Quiet time MEV electron increases at solar maximum: Ulysses cospin/ket observations

Abstract The Ulysses trajectory provides a unique opportunity to study the propagation of MeV electrons in a wide range of heliographic latitudes and during varying conditions in the inner heliosphere. In recent papers we reported Ulysses Kiel Electron Telescope (KET) observations from the Ulysses launch up to the end of the second fast latitude scan in late 2001. While the period until the beginning of 1998 has been consistently described by modulation models taking into account galactic cosmic rays as well as Jovian electrons, the observed electron intensity variation after 1998 needs further investigation. From 1998 onwards KET measures short term electron increases, which were not attributed to solar particle events. When space-probes approached Jupiter in the ecliptic plane such electron intensity increases have been reported and interpreted as a changing magnetic connection from the giant planet to the observer. In spring 2002 Ulysses was at ∼40° N heliographic latitude when KET observed a quiet time electron increase, which showed the same characteristic as the Jovian electron events measured by KET in 1991, when Ulysses was magnetically well connected to Jupiter. This leads to the conclusion that Jovian electron events can unambiguously be observed at heliographic latitudes beyond 40° N. In a Parker-like heliospheric magnetic field, however, there are no field lines connecting Jupiter and Ulysses at >40° N, and therefore, an efficient latitude transport is needed to account for the “high” electron intensities.