Measurements of ultra-relativistic electrons during solar energetic particle events - Results from the Ulysses Kiel Electron Telescope

Solar energetic particle (SEP) events are increases of ions and electrons causedby solar activity namely flares and coronal mass ejections. While the mostenergetic ion population is well studied, SEP events accelerating electrons above20 MeV have only been reported from measurements by ISEE III in the 1980’sand the Kiel Electron Telescope (KET).The KET aboard Ulysses launched in 1990 and measured the electron flux inthe energy range from 4 MeV to above 6 GeV. Here we report on observationsof ultra-relativistic electrons and show spectra of electron events during solarcycle 22 and 23 until the end of 2008. The maximum electron energy exceeded100 MeV during the August 16, 2001 SEP event.This study has received funding from the European Union’s Horizon 2020research and innovation programme under grant agreement No. 101004159(SPEARHEAD).