Seminar: Radial and Temporal Evolution of SIRs and CIRs

Wednesday, November 04, 2020 - 3:00pm to 4:00pm

Speaker: Robert C. Allen, Space Physicist at the Johns Hopkins University Applied Physics Laboratory

Abstract: Parker Solar Probe, as part of the Heliophysics System Observatory, provides a unique opportunity to better understand the radial and temporal evolution of stream interaction regions (SIRs) and co-rotating interaction regions (CIRs). SIRs and CIRs are known to evolve both with radial distance as the structures propagate from the Sun, as well as in time, as the structures co-rotate. While earlier observations were able to investigate the radial evolution of SIRs in a statistical sense, simultaneous, coordinated measurements at different radial distances were unavailable to probe the spatial variation and evolution of SIRs/CIRs unambiguously. Studies involving STEREO, ACE, and Wind have been able to investigate temporal variations of SIRs/CIRs; however, these measurements are all at the same radial distance. With PSP measurements, we have identified SIRs/CIRs for the first five orbits at various radial distances along the PSP orbit, as well as SIR/CIR events with favorable conjunctions between PSP and STEREO-A, Wind, and ACE. Here we focus on two such events, and examine the temporal and radial evolution of the SIRs/CIRs, particularly focusing on the energetic particle population at the SIR/CIR interface. These events will also be put into a broader historical context through comparisons to observations from the Helios era. The PSP observations, in concert with observations at 1 au, enable us to dive further into the different acceleration and transport mechanisms of suprathermal to energetic particle populations associated with SIRs/CIRs.

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