Case studies of multi-day 3 He-rich solar energetic particle periods

Innes

Mason

et al. 2018

ApJ

Self Cite

Particle acceleration in stellar flares is ubiquitous in the Universe, however, our Sun is the only astrophysical object where energetic particles and their source flares can both be observed. The acceleration mechanism in solar flares, tremendously enhancing (up to a factor of ten thousand) rare elements like 3 He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we present some of the most intense 3 He-and Fe-rich solar energetic particle events ever reported. The events were accompanied by non-relativistic electron events and type III radio bursts. The corresponding high-resolution, extreme-ultraviolet imaging observations have revealed for the first time a helical structure in the source flare with a jet-like shape. The helical jets originated in relatively small, compact active regions, located at the coronal hole boundary. A mini-filament at the base of the jet appears to trigger these events. The events were observed with the two Solar Terrestrial Relations Observatories STEREO on the backside of the Sun, during the period of increased solar activity in 2014. The helical jets may be a distinct feature of these intense events that is related to the production of high 3 He and Fe enrichments.

Section: Introduction Particle Acceleration In Solar Flaresmentioning

confidence: 99%

³He-rich Solar Energetic Particles in Helical Jets on the Sun

Innes

Mason

et al. 2018

ApJ

Self Cite

“…Though they are numerous these features make them a less explored phenomenon. Solar sources of 3 He-rich SEPs have been often associated with coronal X-ray and EUV jets (e.g., Nitta et al 2006Nitta et al , 2008Wang et al 2006;Bučík et al 2014;Chen et al 2015;Innes et al 2016) which sometimes show a high altitude extension in jet-like CMEs (Kahler et al 2001;Wang et al 2006Wang et al , 2012. Jets have been considered to be a signature of magnetic reconnection involving open field (e.g., Shibata et al 1992).…”

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confidence: 99%

“…References-(1) Wiedenbeck et al (2010b); (2) Mason et al (2009); (3) Wiedenbeck et al (2013); (4) Bučík et al (2015); (5) Nitta et al (2015); (6) Bučík et al (2013); (7) Chen et al (2015).…”

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confidence: 99%

ASSOCIATION OF ³He-RICH SOLAR ENERGETIC PARTICLES WITH LARGE-SCALE CORONAL WAVES

Innes

Mason

et al. 2016

ApJ

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Small3 He-rich solar energetic particle (SEP) events have been commonly associated with extremeultraviolet (EUV) jets and narrow coronal mass ejections (CMEs) which are believed to be the signatures of magnetic reconnection involving field lines open to interplanetary space. The elemental and isotopic fractionation in these events are thought to be caused by processes confined to the flare sites. In this study we identify 32 3 He-rich SEP events observed by the Advanced Composition Explorer near the Earth during the solar minimum period 2007-2010 and examine their solar sources with the high resolution Solar Terrestrial Relations Observatory (STEREO) EUV images. Leading the Earth, STEREO-A provided for the first time a direct view on 3 He-rich flares, which are generally located on the Sun's western hemisphere. Surprisingly, we find that about half of the 3 He-rich SEP events in this survey are associated with large-scale EUV coronal waves. An examination of the wave front propagation, the source-flare distribution and the coronal magnetic field connections suggests that the EUV waves may affect the injection of 3 He-rich SEPs into interplanetary space.

“…Early studies of 3 He-rich SEP events showed an association with small area Hα (6563Å) 'visible' flares (Zwickl et al 1978;Reames et al 1985;Kahler et al 1987). Further studies have shown that flares associated with 3 He-rich SEPs are commonly observed as collimated or jet-like forms in EUV/X-ray images (Nitta et al 2006(Nitta et al , 2008(Nitta et al , 2015Bučík et al 2014Bučík et al , 2018bChen et al 2015; (Kahler et al 2001;Reames et al 2014b;Wang et al 2012Wang et al , 2016Bronarska et al 2018). The events with higher 3 He enrichment are coupled with narrow CMEs with low speeds much more strongly than events with lower enrichment (Reames et al 2014b).…”

Section: Jetsmentioning

confidence: 99%

3He-Rich Solar Energetic Particles: Solar Sources

2020

Space Sci Rev

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3 He-rich solar energetic particles (SEPs), showing up to a 10,000-fold abundance enhancement of rare elements like 3 He or ultra-heavy nuclei, have been a puzzle for more than 50 years. One reason for the current lack of understanding of 3 He-rich SEPs is the difficulty resolving the source regions of these commonly occurring events. Since their discovery, there has been strong evidence that 3 Herich SEP production is associated with flares on the Sun. Anomalous abundances of 3 He-rich SEPs have been attributed to a unique acceleration mechanism that must routinely operate at flare sites. Flares associated with 3 He-rich SEPs have been often observed in jet-like forms indicating an acceleration in magnetic reconnection involving field lines open to interplanetary space. Owing to a fleet of spacecraft around the Sun, providing a greatly improved resolution of solar imaging observations, 3 He-rich SEP sources are now explored in unprecedented detail. This paper outlines the current understanding of 3 He-rich SEPs, mainly focusing on their solar sources.