THEMIS Summary Data Plots B C D E

Right: AU/AL indices for the interval. Major Conjunction G12 D C B E A G11 Outside-in spreading: B => C => D/E => A Inside-out spreading: A => D/E => C => B Left: positions of five Themis and two GOES satellites for 2008 Jan 29 0700-0900 UT interval. Right: AU/AL indices for the interval. Objective: Examine time history of events (inside-out/outside-in?)

Poleward arc undisturbed Fort Smith (FSMI) Jan 29, 2008 Poleward arc undisturbed Arc brightening with subsequent poleward expansion

Arc brightenings with subsequent poleward expansion. For first and second auroral activation, arc poleward of initial brightening remained undisturbed until poleward expansion reached there. For the third auroral activation, the initial brightening arc is most poleward arc.

THEMIS Vix and Bz ~0714 UT At ~0714 UT, temporal sequence: D/E => B

THEMIS Vix and Bz ~0735 UT At ~0735 UT, temporal sequence: A => D/E => C

THEMIS Vix and Bz ~0835 UT At ~0835 UT, temporal sequence: C => E => D => A

Summary Three auroral activations occurred during a major tail conjunction. First activation is an isolated substorm with time history consistent with an inside-out scenario; it does not involve mangetic reconnection of open magnetic field lines. Second activation is a moderate size substorm with an inside-out time history. Third activation is an intensification of the substorm started with the second activation. Its time history is consistent with outside-in scenario. Second and third auroral activations are different episodes of a weak substorm consistent with the substorm synthesis model. Wavelet analysis suggests that dipolarization originates from waves excited at ~7-30s period.