scholarly journals Comparison of UV Ceti Flares with Solar Flares

1975 ◽  
Vol 67 ◽  
pp. 99-100
Author(s):  
W. Haupt ◽  
W. Schlosser
Keyword(s):  
Solar Flare ◽  
Light Curve ◽  
White Light ◽  
Solar Flares ◽  
Light Emission ◽  
Cosmic Ray ◽  
Slow Phase ◽  
Hα Emission ◽  
Flare Stars ◽  
Several Intervals

During several intervals totalling 26 h, 84 flares of UV Ceti were observed using a photometer with 1 s time resolution. Using solar flare terminology, all flares of UV Ceti observed here can be characterized by a typical light curve, consisting of a preflare, a flash and a slow phase. Observations of Bopp and Moffett (1973) show that the flash phase of UV Ceti is dominated by continuous and Hα emission. UV Ceti flare flash phases are compared with solar ‘white-light’ emission during the flash phase and it is suggested that during all UV Ceti flares strong-particle emission occurs, as is the case for solar white-light flares (Švestka, 1970). The characteristics of the solar flare particles are similar to those of the soft cosmic ray sources (Mogro-Campero and Simpson, 1972). If all flare stars emit particles with these characteristics they could produce the soft cosmic ray component in agreement with the work of Comstock (1969).

scholarly journals Preflare very long-periodic pulsations observed in Hα emission before the onset of a solar flare

2020 ◽  
Vol 639 ◽  
pp. L5
Author(s):  
Dong Li ◽  
Song Feng ◽  
Wei Su ◽  
Yu Huang
Keyword(s):  
Solar Flare ◽  
Light Curve ◽  
Solar Flares ◽  
Extreme Ultraviolet ◽  
Light Curves ◽  
Trigger Mechanism ◽  
X Ray ◽  
Hα Emission ◽  
Plasma Loop ◽  
Full Disk

Context. Very long-periodic pulsations during preflare phases (preflare-VLPs) have been detected in the full-disk solar soft X-ray (SXR) flux. They may be regarded as precursors to solar flares and may help us better understand the trigger mechanism of solar flares. Aims. In this Letter, we report a preflare-VLP event prior to the onset of an M1.1 circular-ribbon flare on 2015 October 16. It was simultaneously observed in Hα, SXR, and extreme ultraviolet (EUV) wavelengths. Methods. The SXR fluxes in 1−8 Å and 1−70 Å were recorded by the Geostationary Operational Environmental Satellite (GOES) and Extreme Ultraviolet Variability Experiment, respectively; the light curves in Hα and EUV 211 Å were integrated over a small local region, which were measured by the 1 m New Vacuum Solar Telescope and the Atmospheric Imaging Assembly (AIA), respectively. The preflare-VLP is identified as the repeat and quasi-periodic pulses in light curves during preflare phase. The quasi-periodicity can be determined from the Fourier power spectrum with Markov chain Monte Carlo-based Bayesian. Results. Seven well-developed pulses are found before the onset of an M1.1 circular-ribbon flare. They are firstly seen in the local light curve in Hα emission and then discovered in full-disk SXR fluxes in GOES 1−8 Å and ESP 1−70 Å, as well as the local light curve in AIA 211 Å. These well-developed pulses can be regarded as the preflare-VLP, which might be modulated by LRC-circuit oscillation in the current-carrying plasma loop. The quasi-period is estimated to be ∼9.3 min. Conclusions. We present the first report of a preflare-VLP event in the local Hα line and EUV wavelength, which could be considered a precursor of a solar flare. This finding should therefore prove useful for the prediction of solar flares, especially for powerful flares.

scholarly journals Electron Beam as Origin of White-Light Solar Flares

1989 ◽  
Vol 104 (1) ◽  
pp. 19-30
Author(s):  
J. Aboudarham ◽  
J. C. Henoux
Keyword(s):  
Electron Beam ◽  
White Light ◽  
Solar Flares ◽  
Light Emission ◽  
Continuum Emission ◽  
Continuum Radiation ◽  
Photospheric Level ◽  
Hydrogen Ionization ◽  
Semi Empirical ◽  
Flare Model

AbstractWe study the effect of chromospheric bombardment by an electron beam during solar flares. Using a semi-empirical flare model, we investigate energy balance at temperature minimum level and in the upper photosphere. We show that non-thermal hydrogen ionization (i.e., due to the electrons of the beam) leads to an increase of chromospheric hydrogen continuum emission, H− population, and absorption of photo-spheric and chromospheric continuum radiation. So, the upper photosphere is radiatively heated by chromospheric continuum radiation produced by the beam. The effect of hydrogen ionization is an enhanced white-light emission both at chromospheric and photospheric level, due to Paschen and H− continua emission, respectively. We then obtain white-light contrasts compatible with observations, obviously showing the link between white-light flares and atmospheric bombardment by electron beams.

scholarly journals Energy Dissipation Mechanisms in Flare Stars

1985 ◽  
Vol 107 ◽  
pp. 245-262
Author(s):  
D. J. Mullan
Keyword(s):  
Solar Flare ◽  
Solar Flares ◽  
Visible Spectrum ◽  
Stellar Disk ◽  
Total Power ◽  
Quiescent State ◽  
Stellar Flare ◽  
Stellar Spectrum ◽  
Flare Stars ◽  
Visible Disk

Flare stars derive their name from intermittent increases in luminosity which have certain characteristics reminiscent of solar flares (e.g. enhanced strengths of emission lines in the stellar spectrum during the outbursts). When a flare star is observed in a filter which transmits, say, the violet part of the visible spectrum, the increase in luminosity during a flare may range from noise level up to perhaps 100 times the quiescent brightness. During a flare, certain spectral features of the quiescent star (e.g. molecular bands) remain visible, indicating that the flare occupies only a fraction of the visible disk. Thus, analagous to a solar flare, a stellar flare is confined to a single active region. However the total power is large enough to affect the integrated light from the stellar disk. In contrast, the largest solar flare (Etot ≈ 1032 ergs) has a rate of energy release (L ≈ 1029 erg/sec) which is so small that a distant observer would record such a flare as a luminosity increase of less than 10−4Lsun. However, even apart from the flares themselves, it has become apparent in recent years that flare stars in their “quiescent state” provide some extreme contrasts with the sun.

Long Duration Solar Flare Events and Cosmic Ray Modulation (1969-1992)

1994 ◽  
Vol 144 ◽  
pp. 499-502
Author(s):  
A. Antalová ◽  
K. Kudela ◽  
D. Venkatesan ◽  
J. Rybák
Keyword(s):  
Solar Cycle ◽  
Solar Flare ◽  
Solar Flares ◽  
Cosmic Ray ◽  
Flare Activity ◽  
Cosmic Ray Intensity ◽  
Cosmic Ray Modulation ◽  
Long Duration ◽  
Flare Index ◽  
Galactic Cosmic Ray

AbstractWe present here the results of the correlation analysis between the galactic cosmic ray intensity decrease p (as observed on Calgary neutron monitor station) and the occurence of SXR long-lasting (LDE-type) solar flares, represented by the LDE-type flare index FI. It is shown, that for the solar cycle with the lower monthly values of FI (the 21-st solar cycle) the correlation coefficient is slighter (about 0.4) comparing to the cycles with the higher LDE-type flare activity (about 0.6, in the 20-th and the 22-nd cycles).

scholarly journals CORRELATION OF HARD X-RAY AND WHITE LIGHT EMISSION IN SOLAR FLARES

2015 ◽  
Vol 816 (1) ◽  
pp. 6 ◽  
Author(s):  
Matej Kuhar ◽  
Säm Krucker ◽  
Juan Carlos Martínez Oliveros ◽  
Marina Battaglia ◽  
Lucia Kleint ◽  
...  
Keyword(s):  
White Light ◽  
Solar Flares ◽  
Light Emission ◽  
White Light Emission ◽  
X Ray

scholarly journals EMISSION HEIGHT AND TEMPERATURE DISTRIBUTION OF WHITE-LIGHT EMISSION OBSERVED BYHINODE/SOT FROM THE 2012 JANUARY 27 X-CLASS SOLAR FLARE

2013 ◽  
Vol 776 (2) ◽  
pp. 123 ◽  
Author(s):  
Kyoko Watanabe ◽  
Toshifumi Shimizu ◽  
Satoshi Masuda ◽  
Kiyoshi Ichimoto ◽  
Masanori Ohno
Keyword(s):  
Temperature Distribution ◽  
Solar Flare ◽  
White Light ◽  
Light Emission ◽  
White Light Emission ◽  
Emission Height

scholarly journals Theoretical and Experimental Aspects of Solar Flares Manifestation in Radiocarbon Abundance in Tree Rings

Radiocarbon ◽  
1992 ◽  
Vol 34 (2) ◽  
pp. 247-253 ◽  
Author(s):  
A. N. Kostantinov ◽  
V. A. Levchenko ◽  
G. E. Kocharov ◽  
I. B. Mikheeva ◽  
Stefano Cecchini ◽  
...  
Keyword(s):  
Tree Rings ◽  
Solar Flares ◽  
High Probability ◽  
Cosmic Ray ◽  
Cosmogenic Isotopes ◽  
The Past ◽  
Cosmic Ray Flux ◽  
Several Intervals

We describe our method of determining solar cosmic-ray flux and spectrum in the past, based on the comparison of different cosmogenic isotopes. For the period, AD 1781–1950, we have detected several intervals with a high probability of powerful solar flares.

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