scholarly journals Energetic particle acceleration and transport by Alfvén/acoustic waves in tokamak-like Solar flares

2010 ◽  
Vol 6 (S274) ◽  
pp. 162-164
Author(s):  
Martin Obergaulinger ◽  
Manuel García-Muñoz
Keyword(s):  
Solar Flares ◽  
Acoustic Waves ◽  
Energetic Particle ◽  
Fusion Plasmas ◽  
Experimental Phase ◽  
Astrophysical Plasmas ◽  
Energetic Ions ◽  
Laboratory Plasmas ◽  
Magnetically Confined ◽  
Particle Exchange

AbstractAlfven/acoustic waves are ubiquitous in astrophysical as well as in laboratory plasmas. Their interplay with energetic ions is of crucial importance to understanding the energy and particle exchange in astrophysical plasmas as well as to obtaining a viable energy source in magnetically confined fusion devices. In magnetically confined fusion plasmas, an experimental phase-space characterisation of convective and diffusive energetic particle losses induced by Alfven/acoustic waves allows for a better understanding of the underlying physics. The relevance of these results in the problem of the anomalous heating of the solar corona is checked by MHD simulations of Tokamak-like Solar flare tubes.

scholarly journals On the accuracy of the binary-collision algorithm in particle-in-cell simulations of magnetically confined fusion plasmas

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Timo P. Kiviniemi ◽  
Eero Hirvijoki ◽  
Antti J. Virtanen
Keyword(s):  
Finite Difference ◽  
Electric Fields ◽  
Finite Size ◽  
Binary Collision ◽  
Conserved Quantities ◽  
Fusion Plasmas ◽  
Fusion Plasma ◽  
Particle In Cell ◽  
Magnetically Confined ◽  
Scale Length

Ideally, binary-collision algorithms conserve kinetic momentum and energy. In practice, the finite size of collision cells and the finite difference in the particle locations affect the conservation properties. In the present work, we investigate numerically how the accuracy of these algorithms is affected when the size of collision cells is large compared with gradient scale length of the background plasma, a parameter essential in full- $f$ fusion plasma simulations. Additionally, we discuss implications for the conserved quantities in drift-kinetic formulations when fluctuating magnetic and electric fields are present: we suggest how the accuracy of the algorithms could potentially be improved with minor modifications.

Observations of the ultraviolet and x-ray brightness profiles and cooling rates of Kr and Ar in magnetically confined fusion plasmas

2000 ◽  
Vol 61 (3) ◽  
pp. 3042-3052 ◽  
Author(s):  
M. May ◽  
K. Fournier ◽  
D. Pacella ◽  
H. Kroegler ◽  
J. Rice ◽  
...  
Keyword(s):  
Fusion Plasmas ◽  
Cooling Rates ◽  
X Ray ◽  
Magnetically Confined

The sheath region of April 2020 magnetic cloud and the associated energetic ions 

2021 ◽  
Author(s):  
Emilia Kilpua ◽  
Simon Good ◽  
Nina Dresing ◽  
Rami Vainio ◽  
Emma Davies ◽  
...  
Keyword(s):  
Flux Rope ◽  
Leading Edge ◽  
Heliospheric Current Sheet ◽  
Acceleration Process ◽  
Astrophysical Plasmas ◽  
Energetic Ions ◽  
Sheath Region ◽  
Open Questions ◽  
Mass Ejection

<p>Acceleration of energetic particles is a fundamental and ubiquitous mechanism in space and astrophysical plasmas. One of the open questions is the role of the sheath region behind the shock in the acceleration process. We analyze observations by Solar Orbiter, BepiColombo and the L1 spacecraft to explore the structure of a coronal mass ejection (CME)-driven sheath and its relation to enhancements of energetic ions that occurred on April 19-20, 2020. Our detailed analysis of the magnetic field, plasma and particle observations show that the enhancements were related to the Heliospheric Current Sheet crossings related to the reconnecting current sheets in the vicinity of the shock and a mini flux rope that was compressed at the leading edge of the CME ejecta. This study highlights the importance of smaller-scale sheath structures for the energization process. These structures likely formed already closer to the Sun and were swept and compressed from the upstream wind past the shock into the sheath. The upcoming observations by the recent missions (Solar Orbiter, Parker Solar Probe and BepiColombo) provide an excellent opportunity to explore further their role.  </p>

ANALYSIS OF ENERGETIC PARTICLE EVENTS FOLLOWING SOLAR FLARES OF SEPTEMBER 24 AND NOVEMBER 22, 1977

1979 ◽  
pp. 413-416 ◽  
Author(s):  
V.G. Kurt ◽  
Yu.I. Logachev ◽  
V.G. Stolpovsky ◽  
N.F. Pissarenko ◽  
M. Gros ◽  
...  
Keyword(s):  
Solar Flares ◽  
Energetic Particle

scholarly journals Mechanisms for Flash Phase Phenomena in Solar Flares

1974 ◽  
Vol 57 ◽  
pp. 253-282 ◽  
Author(s):  
Dean F. Smith
Keyword(s):  
Solar Flares ◽  
Acoustic Waves ◽  
Plasma Waves ◽  
Electron Plasma ◽  
X Rays ◽  
Fermi Acceleration ◽  
Acceleration Region ◽  
Low Frequencies ◽  
Coulomb Collisions ◽  
The Earth

Mechanisms for explaining the various forms of particles and radiation observed during the flash phase of solar flares are reviewed under the working hypothesis that the flash phase is the time in which electrons and to a lesser degree protons are accelerated in less than one second. A succession of such accelerations is allowed to explain longer lasting or quasi-periodic phenomena. Mechanisms capable of such acceleration are reviewed and it is concluded that first-order Fermi acceleration in a reconnecting current sheet is the most likely basic process. Such acceleration, however, gives rise to a rather narrow distribution of particle velocities along a given field line which is unstable to the production of electron plasma and ion-acoustic waves. This plasma turbulence can heat the plasma to produce soft X-rays and filter the initially narrow velocity distribution to produce a power law energy distribution. Electrons travelling inward from the acceleration region produce hard X-rays by bremsstrahlung and microwave bursts by gyro-synchrotron emission. Whereas the interpretation of X-ray spectra is relatively straightforward, the interpretation of microwave spectra is difficult because the source at low frequencies can be made optically thick by several different mechanisms.Electrons travelling further inward presumably thermalize and produce impulsive EUV and Hα emission. The theory for these emissions, although amenable to present techniques in radiative transfer, has not been worked out. Electrons travelling outward give rise to type III radio bursts by excitation of electron plasma waves and the electrons observed at the Earth. Study of the interaction of a stream of electrons with the ambient plasma shows that the electron spectra observed at the Earth do not necessarily reflect their spectrum at the acceleration region since they interact via plasma waves as well as through Coulomb collisions. The mechanisms for the conversion of plasma waves into radiation and the propagation of the radiation from its source to the observer are reviewed.

scholarly journals Magnetohydrodynamic activity and energetic ions in fusion plasmas

2007 ◽  
Vol 49 (5A) ◽  
pp. A159-A166 ◽  
Author(s):  
Ya I Kolesnichenko ◽  
V V Lutsenko ◽  
V S Marchenko ◽  
A Weller ◽  
R B White ◽  
...  
Keyword(s):  
Fusion Plasmas ◽  
Energetic Ions

X-ray Spectral Synthesis in Hydrodynamic Flare Models

1990 ◽  
Vol 115 ◽  
pp. 126-131
Author(s):  
S. Serio ◽  
E. Antonucci ◽  
M.A. Dodero ◽  
G. Peres ◽  
F. Reale
Keyword(s):  
Solar Flares ◽  
Energy Deposition ◽  
Electron Beams ◽  
Spectral Synthesis ◽  
Theoretical Models ◽  
Hydrodynamic Models ◽  
X Ray ◽  
Relativistic Electron Beams ◽  
Stellar Flares ◽  
Magnetically Confined

AbstractCompact solar flares are triggered by sudden energy release in magnetically confined plasma. This class of flares is well suited to be studied with numerical hydrodynamic models. In particular, one can compare the evolution of observed and synthetic X-ray spectra, computed under various assumptions for the mechanism of impulsive energy deposition, to constrain theoretical models and their parameter space. We discuss recent results on solar flares along this line, non thermal to models of energy depositions by relativistic electron beams. We shall also discuss possible applications of X-ray spectral synthesis to stellar flares.

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