A new scenario applying traffic flow analogy to poleward expansion of auroras

Saka, Osuke

doi:https://doi.org/10.5194/angeo-37-381-2019

Articles | Volume 37, issue 3

https://doi.org/10.5194/angeo-37-381-2019

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

https://doi.org/10.5194/angeo-37-381-2019

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

Articles | Volume 37, issue 3

Regular paper

|

05 Jun 2019

Regular paper |

| 05 Jun 2019

A new scenario applying traffic flow analogy to poleward expansion of auroras

Osuke Saka

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Final revised paper (published on 05 Jun 2019)
Preprint (discussion started on 28 Aug 2018)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Reviewer report', Anonymous Referee #1, 12 Sep 2018
- AC1: 'Reply to Referee #1', Osuke Saka, 01 Oct 2018
RC2: 'Reviewer report', Anonymous Referee #2, 10 Oct 2018
- AC2: 'Reply to Referee #2', Osuke Saka, 19 Oct 2018

Peer-review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (12 Nov 2018) by Matina Gkioulidou

AR by Osuke Saka on behalf of the Authors (10 Dec 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (20 Dec 2018) by Matina Gkioulidou

RR by Anonymous Referee #2 (17 Jan 2019)

Suggestions for revision or reasons for rejection

In my original review of this manuscript, I listed several concerns that I felt the author should be able to address with a major re-working of the text of the paper. Two major themes of my original comments were that: 1) there are numerous known observational facts relating to substorms that were completely ignored in the initial manuscript and 2) much of the claims made are not backed up by observational evidence or by reasonable/believable simulation results.

Unfortunately, most of the responses to my comments suffer from the exact same problems and the modifications have not improved the paper substantially. The main problems are:

1) The manuscript does an exceptionally poor job of describing what the current understanding is - both observationally and in terms of models. And the specific problem to be addressed is also poorly articulated.

2) An attempt at clarifying the main problem is added in lines 23-27. This refers to the balloon-measured E-fields, Ba release experiments, and radar studies from the 1970s. As a reader, I am simply not convinced that those studies have led the community to the idea that the poleward motion of auroras travelling at different rates than the equatorward drifts is at all an unanswered question. Surely the author can produce references that have been published over the past 40 years that may have explained these observations?

3) There was an addition of two sentences describing the current understanding on poleward propagation of the substorm auroras. Unfortunately, the explanation is too brief, with no references given and is substantially incorrect. A tailward moving reconnection site is not needed for poleward motion in the reconnection-based model -- simply having reconnection progress to the lobes is enough.

4) There is a very alarming trend in this paper where it seems that every citation of facts relating to observations or causative mechanisms are to the author's own previous publications -- none of which I am familiar with. There certainly are other studies on the aurora and Pi2s, etc. that are relevant to the current topic. It is completely inappropriate not to cite these many other papers.

5) The new section #2 does not provide any confidence at all in the assertions being made. Use of the T89 Kp 4 model to map results is notoriously untrustworthy. The results may or may not be correct -- which doesn't really tell us anything. There are also many facts definitively stated about Pi2s that by themselves warrant much more observational support than is given here. Inclusion of equation (1) is unnecessary since its context is completely lost on the reader. The conclusions drawn from this equation in lines 71-73 require far more convincing explanation than is given. The remainder of this section (on ballooning) is unclear. Is this a new idea? Existing idea? Is it based on models, theory, observations?

The final sentence of this section is typical of the confusing and unsupported claims in the paper; "The convection surge occurred once in the initial pulse of Pi2 pulsation but is not repeated in the following pulses." This statement seems important, but it is incomprehensible to me. How does the author know this? Is this referring to the Rubtsov study? What was that study? Did they demonstrate that this was a universal finding for substorms? How does this relate to the rest of the current paper? None of this is made clear.

6) Section #3 has a paragraph added, but it is also unclear. In line 83 it is stated that "It is reasonable to assume..." Why is it reasonable to assume this? Where does the surge come, from? Why would the high latitude end not expand as stated? Why would the flows be confined as stated? There are simply too many unsupported statements here. And then there is only a single reference to the author's own 2014 publication.

7) Section 4 is all bold-faced implying that there are major modifications to the manuscript, but much of it seems identical. I am not sure what has been changed there. Also, equation (6) is from Kelley's text book. Please indicate where in the textbook it can be found. This section also still reads more like facts are being disclosed rather than like an idea is being proposed. I don't know what's known or what's being proposed from this.

8) Section 5 is also all bold-faced making it difficult to see what has actually been changed.

9) The conclusion is still not supported by the body of the paper. I remain unconvinced that "this scenario, analogous to traffic flow of cars on the crowded roads, partly explains the discrepant time history of the auroras which is often described as the auroras expand opposite to that of plasma drift in the ionosphere." The author claims this, but there are many unsupported components that go into the scenario. A rather disturbing aspect of the paper is that it really still does not articulate what the problem is. Citing a few papers from the 1970's is not adequate here -- note that BBFs, streamers, and their relationship, etc were not known to those authors.

Also, the manuscript is completely devoid of any meaningful description of what the auroral observations really show during substorms. In re-reading this paper many times, my guess (and I have to stress here it is just a guess) is that the author is trying to explain the following observational scenario; a) a BBF-associated streamer propagates equatorward, b) as it interacts with the equatorial region, the presumed density accumulations described in the proposed scenario lead to poleward propagation of the auroras, c) this explains the hypothesized substorm sequence described by Nishimura et al.

If this is the intent of the currently proposed scenario, it is not at all clear from what is written. In addition, it is almost certainly incorrect. The types of events showing rapid poleward motion in response to streamers (the so-called contact breakups discovered by Oguti in the 1970s) tend to be explosive in nature, not just like a sand pile building up or tail lights propagating backward. (Note that this is also a major problem with the flow-braking model.) In addition, as I stated above and in my previous review, the scenario proposed here (as well as the Nishimura one) does not adequately describe things like plasmoid releases that are known to occur with substorms.

Once again, I suggest that the author rewrite the manuscript in a manner that the reader can understand what problem it is that is actually trying to be addressed. I feel that there are interesting and possibly important issues raised by the proposed scenario, but the presentation and conclusions are still very misguided. Below is a suggested outline of topics to cover.

1) Introduction

a) Describe phenomenologically what a substorm is both from an auroral point of view and from a tail point of view. This should not just cite the author's work from a few years ago or papers from 40-60 years ago. It should also be extensive enough to demonstrate to the reader that the author has a good grasp of what the current understanding is. The present manuscript does not convey this at all. This should be more than a quote about the importance of aurora from Oguti or a reference to Akasou's 1960's papers.

b) Describe what models are currently accepted to describe these observations. (Yes they exist and there is more than one.) Again don't just cite the author's work from a few years ago or papers from 40-60 years ago.

b) Have a section on a statement of the specific unresolved issue to be targeted here. What is the current state of understanding on the poleward/equatorward issue in particular? What are the successes/deficiencies in these ideas? Why does it make sense to dismiss them? Or to modify them?

c) briefly describe what the current paper will do to resolve this problem, with a short outline of the sections to follow and how they flow.

2) Proposed new model type of section. Describe the scenario and how it can lead to poleward propagation.

a) Sections on the scenario -- these are largely written already, but need to be drastically cleaned up to read more coherently. (With fewer definitive assertions and more suggestions.)

3) Discussion-like sections

a) Describe what types of poleward propagation it can address? Note that it is totally unbelievable that this scenario can address all facets of poleward motion. Why? Because at the extreme end, the poleward propagating part of the bulge eventually forms a double-oval like configuration that must engage extremely large regions of the magnetotail. Unless the density-accumulation concept proposed here can engage most of the nightside magnetosphere, it seems insufficient.

b) Can the scenario yield explosive poleward motion? Why, why not? Etc.. (Note that tailward-propagating tail-lights doesn't seem explosive.)

c) How does this scenario relate to other ideas and how does it explain all of the observations that were described in the first section? E.g. flow-braking? What has been neglected for the current scenario to ignore flow-braking? Etc..

3) Conclusion/discussion on where the scenario is most likely to fit into the overall picture. My feeling is that it might provide some explanation of the poleward motion during situations where streamers reach the equatorward part of the oval and possibly during some early initial phase of the contact breakup type events. (Note that the first disturbance is not a substorm at all and the second may only relate to the early phases of a complete substorm.) I rather suspect that the scenario is extremely unlikely to be able to explain the entire typical substorm sequence. A competent description of "what a substorm is" in the first section will, almost certainty, lead to the later part of this conclusion. Without that first section, conclusions like the one in the
present manuscript are simply not supported.

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ED: Reconsider after major revisions (further review by editor and referees) (06 Feb 2019) by Matina Gkioulidou

AR by Osuke Saka on behalf of the Authors (24 Feb 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (22 Mar 2019) by Matina Gkioulidou

RR by Anonymous Referee #2 (07 May 2019)

ED: Publish as is (21 May 2019) by Matina Gkioulidou

AR by Osuke Saka on behalf of the Authors (24 May 2019) Manuscript

Short summary

Flow channel extending in north–south directions is produced in the initial pulse of Pi2 pulsations associated with the field line dipolarization. Drifts in the ionosphere of the order of kilometers per second accumulated plasmas at the low-latitude end of the flow channel. The plasma compression in the ionosphere produced field-aligned currents, parallel electric fields, and auroral expansion. We called the compressive ionosphere a "dynamic ionosphere".