The sporadic sodium layer: a possible tracer for the conjunction between the upper and lower atmospheres

Qiu, Shican; Wang, Ning; Soon, Willie; Lu, Gaopeng; Jia, Mingjiao; Wang, Xingjin; Xue, Xianghui; Li, Tao; Dou, Xiankang

doi:https://doi.org/10.5194/acp-21-11927-2021

Articles | Volume 21, issue 15

https://doi.org/10.5194/acp-21-11927-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-21-11927-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 15

Research article

|

10 Aug 2021

Research article |

| 10 Aug 2021

The sporadic sodium layer: a possible tracer for the conjunction between the upper and lower atmospheres

Shican Qiu, Ning Wang, Willie Soon, Gaopeng Lu, Mingjiao Jia, Xingjin Wang, Xianghui Xue, Tao Li, and Xiankang Dou

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Final revised paper (published on 10 Aug 2021)
Preprint (discussion started on 29 Dec 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'referee comment', Anonymous Referee #2, 25 Jan 2021
- AC2: 'Reply on RC1', Shican Qiu, 15 Mar 2021
RC2: 'Review of Sporadic sodium layer: A possible tracer for the conjunction between the upper and lower atmospheres', Anonymous Referee #1, 29 Jan 2021
- AC1: 'Reply on RC2', Shican Qiu, 15 Mar 2021

Peer-review completion

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

AR by Shican Qiu on behalf of the Authors (15 Mar 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (23 Mar 2021) by Gabriele Stiller

RR by Anonymous Referee #2 (11 Apr 2021)

RR by Anonymous Referee #1 (11 Apr 2021)

ED: Reconsider after major revisions (14 Apr 2021) by Gabriele Stiller

AR by Shican Qiu on behalf of the Authors (16 May 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (27 May 2021) by Gabriele Stiller

RR by Anonymous Referee #2 (09 Jun 2021)

Suggestions for revision or reasons for rejection

I am very glad to see that the authors have answered almost all my questions and revised the manuscript under my suggestions. I also support that the authors added a simulation of the chemical reactions to explain the efficient neutralization of Na ions in this Nas case study, which is actually that the enough Na ions were neutralized to from Nas layer, as I have indicated in last referee report. Now the manuscript is rather perfect, but a few issues are needed to be considered:

1. Page 2 line 9, the authors wrote “With an active chemical property and high abundance of sodium atoms, the sodium layer has been widely observed and studied all over the world (Marsh et al., 2013; Collins et al., 2002; Plane, 2003; Plane et al., 1999).”
Here, I need to indicate that there is another reason to the sodium layer has been extensively explored: The sodium atom has large resonant backscatter cross section (especially compare to the cross sections of Fe and Ni atoms). (Collins et al., 2002)

2. In the last version, the differences of sodium density between Figure 1a and Figure 1b were quite large. Now I understand that the reason is the difference of the two lidar directions. The wide band lidar provides the vertical sodium density, while the narrowband lidar observes the oblique direction. In this version, the authors discard the bad data by the wide band lidar. But many parts in paper still mentioned two lidars. (For example: page1 line 26 and page 3 line23). Please check the manuscript carefully and revise these mistakes.

3. The difference between Figure 2 and Figure 5: From Figure 2, the Es was not present between 13:20 to 14:20. But from Figure 5, the obvious Es was observed at 14:00. From Fig.5, the foEs at 1400 UT is about 4.5MHz, and at 1530UT is about 5MHz. But these foEs were not marked in Fig.2.

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RR by Anonymous Referee #1 (28 Jun 2021)

Suggestions for revision or reasons for rejection

This version of the paper is much improved because of the inclusion of the new part of Section 3, and Figure 6, which show that the observed Nas layer can probably be explained by the established ion-molecule chemistry of Na+ ions in a descending sporadic E layer. Therefore, as the authors conclude, it is not necessary to invoke a mechanism involving lightning. However, this does not mean that lightning does not enhance Nas production. This is a novel idea and the publication of the paper will stimulate further interest - in particular, the regarding the precise way in which electric field reversal could cause or amplify Nas formation needs to be modelled properly, and this is beyond the scope of this paper.

I have several suggestions to improve the current version, but these are all minor revisions:

Abstract. These two sentences should be changed: "Our results suggest that lightning strokes would probably have an influence on the ionosphere and thus affecting the occurrence of NaS, with the overturning of electric field playing an important role. Statistical results reveal that the sporadic E layers (ES) could hardly be formed or maintained when the atmospheric electric field turns upward."

I suggest something like: "Our results suggest that a lightning stroke could trigger or amplify the formation of a NaS layer in a descending sporadic E layer, through a mechanism that involves overturning of the electric field. This is based on our observation that, statistically, sporadic E layers disappear rapidly when the atmospheric electric field turns upward".

page 7, line 4: "Normally", not "Nominally"

page 7, line 21: "equates", not "equivalents"

page 8, line 8: "do the opposite"

page 8, line 25: "The electrons would reverse rapidly before the ions can respond similar to the velocity overshoot effect for electrons. During the relaxation phase, the 25 recombination between electrons and ions would probably be triggered through collisions, not unlike how moving cars will crash in a traffic accident if the car behind suddenly accelerates."

I do not understand the second sentence. Ion-electron recombination reactions, whether dissociative or radiative, have small negative temperature dependences i.e. the reactions get slower at higher temperatures, because the impact velocity increases and the long-range attraction between the ion and electron is less effective.

Figure 6. This would be much clearer if you use a log scale for the abscissa (x-axis), for both (a) and (b)

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ED: Publish subject to minor revisions (review by editor) (28 Jun 2021) by Gabriele Stiller

AR by Shican Qiu on behalf of the Authors (02 Jul 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (07 Jul 2021) by Gabriele Stiller

AR by Shican Qiu on behalf of the Authors (13 Jul 2021) Manuscript

Short summary

Our results suggest that lightning strokes would probably influence the ionosphere and thus give rise to the occurrence of a sporadic sodium layer (Na_S), with the overturning of the electric field playing an important role. Model simulation results show that the calculated first-order rate coefficient could explain the efficient recombination of Na⁺→Na in this Na_S case study. A conjunction between the lower and upper atmospheres could be established by these inter-connected phenomena.