A STATISTICAL STUDY OF SPECTRAL HARDENING IN SOLAR FLARES AND RELATED SOLAR ENERGETIC PARTICLE EVENTS

Journal Article · Sun Dec 20 04:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/707/2/1588· OSTI ID:21392521

Grayson, James A; Krucker, Saem ^[1]

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1. Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States)

Using hard X-ray observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we investigate the reliability of spectral hardening during solar flares as an indicator of related solar energetic particle (SEP) events at Earth. All RHESSI data are analyzed, from 2002 February through the end of Solar Cycle 23, thereby expanding upon recent work on a smaller sample of flares. Previous investigations have found very high success when associating soft-hard-harder (SHH) spectral behavior with energetic proton events, and confirmation of this link would suggest a correlation between electron acceleration in solar flares and SEPs seen in interplanetary space. In agreement with these past findings, we find that of 37 magnetically well-connected flares (W30-W90), 12 of 18 flares with SHH behavior produced SEP events and none of 19 flares without SHH behavior produced SEPs. This demonstrates a statistically significant dependence of SHH and SEP observations, a link that is unexplained in the standard scenario of SEP acceleration at the shock front of coronal mass ejections and encourages further investigation of the mechanisms which could be responsible.

• OSTI ID: 21392521
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 707; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
BARYONS
COSMIC PROTONS
COSMIC RADIATION
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
EMISSION
FERMIONS
GAMMA RADIATION
HADRONS
HARD X RADIATION
INTERPLANETARY SPACE
IONIZING RADIATIONS
LEPTONS
MAIN SEQUENCE STARS
MASS
NUCLEONS
PROTONS
RADIATIONS
SOLAR ACTIVITY
SOLAR CYCLE
SOLAR FLARES
SPACE
SPECTRAL HARDENING
STARS
STELLAR ACTIVITY
STELLAR FLARES
SUN
X RADIATION