelova, T. V.; Kozelov, B. V.

doi:10.1002/jgra.50344

Cited by 17 publications

(8 citation statements)

References 70 publications

(137 reference statements)

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“…It is commonly agreed that the appearance of a ballooning perturbation (i.e., a bubble or a bubble-blob pair) in the near-Earth tail provokes its destabilization and under certain conditions may trigger substorm. Previously it was suggested that ballooning-type perturbations can appear in the near tail either due to earthward floating plasma bubbles, as initially proposed by Erickson and Wolf [1980] and observationally evidenced by Baumjohann et al [1989], Angelopoulos et al [1992], and others or in result of ballooning/interchange instability growth [e.g., Roux et al, 1991;Saito et al, 2008;Coroniti, 2010, 2011;Panov et al, 2012;Kozelova and Kozelov, 2013]. The present study points to one more possibility, namely, that ballooning perturbations can be transported to the near tail by propagating ballooning waves.…”

Section: 1002/2014ja020081supporting

confidence: 71%

“…[], Angelopoulos et al . [], and others or in result of ballooning/interchange instability growth [e.g., Roux et al ., ; Saito et al ., ; Pritchett and Coroniti , , ; Panov et al ., ; Kozelova and Kozelov , ]. The present study points to one more possibility, namely, that ballooning perturbations can be transported to the near tail by propagating ballooning waves.…”

Section: Discussionmentioning

confidence: 52%

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

2015

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Using ground-based optical observations, we study an auroral breakup event, focusing on the wave-like signatures of the east-west (E-W) type auroral activities which appear before breakup. By conjunction with the Time History of Events and Macroscale Interactions during Substorms (THEMIS) P2 and P5 measurements, it is shown that the underlying wave mode can be identified as the ballooning mode. Considering the similarity of the wave-like characteristics derived from ground-based auroral and THEMIS spacecraft observations, we argue that the E-W activities under study may be related to ballooning waves propagating in the plasma sheet. The implications for mechanisms of substorm triggering are discussed.

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Section: 1002/2014ja020081supporting

confidence: 71%

Section: Discussionmentioning

confidence: 52%

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

2015

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“…Equatorward movement of the boundaries seen prior to the onset caused by the stretching of field lines in the magnetotail during the growth phase of a substorm [Kozelova and Kozelov 2013]. As seen in Figure 8, the mean field is much weaker (stretching) during sawtooth events compared to shock related onsets as also indicated in Figure 7a, where the oval boundaries, during sawtooth events, were located equatorward of the boundaries during shock related onsets.…”

Section: Discussionmentioning

confidence: 71%

A comparative study of sawtooth events and substorm onsets triggered by interplanetary shocks

Andriyas

2017

Annals of Geophysics

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A comparison of solar wind conditions, geomagnetic response, and auroral boundary movement, using a similar number of sawtooth events and shock induced substorm triggers is carried out. 81% of the sawtooth onsets were triggered at low latitudes compared to 33% for onsets during shocks. Results of superposed epoch analysis indicated that the mean interplanetary magnetic field (IMF) B z remained strongly southward during sawtooth events while it was southward during the loading period and turned northward 20 minutes prior to the onset, during the shock triggered events. During both the event types, the mean energy available in the solar wind was found to be above the substorm threshold level. Relatively high levels of solar wind density indicated to the magnetosphere being compressed to a larger degree during substorms initiated by shocks. The high latitude indices were elevated during sawtooth events with 2-3 hr fluctuations was observed in the AL and PCN indices but AU index after the onset remained at similar levels. SYM-H remained below storm time values during shock related onsets but was much stronger and remained above the storm threshold during sawtooth events, that they occurred embedded in a geomagnetic storm. Comparatively higher mean values of ASYM-H indicated to a much stronger asymmetric ring current during sawtooth events. Mean boundary locations during sawtooth events were located a few degrees equatorward of those during the shock related onsets. Oval in the dawn, dusk, and midnight sectors was much thicker during sawtooth events with clear widening around the onset during both event groups but the thickness in noon sector was similar and remained steady during the epoch window during both the event groups. Elevated driving during sawtooth events was also indicative in a greater stretching and relaxation of the magnetic field lines at geosynchronous orbit in the midnight sector.

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“…A similar outward radial current, inward radial electric field has been suggested by Lui and Kamide [] to develop after substorm current disruption during dipolarization. Recently, using measurements from THEMIS C during two substorms, Kozelova and Kozelov [] found the inner plasma sheet edge outward E ψ ‐inward J ψ signature of Figure during the “explosive” growth phase stretching of the magnetic field, and the reverse‐signed signature after substorm onset when the Harang discontinuity apparently passed earthward of THEMIS.…”

Section: The Quiet Evening Arcmentioning

confidence: 99%

The quiet evening auroral arc and the structure of the growth phase near‐Earth plasma sheet

Coroniti

Pritchett

2014

JGR Space Physics

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The plasma pressure and current configuration of the near-Earth plasma sheet that creates and sustains the quiet evening auroral arc during the growth phase of magnetospheric substorms is investigated. We propose that the quiet evening arc (QEA) connects to the thin near-Earth current sheet, which forms during the development of the growth phase enhancement of convection. The current sheet's large polarization electric fields are shielded from the ionosphere by an Inverted-V parallel potential drop, thereby producing the electron precipitation responsible for the arc's luminosity. The QEA is located in the plasma sheet region of maximal radial pressure gradient and, in the east-west direction, follows the vanishing of the approximately dawn-dusk-directed gradient or fold in the plasma pressure. In the evening sector, the boundary between the Region1 and Region 2 current systems occurs where the pressure maximizes (approximately radial gradient of the pressure vanishes) and where the approximately radial gradient of the magnetic flux tube volume also vanishes in an inflection region. The proposed intricate balance of plasma sheet pressure and currents may well be very sensitive to disruption by the arrival of equatorward traveling auroral streamers and their associated earthward traveling dipolarization fronts.

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Substorm‐associated explosive magnetic field stretching near the earthward edge of the plasma sheet

Cited by 17 publications

References 70 publications

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

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

A comparative study of sawtooth events and substorm onsets triggered by interplanetary shocks

The quiet evening auroral arc and the structure of the growth phase near‐Earth plasma sheet

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