Vlasov simulation of electrons in the context of hybrid global models: an eVlasiator approach

Battarbee, Markus; Brito, Thiago; Alho, Markku; Pfau-Kempf, Yann; Grandin, Maxime; Ganse, Urs; Papadakis, Konstantinos; Johlander, Andreas; Turc, Lucile; Dubart, Maxime; Palmroth, Minna

doi:https://doi.org/10.5194/angeo-39-85-2021

Articles | Volume 39, issue 1

https://doi.org/10.5194/angeo-39-85-2021

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

https://doi.org/10.5194/angeo-39-85-2021

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

Articles | Volume 39, issue 1

Regular paper

|

28 Jan 2021

Regular paper |

| 28 Jan 2021

Vlasov simulation of electrons in the context of hybrid global models: an eVlasiator approach

Markus Battarbee, Thiago Brito, Markku Alho, Yann Pfau-Kempf, Maxime Grandin, Urs Ganse, Konstantinos Papadakis, Andreas Johlander, Lucile Turc, Maxime Dubart, and Minna Palmroth

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Final revised paper (published on 28 Jan 2021)
Preprint (discussion started on 02 Jun 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'review', Anonymous Referee #1, 18 Jun 2020
- AC1: 'Response to review by anonymous referee #1', Markus Battarbee, 26 Aug 2020
SC1: 'Electron vdfs in ion hybrid code?', Enrico Camporeale, 19 Jun 2020
- AC3: 'Response to Enrico Camporeale', Markus Battarbee, 26 Aug 2020
RC2: 'comments', Anonymous Referee #2, 09 Jul 2020
- AC2: 'Response to review by anonymous referee #2', Markus Battarbee, 26 Aug 2020

Peer-review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (26 Aug 2020) by Wen Li

AR by Markus Battarbee on behalf of the Authors (19 Oct 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (20 Oct 2020) by Wen Li

RR by Anonymous Referee #1 (17 Nov 2020)

RR by Anonymous Referee #2 (18 Nov 2020)

Suggestions for revision or reasons for rejection

This manuscript has been improved significantly. However, it is still difficult to understand the algorithm that is described in section 3.2.

The first half of section 3.2 is good (line 190-215), but the second half is confusing. It seems the authors start describing the sub-stepping algorithm before describing the big picture of the whole algorithm. Actually, figure 1 is very informative. If the authors can describe the solver from up to down following figure 1, it will be much easier for readers to understand. Here, I provide my personal suggestions to organize the second half of section 3.2.
1) Describe what is known at the start of a cycle time=t (6D electron phase space distribution at t? EM field at t?) and what is calculated from time=t to time=t+\Delta t.
2) Describe the leapfrog algorithm (‘translation’ and ‘acceleration’). I strongly suggest the authors writing down some expressions to explain the scheme. For example, even though the authors have added a sentence to explain what is a ‘transformation matrix’ in line 155, it is still not straightforward for me to understand the role of the matrix.
3) Explain why a substepping approach is required and why the substepping time step is so small. Simply saying ‘in order to accurately model the electron gyromotion and plasma oscillation’ does not explain too much.
4) Explain why a 4th order scheme is necessary and describe how the substepping scheme works.

The authors do not have to follow the steps strictly but I would like to see something similar. It seems step 4 is described but steps 1-3 are missing.

Minor comments:
1) Line 41: ‘...though the resolution decrease incurs the loss of some electron physics’. This is not fair to the implicit methods. The implicit PIC can use a coarse grid but they do not have to. When an implicit PIC code uses a fine grid resolution as an explicit PIC, they contain the same physics.
2) Line 217: the number ‘22’ is like a magic number, why it is not ‘21’ or ‘23’? I guess there is a range for the time step. Please provide more explanation.
3) Section 3.1:how are the ions handled? Do they keep the initial values and do not change during the simulation?

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ED: Publish subject to revisions (further review by editor and referees) (19 Nov 2020) by Wen Li

AR by Markus Battarbee on behalf of the Authors (01 Dec 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (04 Dec 2020) by Wen Li

RR by Anonymous Referee #2 (08 Dec 2020)

ED: Publish as is (09 Dec 2020) by Wen Li

AR by Markus Battarbee on behalf of the Authors (10 Dec 2020)

Short summary

We investigate local acceleration dynamics of electrons with a new numerical simulation method, which is an extension of a world-leading kinetic plasma simulation. We describe how large supercomputer simulations can be used to initialize the electron simulations and show numerical stability for the electron method. We show that features of our simulated electrons match observations from Earth's magnetic tail region.