AAS 204th Meeting, June 2004
Session 39 Solar Magnetic Fields and Activity
SPD Poster, Tuesday, June 1, 2004, 10:00am-7:00pm, Ballroom

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[39.10] A Model for Dynamic Evolution of Emerging Magnetic Fields in the Sun

T. Magara (NRL/UCB, SSL)

We study the dynamic evolution of emerging magnetic fields in the solar atmosphere by deriving a model based on a three-dimensional MHD simulation. The simulation shows that magnetic field lines initially forming a twisted flux tube below the solar surface emerge into the atmosphere by magnetic buoyancy. Outer field lines of the flux tube are almost free to expand in a wide fan shape without strong confinement by surrounding field lines. On the other hand, inner field lines are subject to strong confinement by adjacent twisted field lines that prevent the lateral expansion of inner field lines. By examining the result of the simulation, we derive a model of emerging field lines to demonstrate that the height of an emerging field line increases at the average rate of (g0 \kappa)1/2H/2, where g0, \kappa, and H are the gravitational acceleration, curvature of the emerging field line, and a scale height of magnetic field strength. Applying this model to the outer and inner field lines, we show that inner field lines are less dynamical than outer field lines and inner field lines are likely to form quasistatic structure in the corona such as prominences and sigmoids. We also discuss that the shape of inner field lines is reflected in the chirality of a modeled sigmoid.

This work is financially supported by NASA ROSS-2000 NRA-00-01-SSS-057 and CISM, center for integrated space weather modeling (ATM-0120950).

If you would like more information about this abstract, please follow the link to http://sprg.ssl.berkeley.edu/~magara/Research/Research_info_MDE.html. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: magara@nrl.navy.mil

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