scholarly journals Interferometry of Solar Flares at 3-mm Wavelength

1994 ◽  
Vol 154 ◽  
pp. 131-135
Author(s):  
M. R. Kundu ◽  
S. M. White ◽  
N. Gopalswamy ◽  
J. Lim
Keyword(s):  
Particle Acceleration ◽  
Solar Flares ◽  
Acceleration Process ◽  
X Ray ◽  
Steep Rise ◽  
Show Evidence ◽  
Rise Phase

We describe a set of millimeter interferometric observations of solar flares carried out in conjunction with GRO experiments during the 1991 June Campaign of the Max'91 Program. We show evidence that millimeter emission probes the most energetic (MeV) electrons in solar flares; we also find that in the same flare there can be both impulsive nonthermal and gradual thermal millimeter emission. Millimeter emission usually occurs at the steep rise phase of the hard X-ray emitting electrons (25-100 KeV). There appears to exist some delay between BIMA mm-emission onset and GRO-BATSE 25-100 KeV X-ray emission. Both results have implications for the particle acceleration process.

scholarly journals Particle Orbits, Trapping, and Acceleration in a Filamentary Current Sheet Model

1994 ◽  
Vol 142 ◽  
pp. 719-728
Author(s):  
Bernhard Kliem
Keyword(s):  
Particle Acceleration ◽  
Electric Field ◽  
Test Particle ◽  
Solar Flares ◽  
Acceleration Of Particles ◽  
Acceleration Process ◽  
Two Dimensional ◽  
Magnetic Island ◽  
Particle Orbits ◽  
Island Dynamics

AbstractTest particle orbits in the two-dimensional Fadeev equilibrium with a perpendicular electric field added are analyzed to show that impulsive bursty reconnection, which has been proposed as a model for fragmentary energy release in solar flares, may account also for particle acceleration to (near) relativistic energies within a fraction of a second. The convective electric field connected with magnetic island dynamics can play an important role in the acceleration process.Subject headings: acceleration of particles — MHD — plasmas — Sun: corona — Sun: flares

Observations of Energetic Electrons in Solar Flares

1990 ◽  
Vol 142 ◽  
pp. 438-438
Author(s):  
B. Lokanadham
Keyword(s):  
Particle Acceleration ◽  
Energy Release ◽  
Observational Data ◽  
Solar Flares ◽  
Energetic Electrons ◽  
X Ray

A study of the simultaneous observations of solar flares in optical, radio and X-ray bands is important in understanding the process of energy release and particle acceleration in the explosive phenomena of solar flares. In order to determine the characteristics of such energetic electrons in solar flares, a total number of 50 two-ribbon flares have been carefully selected during the period 1979-89 having simultaneous observational data in the optical, X-ray and radio bands.

scholarly journals The Flash Phase of Solar Flares: Satellite Observations of Electrons

1974 ◽  
Vol 57 ◽  
pp. 201-223
Author(s):  
R. P. Lin
Keyword(s):  
Solar Flares ◽  
Plasma Waves ◽  
Quantitative Information ◽  
Satellite Observations ◽  
Acceleration Process ◽  
Relativistic Electrons ◽  
Lower Corona ◽  
X Ray ◽  
Type Iii ◽  
Second Stage

Satellite observations of solar electrons bearing on flare particle acceleration and the generation of radio and X-ray emission are reviewed. The observations support a two stage acceleration process for electrons, one stage commonly occurring at the flare flash phase and accelerating electrons up to ~ 100 keV, and a second stage occurring only in large proton flares and accelerating electrons up to relativistic energies. The location of the acceleration region appears to be no lower than the lower corona.The accelerated non-relativistic electrons generate type III radio burst emission as they escape from the Sun. Direct spacecraft observations of the type III emission generated near 1 AU and the energetic electrons, provide quantitative information on the characteristics of the electrons exciting type III emission, the production of plasma waves, and the conversion from plasma waves to electromagnetic radiation.

scholarly journals Radio and X-ray diagnostics of electrons accelerated in solar flares

2006 ◽  
Vol 2 (14) ◽  
pp. 88-88
Author(s):  
Miroslav Bárta ◽  
Marian Karlický
Keyword(s):  
Particle Acceleration ◽  
Solar Flare ◽  
Test Particle ◽  
Solar Flares ◽  
Global Scale ◽  
X Ray ◽  
Particle Simulations

AbstractStarting from 2.5D MHD modelling of solar flares on a global scale we calculate (using the PIC and test-particle simulations) the radio and X-ray emissions generated in solar flare reconnection. Our results – the radio and X-ray spectra and brightness distributions, and their dynamics – are directly comparable with observations providing thus a test of particle acceleration models as well as of the ‘standard’ global flare scenario.

scholarly journals Impulsive (Flash) Phase of Solar Flares: Hard X-Ray, Microwave, EUV and Optical Observations

1974 ◽  
Vol 57 ◽  
pp. 105-141 ◽  
Author(s):  
S. R. Kane
Keyword(s):  
Solar Flares ◽  
Electromagnetic Emission ◽  
Impulsive Phase ◽  
Point Of View ◽  
Optical Observations ◽  
Acceleration Process ◽  
Short Pulses ◽  
X Ray ◽  
High Acceleration ◽  
Electromagnetic Emissions

Recent observations of impulsive hard X-ray, microwave, EUV and optical emissions during solar flares are briefly reviewed in order to deduce the characteristics of the impulsive (flash) phase phenomenon in small solar flares particularly from the point of view of the acceleration of electrons and their role in producing the various impulsive phase emissions. Observed and deduced characteristics of the various electromagnetic emission sources are summarized (Table II). The deduced characteristics of the electron acceleration process (Table III) indicate a process with high acceleration efficiency. The observations are found to be consistent with a model in which electrons are accelerated in a series of short pulses each lasting for ≲ 1 s and the accelerated electrons provide the energy necessary for all the observed electromagnetic emissions produced during the flash phase of small solar flares. Models of the impulsive phase emissions in which energetic electrons play a prominant role are examined and crucial tests to check the accuracy of these models are indicated (Table IV).

Particle acceleration and the decay of soft X-ray non-thermal line broadening in solar flares

Solar Physics ◽  
1994 ◽  
Vol 154 (1) ◽  
pp. 157-175 ◽  
Author(s):  
David Alexander ◽  
Sarah A. Matthews
Keyword(s):  
Particle Acceleration ◽  
Solar Flares ◽  
Line Broadening ◽  
X Ray ◽  
Thermal Line

scholarly journals Particle Acceleration in Solar Flares

1989 ◽  
Vol 104 (1) ◽  
pp. 431-447
Author(s):  
Loukas Vlahos
Keyword(s):  
Particle Acceleration ◽  
Electric Fields ◽  
Solar Flares ◽  
Coherent Radiation ◽  
Acceleration Process ◽  
Physical Processes ◽  
Complex Process ◽  
New Findings ◽  
Short Time ◽  
Scale Length

AbstractParticle acceleration during solar flares is a complex process where the main ‘actors’ (Direct (D.C.) or turbulent electric fields) are hidden from us. It is easy to construct a successful particle accelertion model if we are allowed to impose on the flaring region arbitrary conditions (e.g., strength and scale length of the D.C. or turbulent electric fields), but then we have not solved the acceleration problem; we have simply re-defined it. We outline in this review three recent observations which indicate that the following physical processes may happen during solar flares : (1) Release of energy in a large number of microflares ; (2) short time-scales; (3) small length scales; and (4) coherent radiation and acceleration sources. We propose that these new findings force us to reformulate the acceleration process inside a flaring active region assuming that a large number of reconnection sites will burst almost simultaneously. All the well-known acceleration mechanisms (electric fields, turbulent fields, shock waves, etc.) reviewed briefly here, can be used in a statistical model where each particle is gaining energy through its interaction with many small reconnection sites.

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