ALBERT

Description: The ionospheric plasma convection in the midnight sector for stably northward interplanetary magnetic field (IMF) has been examined using the Dynamics Explorer 2 fields and plasma data. From the 12-months of noon-midnight passes, 67 passes were selected. With the electric field data from these passes, we have focused on the convection occurring in the “boundary plasma region.” The boundary plasma region is defined as a region between the equatorward boundary of the polar cap and the poleward boundary of a central/inner plasma sheet. The convection pattern in the boundary plasma region is controlled by the sign of IMF By, the magnitude of (By2+BZ2)1/2 and the IMF clock angle. For a large IMF (By2+Bz)1/2 and relatively large IMF clock angles (i.e., larger than 30°), the convection tends to show a By dependent flow partern which consists of two or three flow regions having an eastward or westward component. As the clock: angle becomes smaller, the convection tends to be an irregular pattern which has multiple flow regions. Large potential difference can occur in the boundary plasma region. When the potential is more than 15 kV, the convection, in most cases, is the By-controlled pattern. This means that for this convection pattern a significant amount of energy can be deposited in the midnight sector from the tail even if IMF Bz is stably positive. © 1996, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.