the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 16 Aug 2023
A statistical study of the magnetic signatures of the unique Tonga volcanic explosion of 15 January 2022
Abstract. For the first time, a statistical study has been conducted of the geomagnetic bay and quasi-periodic disturbances based on the datasets collected at 19 recording stations participating in INTERMAGNET Magnetic Observatories. In order to identify the disturbances from the volcanic explosion, a preliminary analysis has been used of the state of space weather during the catastrophic Tonga volcanic explosion of 15 January 2022. We summarize the main results as follows: The non-monotony of the variations in the strength of all geomagnetic field components increased appreciably on the day of the explosion as compared to the variations observed during the days used as a quiet time reference, while the eastward component of the geomagnetic field exhibited an up to 60-nT increase in variability. The duration and time delay of the bay disturbances increased with distance from the volcano, while their amplitude decreased. The propagation speeds of the bay disturbances at various observatories were determined to be in the 700–1,000 m/s range. Six groups of time delays of quasi-sinusoidal disturbances have been identified in a simultaneous analysis for the first time; they correspond to the apparent speeds of 4 km/s, 1.5 km/s, 1 km/s, as well as 500 m/s, 313 m/s, and 200 m/s. The time delay in each group increased with distance away from the volcano. The agreement between theoretical estimates and the observational data testify to the adequacy of the mechanism adopted for the generation of the disturbances.
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CC1: 'Comment on angeo-2023-27', Yu Zheng, 27 Aug 2023
After carefully reading the article «A statistical study of the magnetic signatures of the unique Tonga volcanic explosion of 15 January 2022» by L. F. Chernogor, I would like to note the following.
- The article matches the profile of the journal.
- The relevance of the topic is beyond doubt.
- To study the statistical characteristics, the author processed the data from 19 magnetic stations of the INTERMAGNET network.
- The article should be published in the Annales Geophysicae journal after the following minor remarks have been eliminated:
4.1. The wavelet transform was used in the systems spectral analysis, but the mother wavelet was not specified.
4.2. The paper contains a large number of references. Are they all necessary?
4.3. The state of space weather is described in too much detail.
4.4. Does bay disturbances have anisotropy?
Citation: https://doi.org/10.5194/angeo-2023-27-CC1 -
AC1: 'Reply on CC1', Leonid Chernogor, 25 Sep 2023
Dear Prof. Yu Zheng,
Thank you very much for your precious notes.
4.1. The Morlet wavelet was used as a basis function.
4.2. All the references are needed to verify the statements in the manuscript.
4.3. The description of the state of space weather is of importance primarily because it is needed for revealing the geomagnetic field variations caused by the Tonga volcano explosion.
4.4. Most likely.
Sincerely,
Leonid Chernogor.
Citation: https://doi.org/10.5194/angeo-2023-27-AC1 -
CC4: 'Reply on AC1', Yu Zheng, 05 Oct 2023
Dear Professor Leonid Cheronogor!
I have carefully reviewed the responses to my comments and I believe there are no further questions. Therefore, it is recommended that the editor accept your changes and give priority to publication.Kind regards,
Yu Zheng
Citation: https://doi.org/10.5194/angeo-2023-27-CC4
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CC4: 'Reply on AC1', Yu Zheng, 05 Oct 2023
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CC2: 'Comment on angeo-2023-27', Jian Wang, 27 Aug 2023
The manuscript is devoted to a topical issue of the magnetic effects of the explosive Tonga volcano in 2022. The author analyzed a large amount of data and determined the statistical characteristics of geomagnetic field disturbances. At the same time, the manuscript should be modified before it can be accepted for publication. Specific points to be addressed are:
1. The error in estimating the delay times is not indicated; they determine the propagation velocities of disturbances.
2. What is the error in estimating the duration of the disturbances?
3. Three papers in the bibliography are in press. The issue number and page number must be given if they have already been published.
4. Are the geomagnetic field variations after midnight (12:00 P.M.) related to the volcano's explosion?Citation: https://doi.org/10.5194/angeo-2023-27-CC2 -
AC2: 'Reply on CC2', Leonid Chernogor, 25 Sep 2023
Dear Prof. Jian Wang,
Thank you very much for pointing out the necessary modifications to the manuscript.
- The time delay errors have been estimated to be 1–5 min, depending on the time rate of change of the geomagnetic field.
- An error in the estimates of the duration of the perturbations does not exceed 5 min.
- Part of our papers are in press to date.
- After midnight, the variations in the geomagnetic field are due to both Tonga volcano and the geomagnetic substorm.
Sincerely,
Leonid Chernogor.
Citation: https://doi.org/10.5194/angeo-2023-27-AC2 -
CC3: 'Reply on AC2', Jian Wang, 05 Oct 2023
Dear Prof. Leonid Chernogor,
Thank you for addressing the previous comments, and no further comments exist.
As a result, I hope the above content can be specifically reflected in the revised manuscript.
Sincerely,
Jian WangCitation: https://doi.org/10.5194/angeo-2023-27-CC3
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AC2: 'Reply on CC2', Leonid Chernogor, 25 Sep 2023
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RC1: 'Comment on angeo-2023-27', Adrian Hitchman, 18 Sep 2023
The comment was uploaded in the form of a supplement: https://angeo.copernicus.org/preprints/angeo-2023-27/angeo-2023-27-RC1-supplement.pdf
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AC3: 'Reply on RC1', Leonid Chernogor, 25 Sep 2023
Dear Dr. Adrian Hitchman,
Thank you very much for wasting your precious time on checking my manuscript. I am really fortunate to have a world expert on geoscience to discuss my manuscript. Regarding what geomagnetic disturbance features are being identified in the observatory data, briefly, they are any changes in the magnetic field strengths arriving at different observatories with close apparent speeds, which correspond to the known speeds of waves of particular physical nature. This algorithm is described in Steps (i)–(vi) in detail below.
- In comparing the raw data plots in Figures 2 to 20 recorded on the day the volcano exploded and on the quiet days 13 and 17 January, it is apparent that the variations on the quiet days are smoother. On the day of the eruption, the character of the variations notably changed, which attests to the appearance of disturbances.
The method for finding a possible geomagnetic field response to the Tonga volcanic explosion is described in the manuscript (Line 115–128). The algorithm is as follows:
(i) Since the variations in the geomagnetic field may be caused by many powerful sources releasing significant amounts of energy, any characteristic changes in the variations in the strength of the X, Y, and Z components that were observed to occur after the volcanic explosion and could be associated with the explosion are highlighted at the first stage of employing the algorithm. This condition is necessary but insufficient.
(ii) At the second stage, the variations analogous to those that occurred on quiet time days and were due to, for example, diurnal variation, the solar terminator, etc., are filtered out.
(iii) Further, the possible time delays and apparent speeds are determined. The time delay should increase with distance from the volcano.
(iv) If some apparent speeds at different stations are substantially close to each other, they are included in a particular statistic. The closeness of the apparent speeds in this particular statistic is considered a sufficient condition for this particular disturbance to be due to the volcanic explosion.
(v) The physical significance of the apparent speeds is an additional sufficient condition: these speeds must correspond to the known speeds of waves of particular physical nature.
(vi) The results obtained are compared, if possible, with the results obtained for the volcanoes that exploded before.
It should also be mentioned that some of the results on the magnetic effect of Tonga volcano have already been described by other authors [Adushkin et al., 2022; Iyemori et al., 2022; Le et al., 2022; Schnepf et al., 2022; Soares et al., 2022; Yamazaki et al., 2022].
- The author considers that it is obligatory to describe the field variations on reference days because they are in the heart of the algorithm of finding the geomagnetic disturbance features (see Algorithm step (ii) above). This approach is generally accepted in geophysics (see, e.g., the textbook by Robert W. Schunk and Andrew F. Nagy, Ionospheres: Physics, Plasma Physics, and Chemistry, Second Edition, 2009, CUP).
- Megameters are commonly used for designating large distances in the same way as MHz, Mbyte, etc. (see, e.g., the textbook Introduction to Space Physics edited by M. G. Kivelson and C. T. Russell, Reprinted 1996, CUP).
- The transformations specified in the manuscript (Line 134) were used to estimate the periods. Due to the already large volume of the manuscript, the “kitchen” of processing itself is not given here.
- Conclusion. See this reply Section 1 above.
Sincerely,
Leonid Chernogor.
Citation: https://doi.org/10.5194/angeo-2023-27-AC3 -
RC2: 'Reply on AC3', Adrian Hitchman, 03 Oct 2023
The comment was uploaded in the form of a supplement: https://angeo.copernicus.org/preprints/angeo-2023-27/angeo-2023-27-RC2-supplement.pdf
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AC4: 'Reply on RC2', Leonid Chernogor, 04 Nov 2023
The comment was uploaded in the form of a supplement: https://angeo.copernicus.org/preprints/angeo-2023-27/angeo-2023-27-AC4-supplement.pdf
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AC4: 'Reply on RC2', Leonid Chernogor, 04 Nov 2023
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AC3: 'Reply on RC1', Leonid Chernogor, 25 Sep 2023
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RC3: 'Comment on angeo-2023-27', Anonymous Referee #2, 16 Oct 2023
The presentation of the state of the art and the bibliographic research are both quite good. The English form is almost perfect, even if, probably, the paper would benefit from a reading by a mother tongue English speaker. The topic discussed in the paper is well presented and everything goes smoothly until Section 4. Section 4, Instrumentations and tecnhiques, is, in my opinion the weakest section in the paper. Here the algorithm used for the study is presented, but the level of details is not sufficient. The author should go in much more details, explain how the algorithm was implemented, and provide quantitative statements.
Section 5 is, sorry to say, a bit boring. The signals acquired by each of the many stations are presented in Figures, and each of them is commented in the text. This is not the way to proceed. A competent reader can watch the Figure and deduce the most important issues from them. The comment should be collective, and intended to put in evidence the general message, like the ones put in the subsequent sections. I would have expected a different way of treating the data (maybe with figures summarizing the relevant aspects). It is also weird that the author, at some point, start using the word "trend" with a symbol that was never used up to that point (and X with a bar on it, line 197). Anyhow, almost 30 pages are used for this list which are way too much.
Last two Sections, where discussion of the results and drawing of the conclusions are done, are much more interesting, and I think that there good results and considerations there. In general, I think that the paper needs a deep revision, getting rid of the central part (to be strongly reduced, and maybe to be moved in an Appendix), but there is something good in it, so my advice is to reconsider it after the revision will be done.
In the following more specific modifications to be done:
line 42: the current density J should not be expressed in ma/m^2 instead of mA/m?
line 73: "these variations is to advance understanding of this scientific issue"--> "these variations is in order to advance understanding this scientific issue"
line 84: "Table 1. Basic information on volcanos" -->"Table 1. Basic information on largest volcanos eruption recorded"
line 85: the line should not be indented.
line 136: "Figure 1: Map showing the sites of the recording stations."--> "Figure 1: Map showing the sites of the recording stations used for the present study"
line 150: "The more rapid fluctuations"--> "faster fluctuations"
line 443: I guess that R2 is the regression coefficient. Why not calling it like this?
line 449: "The formation of disturbance is close to root mean square deviations in time delays" what is the meaning of this sentence?
line 463: Here the author discusses results presented in Table 3, shown several pages earlier. I would put this section close to the Table.
line 522: Please explain where this equation comes from.
line 529: "take" --> "takes"
line 530: "occur" --> "occurs"
Citation: https://doi.org/10.5194/angeo-2023-27-RC3 -
AC5: 'Reply on RC3', Leonid Chernogor, 04 Nov 2023
The comment was uploaded in the form of a supplement: https://angeo.copernicus.org/preprints/angeo-2023-27/angeo-2023-27-AC5-supplement.pdf
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AC5: 'Reply on RC3', Leonid Chernogor, 04 Nov 2023
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