3He-rich Solar Energetic Particles in Helical Jets on the Sun |
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Radoslav Bučík Submitted: 2018-03-29 11:56
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 10,000) rare elements like 3He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we present some of the most intense 3He- and Fe-rich solar energetic particle events ever reported. The events were accompanied by nonrelativistic 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 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 3He and Fe enrichments.
Authors: R. Bučík, D. E. Innes, G. M. Mason, M. E. Wiedenbeck, R. Gomez-Herrero, N. V. Nitta
Projects: None
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Publication Status: ApJ 852:76 (2018)
Last Modified: 2018-04-04 12:17
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Observations of solar X-ray and EUV jets and their related phenomena |
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Radoslav Bučík Submitted: 2016-09-25 03:06
Solar jets are fast-moving, elongated brightenings related to ejections seen in both images and spectra on all scales from barely visible chromospheric jets to coronal jets extending up to a few solar radii. The largest, most powerful jets are the source of type III radio bursts, energetic electrons and ions with greatly enhanced 3He and heavy element abundances. The frequent coronal jets from polar and equatorial coronal holes may contribute to the solar wind. The primary acceleration mechanism for all jets is believed to be release of magnetic stress via reconnection; however the energy buildup depends on the jets' source environment. In this review, we discuss how certain features of X-ray and EUV jets, such as their repetition rate and association with radio emission, depends on their underlying photospheric field configurations (active regions, polar and equatorial coronal holes, and quiet Sun).
Authors: Davina Innes, Radoslav Bučík, Li-Jia Guo, Nariaki Nitta
Projects: SDO-AIA,SDO-HMI
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Publication Status: Astronomische Nachrichten 337, 1024 (2016)
Last Modified: 2017-04-19 19:54
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Observations of solar X-ray and EUV jets and their related phenomena |
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Radoslav Bučík Submitted: 2016-09-25 03:06
Solar jets are fast-moving, elongated brightenings related to ejections seen in both images and spectra on all scales from barely visible chromospheric jets to coronal jets extending up to a few solar radii. The largest, most powerful jets are the source of type III radio bursts, energetic electrons and ions with greatly enhanced 3He and heavy element abundances. The frequent coronal jets from polar and equatorial coronal holes may contribute to the solar wind. The primary acceleration mechanism for all jets is believed to be release of magnetic stress via reconnection; however the energy buildup depends on the jets' source environment. In this review, we discuss how certain features of X-ray and EUV jets, such as their repetition rate and association with radio emission, depends on their underlying photospheric field configurations (active regions, polar and equatorial coronal holes, and quiet Sun).
Authors: Davina Innes, Radoslav Bučík, Li-Jia Guo, Nariaki Nitta
Projects: SDO-AIA,SDO-HMI
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Publication Status: Astronomische Nachrichten (in press)
Last Modified: 2016-09-26 09:54
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Association of 3He-Rich Solar Energetic Particles with Large-Scale Coronal Waves |
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Radoslav Bučík Submitted: 2016-09-25 02:59
Small, 3He-rich solar energetic particle (SEP) events have been commonly associated with extreme-ultraviolet (EUV) jets and narrow coronal mass ejections (CMEs) that 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 3He-rich SEP events observed by the Advanced Composition Explorer, near the Earth, during the solar minimum period 2007-2010, and we examine their solar sources with the high resolution Solar Terrestrial Relations Observatory (STEREO) EUV images. Leading the Earth, STEREO-A has provided, for the first time, a direct view on 3He-rich flares, which are generally located on the Sun's western hemisphere. Surprisingly, we find that about half of the 3He-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 3He-rich SEPs into interplanetary space.
Authors: Radoslav Bučík, Davina E. Innes, Glenn M. Mason, Mark E. Wiedenbeck
Projects: STEREO
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Publication Status: ApJ 833, 63 (2016)
Last Modified: 2017-04-19 19:55
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Long-lived energetic particle source regions on the Sun |
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Radoslav Bučík Submitted: 2016-02-21 06:26
Discovered more than 40 years ago, impulsive solar energetic particle (SEP) events are still poorly understood. The enormous abundance enhancement of the rare 3He isotope is the most striking feature of these events, though large enhancements in heavy and ultra-heavy nuclei are also observed. Recurrent 3He-rich SEPs in impulsive events have only been observed for limited time periods, up to a few days which is typically the time that a single stationary spacecraft is magnetically connected to the source active regions on the Sun. With the launch of the two STEREO spacecraft we now have the possibility of longer connection time to solar active regions. We examined the evolution of source regions showing repeated 3He-rich SEP emissions for relatively long time periods. We found that recurrent 3He-rich SEPs in these long-lived sources occur after the emergence of magnetic flux.
Authors: Bučík, R.; Innes, D. E.; Chen, N. H.; Mason, G. M.; Gomez-Herrero, R.; Wiedenbeck, M. E.
Projects: STEREO
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Publication Status: J. Phys. Conf. Ser. 642, 012002 (2015)
Last Modified: 2016-02-24 12:02
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Multi-spacecraft Observations of Recurrent 3He-rich Solar Energetic Particles |
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Radoslav Bučík Submitted: 2016-02-21 06:01
We study the origin of 3He-rich solar energetic particles (<1 MeV nucleon?1) that are observed consecutively on STEREO-B, Advanced Composition Explorer (ACE), and STEREO-A spacecraft when they are separated in heliolongitude by more than 90?. The 3He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE 3He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 3He-rich events with the same sizeable active region (AR) producing X-ray flares accompanied by prompt electron events, when it was near the west solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous 3He enrichment, lacking solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged AR near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of (1) solar regions with long-lasting conditions for 3He acceleration and (2) solar energetic 3He that is temporarily confined/re-accelerated in interplanetary space.
Authors: Bučík, R.; Innes, D. E.; Mall, U.; Korth, A.; Mason, G. M.; Gomez-Herrero, R.
Projects: STEREO
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Publication Status: ApJ 786, 71 (2014)
Last Modified: 2016-02-24 12:02
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Observations of EUV Waves in 3He-rich Solar Energetic Particle Events |
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Radoslav Bučík Submitted: 2016-02-21 05:35
Small 3He-rich solar energetic particle (SEP) events with their anomalous abundances, markedly different from the solar system, provide evidence for a unique acceleration mechanism that operates routinely near solar active regions. Although the events are sometimes accompanied by coronal mass ejections (CMEs), it is believed that mass and isotopic fractionation is produced directly in the flare sites on the Sun. We report on a large-scale extreme-ultraviolet (EUV) coronal wave observed in association with 3He-rich SEP events. In the two examples discussed, the observed waves were triggered by minor flares and appeared concurrently with EUV jets and type III radio bursts, but without CMEs. The energy spectra from one event are consistent with so-called class-1 (characterized by power laws) 3He-rich SEP events, while the other with class-2 (characterized by rounded 3He and Fe spectra), suggesting different acceleration mechanisms in the two. The observation of EUV waves suggests that large-scale disturbances, in addition to more commonly associated jets, may be responsible for the production of 3He-rich SEP events.
Authors: Bučík, R.; Innes, D. E.; Guo, L.; Mason, G. M.; Wiedenbeck, M. E.
Projects: STEREO
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Publication Status: ApJ 812, 53 (2015)
Last Modified: 2016-02-24 12:01
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