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 -
AC1: 'Reply on RC1', Somaiyeh Sabri, 20 Nov 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. In fact, 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?
Our reply: I apologise for my bad writing, which resulted in a misunderstanding. We considered the CMEs that happened on 18 and 19 June. I added Table 1 with the CMEs information in the manuscript. Because we had those CMEs on 18 and 19 June that happened before the CME1 (which occurred on 21 June), but we did not have significant CMEs on 23 and 24 June before our second selected CME2, we considered that for CME1, we had the CME interaction, but this did not happen for the CME2. Then, we investigated the CME interaction effect for CME1 that affects its impact on Earth. There are no CME interactions for CME2.
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.
Our reply: It was corrected, and the flare locations were marked with black arrows. In Fig. 2, the location of the flare is not shown. Our main aim was to indicate the M-type flare in panel b of Fig. 2 and also the second picture of panel (a) of Fig. 1 (with a black arrow).
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’.
Our reply: Thanks for your attention. All of these statements were edited in the new version of the manuscript. Besides, all of the manuscript was also edited.
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.
Our reply: There are GOES X-ray intensity plots below the CME height-time plot from the CDAW catalogue.
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?
Our reply: We used the Heliospheric Shock Database generated and maintained at the University of Helsinki, which has this link I cited: http://ipshocks.fi/database.
There are daily graphs of the solar wind and the following properties with different spacecraft, including ACE, Wind, OMNI, etc. The figures that I used were downloaded from this page, and one of them (panel a of Fig. 5) is from OMNI and panel (b) of Fig. 5 is from Wind. of these figures are on the mentioned page, and the spacecraft names are mentioned at the top of the figures. We did not plot these figures and never changed any data. You can find these figures from the mentioned link ( http://ipshocks.fi/database) that depicted these figures with the definite spacecraft at the definite time. I used PNG plots for these figures, but you can find the original figures there. The dotted lines indicate the shocks as the page described. Again, I mentioned that these plots are not my plots; they were downloaded from the link mentioned.
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.
Our reply: The coronal model provides the required MHD input quantities at 21.5 Rs for the heliospheric solar wind module. The coronal module in EUHFORIA is data-driven and combines a PFSS magnetic field extrapolation from GONG or ADAPT magnetograms (1-2.5 Rs) with the semi-empirical Wand-Sheely-Arge (WSA) model and the Schatteen current sheet (SCS) model to extend the velocity and magnetic field from the source surface at 2.5Rs to 21.5 Rs. This is done with other semi-empirical formulas so that the density and temperature are also derived at 21.5 Rs. EUHFORIA consists of two parts: a coronal domain and a heliospheric domain. The coronal part is a 3D semi-empirical model based on the WSA model, which provides the solar wind plasma conditions at the inner boundary of EUHFORIA at 0.1 AU. The photospheric magnetic field drives it via synoptic magnetogram maps. Figure 6 shows the heliosphere EUHFORIA boundary condition obtained from the GONG map input and the coronal model in EUHFORIA.
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?
Our reply: Point 1: I use a self-consistent structure due to the agreement of the overall CME shape of the simulation and observation and especially the arrival time of the CME to the Earth obtained by the simulation and observation velocity value. But if you disagree, I can omit this term.
Point 4: Yes, it was calculated using the linear fit speed based on the SOHO LASCO CME CATALOG.
CME interaction occurred for CME1 because of the other CMEs around CME1. In the CME2 case 2, no other CMEs interacted with CME2. Indeed, we do not see an interaction between CME1 and CME2. CME2 starts only when CME1 arrives at Earth.
Yes, you are right. The CME parameters from the DONKI Catalog are used. I can add the selected CME properties to the manuscript in a table. For the CME speed, we use the SOHO LASCO CME CATALOG, which indicates that the speed of CME1 is 1250 km/s and the speed of CME2 is 1450 km/s. Comparing panels b and d of Figure 8, it was concluded that CME2 has diminished ( it has a negligible size).
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.
Our reply: I must thank you for your help. I applied the suggestions.
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?
Our reply: The background solar wind properties are the same for both CME simulations. We used the DONKI CME catalog for the CME input parameters. The properties of the background solar wind and the CMEs are illustrated in Figure 6.. Thank you for noting the important point about the differences in the pattern of the plasma density around CME2 and CME1. This would be due to the interaction of the background solar wind with the previous CMEs.
Technical :
Full form of Multi-VP
Our reply: MULTi-VP is not the abbreviation.
Please use the same nomenclature, you capitalize ‘Sun’ at some places, and not others.
Our reply: They were changed to Sun. I am sorry for that mistake.
Remove combining - combination– ‘In this line ‘
Our reply: Combining was changed to combination.
Magnetism – magnetic field
Our reply: It was edited.
Please add full forms of acronyms at the first instance they appear. – SWPC,
Our reply: Yes, you are right. It was an abbreviation for Space Weather Prediction Center, so it was added.
Line 99 – repeated full form of STEREO
Our reply: It was deleted.
Line 105 – In according -> According to ..
Our reply: It was changed.
Line 109 – near one day -> within one day
Our reply: I must thank you for your attention, it was changed.
Line 117 – Why is Coronal Mass Ejections spelled ot here, when it has already been abbreviated in the beginning of the article?
Our reply: Yes, you are right. I apologize for that mistake. It was edited.
Time-dependent – time-dependence
Our reply: I am sorry. It was edited.
Line 239 – ‘ We determine that 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?
Our reply: Yes, we obtained this time by following the CME1 and their time by our simulation and found approximately how long it takes to pass 1 AU (as mentioned in Figures 7 and 8, circles depict heliocentric radii at r=0.5, 1, 1.5, and 2AU).
It would be useful to indicate the CME 1 and 2 in the Figures 7 and 8 , so that readers can identify their evolution.
Our reply: Yes, you are right. Thank you for your attention. It was applied.
Line 150 - Add a reference here.
Our reply: We agree. It was added.
Add a reference for Line 59.
Our reply: We agree. It was added.
In Figure 7, it would be useful if the CME 1 and CME 2 are highlighted.
Our reply: Yes, thanks. It was applied.
//////////////////////////////////////////////////////////////////////
Line 213 – ‘Only methods related to space weather …’. What methods?
Our reply: I am sorry for that mistake. It was completed.
//////////////////////////////////////////////////////////////////////
When an equation is listed, please describe all the variables associated with the equation.
Our reply: We agree. It was applied.
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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 -
AC2: 'Reply on RC2', Somaiyeh Sabri, 04 Jan 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1921/egusphere-2024-1921-AC2-supplement.zip
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AC3: 'Reply on RC2', Somaiyeh Sabri, 06 Jan 2025
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)”.
Our reply: Thank you for your consideration, all of the efferences were edited as your suggestion.
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.
Our reply: Kp index index has value between 0 till 9 and the value larger than 5 means the storm which kp=5 determines minor storm, kp=6 moderate, Kp=7 strong, Kp=8 severe and Kp=9 extreme storm. In this work the highest value of the Kp is between 8 and 9 that means we have extreme storm.
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.
Our reply: Thanks for your consideration, it was edited.
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.
Our reply: Thanks for your attention. It was edited.
Line 53 – “which is anchored in two opposite polarities of the sun’s magnetism on its surface [...]” – magnetism -> magnetic field.
Our reply: It was edited.
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.
Our reply: The empirical model employed in EUHFORIA follows the path laid out by the Wang–Sheeley model (Wang & Sheeley 1990; Arge 2003) and the DCHB model (Riley et al., 2001). Namely, the solar wind speed is given as a function of the flux tube expansion factor f and the distance of the foot-point of the flux tube to the nearest coronal hole boundary d. The wind speed is thus determined completely by the properties of the global 3D coronal magnetic field, see Pomoell and Poedts (2018).
Line 143 – “[...] by using a method called Potential Field Source Surface (PESS) extrapolation [...]” – the correct acronym is PFSS. Please change.
Our reply: I have to apologize for that typo mistake. It was edited.
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…[...]”.
Our reply: Thank you for your attention, it was changed.
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.
Our reply: Newell not only investigate the values of Kp but considers ten different magnetospheric state variables, among which both the Kp and Dst indices. It investigates 32 coupling functions, of which twenty are viscously related, and twelve are merging related solar wind-magnetosphere coupling functions. The term coupling function is used because these functions couple the Kp index to the interplanetary conditions.
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.
Our reply: Thank you for your attention, it was deleted.
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.
Our reply: Thank you for your suggestion, it was applied.
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?
Our reply: I added Table 1 with the CMEs information in the manuscript. All that 8 CMEs have inserted in our simulation. Because we had CMEs on 18 and 19 June that happened before the CME1 (which occurred on 21 June), but we did not have significant CMEs on 23 and 24 June before our second selected CME2, we considered that for CME1, we had the CME interaction, but this did not happen for the CME2. Then, we investigated the CME interaction effect for CME1 that affects its impact on Earth. Through the EUHFORIA simulation it was observed that there are no CME interactions for CME2.
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.
Our reply: The observed data that were used for defining arrival time and predicted Kp are completely different. In the case of the observational arrival time it must be noted that speeds projected in the CDAW catalogue (https://cdaw.gsfc.nasa.gov/CME-list/) were used. But the observed Kp index is calculated from the K values or the geomagnetic recordings of 13 geomagnetic observatories.
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).
Our reply: In discussion part we were explained computational arrival time by EUHFORIA and observational arrival time based on the speeds projected in the CDAW catalogue (https://cdaw.gsfc.nasa.gov/CME-list/). The second estimate is a rough approximation that does not consider the impact of drag or the interaction between CMEs as they travel towards Earth. These factors could explain the discrepancies observed. We determine that CME1 will reach the Earth in approximately 46 hours. Based on the speeds projected in the CDAW catalogue (https://cdaw.gsfc.nasa.gov/CME-list/) CME1 has a linear fit speed of 1366.1 km/s, meaning it will take around 30.49 hours to reach the Earth. In the CME2 situation, this distinction becomes notable. The estimated arrival time of CME2 using EUHFORIA results is approximately 70 hours, whereas using the linear fit speed of 1626.7 km/s, the estimated arrival time is around 26 hours. It can be inferred that how CMEs are launched is not particularly significant. Still, their interaction and movement in the heliosphere are the main factors determining their arrival time at Earth.
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AC2: 'Reply on RC2', Somaiyeh Sabri, 04 Jan 2025
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