Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmsh52a0437l&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #SH52A-0437
Physics
7507 Chromosphere, 7509 Corona, 7513 Coronal Mass Ejections, 7835 Magnetic Reconnection, 7843 Numerical Simulation Studies
Scientific paper
Reconnection in the solar corona is believed to be important for a series of processes from flares and CMEs to coronal heating. However, theoretical understanding of the reconnection process still remains elusive. The reconnection rate predicted by the Sweet-Parker model is determined by resistivity and is very many orders of magnitude too small to explain the observations. A possible mechanism that can provide fast reconnection rate is driven reconnection, When external flows drive field lines together, the rate of reconnection is determined by the driving mechanism and is indipendent of resistivity. In related works applied to the Earth's magnetopause [1], it as been shown that a Kelvin Helmholtz instability (KHI) can cause local compressive motions that push field lines together and drive reconnection. We propose here that the same mechanism could conceivably be at work in the solar corona. We propose that photospheric motions cause torsional Alfven waves that propagate in the chromosphere and are amplified in the transition regions, emerging as sizabe velocity shears in the solar corona. Simulaiton works have proposed that such shear can be amplified to a good fraction (e.g. 0.3) of the Alfven speed [2]. The velocity shear injected in the corona can cause magnetic loops previously stressed by photospheric motions [3] to reconnect. We have conducted a series of simulation to prove this scenario and to observe the properties of the reconneciton process. We have shown that indeed reconnection can be achieved trough local compression driven by the KHI and that the reconnection rate in that case is not sensitive to resistivity. [1] Brackbill, J.U., Knoll, D.A., Phys. Rev. Lett., 86, 2329 (2001) [2] Kudoh, T., Shibata K., Ap. J., 514, 493 (1999) [3] Mikic, Z., Barnes, D.C., Schnack, D.D., Ap. J., 328, 830 (1988)
Knoll D.
Lapenta Giovanni
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