Changes in and Recovery of the Turbulence Properties in the Magnetosheath for Different Solar Wind Streams

Round 1

Reviewer 1 Report

The article “Changes and recovery of the turbulence properties in the 2

magnetosheath for different solar wind streams” studies the change of turbulence properties from solar wind to the magnetosheath. The authors find that turbulent cascade is preserves the characteristic properties for fast solar wind streams. The study is very relevant and will be an important contribution to the community. The paper has minor problem with the English, but otherwise I recommend the paper for publication.

Slight improvements can be made.

Author Response

Dear Reviewer 1!

Thank you for reviewing and evaluating our work. We did our best to improve English.

Reviewer 2 Report

The authors elaborate the solar wind data collected by two spacecrafts during years 2008 and 2014, and present some changes (modification) of turbulent properties and restoration of others.

The study of the SW effects on the magnetosphere is based on statistics of the SW measurements. The authors indicate that the region of space between the magnetopause and the bow shock of a planet's magnetosphere (a magnetosheath (MSH)) significantly modifies the SW and IMF (interplanetary magnetic field) parameters. It is associated with plasma heating, deceleration, and compression at the bow shock (BS)( caused by the magnetosphere interaction with the solar wind). Thus, plasma and magnetic field downstream of the BS exhibit high level of fluctuations in a wide range of scales, including the ion and sub-ion scales.

Important finding is that ion and subion-scale structures are the main sources of the MSH fluctuations which are analyzed in a framework of turbulence. The evolution of turbulent cascade is characterized by the spectrum of fluctuations which follow the power laws with power exponents (slopes) varying in different ranges of scales. Turbulent cascade development in the MSH follows different ways depending on SW streams and their coupling with magnetosphere. It is shown that cascade preserves its properties for fast SW streams, which differ by the characteristics of fluctuations. The study addresses the changes of turbulent fluctuations in the magnetosheath – and considers dayside and flank magnetosheath regions.  

Based on the statistics of the simultaneous registration of turbulent fluctuations in the SW and inside the MSH, the authors conclude about the fluctuation spectra regarding their modification and restoration - in four points:

- Modification of the turbulence spectra properties at the MHD scales in the dayside MSH results from interaction of any type of the SW with the quasi-perpendicular BS.

- The spectra of magnetic field fluctuations may become steeper or stay unchanged- at the  kinetic scales.

- Restoration of turbulence spectra properties is observed for the Fast and CIR streams, while for the Slow SW and ICMEs the spectra stay slightly changed. 

- The spectra for Slow and Fast SW at the MSH flanks are similar to those observed in the SW – at the kinetic-scale.

The authors conclude that modification of Kolmogorov scaling at the BS is typical feature of the dayside MSH. They finally conclude that modification of the scaling at the kinetic scales as well as the way of the scaling restoration at the flanks - depend on the SW source at the Sun.

Methods of data selection and processing are described in detail, statistical results are presented and discussed and the final results are summarized .

The paper is interesting, informative and of high scientific quality, (but at some places not easy to follow because of many abbreviations, acronyms and numerical data). The paper contains new results relating to the physics of the solar winds characteristics of turbulence evolving in their complex interaction with magnetosphere. The manuscript presents original results which give deep insight into the subject and I recommend it for publication in Universe.

Author Response

Dear Reviewer 2!

Thank you for reviewing the manuscript and for the high rate of our work!

Reviewer 3 Report

The manuscript statistically analyzes different solar wind streams by evaluating the turbulence/spectra profile upstream (solar wind) and downstream (magnetosheath) for quasi-perpendicular shocks, using THEMIS mission.

Overall, the topic is very interesting and underexplored, which makes the whole paper intriguing. However, the interpretation is somewhat superficial in certain places and most importantly methodologically there are a few prominent caveats. 

I have some questions on the methodology as listed below, while I retain some of the more physical questions for a later iteration as I suspect the approach may influence the result. Having said that, I am positive that after reworking and clarifying some details the paper will be in good shape for publication after some revision.

Major

Evaluation of Quasi-parallel/Quasi-perpendicular shocks

The approach discussed in lines 123-12, subsection 2.2, and eventually result in line 249, is in my opinion not ideal, and could potentially have implications on the results.

(1)   If I understand this right, you are using WIND data and propagate the values to the locations at the flanks because you want to evaluate the two different spectra. However, it might be useful to verify the time lag you find with the one computed from OMNIweb dataset to see if there is any significant disagreement. Although I have strong concerns on this point, I am willing to ignore them as they are fundamental to your goal (i.e., connecting SW turbulence to MSH).  

(2)   Moving on, regarding the qpar/qperp configuration you reference Shevyrev & Zastenker 2008 methodology along with some of your own work. However, our understanding has changed significantly in the last few years on this aspect. It has been shown that classifying the downstream configuration based on propagated upstream measurements can be problematic for multiple reasons and this effect is even more prominent at the flanks of the magnetosheath (see e.g., Case and Wild 2012, Vokhmyanin et al. 2019, and Raptis et al. 2020). On the other hand, classifying the regions based on in-situ properties (see Karlsson et al. 2021) may be useful to remove these issues, although may introduce other problems due to the different types of solar wind involved requiring special treatment when evaluating particle data (see Koller et al. 2024). 

This could explain why you only had only ~200 Qpar cases from the 1000 intervals (lines 248 -249). Observationally for example using MMS it was found that more or less we get equal number of Qpar and Qperp bow shock crossings (see Lalti et al. 2022) which should provide similar statistics for the downstream (magnetosheath) plasma. I am not sure what’s the ratio with THEMIS, but I am surprised to see only 20% of them being Qpar.

A few ways to validate your dataset are:

(1)   Show how the evolution of the spectra would have been for the full ~1000 cases that you had and see if there is a significant difference. If there is limited one, it could be that there is a mix in the dataset of both qpar and qperp plasma.

(2)   Compute theta_bn by other means, like using OMNIweb propagated value (cone angle) and then based on the location of THEMIS estimate the actual theta_Bn for the closest to a shock model location.

(3)   Estimate the theta_Bn by using some of the in-situ metrics (e.g., magnetic field variance or presence of foreshock ions) to see if you are removing the more obvious Qpar cases.

I suggest you try a couple of these before we proceed to the physical evaluation of the results and also keep them in mind for future evaluation of connecting solar wind to processes at the Earth’s dayside. Finally, also good keep in mind that the if one wants to remove the effect of quasi-parallel shock/foreshock, you may need to go beyond 45 measured theta_bn, since the effect of foreshock can appear in larger angles (see some examples shown in Karlsson et al. 2021, and Liu et al. 2021).

Moderate/Minor

Lines 165-167: I am not sure I understand what you mean here. How is the interval bigger? Magnetic structure should have approximately the same observationally speaking duration upstream and downstream (?).

Lines 275-276: Do you think this is due to the shock being weaker at the flanks and therefore having lower heating/compression involved? Could this also be because the downstream plasma gets accelerated back to SW-like values there? 

Other relevant works: Some recent articles that may be interesting for you to compare would be the one by Gurchumelia et al. (2022) and Plank and Gingell (2023). Their results are quite relevant to compare and discuss.

References

Case, N. A., & Wild, J. A. (2012). A statistical comparison of solar wind propagation delays derived from multispacecraft techniques. Journal of Geophysical Research: Space Physics, 117(A2).

Gurchumelia, A., Sorriso-Valvo, L., Burgess, D., Yordanova, E., Elbakidze, K., Kharshiladze, O., & Kvaratskhelia, D. (2022). Comparing quasi-parallel and quasi-perpendicular configuration in the terrestrial magnetosheath: Multifractal analysis. Frontiers in Physics, 10, 903632.

Karlsson, T., Raptis, S., Trollvik, H., & Nilsson, H. (2021). Classifying the Magnetosheath Behind the Quasi‐Parallel and Quasi‐Perpendicular Bow Shock by Local Measurements. Journal of Geophysical Research: Space Physics, 126(9), e2021JA029269.

Koller, F., Raptis, S., Temmer, M., & Karlsson, T. (2024). The Effect of Fast Solar Wind on Ion Distribution Downstream of Earth’s Bow Shock. The Astrophysical Journal Letters, 964(1), L5.

Lalti, A., Khotyaintsev, Y. V., Dimmock, A. P., Johlander, A., Graham, D. B., & Olshevsky, V. (2022). A database of MMS bow shock crossings compiled using machine learning. Journal of Geophysical Research: Space Physics, 127(8), e2022JA030454.

Plank, J., & Gingell, I. L. (2023). Intermittency at Earth's bow shock: Measures of turbulence in quasi-parallel and quasi-perpendicular shocks. Physics of Plasmas, 30(8).

Raptis, S., Karlsson, T., Plaschke, F., Kullen, A., & Lindqvist, P. A. (2020a). Classifying magnetosheath jets using MMS: Statistical properties. Journal of Geophysical Research: Space Physics, 125(11), e2019JA027754.

Shevyrev, N. N., & Zastenker, G. N. (2005). Some features of the plasma flow in the magnetosheath behind quasi-parallel and quasi-perpendicular bow shocks. Planetary and Space Science, 53(1-3), 95-102.

Liu, T. Z., Hao, Y., Wilson III, L. B., Turner, D. L., & Zhang, H. (2021). Magnetospheric Multiscale Observations of Earth's Oblique Bow Shock Reformation by Foreshock Ultralow‐Frequency Waves. Geophysical Research Letters, 48(2), e2020GL091184.

Vokhmyanin, M. V., Stepanov, N. A., & Sergeev, V. A. (2019). On the evaluation of data quality in the OMNI interplanetary magnetic field database. Space Weather, 17(3), 476-486.

Edits:

General: THEMIS should be capitalized across the manuscript. 

Line 124: referencing is not correct. Based on your list it should have been [33]

Lines139-140: "was" may need to change to "is the" (?).

Author Response

Dear Reviewer!

Thank You for reviewing our manuscript. 

Please, find detailed answer on your comments in the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

I thank the authors for addressing the points I raised in the previous report.

Overall, I am convinced that the work is sound. I do however, have a few minor points.

(1) Would it be possible to add on Figures 5,6 the median values for the change of slop for each category ? also adding a metric of spread might be beneficial (e.g., standard deviation).

(2) Figure 2 and 3 have relatively small fonts especially on the y axis, which makes them pretty hard to read when printed or viewed at 100%. Could you please increase them?

Comment: To me it appears that based on your latest reply (figure 3 and 4) Θbn>0 and Θbn>45 have many similarities. Isn't that an indication that there might be some cases that are of quasi-parallel nature there ?  At this point I don't think you should do extra analysis on this, but maybe in the future it might can interesting topic to investigate whether this seperation of Qpar/Qperp via the θBn is not sufficient to capture the physical picture, and the association to foreshock dynamics or not is more vital. Finally, I agree that Indeed, each SW type should have slightly different in-situ thresholds, making fast-SW for example harder to classify, but it should still be doable either by variable thresholds or through manual verification. 

Author Response

Dear Reviewer!

(1) We have intentionally removed text descriptions of the distributions' properties from Figures 5 and 6 as a plenty of text would make these figures hard for understanding. Mean values and standard deviations are specified in the Table 1, and those 4 cases when median value differs significantly from the mean value are denoted in the figures.

We have tried to insert the median values to the figures. Please, find Figure 5_v2 and Figure 6_v2 in the attached file. However, we suppose this to be confusing rather than informative in this case.

If we also add the standard deviations (Figure 5_v3 and Figure 6_v3 in the attached file), it is even harder to observe initial distributions.

We suggest not to change the figures, but to add median values to the Table 1.

(2) We have corrected fonts in Figures 2 and 3, thank you for the comment.

Answer to the Comment:

To our point of view, slight change between whole statistics and the cases with Qbn>45 deg. is due to low number of quasi-parallel cases. Also, we keep in mind that we have averaged Qbn values over ~1 hour intervals, and sometimes short (~10 min) Qpar MSH crossings may be included to our statistics for Qbn>45 deg. Case study is worth to be prepared which uses more detailed separation (based on in-situ metrics as well) and comparison for Qpar\Qperp cases. We will consider it as the next step for our research in this area. Thank you for interesting discussion!

Author Response File: Author Response.pdf