Hemispherical asymmetry in cusp precipitation near solstices

摘要: A statistical comparison of the peak flux in electron and ion polar cusp precipitation summer winter hemispheres as observed by low-altitude DMSP F7 satellite is performed. Data studied encompass four consecutive solstices from December 1983 to June 1985, comprising 77 days data with a total 292 individual passes. On each day, observations were restricted those few hours UT which interhemispherical MLT variation was smallest. After remaining local time effect averaged out, hemisphere (electron) precipitating energy larger, on average, 61 ± 11% (51 5%) than that hemisphere. However, average particle always lower for both species These effects generally hold true northward well southward interplanetary magnetic fields (IMF). It argued asymmetry very hard explain if most intense part lies closed field lines, but it shown standard open line model virtually requires differences occur. The present results thus suggest portion lines even IMF.