The Library

Magnetoacoustic shock formation near a magnetic null point

Tools

Gruszecki, M. (Marcin), Vasheghani Farahani, Soheil, Nakariakov, Valery M. and Arber, T. D.. (2011) Magnetoacoustic shock formation near a magnetic null point. Astronomy & Astrophysics, Vol.531 . Article A63. ISSN 0004-6361 (In Press)

Preview

PDF
WRAP_Arber_aa16753-11.pdf - Published Version - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Download (6Mb)

Official URL: http://dx.doi.org/10.1051/0004-6361/201116753

Abstract

We investigate the interaction of nonlinear fast magnetoacoustic waves with a magnetic null point in connection with the triggering of solar flares. Methods. We model the propagation of fast, initially axisymmetric waves towards a two-dimensional isothermal magnetic null point in terms of ideal magnetohydrodynamic equations. The numerical simulations are carried out with the Lagrangian remap code Lare2D. Results. Dynamics of initially axisymmetric fast pulses of small amplitude is found to be consistent with a linear analytical solution proposed earlier. The increase in the amplitude leads to the nonlinear acceleration of the compression pulse and deceleration of the rarefaction pulse and hence the distortion of the wave front. The pulse experiences nonlinear steepening in the radial direction either on the leading or the back slopes for the compression and rarefaction pulses, respectively. This effect is most pronounced in the directions perpendicular to the field. Hence, the nonlinear evolution of the fast pulse depends on the polar angle. The nonlinear steepening generates the sharp spikes of the electric current density. As in the uniform medium, the position of the shock formation also depends on the initial width of the pulse. Only sufficiently smooth and low-amplitude initial pulses can reach the vicinity of the null point, create there current density spikes, and initiate magnetic reconnection by seeding anomalous electrical resistivity. Steeper and higher amplitude initial pulses overturn at larger distance from the null point, and cannot trigger reconnection.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Magnetohydrodynamics, Solar flares, Sun -- Corona -- Magnetic fields
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	E D P Sciences
ISSN:	0004-6361
Date:	July 2011
Volume:	Vol.531
Page Range:	Article A63
Identification Number:	10.1051/0004-6361/201116753
Status:	Peer Reviewed
Publication Status:	In Press
Access rights to Published version:	Restricted or Subscription Access
Funder:	British Academy (BA), Royal Society (Great Britain)
Grant number:	NF090143 (BA/RS)
References:	Akimov, L. A., Belkina, I. L., Kuzin, S. V., Pertsov, A. A., & Zhitnik, I. A. 2008, Astron. Lett., 34, 851 Arber, T. D., Longbottom, A.W., Gerrard, C. L., & Milne, A. M. 2001, J. Comp. Phys., 171, 151 Büchner, J., & Elkina, N. 2005, Space Sci. Rev., 121, 237 Cally, P. S. 2001, ApJ, 548, 473 Craig, I. J., & Watson, P. G. 1992, ApJ, 393, 385 Chen, P. F., & Priest, E. R. 2006, Sol. Phys., 238, 313 Craig, I. J. D., & McClymont, A. N. 1991, ApJ, 371, L41 Foullon, C., Verwichte, E., Nakariakov, V. M., & Fletcher, L. 2005, A&A, 440, L59 Longcope, D. W., & Priest, E. R. 2007, Phys. Plasmas, 14, 122905 McLaughlin, J. A., & Hood, A. W. 2004, A&A, 420, 1129 McLaughlin, J. A., & Hood, A. W. 2006, A&A, 452, 603 McLaughlin, J. A., De Moortel, I., Hood, A. W., & Brady, C. S. 2009, A&A, 493, 227 Moon, Y., Choe, G. S., Park, Y. D., et al. 2002, ApJ, 574, 434 Nakariakov, V. M., & Melnikov, V. F. 2009, Space Sci. Rev., 149, 119 Nakariakov, V. M., Ofman, L., & Arber, T. D. 2000, A&A, 353, 741 Nakariakov, V. M., Foullon, C., Verwichte, E., & Young, N. P. 2006, A&A, 452, 343 Petkaki, P., Freeman, M. P., Kirk, T., Watt, C. E. J., & Horne, R. B. 2006, J. Geophys. Res. (Space Phys.), 111, A01205 Schrijver, C. J. 2009, Adv. Space Res., 43, 739 Sych, R., Nakariakov, V.M., Karlicky, M., & Anfinogentov, S. 2009, A&A, 505, 791 Zhugzhda, I. D., & Dzhalilov, N. S. 1982, A&A, 112, 16
URI:	http://wrap.warwick.ac.uk/id/eprint/38508