IPST, University of Maryland, College Park, MD
The Anatomy of Solar Energetic Particle Events:Reservoirs, Onsets, and the Streaming Limit
Large solar energetic-particle (SEP) events accelerated by shock waves driven out from the Sun by coronal mass ejections may have several different temporal phases arising from the physics controlling the particles. Major differences in the time variations of the SEP events result primarily from different cuts through the evolving spatial distribution of the particles at different longitudes and radial distances. This space-time distribution ends with the spatially- and spectrally-invariant “reservoir” region behind the shock. In the onsets of the events, velocity dispersion determines the time of the initial acceleration and particle release which usually occurs well after photon maxima. Delayed acceleration is seen from the flanks of the shock, possibly from a local decrease in the shock speed. Intensities on the early intensity plateau are streaming limited by proton-amplified waves that throttle SEP transport and couple ions of different energies to produce intensity peaks at ~10 MeV/n. Different physics determines what we see in different phases of the events.
Dr. Donald V. Reames is being considered for appointment to Senior Research Scientist in the Institute for Physical Science and Technology.