Low-altitude frequency-banded equatorial emissions observed below the electron cyclotron frequency

Boudjada, Mohammed Y.; Galopeau, Patrick H. M.; Sawas, Sami; Denisenko, Valery; Schwingenschuh, Konrad; Lammer, Helmut; Eichelberger, Hans U.; Magnes, Werner; Besser, Bruno

doi:https://doi.org/10.5194/angeo-38-765-2020

Articles | Volume 38, issue 3

https://doi.org/10.5194/angeo-38-765-2020

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

https://doi.org/10.5194/angeo-38-765-2020

© 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

Low-altitude frequency-banded equatorial emissions observed below the electron cyclotron frequency

Mohammed Y. Boudjada, Patrick H. M. Galopeau, Sami Sawas, Valery Denisenko, Konrad Schwingenschuh, Helmut Lammer, Hans U. Eichelberger, Werner Magnes, and Bruno Besser

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Final revised paper (published on 24 Jun 2020)
Preprint (discussion started on 03 Apr 2019)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'see supplement for review', Anonymous Referee #1, 12 Apr 2019
- AC1: 'Replay to Referee 1 comments', Mohammed Y. Boudjada, 24 Jun 2019
RC2: 'Referee Comments', Anonymous Referee #2, 27 Apr 2019
- AC2: 'Replay to Referee 2 comments', Mohammed Y. Boudjada, 24 Jun 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) (17 Jul 2019) by Yoshizumi Miyoshi

AR by Mohammed Y. Boudjada on behalf of the Authors (26 Jul 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (29 Jul 2019) by Yoshizumi Miyoshi

RR by Anonymous Referee #2 (12 Aug 2019)

RR by Anonymous Referee #1 (05 Sep 2019)

Suggestions for revision or reasons for rejection

A paper characterizing these low latitude/altitude emissions below FCE is of scientific interest, however no attempt is made to understand the spacing of the harmonics which highly reduces the potential impact this paper would have. For one of their examples the frequency spacing of the bands is ~25 kHz which is greater than the low hybrid frequency ~20 kHz. Beyond noting the band spacing, no attempt is made to characterize it in this paper. For example, a scatter plot of spacing versus model FLHR, FCE, wave power versus harmonic number etc. Also the emissions of every ~5th harmonic appears to be broader in magnetic latitude compared to the harmonics between them. Why is this? Could this be a saturation effect of the electric field measurements?

Below is an excerpt from the response to the referee reports.

“A1_A: As suggested by the referee, we have checked and found that the considered kilometric wave emissions can’t a free space radiation. In all events the gyrofrequency (FCE) is above the frequency associated to the LF kilometric emission. In Fig.1 or Fig.2 the gyro-frequency is indicated.”

Since these waves are not free space mode radiation calling them “Kilometric wave radiation” a term used for free space mode radiation generated near the plasmapause is confusing. How about calling them something like ‘Low Altitude Banded Equatorial Emissions below the electron cyclotron frequency’. I don’t see evidence of a continuum in Figures 1&2. Do you mean continuum in time or frequency?

The introduction and most of the paper focuses on ‘free space radiation’ not banded emissions below the FCE. The entire paper requires a complete rewrite.

As noted in the other referee report, Whistler waves propagate mainly along the field line. The introduction should mainly focus on previous observations of banded emissions below Fce and propagation characteristics of Whistler waves not escaping continuum.

In the discussion section the author should note that that the frequency range and radiation pattern of these observations below FCE is similar to the ‘Christmas tree pattern’ observed above FCE outside the plasmasphere. Then the authors can speculate on whether this is just a coincidence or if a deeper connection exists.

The Fce line should be labeled in Figures 1 &2.

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ED: Reconsider after major revisions (further review by editor and referees) (05 Sep 2019) by Yoshizumi Miyoshi

AR by Mohammed Y. Boudjada on behalf of the Authors (08 Nov 2019) Author's response

ED: Referee Nomination & Report Request started (22 Nov 2019) by Yoshizumi Miyoshi

RR by Anonymous Referee #2 (13 Dec 2019)

RR by Anonymous Referee #1 (06 Jan 2020)

ED: Reconsider after major revisions (further review by editor and referees) (17 Jan 2020) by Yoshizumi Miyoshi

AR by Mohammed Y. Boudjada on behalf of the Authors (27 Feb 2020) Author's response

ED: Referee Nomination & Report Request started (15 Mar 2020) by Yoshizumi Miyoshi

RR by Anonymous Referee #1 (16 Apr 2020)

ED: Publish subject to minor revisions (review by editor) (21 Apr 2020) by Yoshizumi Miyoshi

AR by Mohammed Y. Boudjada on behalf of the Authors (06 May 2020) Author's response Manuscript

ED: Publish as is (08 May 2020) by Yoshizumi Miyoshi

AR by Mohammed Y. Boudjada on behalf of the Authors (08 May 2020) Manuscript

Post-review adjustments

AA: Author's adjustment | EA: Editor approval

AA by Mohammed Y. Boudjada on behalf of the Authors (19 Jun 2020) Author's adjustment Manuscript

EA: Adjustments approved (19 Jun 2020) by Yoshizumi Miyoshi

Short summary

In this paper, we report on observations of frequency-banded wave emissions by ICE (Instrument Champ Électrique) on board DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions). We distinguish two components: positive and negative frequency drift rates and multiple spaced frequency bands near the magnetic equatorial plane. We show and discuss the non-free-space DEMETER frequency-banded emissions and the free-space terrestrial kilometric radiation.