the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 16 Feb 2023
An Overview of Solar Radio Type II Bursts through analysis of associated solar and near Earth space weather features during Ascending phase of SC 25
Abstract. Type II solar radio bursts are the signatures of particle acceleration caused by shock waves in the solar atmosphere and interplanetary space. Being electromagnetic radiation that travel at the speed of light, they can serve as ground observed data to provide early notice of incoming solar storm disturbances. An observational overview of 31 Type II bursts which occurred in the period between May 2021 to December 2022 is made. We analyzed associated parameters such as bandwidth, drift rates, starting frequency to evaluate their dynamical parameters such as the shock and Alfvén speeds to estimate the Alfvén Mach number as well as the coronal magnetic field strength using Rankine-Hugoniot relation. We also evaluated accompanying space weather implication in terms of ionospheric total electron content (TEC) enhancement. At heliocentric distance ∼ 1−2 R⊙, the shock and the Alfvén speeds are in the range 504–1301 km s−1 and 368–837 km s−1, respectively. The Alfvén Mach number is of the order of 1.2 ≤ MA ≤ 1.8 at the same heliocentric distance, and the magnetic field strength shows excellent consistency and could be fit with a single power-law distribution of the type B(r) = 6.56 r −3.92 G. The study finds that 15/31 type II radio bursts are associated with some aspects of space weather such as radio blackouts and/or polar cap absorption events, that are the signature of solar proton enhancement and solar energetic particle events. Observed and analyzed Type II events correlated well with observed ionospheric storm indicated by the TEC enhancement. The findings from this study indicate that through analysis of type II SRBs observed from the ground and their physical features characteristics, it is possible to monitor the current progress of solar cycle 25 and predict the intensity of associated space weather phenomena.
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RC1: 'Comment on egusphere-2023-201', Costas Alissandrakis, 28 Mar 2023
The authors analysed 31 type II burst from e-CALLISTO observations during the period of May 2021 to December 2022 (ascending phase of the current solar cycle). Based on measurements of dynamic spectra, they estimated physical parameters of the associated shocks. They also examined associated X-ray flares and CMEs. The authors further examined in detail space whether effects of bursts on October 9, 2021 and during March 24 - April 3, 2022. They conclude that 15 out of their events were associated with space whether events.
Their results are new and interesting, hence the article merits publication after some improvements:
1. The authors should provide a table with the statistics of their results (range of values, average, rms), together with values from previous works for easy comparison.
2. Lines 107-109: please provided the values of the slope derived by Vršnak et al., 2002 and Umuhire et al., 2021.
3. The difference between the CME speed derived from the dynamic sectra and that of LASCO should be discussed further.
4. Figure 4: (a) please label the axes (b) add your own measurements (c) In the insert, replace equations with the model names.
Where does the "quiet Sun magnetic field model" come from?
5. Lines 200-220: Can you identify which TEC enhancements are associated with which type II?
6. The authors conclude that 15 out of their events were associated with space whether events. This is an important result and requires further discussion, preferebly in a separate section. For example, what were the differences between these 15 and the other type IIs? are there any observable type II characteristics that enhance the probability of space whether effects?
Finally, the authors may find interesting the review doi: 10.3389/fspas.2020.591075 on radio maesurements of the magnetic field.Citation: https://doi.org/10.5194/egusphere-2023-201-RC1 -
AC1: 'Reply on RC1', Theogene Ndacyayisenga, 29 Mar 2023
On behalf of all Co-authors, I thank the referee for providing the comments on our manuscript. I hereby give the answers in the attached file.
Regards
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RC2: 'Reply on AC1', Costas Alissandrakis, 31 Mar 2023
Thank you for your prompt replies to my comments. However, they were below my expectations, so here are some clarifications.
- I've seen figure 3 and your comparisons in the text, this is not what I am asking for. The table I requested will show to the interested reader at a glance your results and previous values.
- I asked for the values of the slope, not the correlation coefficients
- I suppose you imply that the shock decelerates as it moves up in the corona. This should be included in the text, together examples from the literature.
- I asked you to plot your individual measurements on the plot of Fig 4, which now shows only the fit to your values. By the way, it will be better to use logarithmic scales on both axes. As for the quiet sun magnetic field model, in addition to the reference you should mention how it was derived and the range of its validity.
- You should clarify your criteria of association and, based on these, give the burst numbers (from your table 1) that you can positively associate with space whether effects
- Your answer is very general and does not address my comment. What I am asking you to do is to try to identify any observational differences between the two groups of type IIs, not to state results from the literature. If you succeed, it will be an important contribution. If not, you should still state that you could find no differences between the two type II groups.
Citation: https://doi.org/10.5194/egusphere-2023-201-RC2 - AC2: 'Reply on RC2', Theogene Ndacyayisenga, 05 Apr 2023
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RC2: 'Reply on AC1', Costas Alissandrakis, 31 Mar 2023
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AC1: 'Reply on RC1', Theogene Ndacyayisenga, 29 Mar 2023
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RC3: 'Comment on egusphere-2023-201', Anonymous Referee #2, 27 Apr 2023
The paper presents observations of type II bursts during the ascending phase of SC25 achieved with e-CALISTO instruments as well as some associations of these type II bursts with space weather features. The paper presents potentially interesting events but needs some major improvements before publication. The conclusions on the type II analysis should be more emphasized (what is new with these obsrvations with respect to previous observations?) and the link with the space weather effects should be investigated in more details (the fact that effects are seen at the same time as the type II burst does not explain the physical link between both observations).
Here are some detailed comments and questions :
- Abstract
Line 3 : the authors mention solar storm disturbances but they should precise which kind of disturbances since in the following of the paper they mention TEC enhancement, radio blackouts, polar cap absorption…
Line 12 : the authors mention solar proton enhancements and solar particle events. What is the difference ?
- Observations
-In the section, ‘derivation of shock characteristic parameters’, the authors quote the papers by Vrsnak et al. (2001,2002) to estimate the density jump across the shock. However, in these papers, BDW used in equation 2 refers to the instantaneous band splitting of the type II emission and not to the instantaneous bandwidth mentioned in equation 1. The authors should give clearer explanations on the description of the observations and the use of the relations derived from these papers. Do they observe band-splitting for all the type II bursts they analysed ? They should also correct the wording in section 2 as well as figure 1 caption.
-The authors assume a density variation as r-6.13 as used in Gopalswamy (2011). Given that the different e-CALLISTO instruments observe in different frequency bands (i.e. radio emission produced at different coronal heights), is this choice of density model relevant for all the events?
-In equation 6, the authors should indicate the units.
- The end of section 2.2 contains information on GPS data and is not relevant to the derivation of shock characteristic parameters. A new section should be created for the discussion of the GPS data.
- Results and discussions
The e-CALLISTO network consists of many stations working in different frequency bands. The authors should specify in table 1 the name of the instrument(s) which observed the different type II bursts. Only a small number of the listed type II bursts starts at frequencies above 100 MHz. This may be linked to the instrument or reveal different characteristics of type II bursts. The authors should also discuss how the CME parameters are derived.
-line 102 : the authors use a relationship published by Gopalswamy et al (2013) to derive the shock formation height of the type II . They should discuss how this relationship is found and whether it can be used on another sample of data (like the present one).
- figure 2 : Most of the type II bursts have starting frequencies below 100 MHz. Is the correlation coefficient different if only type II burst with starting frequencies below 100 MHz are considered ? Same questions with the relationship between the frequency drift rate and the starting frequency ?
- figure 3 : It would be interesting to plot v derived from the dynamic spectrum with respect to v derived from the CME.
Section 3.2 : Associated Space Weather implication
-Figure 5 bottom : is this plot showing a prediction or real observations ? Is this HF absorption linked to the arrival of protons or to the ionizing flux from the flare ? How can the type II burst observations explain this HF absorption ?
-Correct the time of the type IV burst time in line 179 as well as in the caption of figure 7
-Similar question for figure 8 as the one asked for figure 5. Are the times the same for figure 8 top and bottom ?
-There are a lot of acronyms from lines 187 to 195 (SPE,SEP,PCAE). Please precise their meaning.
-Figure 9 : The authors should precise the link between the TEC enhancements in the different stations and the many type II bursts reported during this period.
-Last part of section 3.2 : the authors claim that 15/31 events have immediate space weather effects but this is not really shown in the paper. More generally, the discussion between the type II observations and the space weather effects is vague. It is not clear how the observations of type II bursts can allow to predict TEC enhancements since they may be due to the flare ionized flux or to the arrival of energetic particles. Furthermore, it is not clear why some type II burstsare associated with space weather effects and why others are not.
Citation: https://doi.org/10.5194/egusphere-2023-201-RC3 - AC3: 'Reply on RC3', Theogene Ndacyayisenga, 16 May 2023
- AC4: 'Reply on RC3', Theogene Ndacyayisenga, 16 May 2023
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