solar-terrestrial relations

The relativistic solar particle event on 28 October 2021: Evidence of particle acceleration within and escape from the solar corona

*Aims.* We analyse particle, radio, and X-ray observations during the first relativistic proton event of solar cycle 25 detected on Earth. The aim is to gain insight into the relationship between relativistic solar particles detected in space and the …

Multi-spacecraft observations of the structure of the sheath of an interplanetary coronal mass ejection and related energetic ion enhancement

*Context.* Sheath regions ahead of coronal mass ejections (CMEs) are large-scale heliospheric structures that form gradually with CME expansion and propagation from the Sun. Turbulent and compressed sheaths could contribute to the acceleration of …

Connecting solar flare hard X-ray spectra to in situ electron spectra. A comparison of RHESSI and STEREO/SEPT observations

*Aims.* We aim to constrain the acceleration, injection, and transport processes of flare-accelerated energetic electrons by comparing their characteristics at the Sun with those injected into interplanetary space. *Methods.* We have identified 17 …