Probing the Energetic Particle Environment near the Sun

NASA’s Parker Solar Probe mission1 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 accelerat...

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Published inNature (London) Vol. 576; no. 7786; pp. 223 - 227
Main Authors Mccomas, D J, Christian, E R, Cohen, C M S, Cummings, A C, Davis, A J, Desai, M I, Giacalone, J, Hill, M E, Joyce, C J, Krimigis, S M, Labrador, A W, Leske, R A, Malandraki, O, Matthaeus, W H, R L McNutt, Jr, Mewaldt, R A, Mitchell, D G, Posner, Arik, Rankin, J S, Roelof, E C, Schwadron, N A, Stone, E C, Szalay, J R, Wiedenbeck, M E, Bale, S D, Kasper, J C, Case, A W, Korreck, K E, Macdowall, R J, Pulupa, M, Stevens, M L, Rouillard, A P
Format Journal Article
LanguageEnglish
Published Goddard Space Flight Center Nature Research 12.12.2019
Nature Publishing Group UK
Nature Publishing Group
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Summary:NASA’s Parker Solar Probe mission1 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 ions2, and ‘gradual’ events3,4, 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 processes5. 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 spacecraft6. 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.
Bibliography:GSFC
GSFC-E-DAA-TN77243
Goddard Space Flight Center
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Author Contributions D.J.M. is ISʘIS PI and led the data analysis and writing of study. E.R.C is ISʘIS 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 Figures 3 and 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 ISʘIS SOC 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 Figures 1 and 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.
ISSN:0028-0836
1476-4687
DOI:10.1038/s41586-019-1811-1