نتایج جستجو برای: solar flares
تعداد نتایج: 123758 فیلتر نتایج به سال:
Context. The Solar First Ionization Potential (FIP) effect, where low-FIP (FIP <∼10 eV) elements are enriched in the corona relative to the photosphere, while high-FIP abundances remain unchanged, has been known for a long while. High resolution X-ray spectroscopy has revealed that active stellar coronae show an opposite effect, which was labeled the Inverse-FIP (IFIP) effect. The correlation f...
We present a study of the spatial and spectral evolution of the loop-top (LT) sources in a sample of 6 flares near the solar limb observed by RHESSI. A distinct coronal source, which we identify as the LT source, was seen in each of these flares from the early “pre-heating” phase through the late decay phase. Spectral analyses reveal an evident steep power-law component in the pre-heating and i...
We describe the cascade of plasma waves or turbulence injected, presumably by reconnection, at scales comparable to the size of a solar flare loop, L ∼ 109 cm, to scales comparable to elementary particle gyro radii, and evaluate their damping at small scales by various mechanisms. We show that the classical viscous damping valid on scales larger than the collision mean free path (∼ 108 cm) is u...
Most theoretical investigations of particle acceleration during solar flares cannot be applied to observations for detailed study of the time evolution. We propose a phenomenological model for turbulence evolution and stochastic particle acceleration that links observations to the energy release and particle acceleration through two coefficients characterising particle interactions with turbule...
Observations by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) are used to quantitatively study the hard X-ray evolution in 5 large solar flares selected for spectral hardening in the course of the event. The X-ray bremsstrahlung emission from non-thermal electrons is characterized by two spectroscopically distinct phases: impulsive and gradual. The impulsive phase usually consists ...
Previous studies of the statistical behavior of solar flare waiting times are based on the assumptions of Gaussian and Poisson statistics, subject to central limit theorem restrictions. In this study, the results of a rescaled range analysis on the waiting times for two hard x-ray solar flare data sets are presented. The Hurst scaling parameter, H, for both data sets is well above 0.5, clearly ...
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