Time evolution of stream interaction region energetic particle spectra in the inner heliosphere
Creators
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Joyce, C. J.1
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McComas, D. J.1
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Schwadron, N. A.1, 2
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Christian, E. R.3
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Wiedenbeck, M. E.4
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McNutt, R. L.5
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Cohen, C. M. S.6
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Leske, R. A.6
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Mewaldt, R. A.6
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Stone, E. C.6
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Labrador, A. W.6
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Davis, A. J.6
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Cummings, A. C.6
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Mitchell, D. G.5
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Hill, M. E.5
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Roelof, E. C.5
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Allen, R. C.5
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Szalay, J. R.1
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Rankin, J. S.1
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Desai, M. I.7, 8
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Giacalone, J.9
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Matthaeus, W. H.10
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Bale, S. D.11, 12
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Kasper, J. C.13
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1.
Princeton University
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2.
University of New Hampshire
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3.
Goddard Space Flight Center
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4.
Jet Propulsion Lab
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5.
Johns Hopkins University Applied Physics Laboratory
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6.
California Institute of Technology
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7.
Southwest Research Institute
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The University of Texas at San Antonio
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9.
University of Arizona
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University of Delaware
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11.
University of California, Berkeley
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12.
Imperial College London
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13.
University of Michigan–Ann Arbor
Abstract
We analyze an energetic proton event associated with a stream interaction region (SIR) that was observed at Parker Solar Probe on day 320 of 2018 when the spacecraft was just 0.34 AU from the Sun. Using the Integrated Science Investigation of the Sun instrument suite, we perform a spectral analysis of the event and show how the observed spectra evolve over the course of the event. We find that the spectra from the first day of the event are much more consistent with local acceleration at a weak compression, while spectra from later on are more typical of SIR-related events in which particles accelerated at distant shocks dominate. After the first day, the spectra remain approximately constant, which indicates that the modulation of energetic particles during transit from the presumed source region is weaker than previously thought. We argue that these observations can be explained by a sub-Parker spiral magnetic field structure connecting the spacecraft to a source region in the SIR that is relatively close to the Sun. We further propose that acceleration at weak, pre-shock compressions likely plays an important role in observations of SIR-related events in the inner heliosphere and that future modelling of such events should consider acceleration all along the compression region, not just at the distant shock region.
Additional Information
© ESO 2021. Article published by EDP Sciences. Received 2 September 2020; Accepted 30 March 2021. Published online 02 June 2021. This work was supported as a part of the Integrated Science Investigations of the Sun on NASA's Parker Solar Probe mission, under contract NNN06AA01C. 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/).Attached Files
Published - aa39330-20.pdf
Files
aa39330-20.pdf
Additional details
Identifiers
- Eprint ID
- 109438
- Resolver ID
- CaltechAUTHORS:20210608-095304738
Related works
- Describes
- https://spacephysics.princeton.edu/missions-instruments/isois (URL)
- https://spdf.gsfc.nasa.gov (URL)
Funding
- NASA
- NNN06AA01C
Dates
- Created
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2021-06-09Created from EPrint's datestamp field
- Updated
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2021-06-09Created from EPrint's last_modified field
Caltech Custom Metadata
- Caltech groups
- Space Radiation Laboratory