arXiv subjects

M. S. Wheatland

Publications and source records attributed to M. S. Wheatland.

39 records · Page 3Linked to original sources

arXiv2001

The local Poisson hypothesis for solar flares

The question of whether flares occur as a Poisson process has important consequences for flare physics. Recently Lepreti et al. presented evidence for local departure from Poisson statistics in the Geostationary Operational Environmental Satellite (GOES) X-ray flare catalog. Here it is argued that this effect arises from a selection effect inherent in the soft X-ray observations; namely that the slow decay of enhanced flux following a large flare makes detection of subsequent flares less likely. It is also shown that the power-law tail of the GOES waiting-time distribution varies with the solar cycle. This counts against any intrinsic significance to the appearance of a power law, or to the value of its index.

astro-ph↗

arXiv2000

The Origin of the Solar Flare Waiting-Time Distribution

It was recently pointed out that the distribution of times between solar flares (the flare waiting-time distribution) follows a power law, for long waiting times. Based on 25 years of soft X-ray flares observed by Geostationary Operational Environmental Satellite (GOES) instruments it is shown that 1. the waiting-time distribution of flares is consistent with a time-dependent Poisson process, and 2. the fraction of time the Sun spends with different flaring rates approximately follows an exponential distribution. The second result is a new phenomenological law for flares. It is shown analytically how the observed power-law behavior of the waiting times originates in the exponential distribution of flaring rates. These results are argued to be consistent with a non-stationary avalanche model for flares.

astro-ph↗

arXiv1999

Rotational Signature and Possible R-Mode Signature in the GALLEX Solar Neutrino Data

Recent analysis of the Homestake data indicates that the solar neutrino flux contains a periodic variation that may be attributed to rotational modulation occurring deep in the solar interior, either in the tachocline or in the radiative zone. This paper presents an analysis of GALLEX data that yields supporting evidence of this rotational modulation at the 0.1% significance level. The depth of modulation inferred from the rotational signature is large enough to explain the neutrino deficit. The Rieger 157-day periodicity, first discovered in solar gamma-ray flares, is present also in Homestake data. A related oscillation with period 52 days is found in the GALLEX data. The relationship of these periods to the rotational period inferred from neutrino data suggests that they are due to r-mode oscillations.

astro-ph↗