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Small, Low-energy, Dispersive Solar Energetic Particle Events Observed by Parker Solar Probe

Hill, M. E. and Mitchell, D. G. and Allen, R. C. and de Nolfo, G. A. and Vourlidas, A. and Brown, L. E. and Jones, S. I. and McComas, D. J. and McNutt, R. L., Jr. and Mitchell, J. G. and Szalay, J. R. and Wallace, S. and Arge, C. N. and Christian, E. R. and Cohen, C. M. S. and Crew, A. B. and Desai, M. I. and Giacalone, J. and Henney, C. J. and Joyce, C. J. and Krimigis, S. M. and Leske, R. A. and Mewaldt, R. A. and Nelson, K. S. and Roelof, E. C. and Schwadron, N. A. and Wiedenbeck, M. E. (2020) Small, Low-energy, Dispersive Solar Energetic Particle Events Observed by Parker Solar Probe. Astrophysical Journal Supplement Series, 246 (2). Art. No. 65. ISSN 1538-4365.

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The Energetic Particle Instrument–Low Energy (EPI-Lo) experiment has detected several weak, low-energy (~30–300 keV nucleon⁻¹) solar energetic particle (SEP) events during its first two closest approaches to the Sun, providing a unique opportunity to explore the sources of low-energy particle acceleration. As part of the Parker Solar Probe (PSP) Integrated Science Investigation of the Sun (IS⊙IS) suite, EPI-Lo was designed to investigate the physics of energetic particles; however, in the special lowest-energy "time-of-flight only" product used in this study, it also responds to solar photons in a subset of approximately sunward-looking apertures lacking special light-attenuating foils. During the first three perihelia, in a frame rotating with the Sun, PSP undergoes retrograde motion, covering a 17° heliographic longitudinal range three times during the course of the ~11-day perihelion passes, permitting a unique spatial and temporal study into the location, correlation, and persistence of previously unmeasurable SEPs. We examine the signatures of these SEPs (during the first PSP perihelion pass only) and the connection to possible solar sources using remote observations from the Solar Dynamics Observatory (SDO), the Solar TErrestrial RElations Observatory (STEREO), and the ground-based Global Oscillation Network Group (GONG). The orientation of the Sun relative to STEREO, SDO, and GONG makes such identifications challenging, but we do have several candidates, including an equatorial coronal hole at a Carrington longitude of ~335°. To analyze observations from EPI-Lo, which is a new type of particle instrument, we examine instrumental effects and provide a preliminary separation of the ion signal from the photon background.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemIS⊙IS data and visualization tools ItemNASA Space Physics Data Facility
Hill, M. E.0000-0002-5674-4936
Mitchell, D. G.0000-0003-1960-2119
Allen, R. C.0000-0003-2079-5683
de Nolfo, G. A.0000-0002-3677-074X
Vourlidas, A.0000-0002-8164-5948
Jones, S. I.0000-0001-9498-460X
McComas, D. J.0000-0001-6160-1158
McNutt, R. L., Jr.0000-0002-4722-9166
Mitchell, J. G.0000-0003-4501-5452
Szalay, J. R.0000-0003-2685-9801
Wallace, S.0000-0002-1091-4688
Christian, E. R.0000-0003-2134-3937
Cohen, C. M. S.0000-0002-0978-8127
Crew, A. B.0000-0002-7493-2682
Desai, M. I.0000-0002-7318-6008
Henney, C. J.0000-0002-6038-6369
Joyce, C. J.0000-0002-3841-5020
Krimigis, S. M.0000-0003-2781-2386
Leske, R. A.0000-0002-0156-2414
Mewaldt, R. A.0000-0003-2178-9111
Nelson, K. S.0000-0003-3807-4518
Roelof, E. C.0000-0002-2270-0652
Schwadron, N. A.0000-0002-3737-9283
Wiedenbeck, M. E.0000-0002-2825-3128
Additional Information:© 2020. The American Astronomical Society. Received 2019 October 4; revised 2019 November 15; accepted 2019 November 17; published 2020 February 3. Early Results from Parker Solar Probe: Ushering a New Frontier in Space Exploration This work was supported by NASA's Parker Solar Probe mission, contract NNN06AA01C. We are indebted to the exceptional, dedicated efforts of those who have made this mission and this experiment possible, in particular the engineers, scientist, and administrators who designed and built EPI-Lo. P. Kollmann, J. Peachy, and J. Vandegriff (at JHU/APL) are owed special thanks for their contribution to the scientific configuration and instrumental analysis of EPI-Lo. STEREO work is supported by NASA grant 80NSSC19K1261 (A.V.). This work utilizes data produced collaboratively between Air Force Research Laboratory (AFRL) and the National Solar Observatory. The ADAPT model development is supported by AFRL. The IS⊙IS data and visualization tools are available to the community at; data are also available via the NASA Space Physics Data Facility (
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Air Force Research Laboratory (AFRL)UNSPECIFIED
Subject Keywords:The Sun ; Interplanetary particle acceleration ; Solar energetic particles ; Space vehicle instruments ; Solar flares ; Michelson interferometers ; Solar extreme ultraviolet emission ; Solar filament eruptions ; Quiet Sun ; Solar telescopes ; Solar coronal mass ejections ; Space probes
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: The Sun (1693); Interplanetary particle acceleration (826); Solar energetic particles (1491); Space vehicle instruments (1548); Solar flares (1496); Michelson interferometers (1044); Solar extreme ultraviolet emission
Record Number:CaltechAUTHORS:20200203-092722235
Persistent URL:
Official Citation:M. E. Hill et al 2020 ApJS 246 65
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101067
Deposited By: George Porter
Deposited On:03 Feb 2020 23:36
Last Modified:03 Feb 2020 23:36

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