SPEARHEAD Ulysses/KET electrons SEP catalogue

This catalogue contains Solar Energetic Electron (SEE) events identified in measurements from the Kiel Electron Telescope (KET) aboard the Ulysses spacecraft. The event search was performed using six-hour averaged electron count rates in the E12 channel, corresponding to electron energies above approximately 20 MeV. Candidate events were identified through statistically significant increases in three independent electron sub-channels (80<C2≤90, 90<C2≤100, and 100<C2≤110). An event was selected when the count rates in all three sub-channels exceeded three standard deviations above the mean background level calculated from the preceding seven days. To distinguish genuine solar energetic electron events from enhancements caused by Jovian electrons, which were frequently observed during Ulysses' encounters with Jupiter, the corresponding proton measurements were also examined. Solar energetic electron events are typically accompanied by increases in proton intensities, whereas Jovian electron enhancements are not. Therefore, candidate events were required to show a simultaneous increase in the P32 proton channel above the same statistical threshold. Event onset times were refined using measurements from the Ulysses High Energy Telescope (HET), which provides high-statistics observations of electrons in the 5–10 MeV energy range. The onset time was determined from 10-minute averaged count rates exceeding three standard deviations above the 48-hour pre-event background level for at least three consecutive measurements. Applying these criteria to the complete Ulysses mission data set (1990–2009) resulted in the identification of 13 clear solar energetic electron events with electron energies exceeding 20 MeV. The events were observed over a wide range of heliographic latitudes, from approximately −72° to +78°, providing a unique perspective on some of the highest-energy solar electron events recorded in the heliosphere. Most events occurred during periods of elevated solar activity associated with the maxima of Solar Cycles 22 and 23. The catalogue provides the event timings, observational parameters, and associated metadata for all identified events, supporting studies of particle acceleration, transport processes, and the latitudinal distribution of solar energetic particles throughout the heliosphere. In detail, the catalogue is structured as follows: Columns A and B: number and identification of the event Column A: Number in the catalogue Column B: Identifier: a link to the > 100 MeV protons catalogue by Vainio et al. (2024) is provided if the event is listed there. Columns C to M: Instrument data information Column C: Efficient energy determined by bow-tie analysis for times including the maximum period. Column D: Begin of the period for which we determined the background flux. The format is %Y-%m-%d %H:%M:%S+00:00". Column E: End of the period for which we determined the background flux. The format is %Y-%m-%d %H:%M:%S+00:00". Column F: Mean background flux of the channel (1/(s cm2 sr MeV)). Note, for KET the values are given as counts/second. Column G: Onset time determined by analyzing Ulysses HET. Column H: Onset time determined by eye Column I: Time of peak flux Column J: Countrate of subchannel 100<C2≤110 Column K: Begin of the period for which we determined the fluence. The format is %Y-%m-%d %H:%M:%S+00:00". Column L: End of the period for which we determined the fluence. The format is %Y-%m-%d %H:%M:%S+00:00". Column M: Fluence of the event [1/(cm2 sr MeV)] (The PHA statistics determine the time period). Column N - P: spacecraft location (Stoneyhurst) from Solar Mach Column N: radial distance in AU from the Sun Column O: spacecraft longitude Column P: spacecraft latitude Column Q: Any other comments