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The timing of 503 solar flares observed simultaneously in hard X-rays, soft X-rays and H-alpha is analyzed. We investigated the start and the peak time differences in different wavelengths, as well as the differences between the end of the…
From the optical to the X-ray frequencies, most of the continuum emission from AM Her systems originates in the post-shock region. Hence, using multi-spectral data can be useful to restrict the physical and geometrical properties of that…
In a previous study, we investigated the relativistic wind dynamics in the LS 5039 system. In this work, we analyse energetic-particle transport within this modelling context, where we simulate the high-energy particle distribution and…
Simultaneous simulation of HXR and MW emission with the same populations of electrons is still a great challenge for interpretation of observations in real events. In this paper we apply the FP kinetic model of precipitation of electron…
Radio observations of solar flares often reveal various periodic or quasi-periodic oscillations. Most likely, these oscillations are caused by magnetohydrodynamic (MHD) oscillations of flaring loops which modulate the emission.…
We consider particle acceleration to high energy via diffusive shock acceleration in a simple, self-consistent shock in jet model for blazars. Electrons are assumed to be accelerated at a shock front in relativistic jets and radiate…
We develop a model for stochastic acceleration of electrons in solar flares. As in several previous models, the electrons are accelerated by turbulent fast magnetosonic waves ("fast waves") via transit-time-damping (TTD) interactions. (In…
We report solar flare plasma to be multi-thermal in nature based on the theoretical model and study of the energy-dependent timing of thermal emission in ten M-class flares. We employ high-resolution X-ray spectra observed by the Si…
Super-hot looptop sources, detected in some large solar flares, are compact sources of HXR emission with spectra matching thermal electron populations exceeding 30 megakelvins. High observed emission measure, as well as inference of…
A large arcade flare of 2 March 1993 has been investigated using X-ray observations recorded by the {\sl Yohkoh} and GOES satellites and the {\sl Compton Gamma Ray Observatory}. We analyzed quasi-periodicity of the hard-X-ray (HXR) pulses…
In this paper a homomorphic filtering scheme is proposed to improve the estimation of the planet/star radius ratio in astronomical transit signals. The idea is to reduce the effect of the short-term earth atmosphere variations. A two-step…
The model of stochastic acceleration of particles by turbulence has been successful in explaining many observed features of solar flares. Here we demonstrate a new method to obtain the accelerated electron spectrum and important…
The thermal-photon emission from strongly coupled gauge theories at finite temperature is calculated by using holographic models for QCD in the Veneziano limit (V-QCD). These emission rates are then embedded in hydrodynamic simulations…
Quasi-periodic pulsations (QPP) are often observed in X-ray emission from solar flares. To date, it is unclear what their physical origins are. Here, we present a multi-instrument investigation of the nature of QPP during the impulsive and…
Stellar flares are potent drivers of atmospheric evolution on orbiting exoplanets, primarily through extreme ultraviolet (EUV) and soft X-ray (XUV) irradiation. However, the contribution of hard X-rays (HXR; 3--20 keV)-which penetrate…
We present the first joint spectral and imaging analysis of hard X-ray (HXR) emission from 3 microflares observed by the Nuclear Spectroscopic Telescope ARray (NuSTAR) and Solar Orbiter/Spectrometer/Telescope for Imaging X-rays (STIX). We…
Solar flares involve complex processes that are coupled and span a wide range of temporal, spatial, and energy scales. Modeling such processes self-consistently has been a challenge in the past. Here we present results from simulations that…
Solar flares often happen after a preflare / preheating phase, which is almost or entirely thermal. In contrast, there are the so-called early impulsive flares that do not show a (significant) preflare heating but instead often show the…
Solar flare simulations are commonly initialised using non-linear force free field (NLFF) extrapolations derived from photospheric vector magnetograms. However, the force free assumption neglects plasma forces and may limit the available…
Observations with {\em RHESSI} have enabled the detailed study of the structure of dense hard X-ray coronal sources in solar flares. The variation of source extent with electron energy has been discussed in the context of streaming of…