Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 16 1 2009 10.5194/npg-16-1-2009 http://www.nonlin-processes-geophys.net/16/1/2009/ http://www.nonlin-processes-geophys.net/16/1/2009/npg-16-1-2009.html http://www.nonlin-processes-geophys.net/16/1/2009/npg-16-1-2009.pdf 1 10 2009-01-16 Solar wind interaction with the Earth's magnetosphere: the role of reconnection in the presence of a large scale sheared flow F. Califano califano@df.unipi.it M. Faganello F. Pegoraro F. Valentini Physics Dept., University of Pisa, Pisa, Italy Physics Dept., University of Calabria, Arcavacata di Rende, Italy The Earth's magnetosphere and solar wind environment is a laboratory of excellence for the study of the physics of collisionless magnetic reconnection. At low latitude magnetopause, magnetic reconnection develops as a secondary instability due to the stretching of magnetic field lines advected by large scale Kelvin-Helmholtz vortices. In particular, reconnection takes place in the sheared magnetic layer that forms between adjacent vortices during vortex pairing. The process generates magnetic islands with typical size of the order of the ion inertial length, much smaller than the MHD scale of the vortices and much larger than the electron inertial length. The process of reconnection and island formation sets up spontaneously, without any need for special boundary conditions or initial conditions, and independently of the initial in-plane magnetic field topology, whether homogeneous or sheared. Attico, N., Califano, F., and Pegoraro, F.: Fast collisionless reconnection in the whistler frequency range, Phys. Plasmas, 7, 2381–2387, doi:10.1063/1.874076, 2000. Belmont, G. and Chanteur, G.: Kelvin-Helmholtz instability: nonlinear evolution, in: Turbulence and Nonlinear Dynamics in MHD Flows, edited by: Meneguzzi, M., Pouquet, A., and Sulem, P., Elsevier Science Publishers (North Holland), 1989. Bian, N. and Vekstein, G.: On the two-fuid modification of the resistive tearing instability, Phys. Plasmas, 14, 120702, doi:10.1063/1.2820904, 2007. Chen, L., Bhattacharjee, A., Puhl-Quinn, P. A., et al.: Observation of energetic electrons within magnetic islands, Nature Phys., 4, 19–23, doi:10.1038/nphys777, 2008. Coppi, B.: Inertial instabilities in plasmas, Phys. Lett., 11, 226–228, doi:10.1016/0031-9163(64)90419-6, 1964. Deng, X. H. and Matsumoto, H.: Rapid magnetic reconnection in the Earth's magnetosphere mediated by whistler waves, Nature, 410, 557–560, doi:10.1038/35069018, 2001. Drake, J., Shay, M., and Swisdak, M.: The Hall fields and fast magnetic reconnection, Phys. Plasmas, 15, 042306, doi:10.1063/1.2901194, 2008. Frey, H., Phan, T., Fuselier, S., and Mende, S.: Continuous magnetic reconnection at Earth's magnetopause, Nature, 426, 533, doi:10.1038/nature02084, 2003. Faganello, M., Califano, F., and Pegoraro, F.: Competing Mechanisms of Plasma Transport in Inhomogeneous Configurations with Velocity Shear: The Solar-Wind Interaction with Earth's Magnetosphere, Phys. Rev. Lett., 100, 015001, doi:10.1103/PhysRevLett.100.015001, 2008. Faganello, M., Califano, F., and Pegoraro, F.: Numerical Evidence of Undriven, Fast Reconnection in the Solar-Wind Interaction with Earth's Magnetosphere: Formation of Electromagnetic Coherent Structures, Phys. Rev. Lett., 101, 105001, doi:10.1103/PhysRevLett.101.105001, 2008. Faganello, M., Califano, F., and Pegoraro, F.: Time window for magnetic reconnection in plasma configurations with velocity shear, Phys. Rev. Lett., 101, 175003, doi:10.1103/PhysRevLett.101.175003, 2008. Furth, H. P., Killeen, J., Rosenbluth, M. N., et al.: Finite-Resistivity Instabilities of a Sheet Pinch, Phys. Fluids, 6, 459–484, doi:10.1063/1.1706761, 1963. Hasegawa, H., Fujimoto, M., Phan, T.-D., et al.: Transport of solar wind into Earth’s magnetosphere through rolled-up Kelvin-Helmholtz vortices, Nature, 430, 755, doi:10.1038/nature02799, 2004. Hasegawa, H., Sonnerup, B. U. Ö., Klecker, B., Paschmann, G., Dunlop, M. W., and Rème, H.: Optimal reconstruction of magnetopause structures from Cluster data, Ann. Geophys., 23, 973–982, 2005. Hesse, M. and Winske, D.: Hybrid Simulations of Collisionless Reconnection in Current Sheets, J. Geophys. Res., 99, 11177–11192, doi:10.1029/94JA00676, 1998. Landi, S., Velli, M., and Einaudi, G.: Alfvén Waves and Shock Wave Formation at an X-Point Magnetic Field Configuration, Astrophys. J., 624, 392–401, doi:10.1086/428822, 2005. Liu, Z. X. and Hu, Y. D.: Local magnetic reconnection caused by vortices in the flow field, Geophys. Res. Lett., 15, 752–755, doi:10.1029/GL015i008p00752, 1988. Mandt, M., Denton, R., and Drake, J.: Transition to Whistler Mediated Magnetic Reconnection, Geophys. Res. Lett., 21, 73–76, doi:10.1029/93GL03382, 1994. Matsumoto, Y. and Hoshino, M.: Onset of turbulence induced by a Kelvin-Helmholtz vortex, Geophys. Res. Lett., 31, L02807, doi:10.1029/2003GL018195, 2004. Miura, A.: Compressible magnetohydrodynamic Kelvin-Helmholtz instability with vortex pairing in the two-dimensional transverse configuration, Phys. Plasmas, 4, 2871–2885, doi:10.1063/1.872419, 1997. Mozer, F. S., Bale, S. D., and Phan, T. D.: Evidence of Diffusion Regions at a Subsolar Magnetopause Crossing, Phys. Rev. Lett., 89, 015002, doi:10.1103/PhysRevLett.89.015002, 2004. Nagai, T., Shinohara, I., and Fujimoto, M.: Geotail observations of the Hall current system: Evidence of magnetic reconnection in the magnetotail, J. Geophys. Res., 106, 25929–25950, doi:10.1029/2001JA900038, 2001. Nykyri, K. and Otto, A.: Influence of the Hall term on KH instability and reconnection inside KH vortices, Ann. Geophys., 22, 935–949, 2004. Nykyri, K., Otto, A., Lavraud, B., Mouikis, C., Kistler, L. M., Balogh, A., and Rème, H.: Cluster observations of reconnection due to the Kelvin-Helmholtz instability at the dawnside magnetospheric flank, Ann. Geophys., 24, 2619–2643, 2006. Nakamura, T. and Fujimoto, M.: Magnetic reconnection within MHD-scale Kelvin-Helmholtz vortices triggered by electron inertial effects, Adv. Space Res., 37, 522–526, doi:10.1016/j.asr.2005.01.057, 2006. Oieroset, M., Phan, T. D., Fujimoto, M., et al: In situ detection of collisionless reconnection in the Earth’s magnetotail, Nature, 412, 414–417, doi:10.1038/35086520, 2001. Otto, A. and Fairfield, D.: Kelvin-Helmholtz instability at the magnetotail boundary: MHD simulation and comparison with Geotail observations, J. Geophys. Res., 105, 21175–21190, doi:10.1029/1999JA000312, 2000. Retinò, A., Sundkvist, D., Vaivads, A., et al.: In situ evidence of magnetic reconnection in turbulent plasma, Nature Phys., 3, 236–238, doi:10.1038/nphys574, 2007. Shay, M., Drake, J., Denton, R., and Biskamp, D.: Structure of the dissipation region during collisionless magnetic reconnection, J. Geophys. Res., 103, 9165–9176, doi:10.1029/97JA03528, 1998. Shay, M., Drake, J., Rogers, B. N., Denton, R.: The Scaling of Collisionless, Magnetic Reconnection for Large Systems, Geophys. Res. Lett., 26, 2163–2166, doi:10.1029/1999GL900481, 1999. Smyth, W. D.: Secondary Kelvin-Helmholtz instability in weakly stratified shear flow, J. Fluid Mech., 497, 67–98, 2003. Uzdensky, D. A. and Kulsrud, R. M.: Physical origin of the quadrupole out-of-plane magnetic field in Hall-magnetohydrodynamic reconnection, Phys. Plasmas, 13, 062305, doi:10.1063/1.2210504, 2006. Valentini, F., Trávnícek, P., Califano, F., et al.: A Hybrid-Vlasov Model based on the Current Advance Method for the Simulation of Collisionless Magnetized Plasma, J. Comp. Phys., 225, 753–770, doi:10.1016/j.jcp.2007.01.001, 2007. Vaivads, A., Khotyaintsev, Y., André, M., et al.: Structure of the Magnetic Reconnection Diffusion Region from Four-Spacecraft Observations, Phys. Rev. Lett., 93, 105001, doi:10.1103/PhysRevLett.93.105001, 2004. Vekstein, G. and Bian, N.: Hall assisted forced magnetic reconnection, Phys. Plasmas, 13, 122105, doi:10.1063/1.2398933, 2000.