ARE THERE TWO DISTINCT SOLAR ENERGETIC PARTICLE RELEASES IN THE 2012 MAY 17 GROUND LEVEL ENHANCEMENT EVENT?

Journal Article · Sat Feb 20 04:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/818/2/169· OSTI ID:22521525

Ding, Liu-Guan ^[1]; Jiang, Yong; Li, Gang ^[2]

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1. School of Physics and Optoelectronic Engineering, Institue of Space Weather, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, 210044 (China)
2. College of Math and Statistics, Institue of Space Weather, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, 210044 (China)

We examine ion release times in the solar vicinity for the 2012 May 17 Ground Level Enhancement event using the velocity dispersion analysis method. In situ energetic proton data from Solar and Heliospheric Observatory (SOHO)/Energetic and Relativistic Nuclei and Electron and Geostationary Operational Environmental Satellite are used. We find two distinct releases of Solar Energetic Particles (SEPs) near the Sun, separated by ∼40 minutes. From soft X-ray observations, we find that the first release coincides with the solar flare eruption: the release starts from the flare onset and ends near the peak of the soft X-ray; type-III radio bursts also occur when the release starts. A type II radio burst may also start at the begining of the release. However, the associated Coronal Mass Ejection (CME) only has a height of 0.08R{sub s} from extrapolation of SOHO/LASCO data. At the start of the second release, the CME propagates to more than 8.4R{sub s} in height, and there are signatures of an enhanced type II radio burst. The time-integrated spectra for the two releases differ. The spectrum for the second release shows the common double-power-law feature of gradual SEP events. The spectrum for the first release does not resemble power laws because there is considerable modulation at lower energies. Based on our analysis, we suggest that SEPs of the first release were dominated by particles accelerated at the flare, and those of the second release were dominated by particles accelerated at the associated CME-driven shock. Our study may be important to understand certain extreme SEP events.

• OSTI ID: 22521525
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 818; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
EXTRAPOLATION
GOES SATELLITES
HELIOSPHERE
IONS
MASS
MODULATION
RELATIVISTIC RANGE
SOFT X RADIATION
SOLAR FLARES
SOLAR PROTONS
SOLAR RADIO BURSTS
SUN
VELOCITY