Large‐scale hybrid simulations of the magnetotail during reconnection

Large-scale, 2-D hybrid simulations are used to investigate the ion kinetic physics associated with quasi steady-state reconnection in the magnetotail. The simulations encompass a significant portion (20 × 120 RE) of the tail. After formation of transient plasmoids, the results show the features of fast Petschek-type reconnection. There are two pairs of thin transition layers attached to the x-point which divert and accelerate the flow within a few ion inertial lengths. These transition layers do not quite conform to the properties of the expected slow shocks. The reason for this appears to be the fact that the ion dissipation scale is comparable to the thickness of the developing plasma sheet. As a result, we find signatures of only partially thermalized, counterstreaming ions in what resembles the plasma sheet boundary layer. A fast ion beam forms immediately upstream of the boundary layer. The results are consistent with the notion that slow shocks or similar transition layers are responsible for the heating and formation of the central plasma sheet and for the ion beams observed in the plasma sheet boundary layer.

[1]  W. Hughes,et al.  On the formation and evolution of plasmoids: A survey of ISEE 3 geotail data , 1992 .

[2]  L. Frank,et al.  Observations pertaining to the dynamics of the plasma sheet. [in geomagnetic tail] , 1977 .

[3]  J. Slavin,et al.  Slow mode shocks in the Earth' magnetotail: ISEE-3 , 1984 .

[4]  H. Karimabadi,et al.  Collisionless reconnection in two-dimensional magnetotail equilibria , 1991 .

[5]  M. Scholer.  Undriven magnetic reconnection in an isolated current sheet , 1989 .

[6]  S. Schwartz,et al.  Electron dynamics and potential jump across slow mode shocks , 1987 .

[7]  Susumu Kokubun,et al.  GEOTAIL observation of ring‐shaped ion distribution functions in the plasma sheet‐lobe boundary , 1994 .

[8]  W. Feldman,et al.  A detailed examination of a X-line region in the distant tail: ISEE-3 observations of jet flow and B(sub z) reversals and a pair of slow shocks , 1994 .

[9]  Dan Winske,et al.  Hybrid simulations of collisionless reconnection in current sheets , 1994 .

[10]  Tetsuya Sato.  Strong plasma acceleration by slow shocks resulting from magnetic reconnection , 1979 .

[11]  J. Drake,et al.  Structure of the dissipation region during magnetic reconnection in collisionless plasma , 1991 .

[12]  Douglas S. Harned,et al.  Quasineutral hybrid simulation of macroscopic plasma phenomena , 1982 .

[13]  R. Lepping,et al.  Cross‐tail magnetic flux ropes as observed by the GEOTAIL spacecraft , 1995 .

[14]  T. Obara,et al.  Plasma distribution functions in the Earth's magnetotail (XGSM∼ −42RE) at the time of a magnetospheric substorm: GEOTAIL/LEP observation , 1994 .

[15]  T. Mukai,et al.  Acceleration and heating of cold ion beams in the plasma sheet boundary layer observed with GEOTAIL , 1994 .

[16]  T. Forbes,et al.  A numerical simulation of magnetic reconnection and radiative cooling in line-tied current sheets , 1991 .

[17]  M. Kivelson,et al.  Observations of nonadiabatic acceleration of ions in Earth's magnetotail , 1994 .

[18]  E. W. Hones,et al.  Structure of a slow mode shock observed in the plasma sheet boundary layer , 1987 .

[19]  E. W. Hones,et al.  Slow‐mode shocks: A semipermanent feature of the distant geomagnetic tail , 1985 .

[20]  Eric Ronald Priest,et al.  A comparison of analytical and numerical models for steadily driven magnetic reconnection , 1987 .

[21]  D. Winske,et al.  Kinetic structure of slow shocks: Effects of the electromagnetic ion/ion cyclotron instability , 1992 .