Acceleration of electrons and ions by an "almost" astrophysical shock in the heliosphere

TL;DR

This study reports on the first detailed in situ observations of a fast heliospheric shock by the Parker Solar Probe, demonstrating electron and ion acceleration consistent with astrophysical shock models, advancing understanding of particle acceleration in space.

Contribution

The paper provides the first in situ measurements of a near-parallel, high-speed heliospheric shock, confirming theoretical models of shock structure and particle acceleration in astrophysical environments.

Findings

Electrons accelerated up to 6 MeV at the shock

Evidence of variable shock structure capable of ion acceleration

Shock structure aligns with astrophysical shock models

Abstract

Collisionless shock waves, ubiquitous in the universe, are crucial for particle acceleration in various astrophysical systems. Currently, the heliosphere is the only natural environment available for their in situ study. In this work, we showcase the collective acceleration of electrons and ions by one of the fastest in situ shocks ever recorded, observed by the pioneering Parker Solar Probe at only 34.5 million kilometers from the Sun. Our analysis of this unprecedented, near-parallel shock shows electron acceleration up to 6 MeV amidst intense multi-scale electromagnetic wave emissions. We also present evidence of a variable shock structure capable of injecting and accelerating ions from the solar wind to high energies through a self-consistent process. The exceptional capability of the probe's instruments to measure electromagnetic fields in a shock traveling at 1% the speed of light has enabled us, for the first time, to confirm that the structure of a strong heliospheric shock aligns with theoretical models of strong shocks observed in astrophysical environments. This alignment offers viable avenues for understanding astrophysical shock processes and the acceleration of charged particles.