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Probing the energetic particle environment near the Sun
D J McComas1, E R Christian2, C M S Cohen3
1Department of Astrophysical Sciences, Princeton University, Princeton, NJ, USA. dmccomas@princeton.edu.
Nature
|December 6, 2019
Summary
NASA's Parker Solar Probe observed energetic particles near the Sun, revealing diverse acceleration processes. These findings challenge existing models of solar energetic particle events and improve our understanding of space weather.
Area of Science:
- * Heliophysics and space plasma physics.
- * Solar energetic particle (SEP) acceleration and transport.
- * Inner heliosphere and solar corona physics.
Background:
- * Solar energetic particles (SEPs) are accelerated via 'impulsive' (solar flares) and 'gradual' (coronal mass ejections) events.
- * Previous observations, mostly at 1 astronomical unit, faced transport effects obscuring near-Sun acceleration physics.
- * Discrepancies in particle properties suggest complexities beyond the two-process model.
Purpose of the Study:
- * To investigate the near-Sun energetic particle radiation environment using Parker Solar Probe data.
- * To directly observe and analyze SEP acceleration and transport mechanisms close to the Sun.
- * To resolve ambiguities in current SEP acceleration models.
Main Methods:
- * In-situ measurements of energetic particles from Parker Solar Probe during its initial orbits.
- * Analysis of particle event characteristics, including energy spectra and composition.
- * Correlation of particle events with solar phenomena like flares and coronal mass ejections.
Main Results:
- * Observation of diverse energetic particle events, including impulsive and CME-related events, near the Sun.
- * Evidence of local and remote acceleration processes, including corotating interaction regions.
- * Direct data from the inner heliosphere challenging the simple two-process model of SEP acceleration.
Conclusions:
- * The near-Sun environment hosts a variety of SEP acceleration mechanisms.
- * Direct observations resolve ambiguities in understanding particle acceleration and transport.
- * Findings provide crucial insights into the physics governing solar energetic particles close to the Sun.
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