HR: 0800h
AN: SM31B-0420    [Abstracts]
TI: High-altitude Cusp Precipitation for Different IMF Orientations
AU: * Nemecek, Z
EM: zdenek.nemecek@mff.cuni.cz
AF: Charles University, Faculty of Mathematics and Physics, V Holesovickach 2, Prague, 180 00 Czech Republic
AU: Safrankova, J
EM: jana.safrankova@mff.cuni.cz
AF: Charles University, Faculty of Mathematics and Physics, V Holesovickach 2, Prague, 180 00 Czech Republic
AU: Simunek, J
EM: sim@ufa.cas.cz
AF: Institute of Atmospheric Physics, Bocni II 1401, Prague, 141 23 Czech Republic
AB: Reconnection is the most important process in the magnetospheric physics. Dayside reconnection of interplanetary and terrestrial magnetic fields supplies the magnetosphere with a huge amount of the solar wind plasma that is then released due to reconnection occurring in the tail. In spite of its principal importance, reconnection is still understood insufficiently. The main problem is probably connected with the fact that both MHD and kinetic processes are equally important for its initialization and further development. Experimental investigations are difficult because reconnection spots are limited in space and time and a probability that a spacecraft is located in appropriate time at a right position is very low. However, all possible places where magnetopause reconnection can occur are magnetically connected to the cusp and thus the plasma proceeding along reconnected magnetic field lines brings information on reconnection. As observed by the various spacecraft at both low and high altitudes, a cusp precipitation is often characterized by ion energy dispersion. During southward IMF, ion energy falls with increasing magnetic latitudes due to the convection electric field operating as a velocity filter on particles from the injection point to the observation point. The high-energy ions rapidly reach lower latitudes and the lower-energy ions appear later at higher latitudes. By contrast, if reconnection takes place in the tail lobes, the high-energy ions quickly reach higher latitudes, whereas the low-energy ions are convected to lower latitudes and thus the ion energy-latitude dispersion signifies the boundary of open and closed magnetic field lines. We are presenting case studies of crossings of the cusp region at high altitudes which reveal that both spatial and temporal changes should be taken into account for an explanation of the observed features. Moreover, our study shows that the cusp can be supplied from two simultaneously operating reconnection sites located in different latitudes and local times. The observed signatures evolve with the distance from the reconnection site.
DE: 2706 Cusp
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2724 Magnetopause and boundary layers
DE: 2728 Magnetosheath
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005