Journal article
UBIQUITOUS NON-THERMALS IN ASTROPHYSICAL PLASMAS: RESTATING THE DIFFICULTY OF MAINTAINING MAXWELLIANS
The Astrophysical journal, Vol.770(1), pp.1-11
06/10/2013
DOI: 10.1088/0004-637X/770/1/26
Abstract
This paper outlines the rather narrow conditions on a radiatively decoupled plasma where a Maxwell-Boltzmann (MB) distribution can be assumed with confidence. The complementary non-thermal distribution with non-perturbative kurtosis is argued to have a much broader purview than has previously been accepted. These conditions are expressed in terms of the electron Knudsen number, K{sub e} , the ratio of the electron mean free path to the scale length of electron pressure. Rather generally, f(v < v{sub 2}(K{sub e} )) will be Gaussian, so that MB atomic or wave particle effects controlled by speeds v < v{sub 2} {identical_to} w(15/8K{sub e} ){sup 1/4} will remain defensible, where w is the most probable speed. The sufficient condition for Spitzer-Braginskii plasma fluid closure at the energy equation requires globally K{sub e} (s) {<=} 0.01; this global condition pertains to the maximum value of K{sub e} along the arc length s of the magnetic field (to its extremities) provided that contiguous plasma remains uncoupled from the radiation field. The non-thermal regime K{sub e} > 0.01 is common in all main-sequence stellar atmospheres above approximately 0.05 stellar radii from the surface. The entire solar corona and wind are included in this regime where non-thermal distributions with kurtosis are shown to be ubiquitous, heat flux is not well modeled by Spitzer-Braginskii closure, and fluid modeling is qualitative at best.
Details
- Title: Subtitle
- UBIQUITOUS NON-THERMALS IN ASTROPHYSICAL PLASMAS: RESTATING THE DIFFICULTY OF MAINTAINING MAXWELLIANS
- Creators
- J. D Scudder - University of IowaH Karimabadi - SciberQuest (United States)
- Resource Type
- Journal article
- Publication Details
- The Astrophysical journal, Vol.770(1), pp.1-11
- DOI
- 10.1088/0004-637X/770/1/26
- ISSN
- 0004-637X
- eISSN
- 1538-4357
- Publisher
- Institute of Physics (IOP)
- Language
- English
- Date published
- 06/10/2013
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199854002771
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