Science Seminars

2/4/2010 – Enhanced Thermospheric Density: The Roles of East-West and Northward Interplanetary Magnetic Field

Speaker: Delores Knipp (HAO)
Date: Thursday, Feb 04, 2010
Time: 4:00 PM
Location: LSTB 299

Seminar Abstract:

During 2005 solar EUV energy input to the thermosphere waned as Solar Cycle 23
declined. The reduction allowed a clearer delineation of episodic density disturbances caused by geomagnetic storms. We show new views of these disturbances based on Poynting flux calculations from the Defense Meteorological Satellite Program (DMSP) F-series satellites, as well as from 1) accelerometer data from polar orbiting satellites, 2) the assimilative mapping of ionospheric electrodynamics (AMIE) procedure.

The new Poynting flux estimates suggest that the origins of some disturbances are poorly specified by ground indices. In particular we find that intervals of enhanced northward Interplanetary Magnetic Field (IMF) combined with strong east-west components of the IMF allow significant electromagnetic energy input into localized dayside regions of the high-latitude thermosphere. In some cases this energy deposition is consistent with IMF-geomagnetic field merging tailward of the Earth’s magnetic cusps. In other cases the energy is deposited in the vicinity of an extremely narrow convection throat. This mode of interaction provides little energy to the magnetotail; and instead concentrates the energy in the dayside thermosphere. The extreme localized energy flux also appears to be associated with unusual ion upflows. I will discuss examples of poorly specified neutral density enhancements and their likely sources.