1,115 research outputs found
Different Power-law Indices in the Frequency Distributions of Flares with and without Coronal Mass Ejections
We investigated the frequency distributions of flares with and without
coronal mass ejections (CMEs) as a function of flare parameters (peak flux,
fluence, and duration of soft X-ray flares). We used CMEs observed by the Large
Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric
Observatory (SOHO) mission and soft X-ray flares (C3.2 and above) observed by
the GOES satellites during 1996 to 2005. We found that the distributions obey a
power-law of the form: dN/dX~X^-alpha, where X is a flare parameter and dN is
the number of events recorded within the interval [X, X+dX]. For the flares
with (without) CMEs, we obtained the power-law index alpha=1.98+-0.05
(alpha=2.52+-0.03) for the peak flux, alpha=1.79+-0.05 (alpha=2.47+-0.11) for
the fluence, and alpha=2.49+-0.11 (alpha=3.22+-0.15) for the duration. The
power-law indices for flares without CMEs are steeper than those for flares
with CMEs. The larger power-law index for flares without CMEs supports the
possibility that nanoflares contribute to coronal heating.Comment: 4 pages, 2 figures embedded, accepted for publication in ApJ
Spatial Relationship between Solar Flares and Coronal Mass Ejections
We report on the spatial relationship between solar flares and coronal mass
ejections (CMEs) observed during 1996-2005 inclusive. We identified 496
flare-CME pairs considering limb flares (distance from central meridian > 45
deg) with soft X-ray flare size > C3 level. The CMEs were detected by the Large
Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric
Observatory (SOHO). We investigated the flare positions with respect to the CME
span for the events with X-class, M-class, and C-class flares separately. It is
found that the most frequent flare site is at the center of the CME span for
all the three classes, but that frequency is different for the different
classes. Many X-class flares often lie at the center of the associated CME,
while C-class flares widely spread to the outside of the CME span. The former
is different from previous studies, which concluded that no preferred flare
site exists. We compared our result with the previous studies and conclude that
the long-term LASCO observation enabled us to obtain the detailed spatial
relation between flares and CMEs. Our finding calls for a closer flare-CME
relationship and supports eruption models typified by the CSHKP magnetic
reconnection model.Comment: 7 pages; 4 figures; Accepted by the Astrophysical Journa
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