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Observations of the 2019 April 4 Solar Energetic Particle Event at the Parker Solar Probe

Leske, R. A. and Christian, E. R. and Cohen, C. M. S. and Cummings, A. C. and Davis, A. J. and Desai, M. I. and Giacalone, J. and Hill, M. E. and Joyce, C. J. and Krimigis, S. M. and Labrador, A. W. and Malandraki, O. and Matthaeus, W. H. and McComas, D. J. and McNutt, R. L., Jr. and Mewaldt, R. A. and Mitchell, D. G. and Posner, A. and Rankin, J. S. and Roelof, E. C. and Schwadron, N. A. and Stone, E. C. and Szalay, J. R. and Wiedenbeck, M. E. and Vourlidas, A. and Bale, S. D. and MacDowall, R. J. and Pulupa, M. and Kasper, J. C. and Allen, R. C. and Case, A. W. and Korreck, K. E. and Livi, R. and Stevens, M. L. and Whittlesey, P. and Poduval, B. (2020) Observations of the 2019 April 4 Solar Energetic Particle Event at the Parker Solar Probe. Astrophysical Journal Supplement Series, 246 (2). Art. No. 35. ISSN 1538-4365. doi:10.3847/1538-4365/ab5712.

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A solar energetic particle event was detected by the Integrated Science Investigation of the Sun (IS⊙IS) instrument suite on Parker Solar Probe (PSP) on 2019 April 4 when the spacecraft was inside of 0.17 au and less than 1 day before its second perihelion, providing an opportunity to study solar particle acceleration and transport unprecedentedly close to the source. The event was very small, with peak 1 MeV proton intensities of ~0.3 particles (cm² sr s MeV)⁻¹, and was undetectable above background levels at energies above 10 MeV or in particle detectors at 1 au. It was strongly anisotropic, with intensities flowing outward from the Sun up to 30 times greater than those flowing inward persisting throughout the event. Temporal association between particle increases and small brightness surges in the extreme-ultraviolet observed by the Solar TErrestrial RElations Observatory, which were also accompanied by type III radio emission seen by the Electromagnetic Fields Investigation on PSP, indicates that the source of this event was an active region nearly 80° east of the nominal PSP magnetic footpoint. This suggests that the field lines expanded over a wide longitudinal range between the active region in the photosphere and the corona.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemISʘIS data and visualization tools ItemNASA Space Physics Data Facility
Leske, R. A.0000-0002-0156-2414
Christian, E. R.0000-0003-2134-3937
Cohen, C. M. S.0000-0002-0978-8127
Cummings, A. C.0000-0002-3840-7696
Desai, M. I.0000-0002-7318-6008
Hill, M. E.0000-0002-5674-4936
Joyce, C. J.0000-0002-3841-5020
Krimigis, S. M.0000-0003-2781-2386
Labrador, A. W.0000-0001-9178-5349
Malandraki, O.0000-0002-4751-6835
Matthaeus, W. H.0000-0001-7224-6024
McComas, D. J.0000-0001-6160-1158
Mewaldt, R. A.0000-0003-2178-9111
Mitchell, D. G.0000-0003-1960-2119
Posner, A.0000-0003-1572-8734
Rankin, J. S.0000-0002-8111-1444
Schwadron, N. A.0000-0002-3737-9283
Stone, E. C.0000-0002-2010-5462
Szalay, J. R.0000-0003-2685-9801
Wiedenbeck, M. E.0000-0002-2825-3128
Vourlidas, A.0000-0002-8164-5948
Bale, S. D.0000-0002-1989-3596
MacDowall, R. J.0000-0003-3112-4201
Pulupa, M.0000-0002-1573-7457
Kasper, J. C.0000-0002-7077-930X
Allen, R. C.0000-0003-2079-5683
Case, A. W.0000-0002-3520-4041
Korreck, K. E.0000-0001-6095-2490
Livi, R.0000-0002-0396-0547
Stevens, M. L.0000-0002-7728-0085
Whittlesey, P.0000-0002-7287-5098
Poduval, B.0000-0003-1258-0308
Additional Information:© 2020. The American Astronomical Society. Received 2019 September 27; revised 2019 October 31; accepted 2019 November 11; published 2020 February 3. Early Results from Parker Solar Probe: Ushering a New Frontier in Space Exploration This work was supported by NASA under contract NNN06AA01C. Parker Solar Probe was designed, built, and is now operated by the Johns Hopkins University Applied Physics Laboratory as part of NASA's Living With a Star (LWS) program. Support from the LWS management and technical team has played a critical role in the success of this mission. We appreciate the contributions of the many individuals who have made PSP the successful mission that it is, in particular the EPI-Hi engineers W. R. Cook, B. Kecman, G. Dirks, and N. Angold. We gratefully acknowledge the test and calibration support provided by Michigan State University's National Superconducting Cyclotron Laboratory, Texas A&M University's Cyclotron Institute, and the Lawrence Berkeley National Laboratory's 88-inch Cyclotron Laboratory. The ISʘIS data and visualization tools are available to the community at; data are also available via the NASA Space Physics Data Facility ( thank the GONG and Wilcox Solar Observatory teams for making their data readily accessible online. S.D.B. acknowledges the support of the Leverhulme Trust Visiting Professorship program.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Leverhulme TrustUNSPECIFIED
Subject Keywords:The Sun ; Solar energetic particles
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: The Sun (1693); Solar energetic particles (1491)
Record Number:CaltechAUTHORS:20200203-131825142
Persistent URL:
Official Citation:R. A. Leske et al 2020 ApJS 246 35
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101075
Deposited By: George Porter
Deposited On:03 Feb 2020 21:36
Last Modified:16 Nov 2021 17:58

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