3-20 MeV electrons in the inner three-dimensional heliosphere at solar maximum: Ulysses COSPIN/KET observations

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. From the Ulysses launch up to the beginning of 1998, the 3-10 MeV electron count rate of the COSPIN/KET instrument has been consistently described by modulation models taking into account Galactic cosmic rays as well as Jovian electrons. In this paper we focus on the MeV electron observations from 1998 onward, covering Ulysses' second out-of-ecliptic path, which was performed under solar maximum conditions. In contrast to our expectations, the electron intensity stayed at approximately the same level as the one observed in 1991 when Ulysses was magnetically well connected to Jupiter. In this paper we report on the discovery of short-term 3-10 MeV and 7-20 MeV electron intensity increases at the highest southern heliographic latitudes, which are not correlated with solar particle events.