Dear Dr. Lakka,

thank you for submitting your article to Annales Geophysicae and for your efforts to respond to the two reviewers in the interactive discussion session. The reviewers have different opinions on the quality of your initial submission, but both agree that the goals and the motivation of your study as well as the validation of your results are aspects that require improvement and/or a more detailed and clear presentation. They also agree that your study contains new ideas, interesting for the readers of An. Geoph, and thus I would like to give you the opportunity to revise your manuscript.

I find your responses detailed enough such that I am confident that the new manuscript version would be improved. So please revise your manuscript along your responses' lines. Note, however, that a decision on the acceptance of your study for publication in An. Geoph. can only be taken after a second round of reviews, as both referees had many important remarks, suggesting that your study requires significant changes.

I am looking forward to receiving your revised manuscript.

Kind regards,

Elias Roussos

Dear Dr. Lakka,

thank you for submitting the revision of your manuscript "ICME impact at Earth with low and typical Mach number plasma characteristics". As your manuscript required major revisions, I have sent it back to the two original reviewers, but unfortunately got an answer only from one.

As you will see, the reviewer is of the opinion that while there is clear improvement on the presentation aspects of the work, he/she expresses strong concerns about the originality and the validity of your simulation results. In particular, he/she cites large differences between the measured and simulated parameters (e.g. 40-80% in the magnetic field magnitude), the origin of which is not discussed, while there are some concerns about the methodology used for data/simulations comparisons (i.e. the reference parameters used).

I did my own literature search in order to understand what are the typical levels of mismatch between Global MHD simulations and data. The most helpful study in that respect is by Ridley et al. (2016): "Rating global magnetosphere model simulations through statistical data-model comparisons", where GUMICS is also one the codes tested. This statistical study shows differences in the magnetic field components that are typically below 20-30% for Bz and even though differences can be larger in Bx and By, an overall mismatch of 40-80% in your simulations indeed appears large. Smaller differences are also shown in another GUMICS based study by Facsko et al. (2015), "One year in the Earth’s magnetosphere: A global MHD simulation and spacecraft measurements".

However, because my understanding is that you argue about correlated variations between GUMICS simulations and measurements I would like to offer your the opportunity to answer to the referee comments and revise your manuscript.

I strongly recommend to add any relevant discussion points, clarifications and plots that may cover any concerns expressed by Reviewer #1, unless you can justify why there is no need to follow those recommendations:

a) Comparison between magnetic field components, rather than just the magnetic field magnitude
b) Discussion on the choice of parameter for the GUMICS/data comparisons
c) Discussion on the large absolute value deviations between GUMICS and data.

Kind regards,

Elias Roussos

Dear Dr. Lakka,

I have now received the report from your revised article's reviewer. The referee is generally much more positive with regards to the publication of your research in Annales Geophysicae, but still expresses several minor concerns that need to be dealt with before I can proceed with a formal acceptance of your manuscript.

Besides several remarks requesting clarifications & minor changes in wording and/or text flow, he/she notes that BATSRUS simulations were done at medium resolution, and questions whether that affects any of the conclusions. A short remark in the manuscript on that matter would then be appreciated. Similarly, please include some remarks in the manuscript or an answer to your rebuttal about the reviewer's final comment, regarding the disagreement with the Cluster data.

Your revision will be only reviewed by myself - I doubt that another round of review from a referee would be required.

Kind regards,

Elias Roussos