Solar Energetic Proton Events Observed by the High Energy Telescopes on the STEREO Spacecraft or at the Earth During the First Solar Orbit of STEREO A (2006 to 2023)

TL;DR

This paper compiles and analyzes over 450 solar energetic particle events observed by STEREO and Earth-based instruments from 2006 to 2023, offering insights into proton propagation and solar eruption relationships during Solar Cycle 24 and early 25.

Contribution

It updates the SEP event catalog with new observations from STEREO A and Earth, covering a full solar orbit and enhancing understanding of particle propagation in the heliosphere.

Findings

Approximately 450 SEP events cataloged from 2006 to 2023.

Insights into proton propagation in the inner heliosphere.

Correlation between solar eruptions and energetic particle events.

Abstract

The twin STEREO A and B spacecraft were launched in October 2006 into heliocentric orbits at around 1 AU, advancing ahead of or lagging behind Earth, respectively, at around 22 deg./year. The spacecraft provide in-situ observations of the solar wind and energetic particle populations, as well as remote sensing observations of solar activity and the corona. In particular, the High Energy Telescopes (HETs) on the STEREO spacecraft observe 0.7-4 MeV electrons and 13-100 MeV protons. This paper summarizes observations of solar energetic particle (SEP) events made by the STEREO HETs from the beginning of the mission through Solar Cycle 24 to December 2023, approaching the maximum of Solar Cycle 25 and encompassing STEREO A's first full orbit of the Sun relative to Earth, completed in August 2023; contact with STEREO B was lost in October 2014. Specifically, the catalog of SEP events including approximately 25 MeV protons observed by the STEREO HETs and/or instruments on spacecraft near Earth in Richardson et al. (2014) is updated to include around 450 SEP events and a total of around 1000 separate observations of these events from the various spacecraft locations. These extensive observations can provide unique insight into the propagation of energetic protons in the inner heliosphere and how the properties of the particle events are related to those of the associated solar eruptions.