Seasonal Variations in Ion Density, Ion Temperature, and Migrating Tides in the Topside Ionosphere Revealed by ICON/IVM

Round 1

Reviewer 1 Report

In this manuscript authors present results of the research related to seasonal variations of ion density and temperature, and migrating tides in the low-latitude topside ionosphere based on the plasma parameters measured by the Ion Velocity Meter (IVM) instrument on the Ionospheric Connection Explorer (ICON) satellite from 2020 to 2021.

This research provides some new insight to the features of tidal oscillations and the seasonal variations in the ion compositions in the topside in the topside ionosphere.

The abstract clearly and concisely summarizes the paper and state the main results. The manuscript is mostly written clearly and consistently. All parts of the text, references and figures are necessary for the results and main points to be understood.

I have comments that the authors should take into account when finalizing the manuscript.

L. 143 – 146. “The total ion density…” Authors state that around January the high density in the total ion density was observed mainly in the Southern Hemisphere. However, as I can see From Fig.1, the strongest Ni was observed in November 2021 simultaneously in two Hemispheres. Why? What causes this behavior?   Fig. 3 presents the daily indices of F10.7 and state that the solar radiations are generally higher in 2021 than in 2020. It is true. In my opinion, it would be useful to consider the influence of not only solar, but also magnetic activity. Whether or not there is such an influence on the seasonal variations of ion density and temperature and migrating tides? To do this, in Fig. 3 you should add a panel showing the behavior of the sum of Kp indices per day (ΣKp) from December 6, 2019, to December 31, 2021, in correspondence with ICON/IVM observations.

I can recommend the manuscript for publication after a major revision.

Minor editing of English required.

Author Response

Thank you for your review. We have tried our best to revise the manuscript as your suggestions. Please find the point to point response in the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper utilized ICON measured total ion density, O+, H+ and ion temperature in the topside ionosphere (590 km) to report the seasonal variation of them, as well as the migrating tides. They found that O+ is more correlated with the solar activity, while H+ did not. They also extract the non migrating tides and analyze the characters. Hower, from my perspective, I think this paper, especially the part of non migrating tides, is not that convinced. Furthermore, the distribution of Figs also need to be improved. I recommend the paper to have a major revision before it is suitable for publication

Line 50-51 topside ionosphere is dominated by O+, H+ and He+

Line 81 column density ratio of O to N2 ()

Section 3

Here I suggest the author first provide the geomagnetic conditions as Fig 1, not the ion density distribution as Fig 1. The reader shall first have a overview of geomagnetic conditions. Therefore, the author shall also provide a section on describing geomagnetic conditions. The new Fig1 show include F10.7, Kp and Dst, namely 3 subplots.

After they describe the geomagnetic conditions, then they show provide their ion density results (Figure 2 XXX)

Line 141 total ion density at XX km,

Line 146-147 Between 0 and 9N

Line 151-152 The densities of H+ and O+ are presented in Figures 3a and 3b, respectively

Line 171-172 here this Fig 3 shall be combined into the new Fig 1, as I mentioned earlier.

Line 192 between 12 S and 12 N

Line 195 relatively lower

For the non-migrating tides, their amplitude can reach 800 K, while the total ion temperature maximum magnitude is 1700 K. The amplitude reaches almost 50% of the total ion temperature. So is it possible that the non-migrating tides reach that high magnitude in the top ionosphere??

I suggest the author also carry out a spectral and wavelet analysis on the variation of Kp and F10.7 to see whether these oscillations in geomagnetic and solar forcing mixed with the DW1. How much they count in the total variations.  Topside ionosphere is easily impacted by geomagnetic forcing and solar  forcing. The lower atmospheric forcing impact may be minor compared with solar and geomagnetic forcing.  

moderate english revision needed

Author Response

Thank you for your review. We have tried our best to revise the manuscript as your suggestions. Please find the point to point response in the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

My comments were completely taken into account in the revised version of manuscript. I recommend the revised version of the manuscript for the publication in the present form.

Reviewer 2 Report

OK, Now the author has made necessary improvement on the paper, and the paper is ok for publishing

minor english editing needed