scholarly journals Analysis and modeling of the dynamics of the glow of calcium and hydrogen lines in solar and stellar flares

2021 ◽  
Vol 30 (1) ◽  
pp. 91-95
Author(s):  
Yurij Alekseevich Kupryakov ◽  
Konstantin Veniaminovich Bychkov ◽  
Oksana Mikhailovna Belova ◽  
Alexey Borisovich Gorshkov ◽  
Petr Heinzel ◽  
...  
Keyword(s):  
Solar Flares ◽  
Radiation Flux ◽  
Temporal Variations ◽  
Slow Heating ◽  
X Ray ◽  
Stellar Flares ◽  
Flare Stars ◽  
The Difference ◽  
Ev Lac ◽  
Hydrogen Lines

Abstract We present intensity curves of solar flares obtained in the Hα hydrogen line and CaII H, CaIR 8542Å lines using multichannel spectrographs of Ondřejov Observatory (Czech Republic) for the period 2000–2012. The general behavior of observed intensity curves is practically the same for all flares and is consistent with temporal variations of X-ray emission. However, our results differ significantly from those obtained by other authors for selected flare stars, for example, AD Leo; EV Lac; YZ CMi. We tried to explain the difference in the behavior of Ca II and Hα radiation flux by appearance of a shock wave during a flare and slow heating of the plasma.

scholarly journals Hydrodynamic Models of Solar and Stellar Flares

1989 ◽  
Vol 104 (1) ◽  
pp. 289-298
Author(s):  
Giovanni Peres
Keyword(s):  
High Resolution ◽  
Light Curve ◽  
Solar Flares ◽  
Impulsive Phase ◽  
Light Curves ◽  
Physical Parameters ◽  
The Sun ◽  
Hydrodynamic Models ◽  
X Ray ◽  
Stellar Flares

AbstractThis paper discusses the hydrodynamic modeling of flaring plasma confined in magnetic loops and its objectives within the broader scope of flare physics. In particular, the Palermo-Harvard model is discussed along with its applications to the detailed fitting of X-ray light curves of solar flares and to the simulation of high-resolution Caxix spectra in the impulsive phase. These two approaches provide complementary constraints on the relevant features of solar flares. The extension to the stellar case, with the fitting of the light curve of an X-ray flare which occurred on Proxima Centauri, demonstrates the feasibility of using this kind of model for stars too. Although the stellar observations do not provide the wealth of details available for the Sun, and, therefore, constrain the model more loosely, there are strong motivations to pursue this line of research: the wider range of physical parameters in stellar flares and the possibility of studying further the solar-stellar connection.

scholarly journals X-Ray Emission from Stellar Flares: Exosat Results

1989 ◽  
Vol 104 (2) ◽  
pp. 17-20 ◽  
Author(s):  
R. Pallavicini ◽  
G. Tagliaferri
Keyword(s):  
Main Sequence ◽  
Late Type ◽  
X Ray ◽  
Visual Binary ◽  
Stellar Flares ◽  
Flare Stars ◽  
M Dwarf

AbstractWe present an overview of recent observations of stellar X-ray flares obtained with the EXOSAT Observatory. We discuss a few examples of flares from M dwarf flare stars, from RS CVn and Algol-type binaries, from single late-type stars (including a G0 dwarf and an A-type visual binary), and from pre-main-sequence objects. We also draw some general conclusions from the pieliminary analysis of the EXOSAT data sample.

scholarly journals Flares on the Sun: Selected Results from SMM

1983 ◽  
Vol 71 ◽  
pp. 289-305
Author(s):  
G.M. Simnett
Keyword(s):  
Solar Flares ◽  
Solar Maximum ◽  
Electromagnetic Spectrum ◽  
Significant Progress ◽  
X Ray ◽  
Spatially Resolved ◽  
Red Dwarfs ◽  
Important Diagnostic Tool ◽  
Flare Stars ◽  
Made In

Observationally the study of solar flares has reached the stage where intensity-time distributions of emission over broad and resolved regions of the electromagnetic spectrum are obtained for spatially resolved parts of the flare. Polarization measurements add an important diagnostic tool in some wavebands but we shall not report on these here. In the optical band good ground based observations have been available for many years, whereas in the UV, soft X-ray and hard X-ray (> 5 keV) bands recent spacecraft have greatly extended the data base. Good high resolution maps are being made in the microwave region with the ground based VIA. We are now at the point where significant progress into understanding the flare problem has been made, and will continue to be made, during the current solar maximum. This coincides with the development of soft X-ray instruments sensitive enough to detect transient and quiescent emission from flare stars, particularly red dwarfs in the solar neighbourhood (e.g. Kahn et al,1979, Haisch et al, 1980) which previously had only been detected in the optical and radio wavebands.

X-ray Spectral Synthesis in Hydrodynamic Flare Models

1990 ◽  
Vol 115 ◽  
pp. 126-131
Author(s):  
S. Serio ◽  
E. Antonucci ◽  
M.A. Dodero ◽  
G. Peres ◽  
F. Reale
Keyword(s):  
Solar Flares ◽  
Energy Deposition ◽  
Electron Beams ◽  
Spectral Synthesis ◽  
Theoretical Models ◽  
Hydrodynamic Models ◽  
X Ray ◽  
Relativistic Electron Beams ◽  
Stellar Flares ◽  
Magnetically Confined

AbstractCompact solar flares are triggered by sudden energy release in magnetically confined plasma. This class of flares is well suited to be studied with numerical hydrodynamic models. In particular, one can compare the evolution of observed and synthetic X-ray spectra, computed under various assumptions for the mechanism of impulsive energy deposition, to constrain theoretical models and their parameter space. We discuss recent results on solar flares along this line, non thermal to models of energy depositions by relativistic electron beams. We shall also discuss possible applications of X-ray spectral synthesis to stellar flares.

scholarly journals Balmer and soft X-ray emission from solar and stellar flares

1990 ◽  
Vol 137 ◽  
pp. 153-157
Author(s):  
C. J. Butler
Keyword(s):  
Solar Flares ◽  
The Sun ◽  
X Ray ◽  
Stellar Flares ◽  
Basic Similarity ◽  
Good Agreement

Integrated soft X-ray (8-12A) fluxes for solar flares have been scaled to the equivalent EXOSAT fluxes using spectra obtained from a variety of rocket-based experiments. The data show good agreement with the soft X-ray - Hγ correlation established by Butler et al. (1988) for stellar flares and confirm the basic similarity, in this respect, of flares on the Sun to those on dMe stars.

scholarly journals The Magnetic Corona: Magnetic Reconnection in Solar Flares

2004 ◽  
Vol 219 ◽  
pp. 91-102
Author(s):  
Harry P. Warren
Keyword(s):  
Spatial Resolution ◽  
Solar Flares ◽  
Light Curves ◽  
Small Scale ◽  
Flare Loop ◽  
X Ray ◽  
Stellar Flares ◽  
Emission Models ◽  
Reconnection Model ◽  
High Cadence

The ability of the Transition Region and Coronal Explorer (TRACE) to image the Sun at high spatial resolution and high cadence over a very broad range of temperatures makes it a unique instrument for observing solar flare plasma. TRACE observations have confirmed the reconnection model for solar flares, at least qualitatively. TRACE flare observations show impulsive footpoint brightenings that are followed by the formation of high-temperature loops in the corona. These loops then cool to lower temperatures, forming post-flare loop arcades. Comparisons between TRACE and lower spatial resolution Yohkoh Soft X-Ray Telescope (SXT) observations have revealed that solar flares are composed of a multitude of fine coronal loops. Detailed hydrodynamic modeling of flare light curves shows that this fine scale structuring is crucial to understanding the evolution of the observed emission. Models based on single, isothermal loops are not consistent with the TRACE observations. Models based on the sequential heating of small-scale loops, in contrast, are able to reproduce many of the salient features of the observed light curves. We will discuss the implication of these results for more energetic stellar flares as well as smaller-scale events that may be responsible for the heating of solar active region loops.

scholarly journals New Triggering Mechanism for Red Dwarf Flares

1983 ◽  
Vol 71 ◽  
pp. 609-611
Author(s):  
M.K. Das ◽  
J.N. Tandon
Keyword(s):  
Solar Flares ◽  
Galactic Cosmic Rays ◽  
Flare Activity ◽  
Radio Bursts ◽  
Triggering Mechanism ◽  
X Ray ◽  
Flare Stars ◽  
M Stars ◽  
Radio Band ◽  
Radio Flare

The flare phenomenon associated with dMe stars has received much attention in recent years (Gershberg 1975). Most of the flares have been detected in both optical and radio band (Lovell 1969; Kunkel 197U; Karpen et al, 1977). But as expected (Tandon 1976) only a few display weak soft X-ray emission (Karpen et al, 1977; Haisch and Linsky 1978)- Simultaneous X-ray, optical and radio observations of YZ CMi by Karpen et al (1977) shows no X-ray emission above 3σ level accompanying minor flares. Even coincident X-ray coverage with seven radio bursts shows no enhanced X-ray emission. Recently Haisch et al (1981) detected one well resolved X-ray flare on dM5e flare star Proxima Centauri and one coincident optical and radio flare out of five optical and twelve radio flare events. However, the X-ray flare on Proxima Centauri is not accompanied by any ultraviolet, optical or radio emission. Observations on flare stars show that they are more energetic, 102 - 103 times, than the corresponding solar flares. Considering the flare activity in dwarf M-stars to be similar but more energetic to that of a large solar flare, Tandon (1961) proposed red dwarf flares to be the source of low energy galactic cosmic rays. This hypothesis has been reexplored recently by Lovell (1974).

scholarly journals Quiescent And Flaring Radio Emission From dMe Stars

1983 ◽  
Vol 71 ◽  
pp. 273-286 ◽  
Author(s):  
D. M. Gibson
Keyword(s):  
Radio Emission ◽  
Solar Flares ◽  
Expected Value ◽  
Detection Thresholds ◽  
Significant Interest ◽  
Radio Studies ◽  
Flare Stars ◽  
Ev Lac ◽  
M Dwarf

In reviewing radio studies of M-dwarf flare stars one is struck by the curious way in which the field developed. Indeed, that is twenty years old may be the greatest surprise, for if one imagines the largest solar flares occurring at distances comparable to the nearest stars the expected flux densities would be < 10 mJy. Yet, despite the fact that detection thresholds in 1963 were about two orders of magnitude higher than the expected value, Lovell et al. (1963) made extensive observations and reported the. detection of UV Ceti. This remarkable discovery was followed immediately by detections of V371 Ori (Slee et al., 1963) and EV Lac (Lovell et al., 1964). One might have thought that these unexpected discoveries would have spurred significant interest in this new field but they did not.

scholarly journals Balmer lines and Continuum Emission for two Flares of the dMe Star Gliese 729

1989 ◽  
Vol 104 (2) ◽  
pp. 79-82
Author(s):  
A. Falchi ◽  
R. Falciani ◽  
L.A. Smaldone ◽  
G.P. Tozzi
Keyword(s):  
Electron Density ◽  
Solar Flares ◽  
Continuum Emission ◽  
Spectroscopic Observations ◽  
Stellar Flares ◽  
Sensitive Tool ◽  
Balmer Lines ◽  
Flare Stars ◽  
The Continuum

It has been shown for solar flares (Donati-Falchi et al. 1985) that the continuum emission at the Balmer discontinuity (the blue “pseudo-continuum”) is a very sensitive tool to determine the electron density. In order to use the same interpretative scheme for stellar flares (Falchi et al. 1988), spectroscopic observations of various flare stars have been performed in June 1987 at ESO observatory (Chile). In this paper we report the analysis of spectra of the star n. 729 (V 1216 Sgr) of the Gliese catalog.

scholarly journals Solar Flares with SMM and Implications for the Physics of Stellar Flares

1983 ◽  
Vol 71 ◽  
pp. 321-324
Author(s):  
R. Pallavicini
Keyword(s):  
Solar Flares ◽  
X Ray ◽  
Stellar Flares

ABSTRACTXUV flare observations from SMM are discussed and a comparison is made with recent X-ray observations of stellar flares.

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