A new study found that electrons can reach ultra-relativistic energies for very special conditions in the magnetosphere when space is devoid of plasma.
Recent measurements from NASA's Van Allen Probes spacecraft showed that electrons can reach ultra-relativistic energies flying at almost the speed of light. Hayley Allison, Yuri Shprits and collaborators from the German Research Centre for Geosciences have revealed under which conditions such strong accelerations occur. They had already demonstrated in 2020 that during solar storm plasma waves play a crucial role for that. However, it was previously unclear why such high electron energies are not achieved in all solar storms. In the journal Science Advances, Allison, Shprits and colleagues now show that extreme depletions of the background plasma density are crucial.