Observational evidence for an inside-out substorm onset scenario
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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
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Explosive Magnetotail Activity
M. I. Sitnov,Joachim Birn,B. Ferdousi,Evgeny Gordeev,Yuri V. Khotyaintsev,Viacheslav Merkin,Tetsuo Motoba,Antonius Otto,Evgeny V. Panov,P. L. Pritchett,Fulvia Pucci,Fulvia Pucci,Joachim Raeder,Andrei Runov,V. A. Sergeev,Marco Velli,Xu-Zhi Zhou +16 more
TL;DR: Two mechanisms for the generation of the pre-onset current sheet are discussed, namely magnetic flux addition to the tail lobes, or other high-latitude perturbations, and magnetic flux evacuation from the near-Earth tail associated with dayside reconnection.
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Magnetic conjugacy of northern and southern auroral beads
TL;DR: In this paper, the authors used simultaneous ground-based, all-sky camera observations from a geomagnetically conjugate Iceland-Syowa Station pair to demonstrate that the auroral beads, whose wavelength is ∼30-50 km, evolve synchronously in the northern and southern hemispheres and have remarkable interhemispheric similarities.
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Ballooning‐interchange instability in the near‐Earth plasma sheet and auroral beads: Global magnetospheric modeling at the limit of the MHD approximation
Kareem A. Sorathia,Viacheslav Merkin,Evgeny V. Panov,Binzheng Zhang,Binzheng Zhang,John G. Lyon,J. Garretson,A. Y. Ukhorskiy,Shinichi Ohtani,M. I. Sitnov,Michael Wiltberger +10 more
TL;DR: In a global magnetohydrodynamic (MHD) simulation of the growth phase of a synthetic substorm, it is found that the self‐consistent formation and destabilization of localized magnetic field minima in the near‐Earth magnetotail are found.
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Comment on “Tail Reconnection Triggering Substorm Onset”
TL;DR: Evidence is provided that near-Earth current disruption, occurring before the conventional tail reconnection signatures, triggered the onset of a magnetospheric substorm, and the observed auroral intensification and tail reconnections are not causally linked.
Journal ArticleDOI
Statistical properties of substorm auroral onset beads/rays
Yukitoshi Nishimura,Yukitoshi Nishimura,Jian Yang,P. L. Pritchett,Ferdinand V. Coroniti,Eric Donovan,Larry R. Lyons,Richard A. Wolf,Vassilis Angelopoulos,Stephen B. Mende +9 more
TL;DR: In this article, the authors used the Rice Convection Model-Equilibrium (RCM-E) and kinetic instability properties of substorm onsets to characterize the occurrence probabilities and properties of substorm auroral onset waves.
References
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Satellite studies of magnetospheric substorms on August 15, 1968: 1. State of the magnetosphere
TL;DR: In this paper, the authors used ground magnetograms to determine the onset times of two substorms that occurred while the Ogo 5 satellite was inbound on the midnight meridian through the cusp region of the geomagnetic tail (the region of rapid change from taillike to dipolar field).
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Equatorward and poleward expansion of the auroras during auroral substorms
TL;DR: In this article, the formation of the auroral bulge is investigated on the basis of all-sky TV auroral data with high spatial and temporal resolution, and it is suggested that these discrete auroral structures in the bulge develop along the plasma streamlines in a localized distorted two-cell equipotential distribution.
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Estimates of current changes in the geomagnetotail associated with a substorm
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