Context. The diagnostics of stellar flaring coronal loops have been so far largely based on the analysis of the decay phase. Aims. We derive new diagnostics from the analysis of the rise and peak phase of stellar flares. Methods. We release the assumption of full equilibrium of the flaring loop at the flare peak, according to the frequently observed delay between the temperature and the density...

In the framework of solar flare/coronal mass ejection theory, we propose a theoretical model for magnetar giant flare, which can explain the flaring activity on 2004 December 27 from SGR1806-20 comprehensively. As is the case with solar flare, explosive magnetic reconnection in magnetosphere takes a major role in the energetics of magnetar flare. However, cooling and energy transport processes ...

We have obtained high resolution X-ray spectra of the coronally active binary, II Pegasi (HD 224085), covering the wavelength range of 1.5-25Å. For the first half of our 44 ksec observation, the source was in a quiescent state with constant X-ray flux, after which it flared, reaching twice the quiescent flux in 12 ksec, then decreasing. We analyze the emission-line spectrum and continuum during...

Aims. A novel method of using hard X-rays as a diagnostic for chromospheric density and magnetic structures is developed to infer sub-arcsecond vertical variation of magnetic flux tube size and neutral gas density. Methods. Using Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) X-ray data and the newly developed X-ray visibilities forward fitting technique we find the FWHM and cent...

Nanoflares, short and intense heat pulses within spatially unresolved magnetic strands, are now considered a leading candidate to solve the coronal heating problem. However, the frequent occurrence of nanoflares requires that flare-hot plasma be present in the corona at all times. Its detection has proved elusive until now, in part because the intensities are predicted to be very faint. Here we...

Abstract We analyze the formation mechanism of three homologous broad coronal mass ejections (CMEs) resulting from a series solar blowout-eruption flares with successively increasing intensities (M2.0, M2.6, and X1.0). The originated NOAA Active Region 12017 during 2014 March 28–29 within an interval ≈24 hr. Coronal magnetic field modeling based on nonlinear force-free extrapolation helps to id...

In this paper we present a detailed analysis of two X-ray spectra of Capella, taken eleven months apart with the Low Energy Transmission Grating Spectrometer (LETGS) of the Chandra Observatory. We have studied variability of the coronal emission over different time scales, both in the whole X-ray band and in narrow temperature ranges identified by lines. The comparison of the two observations s...

Aims. Estimating Alfvén speeds is of interest in modelling the solar corona, studying the coronal heating problem and understanding the initiation and propagation of coronal mass ejections (CMEs). Methods. We assume here that the corona is in a magnetohydrostatic equilibrium and that, because of the low plasma β, one may decouple the magnetic forces from pressure and gravity. The magnetic field...

We investigate the consequences of magnetic flares on the surface of asymptotic giant branch (AGB) and similar stars. In contrast to the solar wind, in the winds of AGB stars the gas cooling time is much shorter than the outflow time. As a result, we predict that energetic flaring should enhance, rather than inhibit, dust formation around AGB stars. Analysis of an archival ROSAT X-ray spectrum ...

Abstract Slow magnetosonic waves associated with flares were observed in coronal loops by Solar and Heliospheric Observatory/Solar Ultraviolet Measurements of Emitted Radiation, Dynamics Observatory/Atmospheric Imaging Assembly various EUV bandpasses, other instruments. The excitation damping slow provides information on the magnetic, temperature, density structure loops. Recently, it was found...