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
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 -
RC2: 'Comment on egusphere-2024-1921', Anonymous Referee #2, 16 Oct 2024
The paper by Sabri & Poedts models 2 CMEs that impact the Earth. The output of the model provides the expected Kp index. These predictions are then compared with GFZ. At first sight the results seem reasonable, but many other details are needed to evaluate authors’ findings. For example, the comparison between Kp prediction and GFZ lacks a quantitative error estimation in terms of both intensity and timing. Furthermore, information about the hypothetical warning time is not provided. The article could be considered for publication only after major revisions. Specific comments are reported below.
Comment on References: Please, cite in parentheses when needed in order to avoid confusion with the main text. For example “To address this, the ESA Virtual Space Weather Modeling Center (VSWMC) has expanded its capabilities to allow the integration of a series of models for the purpose of forecasting Poedts et al. (2020)” should be “To address this, the ESA Virtual Space Weather Modeling Center (VSWMC) has expanded its capabilities to allow the integration of a series of models for the purpose of forecasting (Poedts et al. 2020)”.
Abstract – Please specify how the impact of the CMEs on Earth is evaluated in the work (e.g. Kp index) in order to better describe the work.
Line 6 – “Comparative examination using data from the WIND and OMNI spacecrafts reveals that the EUHFORIA model offers a moderately precise depiction.” – OMNI is a web data service, not a spacecraft. Please modify.
Lines 7-8 – “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.” – This sentence, which summarizes the main result, is unclear. Please rephrase.
Line 53 – “which is anchored in two opposite polarities of the sun’s magnetism on its surface [...]” – magnetism -> magnetic field.
Lines 136-137 – “One approach is the Wang-Sheeley-Arge model (WSA), which incorporates data from magnetograms to determine the plasma conditions at a distance of 0.1 AU.” – This statement is unclear. Isn't the WSA relation used to determine the radial velocity of the solar wind at the source surface from the expansion factors of open field lines? While the expansion factors (and the magnetic field at the source surface) are determined through the PFSS extrapolation from magnetograms. Please clarify and provide more details.
Line 143 – “[...] by using a method called Potential Field Source Surface (PESS) extrapolation [...]” – the correct acronym is PFSS. Please change.
Lines 150-151 – “This sentence states that a finite volume numerical method and a constrained transport scheme are used to solve the ideal MHD equations with a polytropic index of 1.5, ensuring that the solenoidal criteria are met.” Please change “This sentence states” in something more formal like “In particular, a finite volume…[...]”.
Lines 276-277 – “EUHFORIA utilizes a straightforward approach that is based on the empirical equation for linear prediction of Kp, which was originally proposed by Newell et al. (2008)” – Which is the empirical relation? How is Kp of EUHFORIA calculated? Please provide more details.
Lines 280-281 – “The Kp index is computed by the model and presented as a time series file” -> “The Kp index is computed by the model and presented as a time series”. Remove the word “file” from the sentence. It’s not useful and misleading.
Figure 9 – It would be useful for comparison to show Kp prediction and Kp index from GFZ in the same plot. This would be useful especially for comparing the timings of predicted Kp and GFZ. Furthermore it is strongly recommended to provide an error metric for this event, such as the root mean squared error (RMSE). Please provide these details.
Lines 302-303 – “Out of the various CMEs that happened during that specific time, only two were chosen. These two CMEs had distinct structures, one being a full halo CME and the other being a limb CME. “ Only two CMEs have been inserted into the simulation. Is this choice motivated by scientific reasons or only by technical limitations? It is important to specify that because, as stated in the next sentence (“These interactions between the CMEs could have had a notable impact on Earth’s magnetosphere and ionosphere.”), interaction between multiple CMEs could have a notable impact. Could other CMEs occurred in the time span between CME1 and CME2 interact with them?
Lines 327 - 330 – “The EUHFORIA numerical model’s time variations of the Kp index coincided with the observational GFZ results. This states that EUHFORIA has the capability to accurately determine and possibly forecast the impact of CMEs on Earth. Furthermore, due to the presence of several CMEs in the vicinity of CME1, it is possible that this anticipated severe storm is connected to the interaction of multiple CMEs.” How is it possible that, if there is a significant discrepancy in the estimated arrival time of the CMEs, the predicted KP is aligned (in time) with the observed one? This fact does not make sense to me. Please clarify.
Comment on “Conclusions”: The authors state that the model has the capability to compute and potentially forecast the impact of CMEs on the Earth, but nothing is said about the warning time of their predictions, i.e., computational time vs effective arrival of the CMEs. This would help to understand whether the model can potentially predict the impact of CMEs. Please provide these details/references (in addition to what is already there about the arrival times of CMEs).
Citation: https://doi.org/10.5194/egusphere-2024-1921-RC2
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