A four‐fluid turbulence‐driven solar wind model for preferential acceleration and heating of heavy ions

Abstract

Abstract. We present for the first time a one-dimensional, four-fluid turbulencedriven solar wind model in order to investigate the preferential acceleration and heating of heavy ions by the resonant cyclotron interaction with parallel-propagating left-hand-polarized ion cyclotron waves. The model contains four species: electrons, protons, alpha particles, and one species of minor ions. A Kolmogorov type of cascade effect is introduced to transfer energy from the low-frequency Alfv•n waves to the high-frequency ion cyclotron waves, which are assumed to be entirely dissipated by the wave-particle interaction. The quasi-linear theory of the waveparticle interaction is invoked to distribute the dissipated wave energy among the three ion species based on a given power law spectrum of the ion cyclotron waves and the cold plasma dispersion relation. It is found that in terms of the cold plasma dispersion relation, the dispersion generated by all ion species has an appreciable influence on both the behavior of the major species and the preferential acceleration and heating of the minor ions. The larger the number of species included in the dispersion relation is, the stronger preferential acceleration and heating produced by the waves for the heavy ions close to the Sun will be. A detailed comparison is carried out between two cases, one with and the other without the dispersive effect of the minor ions. Although the solutions for the two cases are somewhat different, they predict a more or less similar behavior of the minor ions, which essentially agrees with recent observations from SOHO. This indicates that the resonant cyclotron interaction may be responsible for the preferential acceleration and heating of minor ions in the fast solar wind. Furthermore, the influence of minor ions on the proton-alpha solar wind is found to be dominated by the dispersive effect of the minor ions. Even though such an influence is exaggerated by the cold plasma dispersion relation, it is still small and remains within the present observational uncertainties. Therefore minor ions may be treated approximately as test particles in the solar wind.

Transition region, coronal heating and the fast solar wind

“…The cascade is able to explain the magnetic field spectrum evolution and to account for the proton heating beyond 10 solar radii (Tu 1987(Tu , 1988. In a series of papers, Hu and his coauthors applied this idea to the inner corona, and found that the cascade indeed is able to account for the heating and acceleration of fast solar wind (including minor ions) originating in coronal holes (Hu et al , 2000. In these studies, a hot corona was treated as a boundary condition, the creation of a steep transition region and a hot corona were not considered.…”

Solar off-limb line widths with SUMER: revised value of the non-thermal velocity and new results

“…Some of them include Alfvén waves and/or ion-cyclotron resonance as a dissipation process of the high frequencies waves (e.g., Tu and Marsch, Correspondence to: L. Dolla (dolla@sidc.be) 1997; Hu et al, 2000;Vocks, 2002;Bourouaine et al, 2008b;Landi and Cranmer, 2009;Isenberg and Vasquez, 2009). In this respect, coronal holes are of particular interest as the source of the fast solar wind.…”

Hybrid models of solar wind plasma heating

“…Theoretical studies of ion-cyclotron resonance have been developed and applied to the heating of the solar corona and the solar wind (Marsch et al, 1982;Axford and McKenzie, 1992;Tu and Marsch, 1997;Li et al, 1999;Hollweg, 2000;Hu et al, 2000;Cranmer, 2000;Hollweg and Isenberg, 2002). However, there are theoretical difficulties with the application of the ion-cyclotron mechanism for coronal heating, and its role is not yet fully understood (Ofman and Davila, 1997;Cranmer, 2000;Isenberg, 2004).…”