Observation of the SAR arc formation due to the interplanetary shock and substorm on December 14, 2006
Abstract
It is known that stable auroral red (SAR) arcs are the consequence of interaction of the outer plasmasphere with energetic ions of the ring current. The diffuse aurora (DA) is caused by the low-energy electron precipitation from the plasma sheet. Our studies at the Yakutsk meridian (199ºE geomagnetic longitude) indicate that the SAR arc appears and/or brightens during the substorm expansion phase. The SAR arc formation begins in the equatorward boundary region of DA (Ievenko, 1999; Ievenko et al, 2008). In this work the results of observations of SAR arc formation by all-sky scanning photometer during a substorm whose expansion phase has begun in 15 minutes after the onset of sudden commencement (SC) due to the impact of the strong interplanetary shock detected by the ACE spacecraft on December 14, 2006 are presented. The intense substorm with amplitudes of AL ~ -1300 and ASY-H ~ 200 nT indices has begun at 1430 UT. In 10 minutes (~2310 MLT) the photometer has registered the 630 nm emission intensification in the form of patch at ~ 61ºN latitude. The red patch with a diameter of ~300 km appears in a vicinity of DA boundary and moves equatorward close to the Yakutsk meridian with the increase of velocity from 100 to 300 m/s. At 1510 UT the 630 nm emission intensification has been already observed in the form of SAR arc at ~57ºN latitude. Geosynchronous observations of the fluxes change of energetic protons and electrons aboard the LANL spacecrafts in the evening and midnight MLT sectors indicates to the location of substorm injection centre close to the Yakutsk meridian. This suggests that the dynamics of SAR arc formation in this event maps a prompt radial diffusion (electric drift) of energetic particles from the central region of substorm injection into the inner magnetosphere.
- Publication:
-
40th COSPAR Scientific Assembly
- Pub Date:
- 2014
- Bibcode:
- 2014cosp...40E1263I