A COMPARISON OF SOLAR ENERGETIC PARTICLE EVENT TIMESCALES WITH PROPERTIES OF ASSOCIATED CORONAL MASS EJECTIONS

The dependence of solar energetic proton (SEP) event peak intensities Ip on properties of associated coronal mass ejections (CMEs) has been extensively examined, but the dependence of SEP event timescales is not well known. We define three timescales of 20 MeV SEP events and ask how they are related...

Full description

Saved in:
Bibliographic Details
Published inThe Astrophysical journal Vol. 769; no. 2; pp. 1 - 10
Main Author Kahler, S W
Format Journal Article
LanguageEnglish
Published United States 01.06.2013
Subjects
ACCELERATION
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPARATIVE EVALUATIONS
Coronal mass ejection
Coronas
Correlation
CORRELATIONS
Ejection
EMISSION
Energetic particles
Launches
Longitude
MASS
MEV RANGE
PARTICLES
PROTONS
PULSE RISE TIME
SOLAR WIND
SUN
Time
VELOCITY
Online AccessGet full text

Cover

More Information
Summary:The dependence of solar energetic proton (SEP) event peak intensities Ip on properties of associated coronal mass ejections (CMEs) has been extensively examined, but the dependence of SEP event timescales is not well known. We define three timescales of 20 MeV SEP events and ask how they are related to speeds [upsilon] sub(CME) or widths W of their associated CMEs observed by LASCO/SOHO. The timescales of the EPACT/Wind 20 MeV events are TO, the onset time from CME launch to SEP onset; TR, the rise time from onset to half the peak intensity (0.5Ip); and TD, the duration of the SEP intensity above 0.5Ip. This is a statistical study based on 217 SEP-CME events observed during 1996-2008. The large number of SEP events allows us to examine the SEP-CME relationship in five solar-source longitude ranges. In general, we statistically find that TO declines slightly with [upsilon] sub(CME), and TR and TD increase with both [upsilon] sub(CME) and W. TO is inversely correlated with log Ip, as expected from a particle background effect. We discuss the implications of this result and find that a background-independent parameter TO+TR also increases with [upsilon] sub(CME) and W. The correlations generally fall below the 98% significance level, but there is a significant correlation between [upsilon] sub(CME) and W which renders interpretation of the timescale results uncertain. We suggest that faster (and wider) CMEs drive shocks and accelerate SEPs over longer times to produce the longer TR and TD SEP timescales.
Bibliography:ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/769/2/110