TAIL-LIKE RECONFIGURATION OF THE PLASMA SHEET DURING THE SUBSTORM GROWTH-PHASE

Tail-like reconfiguration observed in the near-earth plasma sheet during the substorm growth phase is surrounded by enhanced convection except inside and tailward of the reconfiguration region itself. The required distribution of enhanced convection can be driven by an enhanced dayside reconnection. The enhanced dayside convection can be transmitted across open field lines by the tangential discontinuity to reach the last open field line in the tail lobe in about 20 minutes. This can cause B(X) to increase in the plasma sheet. On the other hand, the enhanced dayside convection can also be transmitted across close field lines by the fast rarefaction wave to arrive at the near-earth plasma sheet (x less-than-or-equal-to -10 R(E)) in about 15 minutes, causing B(Z) to decrease in the plasma sheet. Thus, a tail-like reconfiguration can start within about 15 to 20 minutes after a southward turning of the IMF (interplanetary magnetic field). The duration of the growth phase can be identified with the M-I coupling time scale of approximately 30 to approximately 40 minutes. The region-2 field-aligned current is shown to increase to 0.2-mu-A/m2 at the ionospheric level, resulting from the tail-like reconfiguration.