Observational evidence for an inside-out substorm onset scenario
TLDR
In this paper, the authors present observations which provide strong support for a substorm expansion phase onset scenario in which a localized inner magnetospheric instability developed first and was later followed by the development of a Near Earth Neutral Line (NENL) farther down-tail.Abstract:
. We present observations which provide strong support for a substorm expansion phase onset scenario in which a localized inner magnetospheric instability developed first and was later followed by the development of a Near Earth Neutral Line (NENL) farther down-tail. Specifically, we find that the onset began as a localized brightening of an intensified growth phase arc which developed as a periodic series of arc-aligned (i.e. azimuthally arrayed) bright spots. As the disturbance grew, it evolved into vortical structures that propagated poleward and eventually morphed into an east-west aligned arc system at the poleward edge of the auroral substorm bulge. The evolution of the auroral intensity is consistent with an exponential growth with an e-folding time of around 188 s (corresponding to a linear growth rate, γ of 5.33×10−3 s−1). During the initial breakup, no obvious distortions of auroral forms to the north were observed. However, during the expansion phase, intensifications of the poleward boundary of the expanding bulge were observed together with the equatorward ejection of auroral streamers into the bulge. A strong particle injection was observed at geosynchronous orbit, but was delayed by several minutes relative to onset. Ground magnetometer data also shows a two phase development of mid-latitude positive H-bays, with a quasi-linear increase in H between the onset and the injection. We conclude that this event provides strong evidence in favor of the so-called "inside-out" substorm onset scenario in which the near Earth region activates first followed at a later time by the formation of a near-to-mid tail substorm X-line. The ballooning instability is discussed as a likely mechanism for the initial onset.read more
Citations
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Space‐Ground Observations of Dynamics of Substorm Onset Beads
Yugo Nishimura,A. V. Artemyev,Larry R. Lyons,Christine Gabrielse,E. F. Donovan,Vassilis Angelopoulos +5 more
TL;DR: In this paper , the authors present observations during two substorms using simultaneous Time History of Events and Macroscale Interactions During Substorms satellites and all-sky imagers to determine plasma sheet dynamics associated with substorm auroral onset beads.
Journal ArticleDOI
Space‐Ground Observations of Dynamics of Substorm Onset Beads
TL;DR: In this article , the authors present observations during two substorms using simultaneous Time History of Events and Macroscale Interactions During Substorms satellites and all-sky imagers to determine plasma sheet dynamics associated with substorm auroral onset beads.
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Substorm onset process: Ignition of auroral acceleration and related substorm phases
Akira Morioka,Yoshizumi Miyoshi,Yasumasa Kasaba,Natsuo Sato,Akira Kadokura,Hiroaki Misawa,Yukinaga Miyashita,Ian R. Mann +7 more
TL;DR: In this article, the substorm onset process was studied on the basis of the vertical evolution of auroral acceleration regions derived from auroral kilometric radiation (AKR) spectra and Pi pulsations on the ground.
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Recurrent embedded substorms during the 19 October 1998 GEM storm
TL;DR: In this paper, the authors demonstrate that classical substorms occurred throughout the interval and that the storm appears to be comprised of the typical two-mode response consisting of a recurrent loading/unloading cycle on a time-scale of approximately 2-4 hours together with an episodic/bursty continuously-driven component operating on a 5-15 minutes.
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On the magnetospheric ULF wave counterpart of substorm onset
TL;DR: In this article, a case study showing the development of auroral beads from a Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky camera with near simultaneous exponential increases in auroral brightness, ionospheric and conjugate magnetotail ULF wave power, evidencing their intrinsic link.
References
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