Formation of Fine Structures in Incompressible Hall Magnetohydrodynamic Turbulence Simulations

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

Review report for Plasma (Manuscript ID: plasma-3098763) of MDPI

 

The manuscript addresses the review of works relevant to the MHD turbulence, especially isotropic MHD turbulence and also Hall term in the system. The manuscript comprehensively addresses the relevant works, providing a balanced and equitable review. The formation of filamentary structures has been thoroughly investigated by the author and referenced sources, as detailed in the manuscript. Indeed, these investigations are comprehensively reviewed and discussed therein. I am pleased to recommend the manuscript for publication in Plasma. However, I have a very few minor suggestions that may enhance the manuscript for readers with a broader background.

 

1.     In page 1, line 29. It should read ‘The’, not ‘THe’.  

2.     Please add a few sentences to describe the forcing term, how the forcing term is given (proportional to the velocity field?, for example).

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This is a well-written review of Hall MHD simulation suitable for turbulence studies.  The workhorse for turbulence studies is MHD, since MHD is a scale-free model applicable to the solar wind, laboratory modeling, and even astrophysical situations.  This review focusses on the appearance of small scale structures within the Hall MHD framework (with no mention of anisotropy, or critical balance).  The review emphasizes the author's own work.

The author reviews Hall MHD represented by eqs 1-4 (motion, induction, incompressibility div v = 0, and div B = 0).  While MHD admits Alfvenic fluctuations, Hall MHD admits higher frequency, small-scale fluctuations such as nonlinear whistler modes.

In section 3, the author reviews the appearance of power-law spectra in simulations.  The Kolomogorov k^-5/3 scaling is typical in conventional fluids, and MHD (for both kinetic and magnetic energy), but other power laws appear in Hall MHD.  In figure 1, we see a typical HMHD simulation result.

This reviewer appreciated the comparison in section 4.2.1 between a free-decaying MHD simulation and a Hall-MHD simulation.  As shown in figure 2, the differences are clear, Hall generates finer structures. 

In section 4.2.2, the author points out the difference in structure formation by varying the Prandtl number (ie the ratio of viscous diffusion to resistive diffusion).  The emphasis is on large Prandtl  numbers (ie highly viscous magnetofluids), whereas laboratory MHD studies often have extremely low Prandtl numbers (very low viscous diffusion compared to resistive).   In section 4.3, the role of coherent structures in energy transfer is discussed.  The transfer is mostly from the ion cyclotron mode to the smaller scale whistler mode.

Typos:

Line 29: THe applicability

Line 92-93: misspelling of Sridhar in a few places.

Line 96: Kraichnan misspelled

Editorial note:  sometimes et al. has no period, the references look fine but the formatting is inconsistent.  Sometimes the full range of page numbers appears, most of the time just one page.  Most of the time there's a comma after the volume number, sometimes not.

Line 703.  R. first initial missing.

Line 708, 808-843.  All italics, should be roman.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf