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Published February 2020 | Accepted Version + Published
Journal Article Open

Observations of Energetic-particle Population Enhancements along Intermittent Structures near the Sun from the Parker Solar Probe


Observations at 1 au have confirmed that enhancements in measured energetic-particle (EP) fluxes are statistically associated with "rough" magnetic fields, i.e., fields with atypically large spatial derivatives or increments, as measured by the Partial Variance of Increments (PVI) method. One way to interpret this observation is as an association of the EPs with trapping or channeling within magnetic flux tubes, possibly near their boundaries. However, it remains unclear whether this association is a transport or local effect; i.e., the particles might have been energized at a distant location, perhaps by shocks or reconnection, or they might experience local energization or re-acceleration. The Parker Solar Probe (PSP), even in its first two orbits, offers a unique opportunity to study this statistical correlation closer to the corona. As a first step, we analyze the separate correlation properties of the EPs measured by the Integrated Science Investigation of the Sun (IS⊙IS) instruments during the first solar encounter. The distribution of time intervals between a specific type of event, i.e., the waiting time, can indicate the nature of the underlying process. We find that the IS⊙IS observations show a power-law distribution of waiting times, indicating a correlated (non-Poisson) distribution. Analysis of low-energy (~15 – 200 keV/nuc) IS⊙IS data suggests that the results are consistent with the 1 au studies, although we find hints of some unexpected behavior. A more complete understanding of these statistical distributions will provide valuable insights into the origin and propagation of solar EPs, a picture that should become clear with future PSP orbits.

Additional Information

© 2020. The American Astronomical Society. Received 2019 September 14; revised 2019 November 29; accepted 2019 December 16; published 2020 February 3. Early Results from Parker Solar Probe: Ushering a New Frontier in Space Exploration Parker Solar Probe was designed, built, and is now operated by the Johns Hopkins Applied Physics Laboratory as part of NASA's Living with a Star (LWS) program (contract NNN06AA01C). Support from the LWS management and technical team has played a critical role in the success of the Parker Solar Probe mission. We are deeply indebted to everyone who helped make the PSP mission possible. In particular, we thank all of the outstanding scientists, engineers, technicians, and administrative support people across all of the IS⊙IS institutions that produced and supported the IS⊙IS instrument suite and support its operations and the scientific analysis of its data. We also thank the FIELDS and SWEAP teams for cooperation. The IS⊙IS data and visualization tools are available to the community at: https://spacephysics.princeton.edu/missions-instruments/isois; data are also available via the NASA Space Physics Data Facility (https://spdf.gsfc.nasa.gov/). This research was partially supported by the Parker Solar Probe Plus project through Princeton/IS⊙IS subcontract SUB0000165, and in part by NSF-SHINE AGS-1460130, NASA Heliospheric Guest Investigator grant No. 80NSSC19K0284, and grant RTA6280002 from Thailand Science Research and Innovation. S.D.B. acknowledges the support of the Leverhulme Trust Visiting Professorship program.

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August 22, 2023
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