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Probing the energetic particle environment near the Sun

McComas, D. J. and Cohen, C. M. S. and Cummings, A. C. and Davis, A. J. and Labrador, A. W. and Leske, R. A. and Mewaldt, R. A. and Stone, E. C. (2019) Probing the energetic particle environment near the Sun. Nature, 576 (7786). pp. 223-227. ISSN 0028-0836. https://resolver.caltech.edu/CaltechAUTHORS:20190827-123135234

[img] Image (JPEG) (Extended Data Fig. 1: Viewing geometry and observation of coronal mass ejection) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 2: CME model and comparison to magnetic field data) - Supplemental Material
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Abstract

NASA’s Parker Solar Probe mission recently plunged through the inner heliosphere of the Sun to its perihelia, about 24 million kilometres from the Sun. Previous studies farther from the Sun (performed mostly at a distance of 1 astronomical unit) indicate that solar energetic particles are accelerated from a few kiloelectronvolts up to near-relativistic energies via at least two processes: ‘impulsive’ events, which are usually associated with magnetic reconnection in solar flares and are typically enriched in electrons, helium-3 and heavier ions, and ‘gradual’ events, which are typically associated with large coronal-mass-ejection-driven shocks and compressions moving through the corona and inner solar wind and are the dominant source of protons with energies between 1 and 10 megaelectronvolts. However, some events show aspects of both processes and the electron–proton ratio is not bimodally distributed, as would be expected if there were only two possible processes. These processes have been very difficult to resolve from prior observations, owing to the various transport effects that affect the energetic particle population en route to more distant spacecraft. Here we report observations of the near-Sun energetic particle radiation environment over the first two orbits of the probe. We find a variety of energetic particle events accelerated both locally and remotely including by corotating interaction regions, impulsive events driven by acceleration near the Sun, and an event related to a coronal mass ejection. We provide direct observations of the energetic particle radiation environment in the region just above the corona of the Sun and directly explore the physics of particle acceleration and transport.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1038/s41586-019-1811-1DOIArticle
https://rdcu.be/bYiyQPublisherFree ReadCube access
ORCID:
AuthorORCID
McComas, D. J.0000-0001-6160-1158
Cohen, C. M. S.0000-0002-0978-8127
Cummings, A. C.0000-0002-3840-7696
Labrador, A. W.0000-0001-9178-5349
Leske, R. A.0000-0002-0156-2414
Mewaldt, R. A.0000-0003-2178-9111
Stone, E. C.0000-0002-2010-5462
Additional Information:© 2019 Springer Nature Limited. Received 28 June 2019; Accepted 05 September 2019; Published 04 December 2019. We are indebted to everyone who helped make the PSP mission possible. In particular, we thank all of the 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. This work was supported as a part of the PSP mission under contract NNN06AA01C. S.D.B. acknowledges the support of the Leverhulme Trust Visiting Professorship programme and A.P.R. acknowledges financial support from the ANR project COROSHOCK ANR-17-CE31-0006-01 and from the ERC project SLOW_SOURCE – DLV-819189. Data availability: All data used in this study is available to the public via NASA’s Space Physics Data Facility (SPDF) at https://spdf.gsfc.nasa.gov/. Author Contributions: D.J.M. is IS☉IS Principal Investigator (PI) and led the data analysis and writing of the study. E.R.C. is IS☉IS Deputy PI, helped develop EPI-Hi, and participated in the data analysis. C.M.S.C. helped develop EPI-Hi and participated in the data analysis. A.C.C. helped develop EPI-Hi and participated in the data analysis. A.J.D. helped develop EPI-Hi and participated in the data analysis. M.I.D. participated in the data analysis. J.G. participated in the data analysis. M.E.H. helped develop EPI-Lo and participated in the data analysis. C.J.J. produced Figs. 3, 4 and participated in the data analysis. S.M.K. participated in the data analysis. A.W.L. helped develop EPI-Hi and participated in the data analysis. R.A.L. helped develop EPI-Hi and participated in the data analysis. O.M. participated in the data analysis. W.H.M. participated in the data analysis. R.L.M. led the development of EPI-Lo and participated in the data analysis. R.A.M. helped develop EPI-Hi and participated in the data analysis. D.G.M. helped develop EPI-Lo and participated in the data analysis. A.P. participated in the data analysis. J.S.R. helped develop EPI-Hi and participated in the data analysis. E.C.R. participated in the data analysis. N.A.S. led the development of the IS☉IS Science Operations Center and participated in the data analysis. E.C.S. helped develop EPI-Hi and participated in the data analysis. J.R.S. led the development of the analysis tool, produced Figs. 1, 2, and participated in the data analysis. M.E.W. led the development of EPI-Hi and participated in the data analysis. S.D.B. is FIELDS PI and participated in the data analysis. J.C.K. is SWEAP PI and participated in the data analysis. A.W.C. helped develop SWEAP and participated in the data analysis. K.E.K. helped develop SWEAP and participated in the data analysis. R.J.M. helped develop FIELDS and participated in the data analysis. M.P. helped develop FIELDS and participated in the data analysis. M.L.S. helped develop SWEAP and participated in the data analysis. A.P.R. led the CME simulation work and participated in the data analysis. The authors declare no competing interests.
Group:Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NASANNN06AA01C
Leverhulme TrustUNSPECIFIED
Agence Nationale pour la Recherche (ANR)ANR-17-CE31-0006-01
European Research Council (ERC)819189
Subject Keywords:Particle astrophysics; Solar physics
Issue or Number:7786
Record Number:CaltechAUTHORS:20190827-123135234
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190827-123135234
Official Citation:McComas, D.J., Christian, E.R., Cohen, C.M.S. et al. Probing the energetic particle environment near the Sun. Nature 576, 223–227 (2019) doi:10.1038/s41586-019-1811-1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98275
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:04 Dec 2019 21:59
Last Modified:20 Feb 2020 14:33

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