Recurrent Modulation of Jovian Electron intensities: Ulysses KET measurements

Abstract

Abstract: Corotating Interaction Regions (CIRs) are regions in the heliosphere that are formed at the leading edges of high-speed solar wind streams originating in coronal holes. Here we concentrate on the modulation of Jovian electrons by CIRs observed with the Kiel Electron Telescope onboard Ulysses. After its launch on Oct. 6, 1990 Ulysses followed an in-ecliptic path towards Jupiter. The closest approach occurred on Feb. 8, 1992, when Ulysses began its out-of-ecliptic dive. During that period the flux of 2-10 MeV electrons, originating from Jupiter, were modulated by Corotating Interaction Regions until the spacecraft (s/c) reached a latitude of ∼ 30 • . Due to the orbital periods of Jupiter and Ulysses, the s/c came again close to the planet in 2004. As in 1992 and 1993 the MeV electron fluxes were modulated by CIRs in 2005. In 2006 this modulation stopped again, when the s/c was above 30 degree latitude. In order to understand this decay we present a detailed analysis of a series of recurrent Jovian electron decreases and its relation to the solar wind plasma parameters