The THEMIS satellites provided an unprecedented opportunity to monitor the dayside magnetospheric boundary while magnetically conjugate auroras were also observed by the monochromatic imagers at South Pole and at other Antarctic stations of Automatic Geophysical Observatories (AGO) chain. This allowed joint observations of magnetopause activity and the aurora at its magnetic foot print. Field line mapping should be relatively accurate on the dayside because the magnetic field is strong and the distance to the magnetopause is relatively short. The THEMIS configuration allowed to monitor the solar wind directly in front of the magnetosphere removing any ambiguities due to the long propagation of the solar wind from distant satellites. THEMIS satellites that were crossing the magnetopause almost always saw multiple crossings caused by magnetospheric boundaries rapidly moving in and out. A large fraction of these movements appeared to be spontaneous and were not related to external impulses from the solar wind plasma. However response to pressure pulses or spontaneous reconnection could also be distinguished at times. From ground based observations we were able to distinguish several Pole-ward Moving Auroral Forms. The brighter PMAF-s generally dissipate near the location where they were formed but in several cases faint emissions seem to indicate a larger extent of diffuse aurora and associated persistent anti-sunward flows. According to recent observations anti-sunward flows across the polar cap can be frequently associated with Polar Boundary Intensifications (PBI-s). The THEMIS Ground Based Observatory (GBO) network allowed the identification of the substorm triggering role of PBIs and subsequent north south aligned auroral features. In summary there is evidence in the auroral foot-print for every step of the "Dungey cycle" from dayside reconnection opening of closed field lines to night-side re-closing via triggering of substorms.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- 2704 MAGNETOSPHERIC PHYSICS / Auroral phenomena;
- 2706 MAGNETOSPHERIC PHYSICS / Cusp;
- 2776 MAGNETOSPHERIC PHYSICS / Polar cap phenomena;
- 2790 MAGNETOSPHERIC PHYSICS / Substorms