Simultaneous DMSP, All-Sky Camera, and IMAGE FUV Observations of the Brightening Arc at a Substorm Pseudo-Breakup
AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE
Pagination or Media Count:
Auroral particles, field-aligned currents. and plasma convections in the vicinity of the brightening arc at substorm onset are still not well understood, since it is very rare to have conjugate satellite measurements above the brightening arc. In this paper, we investigate the characteristics of auroral particles and fields associated with the brightening arc at a pseudo-onset of substorm on October 31, 2000, using ground all-sky TV images, IMAGE FUV auroral images, and particle, magnetic field, and plasma flow data obtained by the DMSP F12 satellite. The arc brightening at Tixie 66.0 MLAT, Russia, occurred at 1004 UT 18.75 MLT coincident with a coherent Pi 2 pulsation at midlatitudes and with the DMSP crossing above the arc. The brightening arc did not develop on a global scale, indicating that this event is a pseudo auroral breakup, which occurred approximately 16 min before the major substorm expansion onset. IMAGE aurora images indicate that the longitude of the brightening center was approximately 2.5 h nightside of Tixie. The DMSP data show that the precipitating particles associated with the brightening arc correspond to an electron inverted-V structure at the equatorward edge of the electron precipitation region, near the equatorward boundary of the upward region I field-aligned current, and at the peak of the sunward convection velocity. These facts indicate that the brightening arc at duskside of the onset local time was located in the inner plasma sheet at the inner edge of the region I current source in the sunward convection region.
- Atmospheric Physics