Energetic electron enhancements under the radiation belt (<i>L</i> &lt; 1.2) during a non-storm interval on 1 August 2008

Suvorova, Alla V.; Dmitriev, Alexei V.; Parkhomov, Vladimir A.

doi:https://doi.org/10.5194/angeo-37-1223-2019

Articles | Volume 37, issue 6

https://doi.org/10.5194/angeo-37-1223-2019

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

https://doi.org/10.5194/angeo-37-1223-2019

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

Articles | Volume 37, issue 6

Regular paper

|

20 Dec 2019

Regular paper |

| 20 Dec 2019

Energetic electron enhancements under the radiation belt (L < 1.2) during a non-storm interval on 1 August 2008

Alla V. Suvorova, Alexei V. Dmitriev, and Vladimir A. Parkhomov

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Final revised paper (published on 20 Dec 2019)
Supplement to the final revised paper
Preprint (discussion started on 21 Jan 2019)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Comments', Anonymous Referee #1, 19 Feb 2019
- SC1: 'clarifications of main points', Alla Suvorova, 21 Feb 2019
- SC2: 'revised Figure 2', Alla Suvorova, 22 Feb 2019
  - SC3: 'additional comments for Figure 2', Alla Suvorova, 22 Feb 2019
- AC1: 'Reply to Referee-1', Alla Suvorova, 04 Mar 2019
RC2: 'Interactive review comment on “Energetic electron enhancements under radiation belt (L < 1.2) during nonstorm interval on August 1, 2008” by Alla V. Suvorova et al. (MS No.: angeo-2019-5)', Anonymous Referee #2, 25 Feb 2019
- AC2: 'Reply to Referee-2', Alla Suvorova, 12 Mar 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) (10 Apr 2019) by Wen Li

AR by Alla Suvorova on behalf of the Authors (14 Apr 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (19 Apr 2019) by Wen Li

RR by Anonymous Referee #1 (20 May 2019)

RR by Anonymous Referee #3 (20 May 2019)

ED: Reconsider after major revisions (further review by editor and referees) (26 May 2019) by Wen Li

AR by Alla Suvorova on behalf of the Authors (27 Jun 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (27 Jun 2019) by Wen Li

RR by Anonymous Referee #3 (27 Jul 2019)

RR by Anonymous Referee #4 (13 Aug 2019)

Suggestions for revision or reasons for rejection

Suvorova et al. present an analysis of energetic electron data on August 1, 2008 at L < 1.2. They report enhanced >30 keV flux during a quiet time and discussed the upstream pressure pulses as a possible origin. The results are interesting if they are true, but the causal connection between the pressure pulses and flux enhancements are not presented convincingly. I overall agree with reviewer #1's concerns about the realism of the mechanism. The proposed mechanism requires strong acceleration in the inner radiation belt, but there is no evidence that such an acceleration is possible by small quiet-time pressure pulses. Also, when the flux enhancements were observed, other types of magnetic activities were present, but the authors didn't check if pressure pulses are uniquely related to the flux enhancements. M-I responses are larger in the night-dawn side but there is no concrete demonstration of how dayside pressure pulses are causally related to night-dawn phenomena. Specific comments are given below.

The authors estimated that a 5 mV/m electric field is needed for the acceleration. This is an unrealistically large number. The cited reference by Selesnick et al. [2016] concerned a storm time event and it's not relevant for the quiet time where such a strong electric field isn't expected. Although there is no direct observations in the inner belt for this event, the THEMIS electric field data should be analyzed to check if such a large electric field exists. It is even more desirable to use other events with satellites in the inner belt to demonstrate strong electric field and particle acceleration when NOAA measures flux enhancements.

If a strong electric field exists, other energy ranges of electrons and ions should also be accelerated. Also, flux enhancements should occur at all L-shells. However, there is no evidence of flux enhancements in other energies, species or L-shells. The paper needs to provide a mechanism of how flux enhancements can occur without affecting other energies of electrons or ions. An investigation of NOAA fluxes at higher L-shells are also needed to check if the slot region and the outer radiation belt responded. The authors mentioned that the ring current flux enhancements (and thus ENA flux enhancements) aren't expected. It is hard to understand why the inner belt can respond to pressure pulses without affecting the ring current.

The correlation between pressure pulses and flux enhancements is interesting if it is real, but it is difficult to draw a firm conclusion from the limited event presented in this paper. The time interval of interest includes PC index enhancements due to the southward IMF. The convection electric field can increase under southward IMF, though it won't be as large as 5 mV/m. The authors didn't rule out the possibilities that non-pressure-pulse effects are responsible for the flux enhancements. It would be necessary to analyze more events to clearly show that pressure pulses are the only cause of the flux enhancements.

Line 479: If pressure pulses cause the ground magnetic field perturbation, the largest magnetic field signal should occur near noon, but the actual largest signal was measured near dawn. It doesn't support the pressure pulse source but some other phenomena are more important for creating the ground magnetic field changes.

High-latitude magnetometer data should also be presented. Although the authors state that substorms occur after the flux enhancement, in the equivalent current maps in the SuperMAG website, the largest enhancements at ~13:30 UT were seen in the nightside, while angle changes were seen in the dayside and dawnside. This plot suggests that a substorm-like nightside high-latitude auroral activity was present. The authors should discuss how it may be related to flux enhancements. The manuscript repeatedly mention injection, but there is no discussion about how injection and pressure pulses are causally related. The analysis doesn't rule out the possibility that injection is not related to pressure pulses but is caused by independent nightside processes.
http://supermag.jhuapl.edu/rBrowse/?fidelity=low&start=2008-08-01T13%3A00%3A00.000Z&step=600&magvec=0-15&magfit=0-15&layers=bg-bump-fg-imagefuv-polarvis-magfit-magvec-rbsp.foot-swarm.foot-tgrd-imf.clock-refvec.supermag-refvec.ulf-colorkey.imagefuv-colorkey.polarvis-colorkey.ulf-time-&tab=small&projection=north%2Cmag%2Cstereo-50%2C1%2C0

The peak magnetic field perturbation occurs near dawn and the authors inferred that the injection occurred at 0-6 LT. But if upstream pressure pulses drive injection, the peak magnetic field perturbation should be seen near noon. The authors should discuss how pressure pulses cause nightside injection without much dayside perturbations. Nightside auroral activity could occur without a causal connection to pressure pulses. This possibility should be discussed.

Line 1 under radiation belt -> earthward of the inner radiation belt

Line 2 nonstorm -> a nonstorm

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ED: Reconsider after major revisions (further review by editor and referees) (14 Aug 2019) by Wen Li

AR by Alla Suvorova on behalf of the Authors (25 Sep 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (30 Sep 2019) by Wen Li

RR by Anonymous Referee #4 (06 Oct 2019)

RR by Anonymous Referee #3 (18 Oct 2019)

ED: Publish subject to revisions (further review by editor and referees) (29 Oct 2019) by Wen Li

AR by Alla Suvorova on behalf of the Authors (07 Nov 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (10 Nov 2019) by Wen Li

RR by Anonymous Referee #4 (16 Nov 2019)

ED: Publish as is (24 Nov 2019) by Wen Li

Short summary

The Earth's radiation belts control the space environment, often affecting the GPS signal propagation and satellite operations. Intense fluxes of energetic particles can penetrate even below the inner belt near the Equator. We analysed electron penetrations under geomagnetic quiet conditions and found in the solar wind an external driver cause. Satellite observations prove that disturbance of the inner belt was associated with impact of plasma jets formed in the solar wind nearby the Earth.