Magnetic local time asymmetries in precipitating electron and proton populations with and without substorm activity

Yakovchuk, Olesya; Wissing, Jan Maik

doi:https://doi.org/10.5194/angeo-37-1063-2019

Articles | Volume 37, issue 6

https://doi.org/10.5194/angeo-37-1063-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Vertical coupling in the atmosphere–ionosphere system

https://doi.org/10.5194/angeo-37-1063-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 37, issue 6

Regular paper

|

28 Nov 2019

Regular paper |

| 28 Nov 2019

Magnetic local time asymmetries in precipitating electron and proton populations with and without substorm activity

Olesya Yakovchuk and Jan Maik Wissing

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Final revised paper (published on 28 Nov 2019)
Preprint (discussion started on 24 Apr 2019)

Interactive discussion

Status: closed

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

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RC1: 'Review of manuscript', Anonymous Referee #1, 28 May 2019
- AC1: 'Reply to all comments from reviewer 1', Olesya Yakovchuk, 28 Jul 2019
RC2: 'Review of Manuscript', Anonymous Referee #2, 25 Jun 2019
- AC2: 'Reply to all reviewers.', Olesya Yakovchuk, 13 Aug 2019
AC3: 'Paper - revised version', Olesya Yakovchuk, 13 Aug 2019

Peer-review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (19 Aug 2019) by Elias Roussos

AR by Olesya Yakovchuk on behalf of the Authors (21 Aug 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (26 Aug 2019) by Elias Roussos

RR by Anonymous Referee #1 (23 Sep 2019)

RR by Anonymous Referee #2 (24 Sep 2019)

Suggestions for revision or reasons for rejection

The paper describes electron and proton differential number flux measured in various energy channels by detectors on POES and METOP from 2001-2008 in the radial direction away from Earth for electrons and 9 degrees from that in protons mapped to 110 km altitude, primarily using the APEX coordinate system and focusing on non-substorm and isolated substorm times, MLT and Kp index dependencies.

The paper is generally well written and presented well (with some exceptions noted below) and will provide useful contributions to the field with some minor modifications. The material is presented with reasonable background and within a reasonable context.

There are no major issues with the paper although there are several minor to mid-level issues that need to be addressed before publication.

1) First, the abstract lists four findings a), b), c), and d). Strictly speaking neither b nor c are new results. b) (as pointed out later in the paper) is in agreement with conjectures in Newell et al . 2009, and c) has been presented before (although not with a focus on asymmetry) in plots by several authors, at least for some of the energy bands. The consistence of b) with previous results is still a useful finding, so should be included, just reworded. c) also is setup for d) and putting the numerical value on asymmetry is useful. So it is still a useful result, but should be reworded to indicate that it is not a completely new finding.

2) The text in all of the figures is dramatically too small.

3) The colors are missing on the color particle flux scale in Figure 2.

4) Text (e.g a paragraph) needs to be added to discuss the limitations of the chosen color scaling in Figures 3 and 4. While the authors’ choice of scale is appropriate for examining and comparing asymmetry as described. It is atypical and many conclusions that can usually be drawn from color scales in figures do not apply with this choice. For example, the step jumps in the scale creates observable boundaries and structure in some places and plots that may also exist in other places and plots with the same magnitude, but in one case the variations happen to straddle the color boundary, while not in another. For example, the few orange colored pixels about 0 MLT in the upper right (TED4 substorm) plot of Figure 3, seem to indicate higher magnitude and definitive structure, and not having such pixels in the upper left (TED4 non-substorm) plot seems to indicate that structure structure does not exist in that case. But the color scale hard boundaries may be the only cause of these features.
Additionally the color magnitudes between plots cannot be directly compared with each other as absolutes or even as relatives. Only the relative color changes/ranges within each given plot is comparable (as well as that variation pattern).
The authors use the color scale appropriately and do not make any interpretations outside of the limitations of the color scale, but these limitations need to be expressly stated, at least briefly, to avoid readers from drawing inappropriate meaning from the presented data.

5) A statement needs to be included that indicates how the limitations summed up in the final paragraph of section 3.1 (Page 10, lines 4-7) affect the findings and results of the study. That is, could it changes the findings entirely? Change the magnitude of the findings? or just have minor affects on the results, but not the overall findings and trends?

6) The reference at the end of the second paragraph of section 4.4 (page 15, line 26) should be Figure 14 of Dombeck et al, 2018, rather than Figure 4 of Newell et al. 2009), and “Alfvén waves” immediately preceding the reference should be changed to “Alfvénic acceleration”.
There is no need for the authors to go into the depth of literature on Alfvén waves and Alfvénic acceleration of precipitating electrons by the likes of (Keiling, Chaston, Hatch, and Wygant, etc. etc.) But there has been significant work in this area, including many, many maps of Alfvén waves, etc. In short, precipitation is caused by some (and only some) Alfvén waves, and it is then called Alfvénic acceleration. Newell at al. 2009, does not investigate Alfvénic acceleration at all, instead analyzing “broadband” spectra, which Dombeck et al., 2018 indicate is a somewhat/rather imperfect proxy for Alfvénic acceleration. For the purposes of this paper it is better to use the Dombeck et al. 2018 figure reference, as it directly indicates the point the authors are attempting to make, i.e. Alfvénic accelerated precipitation is observed in the mentioned region.

In summary, with the relatively minor correction indicated: The conclusions of the paper are of reasonable significance and of importance to the community. The paper length is adequate. The language is fluent and the presentation clear and organized. The figures could be larger but are ok, but the text needs to be made significantly larger, and not at the expense of the size of the data presentation.

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ED: Publish subject to minor revisions (review by editor) (27 Sep 2019) by Elias Roussos

AR by Olesya Yakovchuk on behalf of the Authors (13 Oct 2019) Author's response Manuscript

ED: Publish as is (14 Oct 2019) by Elias Roussos

AR by Olesya Yakovchuk on behalf of the Authors (17 Oct 2019) Manuscript

Short summary

We present the magnetic local time (MLT) distribution of energetic particle precipitation into the ionosphere in combination with different substorm activities. In the long term average substorms may increase the night-sector flux by factor 2–4 and eventually reduce the day-time flux. The MLT flux differences themselves may even reach 2 orders of magnitude independently of substorm activity level. Since precipitating particles impact the ozone chemistry, this may have atmospheric implications.