Theoretical studies of magnetohydrodynamic equilibria and dynamics of a solar coronal loop

Details Theoretical studies of magnetohydrodynamic equilibria and dynamics of a solar coronal loop Theoretical studies of magnetohydrodynamic equilibria and dynamics of a solar coronal loop

Sep 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt.........1l&link_type=abstract

Ph.D. Thesis Cornell Univ., Ithaca, NY.

Physics

5

Coronal Loops, Magnetohydrodynamic Stability, Magnetohydrodynamics, Solar Magnetic Field, Solar Physics, Stellar Models, Current Sheets, Heating, Magnetic Field Configurations, Magnetic Field Reconnection, Magnetic Flux, Photosphere

Scientific paper

This work is concerned with the time evolution, both quasistatic and dynamical, of the magnetic fields in the solar corona, and its implications for the problem of solar coronal heating. A theoretical study is made of a collection of closed magnetic flux tubes whose footpoints are subject to slow, complicated photospheric displacements. A simple model is developed in which the effects of gravitation and curvature are ignored and the flux tubes are assumed to be long and thin. The governing equations for this model are those of nonideal reduced magnetohydrodynamics. A formalism is developed for isolating the purely quasistatic component of the system's evolution. Analytic calculations are carried out using this formalism to investigate the development of small-scale magnetic structure resulting from the footpoint motions, called a magnetic cascade. Furthermore the formalism admits a scenario whereby quasistatic evolution is interrupted by spontaneous dynamical behavior. This occurs when the present equilibrium is neutrally stable to a current driven MHD instability. The nonideal equations are solved under conditions of slow, continuous, random driving using a time dependent three dimensional computer code. The system is found to achieve a statistical steady state in which the electromechanical work done by the driving is balanced by ohmic and viscous dissipation. The most evident spatial features of these solutions are three dimensional current sheets which develop spontaneously in the interior. These are analyzed using Sweet-Parker reconnection theory. The global properties of the statistical steady state can be explained in terms of these current sheets. It is proposed that the observed current sheets develop when the present MHD equilibrium becomes unstable to current driven instabilities. At such a point the system would relax abruptly to a new equilibrium with lower magnetic energy, thereby liberating its excess energy as heat. A picture of this process is presented in terms of a greatly simplified low-dimensional analog of the reduced MHD system. This low-dimensional system is evolved numerically for long times and found to exhibit relaxations of varying amplitudes at random intervals. The statistical distribution of these events is compared to similar distributions observed in the solar corona.

Affiliated with

Also associated with

No associations

Rating

Theoretical studies of magnetohydrodynamic equilibria and dynamics of a solar coronal loop does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Theoretical studies of magnetohydrodynamic equilibria and dynamics of a solar coronal loop, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Theoretical studies of magnetohydrodynamic equilibria and dynamics of a solar coronal loop will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1565758