Relation between the asymmetric ring current effect and the anti-sunward auroral currents, as deduced from CHAMP observations

Lühr, Hermann; Zhou, Yun-Liang

doi:https://doi.org/10.5194/angeo-38-749-2020

Articles | Volume 38, issue 3

https://doi.org/10.5194/angeo-38-749-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/angeo-38-749-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 38, issue 3

Regular paper

|

24 Jun 2020

Regular paper |

| 24 Jun 2020

Relation between the asymmetric ring current effect and the anti-sunward auroral currents, as deduced from CHAMP observations

Hermann Lühr and Yun-Liang Zhou

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Final revised paper (published on 24 Jun 2020)
Preprint (discussion started on 28 Jan 2020)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Referee's report', Anonymous Referee #1, 10 Mar 2020
- AC2: 'Authors responses to referee comments on angeo-3', Hermann Lühr, 17 Apr 2020
- AC1: 'Responses to comments of Referees 1 and 2', Hermann Lühr, 14 Apr 2020
RC2: 'Referee comment', Anonymous Referee #2, 02 Apr 2020
- AC1: 'Responses to comments of Referees 1 and 2', Hermann Lühr, 14 Apr 2020
- AC2: 'Authors responses to referee comments on angeo-3', Hermann Lühr, 17 Apr 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Publish subject to revisions (further review by editor and referees) (21 Apr 2020) by Anna Milillo

AR by Hermann Lühr on behalf of the Authors (21 Apr 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (23 Apr 2020) by Anna Milillo

RR by Anonymous Referee #1 (29 Apr 2020)

Suggestions for revision or reasons for rejection

Referee #1’s report on “Relation between the asymmetric ring current effect and the anti-sunward auroral currents, as deduced from CHAMP observations” by Lühr and Zhou (MS#angeo-2020-3R)

The manuscript is revised according to the comments from the referees and is much improved. However, as stated below, there are a few points to be further considered before publishing in Annales Geophysicae.

1. The revised manuscript refers to the previous papers studying the anti-sunward FAC current. Thus, reply is OK. But, the referee does not agree with the sentence “Conversely, our ring integral of the along-track component is a more straight-forward approach that return quantitative values for the net current passing the polar region.”, because the method of authors includes a lot of assumptions to estimate the contributions from the unsampled parts and to calculate the ring integral.

2. Figure 4 is fundamentally the same as Figure 6 of paper by Zhou and Lühr [2017]. This figure is only stated and discussed in a very short paragraph (Lines 220–224). Thus, the referee is still uncomfortable in section 3. Either Figure 3 or Figure 4 is enough to demonstrate the full distribution of the net currents.

3. (a) Some tables are converted into figures, which greatly improve section 6. It becomes easier to understand the results of ground observations. However, Table 2 is yet something redundant. If the authors want to show the numbers, please indicate in each panel of Figure 10.
(b) Reply is OK.

4. Reply is fine.

5. Replies are fine.

R1. The revised manuscript includes significant parts of addition in Lines 400–434 and Lines 493–502. In these additions, there are sentences “As a consequence, we have to state, our ground-based observations are not sufficient to reveal a possible seasonal effect of the storm-time disturbance asymmetry.” (Lines 430–432) and “However, our statistical study of recordings from a single European-African meridional chain is not sufficient to confirm the seasonal difference between hemispheres.” (Lines 493–494). This is a negative answer to a question raised in Lines 376–377, that is, “In order to obtain more information on the net current seasonal effects in ground observations we analysed magnetic field data from a meridional chain of observatories.”, indicating the analysis of the ground station data provides no useful information. The analysis result does not have any consequence in interpretation of the anti-sunward net current. Thus, the part of these ground stations (i.e., the latter part of section 6) and related figures and tables can be deleted.

R2. In titles of sections 4 and 5, “anti-sunward net current” may be better to understand the contents of these sections.

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ED: Publish subject to minor revisions (review by editor) (29 Apr 2020) by Anna Milillo

AR by Hermann Lühr on behalf of the Authors (04 May 2020) Author's response Manuscript

ED: Publish as is (20 May 2020) by Anna Milillo

AR by Hermann Lühr on behalf of the Authors (23 May 2020)

Short summary

During magnetic storms the magnetic disturbance at low latitudes becomes asymmetric, enhanced in the evening sector and reduced around morning. This has been attributed to the asymmetric ring current. Here a new 3D current system is proposed for explaining the asymmetric signal. Anti-sunward net currents at high latitude are connected at their noon and night ends to field-aligned currents that lead the currents to the magnetopause on the dawn and dusk flanks where the current closure occurs.