E-Print Archive

There are 4002 abstracts currently viewable.


Advanced Search
Main Page Add New E-Print Submitter
News Help/FAQ About Preferences
Manage Key Phrase
Determination of Stochastic Acceleration Model Characteristics in Solar Flares View all abstracts by submitter

Qingrong Chen   Submitted: 2013-07-09 15:23

Following our recent paper (Petrosian & Chen 2010), we have developed an inversion method to determine the basic characteristics for the model of stochastic acceleration of particles by plasma waves or turbulence directly and non-parametrically from observations in the framework of the leaky box version of the Fokker-Planck kinetic equation. These characteristics are determined by wave-particle interactions as described by the momentum and pitch angle diffusion coefficients. Our method relates these coefficients directly to observations. In particular, we show that by inverting the Fokker-Planck equation to its integral form, one can derive the energy diffusion coefficient and direct acceleration rate by turbulence in terms of the accelerated and escaping particle spectra. We apply the analytic formulas to the suprathermal electrons in solar flares, which produce hard X-ray emission at the coronal loop top (LT) region and two thick target footpoint regions of the flare loop. We utilize the regularized electron flux spectral images recently developed for the Reuven Ramaty High Energy Solar Spectroscopic Imager ({it RHESSI}). From the spatially resolved electron flux spectra, we determine the electron escape time, which is related to the pitch angle scattering rate, and the energy diffusion coefficient at the LT acceleration region. Results obtained from two relatively intense {it RHESSI} events indicate that the escape time increases with energy and the energy diffusion (or direct acceleration) time and scattering time have dramatically different energy dependences. Such behaviors may be difficult to explain by existing wave-particle interaction models, and may indicate that a different acceleration mechanism is at work or imply a breakdown of the basic interpretation of the escape of electrons being a random walk process. The discrepant energy dependences can be alleviated somewhat by a turbulence spectrum that is much steeper than the Kolmogorov-type spectrum. On the other hand, a more likely explanation could be that the escape of electrons out of the LT acceleration region is governed by converging field lines in a magnetic mirror geometry, in which the escape time is proportional to scattering time. The results demonstrate the critical importance of combined modeling of electron acceleration by plasma wave turbulence and the large scale magnetic field variations in a reconnection environment.

Authors: Qingrong Chen and Vahé Petrosian
Projects: RHESSI

Publication Status: submitted to ApJ
Last Modified: 2013-07-10 13:40
Go to main E-Print page  The multi-thermal  emission in solar active regions  Cross-sectional area and intensity variations of sausage modes  Edit Entry  Download Preprint  Delete Entry 

Go to main E-Print pageGo to main E-Print page.
Previous AbstractPrevious Abstract.
Next AbstractNext Abstract.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
View All Abstracts By SubmitterView all abstracts by submitter.
Delete AbstractDelete abstract.

Latest Entries
The Role of a Tiny Brightening in a Huge Geo-effective Solar Eruption Leading to the St Patrick's Day Storm
A basal contribution from p-modes to the Alfvénic wave flux in the corona
Multiwavelength Study of Equatorial Coronal-Hole Jets
Non-thermal hydrogen Lyman line and continuum emission in solar flares generated by electron beams
Determining normal mode features from numerical simulations using CEOF analysis: I. Test case using transverse oscillations of a magnetic slab
Modelling the Effect of Mass-Draining on Prominence Eruptions
Transverse waves in coronal flux tubes with thick boundaries: The effect of longitudinal flows
Electron distribution and energy release in magnetic reconnection outflow regions during the pre-impulsive phase of a solar flare
Benchmarking CME arrival time and impact: Progress on metadata, metrics, and events
First Unambiguous Imaging of Large-Scale Quasi-Periodic Extreme-Ultraviolet Wave or Shock
Coronal Imaging with the Solar UltraViolet Imager
Investigation of pre-flare dynamics using the weighted horizontal magnetic gradient method: From small to major flare classes
Seismological determination of the Alfvén speed and plasma-beta in solar photospheric bright points
Dynamo Wave Patterns Inside the Sun Revealed by Torsional Oscillations
Evidence of Twisting and Mixed-polarity Solar Photospheric Magnetic Field in Large Penumbral Jets: IRIS and Hinode Observations
Dissipation scale lengths of density turbulence in the inner solar wind
On the Possibility of Generating Harmonics of the Electron Plasma Frequency in the Solar Atmosphere due to Explosive Instability in a System of Interpenetrating Electron and Ion Flows
Determination of the total accelerated electron rate and power using solar flare hard X-ray spectra
Transition from axi- to nonaxisymmetric dynamo modes in spherical convection models of solar-like stars
Can high-mode magnetohydrodynamic waves propagating in a spinning macrospicule be unstable due to the Kelvin-Helmholtz instability?

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey

© 2003 Solar Physics Group - Montana State University