[1] We report a detailed analysis of explosive local magnetic field line stretching just before dipolarization observed by one of Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites during the pseudo-breakup followed by local substorm of 6 January 2008. At the end of the substorm growth phase, this satellite (THEMIS-C) was located at r~6.3 R E near the convection boundary of 10 keV electrons. Penetration of the hot electron plasma sheet to the region of trapped energetic ions was a precondition for the substorm onset in the premidnight sector. Observed oscillations of fields and particles with period 50-60 s are consistent with the ballooning mode in the near-Earth magnetotail and with the near-Earth initiation current disruption model. Basing on the simple line-current model, the explosive stretching and following dipolarization observed by THEMIS-C satellite are interpreted as a manifestation of the magnetospheric generator of the 3-D meridional current system with the driving electric field in the meridional direction during nonlinear growth of ballooning instability when non-MHD processes are also turning on.Citation: Kozelova, T. V., and B. V. Kozelov (2013), Substorm-associated explosive magnetic field stretching near the earthward edge of the plasma sheet,
Abstract. The substorm associated behavior of the low energy particles (30 eV-28.5 keV) near the earthward edge of the plasma sheet is examined using data from CRRES during the late growth and early expansion phases of a substorm on 12 March 1991 and their significance for the substorm onset mechanism is discussed. In this substorm, the CRRES was located on L ∼6.3 and ∼20 • westward of the substorm onset and observed the sequence of the alternating bursts of the low energy ions and electrons. The bursts of the 0.633-9.6 keV ions occurred 1-2 min before the (7.31-21.7 keV) electron bursts. The first ion burst happened 2 min before the substorm onset, at the moment of weak brightening of the most equatorial pre-breakup arc near the latitude ∼62 • . The alternation of the ion and electron bursts may be a signature of a drift-Alfvén ballooning instability on the inner edge of the plasma sheet near substorm onset.
Abstract. Auroral TV observations at Loparskaya, Kola Peninsula, and CRRES energetic electron and proton measurements during a moderate isolated substorm at 2000-2100 UT on February 13, 1991, are compared. The CRRES was at the apogee of orbit 494 in the outer radiation belt near the magnetic equator. CRRES footprint projection estimated by using a Tsyganenko magnetic field model was situated at the same latitudes several degrees eastward of active aurora during the substorm breakup or the intensification. The intensification consists of several activations of 1-min duration, and this fine spatial and temporal structure is important for the conjugacy investigations. It is shown that injected energetic electrons have been accelerated at the same time as one of the auroral activations at the same latitude and approximately the same azimuthal extended region. The lack of enhanced electrons during other activations suggests that the acceleration region has a sharp equatorial boundary.
Abstract. We propose a cellular automata model (CAM) to describe the substorm activity of the magnetosphericionospheric system. The state of each cell in the model is described by two numbers that correspond to the energy content in a region of the current sheet in the magnetospheric tail and to the conductivity of the ionospheric domain that is magnetically connected with this region.The driving force of the system is supposed to be provided by the solar wind that is convected along the two boundaries of the system. The energy flux inside is ensured by the penetration of the energy from the solar wind into the array of cells (magnetospheric tail) with a finite velocity. The third boundary (near to the Earth) is closed and the fourth boundary is opened, thereby modeling the flux far away from the tail. The energy dissipation in the system is quite similar to other CAM models, when the energy in a particular cell exceeds some pre-defined threshold, and the part of the energy excess is redistributed between the neighbouring cells. The second number attributed to each cell mimics ionospheric conductivity that can allow for a part of the energy to be shed on field-aligned currents. The feedback between "ionosphere" and "magnetospheric tail" is provided by the change in a part of the energy, which is redistributed in the tail when the threshold is surpassed.The control parameter of the model is the z-component of the interplanetary magnetic field (B z IMF), "frozen" into the solar wind. To study the internal dynamics of the system at the beginning, this control parameter is taken to be constant. The dynamics of the system undergoes several bifurcations, when the constant varies from −0.6 to −6.0. The B z IMF input results in the periodic transients (activation regions) and the inter-transient period decreases with the decrease of B z . At the same time the onset of activations in the array shifts towards the "Earth". When the modulus of the B z IMF exceeds some threshold value, the transition takes place from periodic to chaotic dynamics.Correspondence to: B. V. Kozelov (kozelov@pgi.kolasc.net.ru)In the second part of the work we have chosen as the source the real values of the z-component of the interplanetary magnetic field taken from satellite observations. We have shown that in this case the statistical properties of the transients reproduce the characteristic features observed by Lui et al. (2000).
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