TY - JOUR

T1 - Nonlinear fast magnetoacoustic wave propagation in the neighbourhood of a 2D magnetic X-point: oscillatory reconnection

AU - McLaughlin, James

AU - de Moortel, Ineke

AU - Hood, Alan William

AU - Brady, Christopher S.

PY - 2009/1

Y1 - 2009/1

N2 - Context: This paper extends the models of Craig & McClymont (1991, ApJ, 371, L41) and McLaughlin & Hood (2004, A&A, 420, 1129) to include finite β and nonlinear effects.
Aims: We investigate the nature of nonlinear fast magnetoacoustic waves about a 2D magnetic X-point.
Methods: We solve the compressible and resistive MHD equations using a Lagrangian remap, shock capturing code (Arber et al. 2001, J. Comp. Phys., 171, 151) and consider an initial condition in {v}×{B} \cdot {hat{z}} (a natural variable of the system).
Results: We observe the formation of both fast and slow oblique magnetic shocks. The nonlinear wave deforms the X-point into a “cusp-like” point which in turn collapses to a current sheet. The system then evolves through a series of horizontal and vertical current sheets, with associated changes in connectivity, i.e. the system exhibits oscillatory reconnection. Our final state is non-potential (but in force balance) due to asymmetric heating from the shocks. Larger amplitudes in our initial condition correspond to larger values of the final current density left in the system.
Conclusions: The inclusion of nonlinear terms introduces several new features to the system that were absent from the linear regime.

AB - Context: This paper extends the models of Craig & McClymont (1991, ApJ, 371, L41) and McLaughlin & Hood (2004, A&A, 420, 1129) to include finite β and nonlinear effects.
Aims: We investigate the nature of nonlinear fast magnetoacoustic waves about a 2D magnetic X-point.
Methods: We solve the compressible and resistive MHD equations using a Lagrangian remap, shock capturing code (Arber et al. 2001, J. Comp. Phys., 171, 151) and consider an initial condition in {v}×{B} \cdot {hat{z}} (a natural variable of the system).
Results: We observe the formation of both fast and slow oblique magnetic shocks. The nonlinear wave deforms the X-point into a “cusp-like” point which in turn collapses to a current sheet. The system then evolves through a series of horizontal and vertical current sheets, with associated changes in connectivity, i.e. the system exhibits oscillatory reconnection. Our final state is non-potential (but in force balance) due to asymmetric heating from the shocks. Larger amplitudes in our initial condition correspond to larger values of the final current density left in the system.
Conclusions: The inclusion of nonlinear terms introduces several new features to the system that were absent from the linear regime.

UR - http://adsabs.harvard.edu/abs/2009A%26A...493..227M

U2 - 10.1051/0004-6361:200810465

DO - 10.1051/0004-6361:200810465

M3 - Article

VL - 493

SP - 227

EP - 240

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 1

ER -