Speaker
Description
See the full abstract here http://ocs.ciemat.es/EPS2019ABS/pdf/O4.403.pdf
The properties of magnetohydrodynamic (MHD) turbulence have significant implications for astrophysical phenomena like cosmic ray scattering. We study properties of MHD modes by decomposing data of MHD simulations into linear MHD eigenmodes - namely the Alfvén, slow, and fast modes. Some earlier studies have shown the differences in the turbulent spectrum and anisotropy characteristics of these different modes [1, 2]. However, several open questions still remain. We vary the nature of the turbulence in our simulations by varying the forcing from solenoidal to compressive, while also varying the plasma beta and Mach number. We find that the proportion of the magnetosonic (fast and slow) modes in the mode mixture increases with increasing fraction of compressive forcing and higher plasma beta. As a result, the compressible magnetosonic modes can become the dominant fraction in the MHD mode mixture. The Alfvén mode shows the well-known anisotropic Goldreich-Sridhar spectrum characteristics. We also find a transition from strong to weak Alfvénic turbulence at low Alfvén Mach numbers. In cases where the fast mode is strong, the isotropic nature of the fast mode cascade is verified with higher resolution and better diagnostics compared to previous studies. These results also indicate that there can be significant coupling between the different MHD modes depending on which mode is dominant. This study motivates the development of a better theory of magnetosonic modes turbulence.
References
[1] Jungyeon Cho and A. Lazarian, Physical Review Letters 88, 245001 (2002)
[2] Jungyeon Cho and A. Lazarian, Mon. Not. R. Astron. Soc. 345, 325-339 (2003)
