New aspects in plasmaspheric ion temperature variations from INTERBALL 2 and MAGION 5 measurements

Abstract

INTERBALL 2 (1996) and MAGION 5 (1999–2001) cold plasma measurements provided the possibility to deduce new aspects of ion temperature distributions in the Earth's plasmasphere during magnetically quiet and moderately disturbed times. Proton temperatures in the plasmasphere were compared along the magnetic field lines to electron and ion temperatures measured by DMSP satellites in the upper (∼840 km) ionosphere. On the nightside for 1.4< L<2.8, plasmaspheric temperatures were found to be quite close to ionospheric electron temperatures. At L=2.5–2.8, ion temperatures in the plasmasphere were close to electron temperatures in the upper ionosphere everywhere except for the noon-to-dusk MLT sector. At higher L ( L>3), the plasmasphere-to-ionosphere temperature ratio was greater than 1, and there was also an increase in the 12–20 MLT sector. Apparently there is a heating source at high L that is strongest in the noon-to-dusk MLT sector. It was revealed that during moderate magnetic storm development, nighttime ion temperature was depressed in the storm main phase, but exceeded quiet time values in the storm recovery phase. Possible reasons of such temperature behavior are briefly discussed.