Sub-Auroral, Mid-Latitude, and Low-Latitude Troughs during Severe Geomagnetic Storms

Round 1

Reviewer 1 Report

I’m happy to suggest this paper for publication. The work is easy to follow and the results are based on solid reasoning. I have nothing really to criticise, the paper describes well the relations between MIT, RIT and LLT. Maybe it would have been more complete also to include traces of a HLT in one of the examples or in an extra case, although that’s really out of the scope of the message.

Author Response

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Author Response File: Author Response.doc

Reviewer 2 Report

The authors investigate the mid-latitude trough in response to the geomagnetic storm by using electron density measurement by CHAMP. I find this manuscript does not fit in the scope of this Journal and suggest the authors submit to the other journals such as JGR, JASTP, or ASR.

My main comments are as follows:

1) the introduction part did not present the scope and status of this research in an appropriate way, which hinder and confuse the reader.

2)Due to the coverage of CHAMP observation, the authors could used ground-based observations such as ionosonde and GNSS-TEC.

Author Response

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Author Response File: Author Response.doc

Reviewer 3 Report

Line 35

The first, main, link to a literary source should be given to an English-language article available to readers on the Internet.

Lines 76-78

This corresponds to the latitudes of the inner radiation belt (IRB) L=1.5–2.0. Therefore, it was assumed that the low-latitude trough (LLT) is formed by precipitation of energetic IRB particles during a severe storm.

A logical contradiction, namely, precipitation of particles, that is, an increase in the number of particles entering the ionosphere, according to the author, somehow leads to a decrease in the concentration of electrons - a trough.

Figure 1 and the rest are insufficiently described in the captions below and are executed carelessly, in particular, unnecessarily long ticks.

Lines 192-193

The cases of simultaneous observation of all three troughs are shown in Figure 2 by vertical lines.

There are no any vertical lines in Figure 2.

Lines 200-201

In the daytime, all the troughs are weakly expressed and are not always clearly revealed in the satellite data.

It will be very helpful to give some words about the physical reasons such day-night asymmetry.

Lines 201-204

During the event in question, they were clearly visible only in the Southern hemisphere. Figure 3 shows variations in the troughs position in this hemisphere for ~14.3 LT. The MIT, as a rule, manifests itself as a shallow minimum of fp. Nevertheless, the MIT position was determined quite accurately; it also tracks variations in the Kp-index (with a delay of about 2.5 hours), as at night.

Expressions, like: “clearly visible”, “position was determined quite accurately” are not quite in line with the style of a scientific article

Lines 343-344

Therefore, on the joint plot, the arrays of the MIT and RIT overlap. Nevertheless, both branches of the trough are determined quite confidently.

Two sentenses describe the manuscript as a declaration on the need to use an another, modern datasets, ground, and other space missions, not only CHAMP, for reliable selection and classification of the ionospheric troughs.

Lines 387-388

This fully applies to the LLT, which is undoubtedly formed by precipitation of energetic particles from the inner radiation belt [20].

Again, a contradictory statement. The precipitation of energetic particles that may cause additional ionization, according to the author of the manuscript, is the cause of ionospheric troughs, that is, a decrease in the concentration of electrons.

Author Response

Please see the attachment

Author Response File: Author Response.doc