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Energy spectra of 3He-rich solar energetic particles associated with coronal waves  

Radoslav Bučík   Submitted: 2016-09-26 12:19

In addition to their anomalous abundances, 3He-rich solar energetic particles (SEPs) show puzzling energy spectral shapes varying from rounded forms to power laws where the later are characteristics of shock acceleration. Solar sources of these particles have been often associated with jets and narrow CMEs, which are the signatures of magnetic reconnection involving open field. Recent reports on new associations with large-scale EUV waves bring new insights on acceleration and transport of 3He-rich SEPs in the corona. We examined energy spectra for 32 3He-rich SEP events observed by ACE at L1 near solar minimum in 2007-2010 and compared the spectral shapes with solar flare signatures obtained from STEREO EUV images. We found the events with jets or brightenings tend to be associated with rounded spectra and the events with coronal waves with power laws. This suggests that coronal waves may be related to the unknown second stage mechanism commonly used to interpret spectral forms of 3He-rich SEPs.

Authors: R. Bučík, D. E. Innes, G. M. Mason, M. E. Wiedenbeck
Projects: ACE

Publication Status: JPCS (in press)
Last Modified: 2016-09-27 15:38
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Observations of solar X-ray and EUV jets and their related phenomena  

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

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  

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

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  

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

Publication Status: ApJ 833, 63 (2016)
Last Modified: 2017-04-19 19:55
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Association of 3He-Rich Solar Energetic Particles with Large-Scale Coronal Waves  

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) 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 3He-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 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

Publication Status: ApJ (in press)
Last Modified: 2016-09-26 09:54
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Case studies of multi-day 3He-rich solar energetic particle periods  

Radoslav Bučík   Submitted: 2016-09-25 02:53

Context: Impulsive solar energetic particle events in the inner heliosphere show the long-lasting enrichment of 3He. Aims: We study the source regions of long-lasting 3He-rich solar energetic particle (SEP) events Methods: We located the responsible open magnetic field regions, we combined potential field source surface extrapolations with the Parker spiral, and compared the magnetic field of the identified source regions with in situ magnetic fields. The candidate open field regions are active region plages. The activity was examined by using extreme ultraviolet images from the Solar Dynamics Observatory (SDO) and STEREO together with radio observations from STEREO and WIND. Results: Multi-day periods of 3He-rich SEP events are associated with ion production in single active region. Small flares or coronal jets are their responsible solar sources. We also find that the 3He enrichment may depend on the occurrence rate of coronal jets.

Authors: Nai-hwa Chen, Radoslav Bučík, Davina E. Innes, Glenn M. Mason
Projects: SDO-AIA,SDO-HMI

Publication Status: A&A 580, A16 (2015)
Last Modified: 2016-09-26 09:54
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Long-lived energetic particle source regions on the Sun  

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

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  

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

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  

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

Publication Status: ApJ 812, 53 (2015)
Last Modified: 2016-02-24 12:01
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Abstracts by Author
Energy spectra of 3He-rich solar energetic particles associated with coronal waves
Observations of solar X-ray and EUV jets and their related phenomena
Observations of solar X-ray and EUV jets and their related phenomena
Association of 3He-Rich Solar Energetic Particles with Large-Scale Coronal Waves
Association of 3He-Rich Solar Energetic Particles with Large-Scale Coronal Waves
Case studies of multi-day 3He-rich solar energetic particle periods
Long-lived energetic particle source regions on the Sun
Multi-spacecraft Observations of Recurrent 3He-rich Solar Energetic Particles
Observations of EUV Waves in 3He-rich Solar Energetic Particle Events

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