Modulation of Jovian electrons at 1 AU during solar cycles 22-23

Abstract

We report here, on the observation of Jovian electrons during the time period 1992 to 2002, using instruments on board SAMPEX and IMP8 at 1 AU. The Jovian electron flux diminished greatly from early 1996 to the end of 1997 and recovered subsequently and was observed till the end of 2001. The decrease in the Jovian flux was seen in three distinct instruments lasting for about two Jovian synodic periods. Such a dramatic and persistent decrease has not been observed before. The observed decrease could be due to changes at the source or variations in interplanetary conditions affecting transport of these particles. The latter may be solar cycle dependent as in the heliospheric modulation of cosmic rays. Long-term measurements from IMP8 suggest that solar cycle related propagation effects may not be responsible for the observed decrease. We suggest that either a change in the Jovian source strength or a softening of the Jovian electron energy spectrum produced the observed attenuation.