Parametric Study of Preferential Ion Heating Due to Intermittent Magnetic Fields in the Solar Wind

Leopoldo Carbajal Gomez1, Sandra C Chapman1,2, Richard O Dendy3,4 and Nicholas Wynn Watkins2,5, (1)University of Warwick, Centre for Fusion, Space and Astrophysics, Department of Physics, Coventry, CV4, United Kingdom, (2)Max Planck Institute for the Physics of Complex Systems, Dresden, Germany, (3)EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, United Kingdom, (4)University of Warwick, Centre for Fusion, Space and Astrophysics, Department of Physics, Coventry, United Kingdom, (5)London School of Economics, London, United Kingdom
Abstract:
In situ observations and remote measurements of the solar wind show strong preferential heating of ions along the ambient magnetic field. Understanding the mechanism for this heating process is an open problem. The observed broad-band spectrum of Alfven waves permeating the fast solar wind provide a candidate mechanism for this preferential heating through wave-particle interactions on ion kinetic scales. Previous analytical and numerical studies have considered a single pump wave [1, 2] or a turbulent, broad-band spectra of Alfven waves [3, 4, 5] to drive the ion heating. The latter studies investigated the effects on ion heating due to different initial 1/fγpower spectral exponents and number of modes and the signals were random phase. However, the observed solar wind fluctuations are intermittent so that the phases of the modes comprising the power spectrum are not random. Non-Gaussian fluctuations are seen both on scales identified with the inertial range of Alfvenic turbulence [6], and on longer scales typified by ‘1/f’ spectra [7].

We present results of the first parametric numerical simulations on the effects of different levels of intermittency of the broad-band spectra of Alfven waves on the preferential heating of ions in the solar wind. We performed hybrid simulations for the local heating of the solar wind, which resolves the full kinetic physics of the ions and treats the electrons as a charge-neutralizing fluid. Our simulations evolve the full vector velocities and electromagnetic fields in one configuration space coordinate and in time.We compare the efficiency of different levels of intermittency of the initial turbulent fields and their effect on the efficiency of the wave-particle interactions which are a mechanism for driving preferential ion heating in the solar wind.

[1] J. A. Araneda, E. Marsh, A. F. Viñas, J. Geophys. Res. 112, A04104 (2007).

[2] J. A. Araneda, E. Marsh, A. F. Viñas, Phys. Rev. Lett. 100, 125003 (2008)

[3] Y. G. Maneva, A. F. Viñas, L. Ofman, J. Geophys. Res. 118, 2842 (2013).

[4] L. Ofman, J. Geophys. Res. 115, 1461 (2010).

[5] L. Ofman, S. P. Gary, A. Viñas, J. Geophys. Res. 107, 1461 (2002).

[6] R. Bruno, V. Carbone, Living Rev. Solar Phys. 10, 2 (2013).

[7] R. M. Nicol, S. C. Chapman, R. O. Dendy, The Astrophysical Journal 703, 2138 (2009).

Back to: Evolution and Dynamics of Turbulence in the Heliosphere II