HR: 10:20h
AN: SM32A-01    [Abstracts]
TI: The Annual Variation in Plasmaspheric Mass Density
AU: * Menk, F W
EM: fred.menk@newcastle.edu.au
AF: The University of Newcastle, School of Mathematical and Physical Science, Callaghan, NSW 2308, Australia
AU: Clilverd, M A
EM: macl@bas.ac.uk
AF: British Antarctic Survey, Madingley Road, Cambridge, CB3 0ET, United Kingdom
AU: Grew, R S
EM: russell.grew@newcastle.edu.au
AF: The University of Newcastle, School of Mathematical and Physical Science, Callaghan, NSW 2308, Australia
AB: Due to the tilt of the geomagnetic field, there is a longitude-dependent asymmetry in ionospheric solar illumination at conjugate points in winter and summer months. This difference is greatest at American longitudes, where, for example, the L=2.5 field line with footprint in Antarctica near 65^o geographic latitude and 300^o longitude, has its conjugate point at 42^o geographic latitude in the northern hemisphere. Previous VLF whistler-based and CRRES spacecraft observations have shown that plasmaspheric electron density is larger by a factor of 2.7 (at solar maximum) in December than in June at L=3.0 at American longitudes. There is a corresponding minimum in electron density at American longitudes in June. Using ground magnetometer data, we determined seasonal average ion mass densities in the equatorial plane at L=2.5 for a range of longitudes. These were compared with the annual variation in electron density and in IMAGE EUV He+ densities. This provides new insight on the seasonal/longitudinal variation in mass density, and also furnishes an estimate of the seasonal variation in plasmaspheric mass loading.
DE: 2730 Magnetosphere: inner
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2768 Plasmasphere
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting