scholarly journals Radio Emission from the Sun and Stars: New Insights into Energetic Phenomena

2004 ◽  
Vol 219 ◽  
pp. 145-158
Author(s):  
T. S. Bastian
Keyword(s):  
Radio Emission ◽  
Energy Release ◽  
Coronal Mass Ejections ◽  
Magnetic Energy ◽  
Spectroscopic Techniques ◽  
The Sun ◽  
Late Type ◽  
Radio Observations ◽  
Dwarf Stars ◽  
Magnetic Energy Release

Energetic phenomena on the Sun and late-type stars pose a number of fascinating puzzles. These include coronal heating, flares, and coronal mass ejections, all believed to be manifestations of magnetic energy release. Radio radiation is a sensitive tracer of energetic phenomena on both the Sun and stars. Radio observations of the Sun over the past decade have produced new insights into the physics of magnetic energy release in flares and coronal mass ejections. Radio observations of late-type stars have exploited sensitive imaging and spectroscopic techniques to further constrain the nature of the relevant emission mechanisms. A surprise has been the recent discovery of radio emission from brown dwarf stars, implying the existence of substantial magnetic fields and a means of dissipating magnetic energy, neither of which are understood.

scholarly journals Magnetic energy release: flares and coronal mass ejections

2009 ◽  
Vol 5 (S264) ◽  
pp. 257-266 ◽  
Author(s):  
Cristina H. Mandrini
Keyword(s):  
Magnetic Field ◽  
Energy Release ◽  
Coronal Mass Ejections ◽  
Magnetic Energy ◽  
Radiative Energy ◽  
Electromagnetic Spectrum ◽  
Combined Analysis ◽  
Magnetic Field Topology ◽  
The Magnetic Field ◽  
Magnetic Energy Release

AbstractFree energy stored in the magnetic field is the source that powers solar and stellar activity at all temporal and spatial scales. The energy released during transient atmospheric events is contained in current-carrying magnetic fields that have emerged twisted and may be further stressed via motions in the lower atmospheric layers (i.e. loop-footpoint motions). Magnetic reconnection is thought to be the mechanism through which the stored magnetic energy is transformed into kinetic energy of accelerated particles and mass flows, and radiative energy along the whole electromagnetic spectrum. This mechanism works efficiently at scale lengths much below the spatial resolution of even the highest resolution solar instruments; however, it may imply a large-scale restructuring of the magnetic field inferred indirectly from the combined analysis of observations and models of the magnetic field topology. The aftermath of magnetic energy release includes events ranging from nanoflares, which are below our detection limit, to powerful flares, which may be accompanied by the ejection of large amounts of plasma and magnetic field (so called coronal mass ejections, CMEs), depending on the amount of total available free magnetic energy, the magnetic flux density distribution, the magnetic field configuration, etc. We describe key observational signatures of flares and CMEs on the Sun, their magnetic field topology, and discuss how the combined analysis of solar and interplanetary observations can be used to constrain the flare/CME ejection mechanism.

Magnetic energy release on the Sun

Nature ◽  
1997 ◽  
Vol 386 (6627) ◽  
pp. 760-761 ◽  
Author(s):  
James A. Klimchuk
Keyword(s):  
Energy Release ◽  
Magnetic Energy ◽  
The Sun ◽  
Magnetic Energy Release

Magnetic Energy Release and Transients in the Solar Flare of 2000 July 14

2001 ◽  
Vol 550 (1) ◽  
pp. L105-L108 ◽  
Author(s):  
A. G. Kosovichev ◽  
V. V. Zharkova
Keyword(s):  
Solar Flare ◽  
Energy Release ◽  
Magnetic Energy ◽  
Magnetic Energy Release

scholarly journals Hunting for Stellar Coronal Mass Ejections

2016 ◽  
Vol 12 (S328) ◽  
pp. 198-203
Author(s):  
Heidi Korhonen ◽  
Krisztián Vida ◽  
Martin Leitzinger ◽  
Petra Odert ◽  
Orsolya Eszter Kovács
Keyword(s):  
Time Series ◽  
Coronal Mass Ejections ◽  
Detection Probability ◽  
Open Clusters ◽  
Occurrence Rate ◽  
Archival Data ◽  
The Sun ◽  
Late Type ◽  
Optical Telescope ◽  
Balmer Lines

AbstractCoronal mass ejections (CMEs) are explosive events that occur basically daily on the Sun. It is thought that these events play a crucial role in the angular momentum and mass loss of late-type stars, and also shape the environment in which planets form and live. Stellar CMEs can be detected in optical spectra in the Balmer lines, especially in Hα, as blue-shifted extra emission/absorption. To increase the detection probability one can monitor young open clusters, in which the stars are due to their youth still rapid rotators, and thus magnetically active and likely to exhibit a large number of CMEs. Using ESO facilities and the Nordic Optical Telescope we have obtained time series of multi-object spectroscopic observations of late-type stars in six open clusters with ages ranging from 15 Myrs to 300 Myrs. Additionally, we have studied archival data of numerous active stars. These observations will allow us to obtain information on the occurrence rate of CMEs in late-type stars with different ages and spectral types. Here we report on the preliminary outcome of our studies.

scholarly journals Magnetic Energy Release in Dynamic Fan Reconnection Models

1999 ◽  
Vol 510 (2) ◽  
pp. 1045-1052 ◽  
Author(s):  
I. J. D. Craig ◽  
A. N. McClymont
Keyword(s):  
Energy Release ◽  
Magnetic Energy ◽  
Magnetic Energy Release

scholarly journals Large polar caps for twisted magnetosphere of magnetars

2019 ◽  
Author(s):  
H Tong
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Energy Release ◽  
Open Field ◽  
Magnetic Energy ◽  
Hot Spot ◽  
Open Field Line ◽  
Field Lines ◽  
The Magnetic Field ◽  
Magnetic Energy Release

Abstract The magnetic field of magnetars may be twisted compared with that of normal pulsars. Previous works mainly discussed magnetic energy release in the closed field line regions of magnetars. For a twisted magnetic field, the field lines will inflate in the radial direction. Similar to normal pulsars, the idea of light cylinder radius is introduced. More field lines will cross the light cylinder and become open for a twisted magnetic field. Therefore, magnetars may have a large polar cap, which may correspond to the hot spot during outburst. Particle flow in the open field line regions will result in the untwisting of the magnetic field. Magnetic energy release in the open field line regions can be calculated. The model calculations can catch the general trend of magnetar outburst: decreasing X-ray luminosity, shrinking hot spot etc. For magnetic energy release in the open field line regions, the geometry will be the same for different outburst in one magnetar.

scholarly journals Clark Lake Radio Observations of Coronal Mass Ejections

1990 ◽  
Vol 142 ◽  
pp. 495-500
Author(s):  
N. Gopalswamy
Keyword(s):  
White Light ◽  
Coronal Mass Ejections ◽  
The Sun ◽  
Type Ii ◽  
Radio Observations ◽  
Magnetic Structures ◽  
Effect Relationship ◽  
Positional Analysis ◽  
Type Iv ◽  
Nonthermal Particles

We review some recent studies of mass ejections from the Sun using 2-D imaging observations of the Clark Lake multifrequency radioheliograph. Radio signatures of both fast and slow coronal mass ejections (CMEs) have been observed using the Clark Lake radioheliograph. Using temporal and positional analysis of moving type IV and type II bursts, and white light CMEs we find that the type II's and CMEs need not have a direct cause and effect relationship. Instead, the type II seems to be generated by a “decoupled shock”, probably due to an associated flare. The moving type IV burst requires nonthermal particles trapped in magnetic structures associated with the CME. Since nonthermal particles can be generated independent of the speed of CMEs, moving type IV bursts need not be associated only with fast CMEs. Specific examples are presented to support these views.

On the stellar origin of low energy cosmic rays

1975 ◽  
Vol 277 (1270) ◽  
pp. 489-501 ◽  
Keyword(s):  
Cosmic Rays ◽  
Energy Release ◽  
Solar Flares ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Optical Observations ◽  
Energy Estimates ◽  
The Sun ◽  
Dwarf Stars ◽  
Evolutionary Condition

The large solar flares associated with cosmic-ray events release total bolometric energies in the region 1024-1 0 25 J. This is of the order 10~5-10~6 of the normal bolometric energy emission of the Sun. The condition of the M and K type stars when they flare is entirely different; the rate of energy release during the flare is of the same order as the normal energy release of the star in the quiescent condition. Although these dwarf stars are in a markedly different evolutionary condition compared with the Sun recent simultaneous radio and optical observations of the flares have given decisive indications that the physical processes, involving magnetic field collapse of several hundredths of a tesla, must be similar to the flare mechanism in the Sun. Adopting the factor, which has been determined empirically in the case of the Sun, for the conversion of flare energy to cosmic-ray energy, estimates are made of the fraction of galactic cosmic rays which may be generated in the flares on the M and K type stars. It is shown that these stars may be the major source of the galactic cosmic rays for energies from 106-3 x 108 eV and that the K type stars may contribute one fifth of the total cosmic-ray energy up to 109 eV.

Turbulent impulsive magnetic energy release from electron scale reconnection

2007 ◽  
Vol 14 (1) ◽  
pp. 012902 ◽  
Author(s):  
W. Horton ◽  
J.-H. Kim ◽  
F. Militello ◽  
M. Ottaviani
Keyword(s):  
Energy Release ◽  
Magnetic Energy ◽  
Magnetic Energy Release
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