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 Radio Flare Activity of RS CVn Stars

1980 ◽  
Vol 88 ◽  
pp. 403-403
Author(s):  
Paul A. Feldman
Keyword(s):  
Binary Star ◽  
Quantitative Model ◽  
Magnetic Activity ◽  
Flare Activity ◽  
Radio Observatory ◽  
X Ray ◽  
Rs Cvn Stars ◽  
Solar Magnetic Activity ◽  
Radio Flare ◽  
Systematic Program

For several years, a systematic program to observe RS CVn and similar binaries has been undertaken with the 46-m telescope of the Algonquin Radio Observatory. A number of large radio outbursts at 2.8 cm wavelength has been found from HR 1099, AR Lac, SZ Psc, UX Ari, and HR 5110. In several cases, simultaneous, or nearly simultaneous, observations of these stars were made by cooperating observers at (other) radio, optical, UV, and X-ray wavelengths. It is now clearly established that the mechanism responsible for the cm-wavelength radio emission is nonthermal gyrosynchrotron radiation in a volume whose characteristic dimension is comparable with the binary star separation. More generally, a semi-quantitative model for the radio flare activity of these stars seems to be possible using greatly scaled-up analogues of solar magnetic activity.

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.

The record of solar and galactic radiations in the ancient lunar regolith and their implications for the early history of the Sun and Moon

1977 ◽  
Vol 285 (1327) ◽  
pp. 587-592 ◽  
Keyword(s):  
Solar Wind ◽  
Solar Flare ◽  
Solar Flares ◽  
Lunar Regolith ◽  
Galactic Cosmic Rays ◽  
Flare Activity ◽  
New Techniques ◽  
The Past ◽  
History Of ◽  
Individual Grains

A variety of techniques are available for studying past variations of solar wind, solar flares, galactic cosmic rays, and micrometeorites. Lumar rock results which average over the recent past ( ~ 10 Ma) indicate no major changes in any of these components. At longer times, recent data suggest secular changes in the 15N/14N ratio in the solar wind, possibly due to enhanced solar flare activity. With the deployment of new techniques, it now appears possible to measure solar wind, solar flare, and micrometeorite records in individual grains removed from different layers of lunar cores. Such grains have been exposed for brief intervals of time (103-104 a) for times extending at least 109 a in the past. Lunar and meteoritic breccias are promising candidates for extending the record back still further, perhaps close to the beginning of the solar system.

Comparing different types of solar flares with radio bursts detected by SMOS

2020 ◽  
Author(s):  
Manuel Flores Soriano ◽  
Consuelo Cid
Keyword(s):  
Space Weather ◽  
Early Warning ◽  
Solar Flares ◽  
Solar Radio ◽  
The Sun ◽  
Radio Bursts ◽  
Radio Observatory ◽  
X Ray ◽  
Different Types ◽  
Mass Ejection

<p>SMOS is an Earth observing satellite that is been adapted to provide full polarization observations of the Sun at 1.4 GHz 24 hours a day. Its solar radio observations from the last decade will be released to the community by the middle of this year. In this presentation we show the capabilities of SMOS as a solar radio observatory and compare some of the most relevant radio bursts with data from GOES, LASCO, SDO and RSTN. We show how SMOS responds to different kinds of solar flares depending on their x-ray flux, and the kind of mass ejection or solar dimming that they have produced, if any. In addition to this we also show the potential of SMOS as a space weather tool to monitor GNSS satellites signal fades and to provide an early warning of Earth-directed coronal mass ejections.</p>

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 Plasma Processes in Solar Flares

1990 ◽  
Vol 142 ◽  
pp. 355-364
Author(s):  
V.M. Tomozov
Keyword(s):  
Solar Flares ◽  
Large Scale ◽  
Stark Effect ◽  
Active Regions ◽  
Theoretical Models ◽  
Radio Bursts ◽  
X Ray ◽  
Plasma Effects ◽  
Collective Plasma

A rationale is presented for a conception that appearance of flares in active regions is due to the interaction of large-scale convective elements. Such an interaction gives rise to shear motions in the vicinity of the inverse polarity line of the photospheric magnetic field which generate vortical motions leading to non-equilibrium state of the magnetic configuration. Modern concepts of manifestations of turbulent plasma processes are described in terms of theoretical models for solar flares. Plasma effects arising at propagation of electron beams and thermal fluxes in the solar atmosphere are considered. Their role in the interpretation of hard X-ray and type III radio bursts is pointed out. The role of the turbulent Stark effect for diagnostics of collective plasma processes in solar flares is emphasized.

scholarly journals Type II Solar Radio Bursts in the Decimeter Band

1974 ◽  
Vol 57 ◽  
pp. 343-343
Author(s):  
Alan Maxwell
Keyword(s):  
Shock Waves ◽  
Solar Flares ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Lower Corona ◽  
Previous Discussion ◽  
Radio Equipment ◽  
Interplanetary Plasma ◽  
Radio Band

(Solar Phys.) The progress of shock waves generated by solar flares through the corona is delineated in the radio band by radio bursts of spectral type II. Previous discussion of these bursts has been mainly concerned with their characteristics at frequencies below 200 MHz. This paper discusses the characteristics of the bursts in the range 2000–200 MHz, and the information that may then be deduced about the propagation of shock waves through the lower corona. Particular attention is paid to the type II burst emitted by the flare of 1972 August 7, 1500 UT. The shock from this flare was subsequently tracked (by radio equipment on the IMP-6 satellite) through the interplanetary plasma right to the Earth.

scholarly journals Analysis of some solar flares from optical, X-ray, and radio observations

1968 ◽  
Vol 35 ◽  
pp. 449-464
Author(s):  
R. Falciani ◽  
M. Landini ◽  
A. Righini ◽  
M. Rigutti
Keyword(s):  
Solar Flares ◽  
High Intensity ◽  
Radio Bursts ◽  
X Rays ◽  
Radio Observations ◽  
X Ray ◽  
Optical Flare

Using an improved isodensitometric technique it has been possible to study in great detail the photometric structure and the evolution of eight flares. A comparison has been made between the evolutive curves and the ones obtained from measurements of solar X-rays and radio fluxes at λλ 3·2 and 21 cm.A reduction of the flare areas (and of the emitted energies) before the flash phase and a continuous pulsation of the flare have been observed. Further it seems that the flares associated with radio bursts or X-ray events are those which show regions of a sufficiently high intensity, the emitting areas not being a very important parameter.The correlation in time between the various examined aspects of the AR seems to indicate that the sequence for the beginning of the different phenomena is, in general: optical flare, X-ray events, radio events.

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