IONIZATION EQUILIBRIUM TIMESCALES IN COLLISIONAL PLASMAS

Smith, Randall K

doi:10.1088/0004-637X/718/1/583

Title: IONIZATION EQUILIBRIUM TIMESCALES IN COLLISIONAL PLASMAS

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Abstract

Astrophysical shocks or bursts from a photoionizing source can disturb the typical collisional plasma found in galactic interstellar media or the intergalactic medium. The spectrum emitted by this plasma contains diagnostics that have been used to determine the time since the disturbing event, although this determination becomes uncertain as the elements in the plasma return to ionization equilibrium. A general solution for the equilibrium timescale for each element arises from the elegant eigenvector method of solution to the problem of a non-equilibrium plasma described by Masai and Hughes and Helfand. In general, the ionization evolution of an element Z in a constant electron temperature plasma is given by a coupled set of Z + 1 first-order differential equations. However, they can be recast as Z uncoupled first-order differential equations using an eigenvector basis for the system. The solution is then Z separate exponential functions, with the time constants given by the eigenvalues of the rate matrix. The smallest of these eigenvalues gives the scale of the slowest return to equilibrium independent of the initial conditions, while conversely the largest eigenvalue is the scale of the fastest change in the ion population. These results hold for an ionizing plasma, a recombiningmore »« less

Authors:

Smith, Randall K ^[1]

Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

Publication Date:: Tue Jul 20 00:00:00 EDT 2010

OSTI Identifier:: 21457117

Resource Type:: Journal Article

Journal Name:: Astrophysical Journal

Additional Journal Information:: Journal Volume: 718; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/718/1/583; Journal ID: ISSN 0004-637X

Country of Publication:: United States

Language:: English

Subject:: 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; COLLISIONAL PLASMA; DIFFERENTIAL EQUATIONS; EIGENVALUES; EIGENVECTORS; ELECTRON TEMPERATURE; EVOLUTION; IONIZATION; NON-EQUILIBRIUM PLASMA; EQUATIONS; PHYSICS; PLASMA

Citation Formats


                    Smith, Randall K, and Hughes, John P., E-mail: rsmith@cfa.harvard.ed, E-mail: jph@physics.rutgers.ed. IONIZATION EQUILIBRIUM TIMESCALES IN COLLISIONAL PLASMAS.  United States: N. p., 2010. 
        Web.  doi:10.1088/0004-637X/718/1/583.

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                    Smith, Randall K, & Hughes, John P., E-mail: rsmith@cfa.harvard.ed, E-mail: jph@physics.rutgers.ed. IONIZATION EQUILIBRIUM TIMESCALES IN COLLISIONAL PLASMAS.  United States.  https://doi.org/10.1088/0004-637X/718/1/583

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                    Smith, Randall K, and Hughes, John P., E-mail: rsmith@cfa.harvard.ed, E-mail: jph@physics.rutgers.ed. 2010.  
        "IONIZATION EQUILIBRIUM TIMESCALES IN COLLISIONAL PLASMAS".  United States.  https://doi.org/10.1088/0004-637X/718/1/583.

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@article{osti_21457117,

  title        = {IONIZATION EQUILIBRIUM TIMESCALES IN COLLISIONAL PLASMAS},

  author       = {Smith, Randall K and Hughes, John P., E-mail: rsmith@cfa.harvard.ed, E-mail: jph@physics.rutgers.ed},

  abstractNote = {Astrophysical shocks or bursts from a photoionizing source can disturb the typical collisional plasma found in galactic interstellar media or the intergalactic medium. The spectrum emitted by this plasma contains diagnostics that have been used to determine the time since the disturbing event, although this determination becomes uncertain as the elements in the plasma return to ionization equilibrium. A general solution for the equilibrium timescale for each element arises from the elegant eigenvector method of solution to the problem of a non-equilibrium plasma described by Masai and Hughes and Helfand. In general, the ionization evolution of an element Z in a constant electron temperature plasma is given by a coupled set of Z + 1 first-order differential equations. However, they can be recast as Z uncoupled first-order differential equations using an eigenvector basis for the system. The solution is then Z separate exponential functions, with the time constants given by the eigenvalues of the rate matrix. The smallest of these eigenvalues gives the scale of the slowest return to equilibrium independent of the initial conditions, while conversely the largest eigenvalue is the scale of the fastest change in the ion population. These results hold for an ionizing plasma, a recombining plasma, or even a plasma with random initial conditions, and will allow users of these diagnostics to determine directly if their best-fit result significantly limits the timescale since a disturbance or is so close to equilibrium as to include an arbitrarily long time.},

  doi          = {10.1088/0004-637X/718/1/583},

  url          = {https://www.osti.gov/biblio/21457117},
  journal      = {Astrophysical Journal},

  issn         = {0004-637X},

  number       = 1,

  volume       = 718,

  place        = {United States},

  year         = {Tue Jul 20 00:00:00 EDT 2010},

  month        = {Tue Jul 20 00:00:00 EDT 2010}

}

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