the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Jul 2024
The investigation of June 21 and 25, 2015 CMEs using EUHFORIA
Abstract. In this research, the EUropean Heliosphere FORecasting Information Asset (EUHFORIA) is used as a mathematical model to examine how coronal mass ejections (CMEs) move through a solar wind flow that is not consistent in all areas, taking into account three dimensions and changes over time. Magnetohydrodynamic (MHD) simulations were conducted to analyze the propagation patterns of two specific CMEs that occurred on June 21 and 25, 2015. The EUHFORIA simulations for the inner region of the heliosphere involve incorporating conditions related to CMEs and the solar wind at the boundaries. Comparative examination using data from the WIND and OMNI spacecrafts reveals that the EUHFORIA model offers a moderately precise depiction. The study highlights that interactions of CMEs play a significant role in determining their impact on Earth, highlighting that their initial speeds, while similar, are less influential. Besides, the EUHFORIA numerical model align with the findings of the GFZ German research center, this implies that EUHFORIA has also the capability to compute and potentially forecast the impact of CMEs on the Earth.
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RC1: 'Comment on egusphere-2024-1921', Anonymous Referee #1, 23 Sep 2024
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The article titled – ‘The investigation of June 21 and 35, 2015 CMEs using EUHFORIA’ models 2 CMEs that impact Earth and calculate the Kp index of the associated storm comparing it with the GFZ predictions’. The work has some merit in Kp prediction; however, the article lacks clear details of the numerical investigation and does not provide scientific evaluation of the CME evolution. The article is also not well written and touches on ideas without clear explanations or examples/citations. A major rewrite is needed. The comments below have addressed these shortcomings.
Specific comments:
- Section 3 is titled ‘June 17-25 CMEs’ without any mention of the other CMEs associated with the CMEs studied in this work. According to the SOHO LASCO CME Catalog, there are multiple halo CMEs during June 17-25 including fast CMEs on June 18, June 19 before the studied June 21 and 25 events. On Line 155, the authors state that they examine the 8 specific CMEs, without any mention of these CMEs in the article. Infact, the authors only describe 2 CMEs on June 21 and June 25. Nowhere these 8 CMEs are described, identified, or even modeled. Were these CMEs geoeffective? Did they interact with the CMEs 1 and 2 causing a strong storm? The authors state that they examined the developed of these CMEs that impacted Earth, but it is not described in the text. The results of modeling 2 CMEs match with the Kp index, but the model has used only 2 events out of the mentioned 8 – does it mean that the interaction of the 2 CMEs has been overpredicted? Do the remaining 6 have no impact at earth? Why were they excluded?
- Line 93 – The CME 1 is shown to be associated with M2.6 flare at N12W08 – which is compared to Figure 2 and said to agree. However, nowhere on Figure 1 Panel (a) is the N12W08 flare listed. Please correct and mark the location of the flare associated with this CME. Line 100 – Incorrect, the location of the flare does not agree with the figure 1.
- A major concern in this article is the use of language that does not indicate a scientific statement. ‘kind of a limb CME’ – is not a scientific way of describing the observations. Based on the width/ position angle of the CME please say if it is a limb CME or not.Line 107 – Again, the use of ‘kind of fast’ should be removed. This is a moderately fast CME. Line 110 – saying that a CME is ‘somehow faster than the first CME’ should be removed. The usage of words like, ‘somehow’, ‘kind of’ is not scientific and needs to be removed from the article. Please write statements that are more concrete. General statement like – ‘jumps should be considerable enough’ are not useful for a reader. – Please state what is considered ‘considerable enough’.
- Line 94 – This is incorrect – the first image in each panel shows the height-time plot for CME and not the flare observation or type. The flare observations are from the GOES satellite not LASCO. Please rewrite and correct the description of the figure and instruments used.
- What is the source of the daily graphs of the solar wind plasma and magnetic field characteristics? Is OMNI data used, or Wind/ ACE? Please cite the correct data source. In Figure 5 – All panels include symbols extracted from OMNI data connected by a line. However, panel b – B[nT] plot shows a continuous line (not symbols and connecting line). Do the authors change the way the data is used to make this portion of the plot. Please be consistent. What are the dotted lines representing in these plots?
- Line 165 – Figure 6 displace the magnetic map --- No, the figure 6 does not display the magnetic map that is used as input. It shows the EUHFORIA boundary conditions NOT the GONG input map.
- At the 0.1 au limit, ‘scientists’ determine the speed of the solar wind – the WSA model provides these speeds at 1 au based on an empirical formula. Please describe it correctly. What is the outer boundary? Isn’t it 0.1 au? This statement is misleading.
- Conclusion – Point 1 – self consistent structure – no observation or model comparison is shown to substantiate this claim. Point 4 – what observation data was used to calculate the arrival time , is it the linear CME velocity fit to LASCO observations ? No discussion of the interaction is included for the two CMEs. At what distance did they interact? Infact, the authors state that CME 1 and 2 arrive at different time at 1 au. If cme2 was weaker, it never overtook cme 1 , so was there any interaction? Line 218 – Figure 7 shows the result at a time instant of the solar wind AND the CMEs . It is not ‘specifically focusing on the simulation of the solar wind’. This figure ONLY shows the CME evolution in the heliospheric part of EIHFORIA, without describing how the parameters of the CME model were set, tested or validated. In the text it was mentioned that CME2 is faster and expected to produce strong geomagnetic storm. And in lines 245-250 , the authors say that CME2 has diminished and less powerful. What is the reason for this?
- Line 229 – ‘due to the development of magnetic field’ – This description of the force dynamics is confusing. Explain the ‘shrinking and expanding ‘ – magnetic field exists and Lorentz force is dominant in the initial phase of the CME causing acceleration before the drag takes over. Drag can accelerate or decelerate depending on the relative speeds of the CME and the solar wind.
- Line 330 –Once the CME 1 travels out, it clears out a lot of the solar wind plasma, leaving a less dense environment into which the CME 2 will travel. So, how is the solar wind identical? Is it in the code?
Technical :
Full form of Multi-VP
Please use the same nomenclature, you capitalize ‘Sun’ at some places, and not others.
Remove combining - combination– ‘In this line ‘
Magnetism – magnetic field
Please add full forms of acronyms at the first instance they appear. – SWPC,
Line 99 – repeated full form of STEREO
Line 105 – In according -> According to ..
Line 109 – near one day -> within one day
Line 117 – Why is Coronal Mass Ejections spelled ot here, when it has already been abbreviated in the beginning of the article?
Time-dependent – time-dependence
Line 239 – ‘ We determine theat CME 1 will reach the Earth in approximately 46 hours ‘  - is this estimation based on the arrival of CME 1 in the EUHFORIA model? So, your simulated CME reaches 1 au in 46 hours?
It would be useful to indicate the CME 1 and 2 in the Figures 7 and 8 , so that readers can identify their evolution.
Line 150 - Add a reference here.
Add a reference for Line 59.
In Figure 7, it would be useful if the CME 1 and CME 2 are highlighted.
Line 213 – ‘Only methods related to space weather …’.   What methods?
When an equation is listed, please describe all the variables associated with the equation.
Citation: https://doi.org/10.5194/egusphere-2024-1921-RC1
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