Dependence of the evening prereversal enhancement of the verticalplasma drift on geophysical parameters

摘要

The variability of the evening prereversal enhancement (PRE) of the vertical plasmadrift has been investigated by using the average velocity at a fixed local time range,but this method does not provide a clear distinction between the PRE occurrence frequencyand magnitude. In this study, we examine the dependence of the occurrence frequency,occurrence local time, and magnitude of the PRE on geophysical parameters by using theretrievals of the individual PRE from the first Republic of China satellite data. Our resultshows that the seasonal-longitudinal variation of the average vertical velocity in theevening that has been identified in previous studies is associated with both the PREoccurrence frequency and PRE magnitude. The magnitude of the PRE shows an increasingtrend with an increase of the solar flux and with a decrease of the conjugate E region sunsettime lag. The seasonal-longitudinal variation of the occurrence local time of the peakPRE shows a dependence on the E region sunset time at the magnetic equator rather thanon the magnetic declination or the sunset time lag in the conjugate E regions. Thisobservation indicates that the optimum time for the creation of the peak PRE is when thesunset terminator at the E region height and the magnetic meridian intersect near themagnetic equator.