AMPERE polar cap boundaries

Burrell, Angeline G.; Chisham, Gareth; Milan, Stephen E.; Kilcommons, Liam; Chen, Yun-Ju; Thomas, Evan G.; Anderson, Brian

doi:https://doi.org/10.5194/angeo-38-481-2020

Articles | Volume 38, issue 2

https://doi.org/10.5194/angeo-38-481-2020

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

https://doi.org/10.5194/angeo-38-481-2020

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

Articles | Volume 38, issue 2

Regular paper

|

08 Apr 2020

Regular paper |

| 08 Apr 2020

AMPERE polar cap boundaries

Angeline G. Burrell, Gareth Chisham, Stephen E. Milan, Liam Kilcommons, Yun-Ju Chen, Evan G. Thomas, and Brian Anderson

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Final revised paper (published on 08 Apr 2020)
Preprint (discussion started on 21 Aug 2019)

Interactive discussion

Status: closed

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

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- Supplement

SC1: 'AMPERE reference', Colin L. Waters, 27 Aug 2019
AC1: 'Response to SC1 'AMPERE reference'', Angeline Burrell, 03 Sep 2019
RC1: 'Comments on A.G. Burrell et al. AMPERE Polar CAP Boundaries', Anonymous Referee #1, 16 Sep 2019
- AC2: 'Authors' response to RC1', Angeline Burrell, 09 Oct 2019
RC2: 'Review of angeo-2019-113: AMPERE Polar Cap Boundaries by Burrell et al.', Anonymous Referee #2, 24 Oct 2019
- AC3: 'Authors' response to RC2', Angeline Burrell, 13 Nov 2019

Peer-review completion

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

ED: Publish subject to revisions (further review by editor and referees) (15 Nov 2019) by Keisuke Hosokawa

AR by Angeline Burrell on behalf of the Authors (18 Nov 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (21 Nov 2019) by Keisuke Hosokawa

RR by Anonymous Referee #2 (21 Nov 2019)

Suggestions for revision or reasons for rejection

The authors have attempted to answer the points of my earlier review, which has improved the manuscript though not all points were considered adequately:

2: regarding the offset created by the choice of only using the dusk-dawn meridian to choose the CRBs:
This point was not adequately addressed by the reviewers. The choice of using only values along the dusk-dawn meridian for the CRB has implications for the rest of the analysis, which is why it is crucial to discuss it sooner in the paper. If the authors are not going to discuss it at this stage, they should at the very least add some error calculations to see how large the effect may be. It could explain the large errors seen in Figure 4, which are not even discussed in the paper.

3: regarding the peak-to-peak ratio:
I think the authors have misinterpreted my comment. Whilst the AMPERE data may be well established, the peak-to-peak ratio derived from it is not. Taking a set number of points along a circle and summing up the values along this circle means the end result is highly dependent on the circle radius and it is therefore not a robust method. One way to solve this problem would be to normalise the sums by the number of AMPERE bins falling onto the radius or to sum up the values in the AMPERE bins instead (rather than choosing an arbitrary value as was done here). Furthermore, if it was as well established a method as the authors claim, then why does the Milan et al. 2015 paper use 48 equally spaced points as opposed to the 200 points presented here? Page 4, line 26 reads "greater than 3.0 and calculating the AACGM-v2 coordinates at each location (Shepherd, 2014; Burrell et al., 2018b)." and it does not talk about this dataset.
The reply of the authors does not sufficiently address my point.

5: regarding the median/quartiles on the Figure:
Could you make the lines indicating the MLT sectors longer/shorter depending to reflect the quartiles?

7: regarding the fitting of an ellipse/circle:
This does not adequately answer my questions. The Milan et al. 2015 paper simply states "we assume that the R1/R2 current regions are approximately circles centered on a point displaced a few degrees antisunward from the geomagnetic pole", which does not explain this further.

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RR by Anonymous Referee #1 (07 Dec 2019)

ED: Publish subject to revisions (further review by editor and referees) (11 Dec 2019) by Keisuke Hosokawa

AR by Angeline Burrell on behalf of the Authors (21 Jan 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (28 Jan 2020) by Keisuke Hosokawa

RR by Anonymous Referee #2 (10 Mar 2020)

ED: Publish as is (11 Mar 2020) by Keisuke Hosokawa

Short summary

The Earth's polar upper atmosphere changes along with the magnetic field, other parts of the atmosphere, and the Sun. When studying these changes, knowing the polar region that the data come from is vital, as different processes dominate the area where the aurora is and poleward of the aurora (the polar cap). The boundary between these areas is hard to find, so this study used a different boundary and figured out how they are related. Future studies can now find their polar region more easily.