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Size distributions of solar proton events and their asso-ciated soft X-ray flares based on the maximum likelihood estimator by E.W. Cliver and E. D’Huys

18 Sep 2018, 09:30 UTC
Size distributions of solar proton events and their asso-ciated soft X-ray flares based on the maximum likelihood estimator  by E.W. Cliver and E. D’Huys
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It has been known for some time that the size distributions of solar radio bursts and soft X-ray (SXR) flares have steeper power-law slopes (~1.8) than those (~1.2) of solar energetic proton (SEP) events. Hudson (1978) suggested three possibilities for this difference: (1) proton flares are fundamentally different from ordinary flares; (2) proton flares represent the large end of the total energy distribution of ordinary flares; and (3) proton flare characteristics have a threshold behavior. In some sense, each of these conjectures applies, although (1) and (3) are paramount.
Cliver et al. (2012) argued that proton flares are fundamentally different from ordinary flares (hypothesis (1)) because they are eruptive (Kahler et al. 1978). Because of their associated coronal mass ejections (CMEs), proton flares are intrinsically more energetic, satisfying hypothesis (2). Cliver et al. presented evidence for these points by constructing power-law size distributions for (relatively small) samples of large (“gradual”) >10 MeV proton events (58 events), their associated ≥M1 SXR flares (52 events), ≥M1 SXR flares associated with fast (≥1000 km s-1) CMEs (59 events), and ≥M1 soft X-ray flares (540 events). They found that the power-law slopes of distributions of SEP intensity (~1.2) and the peak SXR fluxes of ...

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