scholarly journals Solar and stellar flares and their impact on planets

2015 ◽  
Vol 11 (S320) ◽  
pp. 3-24
Author(s):  
Kazunari Shibata
Keyword(s):  
Solar Flare ◽  
Total Energy ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Slow Rotation ◽  
The Sun ◽  
Stellar Flare ◽  
Terrestrial Environment ◽  
The Earth ◽  
Stellar Flares

AbstractRecent observations of the Sun revealed that the solar atmosphere is full of flares and flare-like phenomena, which affect terrestrial environment and our civilization. It has been established that flares are caused by the release of magnetic energy through magnetic reconnection. Many stars show flares similar to solar flares, and such stellar flares especially in stars with fast rotation are much more energetic than solar flares. These are called superflares. The total energy of a solar flare is 1029 − 1032 erg, while that of a superflare is 1033 − 1038 erg. Recently, it was found that superflares (with 1034 − 1035 erg) occur on Sun-like stars with slow rotation with frequency once in 800 - 5000 years. This suggests the possibility of superflares on the Sun. We review recent development of solar and stellar flare research, and briefly discuss possible impacts of superflares on the Earth and exoplanets.

scholarly journals Synergy between solar and stellar flares: challenges and perspectives

2015 ◽  
Vol 11 (S320) ◽  
pp. 419-426
Author(s):  
Suzanne L. Hawley
Keyword(s):  
Solar Flares ◽  
Additional Data ◽  
Current Status ◽  
The Sun ◽  
Stellar Flare ◽  
Stellar Flares ◽  
Similarities And Differences

AbstractI will review the current status of stellar flare observations and models, highlight similarities and differences with solar flares, and plead for additional data and insight from the “Sun as a Star”.

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.

Influence of supernovae, gamma-ray bursts, solar flares, and cosmic rays on the terrestrial environment

2008 ◽  
Author(s):  
Arnon Dar
Keyword(s):  
Solar Activity ◽  
Cosmic Rays ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
Gamma Ray Bursts ◽  
The Sun ◽  
Terrestrial Environment ◽  
The Earth ◽  
The Galaxy ◽  
Threat To Life

Changes in the solar neighbourhood due to the motion of the sun in the Galaxy, solar evolution, and Galactic stellar evolution influence the terrestrial environment and expose life on the Earth to cosmic hazards. Such cosmic hazards include impact of near-Earth objects (NEOs), global climatic changes due to variations in solar activity and exposure of the Earth to very large fluxes of radiations and cosmic rays from Galactic supernova (SN) explosions and gamma-ray bursts (GRBs). Such cosmic hazards are of low probability, but their influence on the terrestrial environment and their catastrophic consequences, as evident from geological records, justify their detailed study, and the development of rational strategies, which may minimize their threat to life and to the survival of the human race on this planet. In this chapter I shall concentrate on threats to life from increased levels of radiation and cosmic ray (CR) flux that reach the atmosphere as a result of (1) changes in solar luminosity, (2) changes in the solar environment owing to the motion of the sun around the Galactic centre and in particular, owing to its passage through the spiral arms of the Galaxy, (3) the oscillatory displacement of the solar system perpendicular to the Galactic plane, (4) solar activity, (5) Galactic SN explosions, (6) GRBs, and (7) cosmic ray bursts (CRBs). The credibility of various cosmic threats will be tested by examining whether such events could have caused some of the major mass extinctions that took place on planet Earth and were documented relatively well in the geological records of the past 500 million years (Myr). A credible claim of a global threat to life from a change in global irradiation must first demonstrate that the anticipated change is larger than the periodical changes in irradiation caused by the motions of the Earth, to which terrestrial life has adjusted itself. Most of the energy of the sun is radiated in the visible range. The atmosphere is highly transparent to this visible light but is very opaque to almost all other bands of the electromagnetic spectrum except radio waves, whose production by the sun is rather small.

scholarly journals A Historical Perspective on Measurements of Solar Irradiance

1994 ◽  
Vol 143 ◽  
pp. 1-3
Author(s):  
V. Gaizauskas
Keyword(s):  
Historical Perspective ◽  
Radiant Energy ◽  
Modern Science ◽  
Past Century ◽  
The Sun ◽  
Solar Constant ◽  
Terrestrial Environment ◽  
The Past ◽  
The Earth ◽  
Wide Range

Recent measurements made from platforms in space prove beyond question that the radiant energy received from the Sun at the Earth, once called the ‘solar constant’, fluctuates over a wide range of amplitudes and time scales. The source of that variability and its impact on our terrestrial environment pose major challenges for modern science. We are confronted with a tangled web of facts which requires the combined ingenuity of solar, stellar, planetary and atmospheric scientists to unravel. This brief overview draws attention to key developments during the past century which shaped our concepts about sources of solar variability and their connection with solar activity.

scholarly journals Evaluating the Impact of Pre-clustering and Class Imbalance on Solar Flare Forecasting

2018 ◽  
Author(s):  
Mirelle C. Bueno ◽  
Guilherme P. Coelho ◽  
Ana Estela A. Da Silva ◽  
André L. S. Gradvohl
Keyword(s):  
Machine Learning ◽  
Solar Flare ◽  
Transmission Lines ◽  
Solar Flares ◽  
Power Transmission ◽  
Class Imbalance ◽  
The Sun ◽  
Power Transmission Lines ◽  
Short Circuits ◽  
The Impact

Among the phenomena that occur on the surface of the Sun, solar flares may cause several damages, from short circuits in power transmission lines to complete interruptions in telecommunications systems. In order to mitigate these effects, many works have been dedicated to the proposal of mechanisms capable of predicting the occurrence of solar flares. In this context, the present work sought to evaluate two aspects related to machine learning-based solar flare forecasting: (i) the impact of class imbalance in training datasets on the performance of the predictors; and (ii) whether the incorporation of a pre-clustering step prior to the classifiers training contributes to a better prediction.

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.

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.

Failure to forecast: A case study in nowcasting and forecasting the eruption of a coronal mass ejection and its geomagnetic impacts on Dec 7-10, 2020. 

2021 ◽  
Author(s):  
Peter Gallagher ◽  
Sophie Murray ◽  
John Malone-Leigh ◽  
Joan Campanyà ◽  
Alberto Cañizares ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Flares ◽  
Theoretical Models ◽  
Western Hemisphere ◽  
The Sun ◽  
The Earth ◽  
Simple Event ◽  
Mass Ejection

<p>Forecasting solar flares based on while-light images and photospheric magnetograms of sunspots is notoriously challenging, while accurate forecasting of coronal mass ejections (CME) is still in its infancy. That said, the chances of a CME being launched is more likely following a flare. CMEs launched from the western hemisphere and “halo” CMEs are the most likely to be geomagnetically impactful, but forecasting their arrival and impact at Earth depends on how well their velocity is known near the Sun, the solar wind conditions between the Sun and the Earth, the accuracy of theoretical models and on the orientation of the CME magnetic field.  In this presentation, we describe a well observed active region, flare, CME, radio burst and sudden geomagnetic impulse that was observed on December 7-10, 2020 by a slew of instruments (SDO, ACE, DSCOVR, PSP, US and European magnetometers). This was a solar eruption that was not expected, but the CME and resulting geomagnetic impact should have been straight-forward to model and forecast. What can we learn from our failure to forecast this simple event and its impacts at Earth? </p>

scholarly journals New improvements of HASTA for the analysis of chomospheric solar events

2009 ◽  
Vol 5 (S264) ◽  
pp. 93-95 ◽  
Author(s):  
L. Leuzzi ◽  
C. Francile ◽  
M. L. Luoni ◽  
M. Rovira ◽  
J. I. Castro
Keyword(s):  
Solar Activity ◽  
Solar Flare ◽  
Solar Flares ◽  
Scientific Community ◽  
Ccd Camera ◽  
Relevant Information ◽  
The Sun ◽  
Permanent Staff ◽  
The University ◽  
Automatic Focusing

AbstractIt is well known that chromospheric observations in the hydrogen alpha line give relevant information about solar flares, plages and protuberances, among other typical features of the Sun. From 1998 to 2006, the HAlpha Solar Telescope of Argentina (HASTA) has provided solar images to the scientific community with the technological resources available at that time. Starting in 2007, major improvements have been incorporated, like a new CCD camera with enhanced spatial and temporal resolution, filter replacement, the automatic focusing system, and a new flat-fielding procedure. The hardware changes also called for software improvements, and a new solar-flare classification routine was implemented. At present, the Félix Aguilar Observatory (OAFA) of the University of San Juan (UNSJ) has a permanent staff of observers which now permits continuous solar monitoring. We expect that all these advances will allow to analyze chromospheric solar activity, especially solar flares, in more detail.

scholarly journals Sunquakes and starquakes

2013 ◽  
Vol 9 (S301) ◽  
pp. 349-352 ◽  
Author(s):  
Alexander G. Kosovichev
Keyword(s):  
Solar Flares ◽  
High Frequency ◽  
Turbulent Convection ◽  
The Sun ◽  
Stellar Oscillations ◽  
Impulsive Excitation ◽  
Physical Mechanisms ◽  
Stellar Flares ◽  
Low Degree ◽  
High Degree

AbstractIn addition to well-known mechanisms of excitation of solar and stellar oscillations by turbulent convection and instabilities, the oscillations can be excited by an impulsive localized force caused by the energy release in solar and stellar flares. Such oscillations have been observed on the Sun (‘sunquakes’), and created a lot of interesting discussions about physical mechanisms of the impulsive excitation and their relationship to the flare physics. The observation and theory have shown that most of a sunquake's energy is released in high-degree, high-frequency p modes. In addition, there have been reports on helioseismic observations of low-degree modes excited by strong solar flares. Much more powerful flares observed on other stars can cause ‘starquakes’ of substantially higher amplitude. Observations of such oscillations can provide new asteroseismic information and also constraints on mechanisms of stellar flares. I discuss the basic properties of sunquakes, and initial attempts to detect flare-excited oscillations in Kepler short-cadence data.

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