Dear Authors,

First of all, thank you for your response to the referees’ comments. The referees found your paper as interesting and important contribution to the ionospheric research. However, referees had some important objections to the present version of the manuscript, and this is a reason why I suggest a major revision. Please, consider carefully and discuss in the revised version of the manuscript all comments of the referees. Me and one of the referees will review the manuscript again.
If you are prepared to undertake the improvements required, please submit the revised manuscript as well as a list of changes or a rebuttal against each point, which is being raised when you submit the revised manuscript.

Kindest regards

Yours sincerely
D. Buresova

Dear Authors,

Thank you for your work you did when improving the manuscript according to the referees’ comments and suggestions. The manuscript has underdone the second revision. After the revision, the submission’s status changed from "major revision" to "minor revision". Please, consider carefully the additional comments of the referee. After you’ll send us the revised version, including your response, I’ll read the manuscript again. I believe that this will be a last step for the manuscript to be recommended for publication.
Kindest regards

Yours sincerely
D. Buresova

Referee’s comments:
Manuscript title: Global sounding of F region irregularities by COSMIC during a geomagnetic storm
The addition of the new Figure gave more confidence on the method presented in the manuscript. But I suppose that a few more corrections are needed before possible publication.
The main recommendation is to include some sort of small validation of the method during the geomagnetic storm. The calculation of the correlation between S4 indexes and ΔTEC values would be a significant incorporation to the manuscript. S4 indexes can be retrieved by the same RO observations used to derive TEC, which would incorporate a strong analysis. But if this is too much to add, a more feasible validation would be to show a few ionograms with Spread-F during 20:00-24:00 LT at 15 July 2012, confirming the performance of the method.
Pg. 1, line 14 (Abstract): Please, check if it would be better to use “We obtained new results” instead of “We obtain new results”.
In my point of view, the following statement is a bit not connected with the first paragraph of Introduction (pg. 1, line 21):
“GPS radio occultation was already utilized to derive global maps of sporadic E layers around 90-120 km altitude”.
Perhaps, it would fit better in the second paragraph.
Pg. 2, line 1: “One of the main advantages of the GPS radio occultation technique is the high vertical resolution of about 1 km.” Advantages in comparison to what? And this sentence is referring to what kind of applications? Ionospheric sounding?
Pg. 2, line 12: “In addition, quasi-dc electric fields”. Is DC meaning “direct current”?
Pg. 2, line 26: what is MLT?

Pg. 2, line 27: “Our study is related to the study of Watson and Pedatella (2018) but we will add”
In my point of view, it would better to use: “Our study is related to the study of Watson and Pedatella (2018) but we are now including”
Pg. 2, line 30: “The new result and the focus of the study is the behaviour of the ionospheric irregularities during the geomagnetic storm of 15 July 2012”. A complete analysis of the ionospheric irregularities during geomagnetic storm would depend on several analysis and several instruments. To keep this sentence, I suggest including more instrumental observation and analysis. Otherwise, I would say that the main goal was not to analyze the irregularities during the storm, but the storm is just a case study to show the performance of the proposed method. Suggestion: “The new result and the focus of this work is to study the behaviour of the method presented by Watson and Pedatella (2018) under the presence of ionospheric irregularities during the geomagnetic storm of 15 July, 2012”
pg. 4, line 10: when referring to Fig. 1b, it should be Fig. 1 (right panel). There is no b) in Fig. 1.
I got a bit confused with the meaning of ΔTEC. As far as I understood, a TEC profile is a plot of TEC versus time (or altitude) along with the tangent point of each occultation. Therefore, a RO-TEC refers to one occulting observation and a RO-TEC profile is all TEC from all observations of the complete occultation of one satellite, which takes some minutes. It took me some time to understand that because, in principle, I was thinking that a TEC profile would be the integral of electron density along with a RO-Ne profile. I would recommend including a plot showing the TEC profile in order to avoid misunderstanding (Like Fig. 1 but for TEC instead of Ne) and explaining it better. Sorry if it obvious for you, but this is an unusual way to see plots of TEC for general readers. Also, it would be interesting to include such kind of plot in order to the reader have a better idea of how is the behavior of a RO-TEC profile.
I still think that the authors should include an explanation of what is the bottom tangent point. Is this the location of the tangent point obtained in the last (or first) occultation per each profile? I. e., is the bottom tangent point referred to the lowest altitude of each occultation profile?