Slow shock characteristics as a function of distance from the X‐line in the magnetotail

Abstract

Both particle and MHD simulations are performed to study the characteristics of slow shocks in the magnetotail. The particle simulations indicate that switch-off shocks exhibit large amplitude rotational wave trains, while magnetotail slow shocks with an intermediate Mach number MA• < M,: _• 0.98 do not display such rotational wave trains. The MHD simulations show that the spontaneous reconnection process in the near-earth plasma sheet leads to the formation of a pair of slow shocks tailward of the reconnection line (X-line). The properties of slow shocks are found to vary as a function of the distance from X-line due to the formation of plasmoid. Slow shocks in most regions of the magnetotail are found to be non-switch-off shocks with M A• < 0.98. The present results are used to discuss the lack of large amplitude rotational wave trains at slow shocks in the deep magnetotail.

Generation of shock/discontinuity compound structures through magnetic reconnection in the geomagnetic tail

“…A series of MHD discontinuities can be generated by magnetic reconnection. [2][3][4][5][6] Observations of slow shocks in the solar wind have been reported by Chao and Olbert, 7 Feldman et al, 8 and Saito et al 9 In hybrid simulations of slow shock, leakage of downstream heated ions to the upstream leads to an anisotropy pressure in the foreshock region, [10][11][12][13][14] in which the local intermediate-mode speed is highly reduced. Rotational discontinuities have been observed in the solar wind.…”

“…Previous studies have also shown that the tail lobe-plasma sheet boundary in the mid-and distant tail often behaves as a quasi-perpendicular slow shock, which may be due to the Petschek-type reconnection occurring in the tail. 8,9,12,14,[24][25][26][27][28][29][30][31][32][33] However, with a statistical survey from Geotail and Wind data, Whang et al 22 argued that occurrence of DDs in the tail lobe-plasma sheet boundary is no less than the stand-along slow shocks, which implies that the DDs are easy to be generated in the geomagnetic tail.…”

Hybrid simulation of space plasmas: Models with massless fluid representation of electrons. II. Slow and intermediate shocks

“…However, observations in the geomagnetic tail (on board the ISEE-3 rocket) failed to detect the presence of such waves. To eliminate the inconsistency between theoretical predictions and observations, researchers have conducted a multitude of calculations using hybrid models [70][71][72][73][74][75][76]. These studies have obtained shocktype solutions both with and without a wave chain.…”

“…These studies have obtained shocktype solutions both with and without a wave chain. According to [70,73], there is a critical Mach number Me = 0.98 such that for SS with 1 > M~ > Mc the downstream region contains a coherent wave chain, while for SS with MI < Me the rotational wave in the downstream region decays over a distance shorter than the wavelength. (For the magnetic tail SS with 0Bn= 75 ~ [~ 1 = 0.1, and Tel / Til = 0, the critical value is Me = 0.975 [73].)…”

A Quasi-stagnant Plasmoid Observed With Geotail on October 15, 1993

“…The two distances for the first plasmoid are consistent with the mid-tail and distant X-lines, and for the second plasmoid with the near-Earth and distant X-lines. However the size of the plasmoid in X may be less than the distance between the two X-lines, because a plasmoid is a plasma bulge and the bulge does not necessarily start from the position of the X-line: there can be a thin plasma sheet region between the X-line and the bulge (e.g., Lee et al, 1989). Also, the spacecraft may not encounter the full length of the plasmoid, leading to an underestimation of the plasmoid length.…”