The origin of 3He-rich solar energetic particles
Final Report Abstract
We found very common (60%) association of 3He-rich SEP sources with large-scale coronal EUV waves. This discovery was achieved using multi-spacecraft EUV imaging observations on angularly separated STEREO that provided the most reliable identification of 3He-rich SEP sources that we have ever had. We conclude that 1) EUV waves may affect the injection of 3He-rich SEPs into interplanetary space, and 2) be responsible for the production of 3He-rich SEPs with power-law energy spectra. Sometimes coronal field may be extremely divergent facilitating access of 3He-rich SEPs to spacecraft foot-point separated by even 90° from the source flare. We found that the unwinding helical jets may be related to the production of high 3He and Fe enrichments. In view of present models, Alvfén waves of helical jets may account for the Fe enrichment and 3He enhancements may be related to efficient electron acceleration in the twisted magnetic configuration of the solar source. It has been confirmed that suprathermal 3He-rich SEPs have their source (a jet) in small and compact active regions at the boundary of coronal holes or at the plage regions. The sources are newly emerging with a few days of buildup phase. The high energy 3He-rich SEPs, in the most intense events examined in this project, have their source (a jet) at the boundary of large sunspots with complex magnetic configuration. Thus, the results of the project suggest that details of the underlying photospheric field may be important for the energy content of 3He-rich SEPs while the shape of the flare is more related to the ion enrichment and escape into interplanetary space. Though not yet fully explored, the knowledge gained in 3He-rich SEP research is apparently essential for acceleration and confinement of plasma in magnetic fusion devices. "Surprises" were: i) Unexpected observations of large-scale coronal waves in the solar source of 3He-rich SEPs with multi-point spacecraft, ii) extreme simultaneous enrichments in 3He and heavier ions (like Fe) in solar sources with unwinding jets, iii) the highest energy 3He-rich SEPs associated with largest sunspots in a solar cycle with the most complex magnetic configuration. The science results published in Bučík et al. 2015 and 2016 appeared: as MPS, UPJŠ Press Releases, NASA STEREO Science Highlight; in 70+ newspapers (e.g. BBC Sky at Night, The Independent, Die Welt, Die Zeit, Frankfurter Rundschau, NDR, ARTE, ORF, Der Standard); in AAS Press List. The animation of this result achieved 26k+views on YouTube. Furthermore, the results were posted on the official front page of the ACE mission (at Caltech) with 1.8M visitors (as one of the nineteen most important results in the last 20 years obtained by ACE). A video profile, where applicant (R. Bučík) is presenting project results, was recorded by Slovak Center of Scientific and Technical Information (Ministry of Education, Science, Research and Sport of the Slovak Republic) and included among 64 outstanding Slovak Scientists. A summary of all outreach activities can be found here https://radoslavbucik.wordpress.com/outreach/.
Publications
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(2018) 3 He-rich Solar Energetic Particles from Sunspot Jets. ApJ (The Astrophysical Journal) 869 (1) L21
Bučík, Radoslav; Wiedenbeck, Mark E.; Mason, Glenn M.; Gómez-Herrero, Raúl; Nitta, Nariaki V.; Wang, Linghua
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(2015), Observations of EUV waves in 3He-rich solar energetic particle events, Astrophys. J. 812, 53
Bučík, R., D. E. Innes, L.-J. Guo, G. M. Mason, M. E. Wiedenbeck
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(2016), Association of 3He-rich solar energetic particles with large-scale coronal waves, Astrophys. J. 833, 63
Bučík, R., D. E. Innes, G. M. Mason, M. E. Wiedenbeck
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(2016), Observations of solar X-ray and EUV jets and their related phenomena, Astron. Nachr. 337, 1024
Innes, D. E., R. Bučík, L.-J. Guo, N. V. Nitta
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(2018), 3He-rich solar energetic particles in helical jets on the Sun, Astrophys. J. 852, 76
Bučík, R., D. E. Innes, G. M. Mason, M. E. Wiedenbeck, R. Gómez-Herrero, N. V. Nitta
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(2018), Spectroscopic EUV observations of impulsive SEP event sources, Astron. & Astrophys. 617, A40
Bučík, R., A. Fludra, R. Gómez-Herrero, D. E. Innes, B. Kellet, R. Kumar, Š. Mackovjak
