the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Oct 2022
Ionosonde and GPS Total Electron Content Observations during the 26 December 2019 Annular Solar Eclipse over Indonesia
Abstract. We report our investigation of ionospheric effects due to the passage of an annular solar eclipse over Southeast Asia on 26 December 2019, using multiple set of observations. Two ionosondes (one at Kototabang and another at Pontianak) were used to measure dynamical changes in the ionospheric layer during the event. A network of ground-based GPS receiver stations in Indonesia were used to derive the distribution of total electron content (TEC) over the region. In addition, extreme ultraviolet (EUV) images of the Sun from the Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamics Observatory (SDO) satellite were also analyzed to determine possible impacts of solar active regions on the changes that occurred in the ionosphere during the eclipse. We found −1.67 MHz and −1.58 MHz reduction (23.2 % and 22.4 % relative reduction) in foF2 during the solar eclipse over Kototabang and Pontianak, respectively. The respective TEC reduction over Kototabang and Pontianak during the eclipse was −4.34 TECU and −5.45 TECU (24.9 % and 27.9 % relative reduction). Overall, there was 34–36 minutes delay from maximum eclipse until minimum foF2 was reached at these two locations. The corresponding time delays for eclipse-related TEC reduction at these two locations were 40 minutes and 16 minutes, respectively. The ionospheric F-layer was found to descend with a speed of 9–19 m/s during the first half of the eclipse period. We also found an apparent rise of the ionospheric F-layer height near the end of the solar eclipse period, equivalent to vertical drift velocity of 44–47 m/s. The GPS TEC data mapping along a set of cross-sectional cut lines indicate that the greatest TEC reduction actually occurred to the north of the solar eclipse path, opposite of the direction from which the lunar shadow fell. As the central path of the solar eclipse was located just to the north of the southern equatorial ionization anomaly (EIA) crest, it is suspected that such a peculiar TEC reduction pattern was caused by plasma flow associated with the equatorial fountain effect. Net perturbations of TEC were also computed and analyzed, which revealed the presence some wavelike fluctuations associated with the solar eclipse event. Some of the observed TEC perturbation patterns that propagated with a velocity matching the lunar shadow may be explained in terms of non-uniform EUV illumination that arose as various active regions on the Sun went obstructed and unobstructed during the eclipse. The remaining wavelike features are likely to be traveling ionospheric disturbances (TIDs) driven by acoustic-gravity waves (AGWs), generated by the passage of the solar eclipse on top of other diurnal factors.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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RC1: 'Comment on egusphere-2022-909', Anonymous Referee #1, 10 Nov 2022
The authors present evidence of the effect of the 26 December 2019 solar eclipse on the ionosphere. They showed this using Total Electron Content (TEC) data from Global Navigation Satellite System (GNSS) receivers over the Indonesian region. Also, ionosonde data from Canadian Advanced Digital Ionosonde (CADI) in two locations were used to complement the TEC observation. Using the Solar Dynamics Observatory (SDO), they tracked the umbra of the eclipse spatiotemporally. Their investigation methods are clear. The authors gave much emphasis to the effect of the eclipse on the ionosphere particularly the reduction in the TEC and Ionosonde observations as well as the time delay. This current work contributes to literature by showing how this type of eclipse affects the ionosphere in the Indonesian region. However, the structure of the paper needs to be improved, especially the methodology and the results. Also, there are quite a number of repetitions of some sentences (please kindly rephrase). I, therefore, recommend the work be published after the implementation of the comments and corrections.
Major comments:
Introduction:
Kindly mention clearly what is the new findings of this work.
Figures:
The resolution of some of the labels of some Figures needs to increase, they appear blurred.
Methodology and Results:
Please improve the methodology. I suggest you give more details on how the TEC was estimated with some equations and references. Similarly, the methodology of the keogram should be elaborated in detail. I would like to encourage the authors not to assume, the readers are already familiar with the techniques.
Specific comments:
Figure 2, if it is possible I will suggest the authors improve the resolution.
For the Figures with subpanels, please label them for easy identification. E.g., Figure 14(a(i)).
Minor comments and technical correctionsAbstract:
#1. Line 10: Kindly rewrite this sentence for clarity.
#2. Line 18: Put "of" before “some”.
Introduction:
#1. Line 36: Change “solar local time” to “local solar time”.
#2. Lines 45-48: Please kindly rewrite “For many decades ... ; ...Hairston et al., 2018)
Instrumentation and Methodology:
#1. Line 73: Please remove “Relatively”.
#2. Lines 92 - 93: Change (x.xx°S yyy.yy°E) and anywhere in the text to (x.xx°S, yyy.yy°E).
#3. Line 128: Kindly rephrase the sentence “Further in the analysis, TEC data detrending was also performed”.
#4. Lines 128 - 130: Change “Two types of data detrending were performed: one to derive âTEC (general deviations from the normal condition) and another to derive TECP (wavelike perturbations with much smaller 130 amplitudes and finer structures)” to “Two types of data detrending were performed: (1) to derive âTEC (general deviations from the normal condition) and (2) to derive TECP (wavelike perturbations with much smaller 130 amplitudes and finer structures)”.
#5. Lines 133 - 134: Kindly rephrase the sentence “Only after completing the detrending process on the IPPs did we spatially map the TECP values onto fixed grid point(s) for data display.”
Observation Results:
Ionosonde Observations
#1. Lines 144 - 145: Rewrite as ……….: one in the southeast of the solar disk and the other in the northwest of the solar disk.
#2. Lines 188 - 190: Please rephrase as: The recovery phase occurred over a duration of 155 minutes, starting at 06:20 UTC (13:20 LT) until 08:55 UTC (15:55 LT) with an increase in foF2 by 1.23 MHz (from 5.44 MHz to 6.67 MHz).
#3. Lines 195 - 196: change “……. while that over Pontianak was 83 minutes” to “……. whereas that over Pontianak was 83 minutes”.
#4. Line 235: …… climb …… to ……. ascent…. .
#5. Line 242: …… climb …… to ……. ascent…. .
GPS TEC Observations
#1. I will suggest the authors “change keogram” plot to “keogram”.
#2. Line 293: Kindly change “…… since at this time of day, …….. maximum level.” to “…… since at this time of the day, …….. maximum level.”
#3. Line 303 - 304: Please rephrase this sentence - “Not until nearing the maximum eclipse did âTEC started to drop, which eventually reached approximately -6 TECU at its lowest”.
#4. Line 342 -343: Change to: “The further away the striped patterns were from the alignment with the C1/max/C4 epoch lines, the more likely they are to be associated with AGW/TID.”
Solar EUV Illumination Variability
#1. Line 370: Please change “Further,……” to “Furthermore, …”
Discussion
#1. Line 404: I suggest you change “…… 97 minutes and 83 minutes.” to “…… 97 and 83 minutes.”
#2. Line 408-409: Please insert “e.g.,” in the citation as (e.g., Farges et al., 2001; Adeniyi et al., 2007; Goncharenko et al., 2018), …. .
#3. Line 417: Same as comment #1, line 404.
#4. Line 438 - 440: This overshoot might have been caused by an inward shift of the EIA crest position during the post-eclipse period, after an outward shift that happened earlier during the eclipse (Aa et al., 2020). Please have done any analysis to prove this point in this study?
#5. Line 469: Please put a colon after “includes” as … includes: (1) ….
Citation: https://doi.org/10.5194/egusphere-2022-909-RC1 -
AC1: 'Reply on RC1', Rezy Pradipta, 09 Dec 2022
We thank the referee for many useful comments (including suggestions and questions) on the material presented in the manuscript. Below are our item-by-item responses to the referee's comments.
As suggested by the referee, we are going to emphasize the mention of new findings from this investigation in the Introduction section of the revised manuscript.
In the revision, we are going to enhance the resolution of figure labels that appear blurred in the preprint.
As part of the revision, we are going to include some additional details regarding the TEC calculation, including fundamental equations and related references. Similarly, we are also going to include a more detailed description on the methodology surrounding the keograms.
More specifically regarding Figures 2, we are going to enhance the resolution of the figure labels which presently appear blurred. For Figures 12-15 which contain multiple subpanels (in rows and columns), we are going to add additional labeling with roman numerals (i-iv) in addition to the letters (a, b, c) for ease of identification.
Based on the suggested technical corrections by the referee, we are making the following changes to the manuscript.
The sentence in Line 10 will be modified in order to improve clarity.
In Line 18, we will change “some” into “of some”
In Line 36, we will change “solar local time” into “local solar time”
The sentence in Lines 45-48 will be modified in order to make it simpler and easier to understand by the readers.
We will remove the word “relatively” in Line 73 of the manuscript.
We will modify the format of geographic coordinates used throughout the manuscript.
We will restructure the sentence in Line 128 to make it clearer and more coherent.
In Lines 128-130 of the manuscript, we are modifying the sentence based on the suggestion given by the referee.
We will restructure the sentence in Lines 133-134 in order to improve its clarity.
We will rewrite the sentence in Lines 144-145 following the given suggestion.
We will rephrase the sentence in Lines 188-190 based on the suggested sentence structure.
We will modify the sentence in Lines 195-196 following the suggested wording.
In Lines 235 and 242, we will modify the vocabulary/wording of “climb” into “ascent”
We will change the phrase “keogram plot” into “keogram”
We will rephrase the sentence in Line 293 following the given suggestion.
We will rephrase the sentence in Lines 303-304 in order to make it simpler and easier to understand by the readers.
We will modify the sentence in Lines 342-343 following the given suggestion.
We will rephrase Line 370 following the suggestion.
We will modify Lines 404 and 417 following the suggestion in order to make them more compact.
In Lines 408-409, we will add “e.g.” based on the suggestion.
Regarding the overshoot phenomenon during recovery (Lines 438-440), a more detailed description and chain of logic are as follows. In a past research work reported by Aa et al. (2020) <https://doi.org/10.1029/2020JA028296> on the same solar eclipse event, there was an outward shift of the EIA crest during the eclipse based on TEC and satellite measurement data. This outward shift was explained in terms of enhanced eastward polarization electric field during the eclipse which strengthened the equatorial fountain, making the fountain flow landed over the greater |MLAT| locations. In the analysis of our processed TEC data, we confirmed that the maximum TEC in the EIA zone during the eclipse was located farther away from the geomagnetic equator line, compared to pre-eclipse. Further, we also found that several hours after the eclipse had ended, the EIA crest configuration was back to normal, just like EIA configuration on regular days. This is consistent with the fountain returning to normal strength as the enhanced polarization electric field diminished. Thus, we conclude that the calming of the fountain effect must have acted as a restoring process to reverse the outward shift of the EIA crest from earlier stage, which would mean an inward shift of the EIA crest as part of the recovery toward the end of the eclipse. In the manuscript revision, we are expanding the discussion with this additional set of information in order to fill the gap in the overall chain of logic and analysis.
We will modify Line 469 in the manuscript following the suggestion.
Citation: https://doi.org/10.5194/egusphere-2022-909-AC1
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AC1: 'Reply on RC1', Rezy Pradipta, 09 Dec 2022
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RC2: 'Comment on egusphere-2022-909', Anonymous Referee #2, 11 Nov 2022
Review report of “Ionosonde and GPS Total Electron Content Observations during the 26 December 2019 Annular Solar Eclipse over Indonesia” by Harjosuwito et al.
The main goal of this paper is to present the ionospheric effects of the annular solar eclipse on 26 December 2019 using ionosonde and GNSS receivers and models. The analysis is sound and their results are important to the scientific community. However, the manuscript needs minor improvements.
Line 121: I suggest including information about elevation angles used in TEC calculation.
Line 192: Correct the word "ecipse" to eclipse.
Figures 5-7: It is clear that IRI does not represent the ionospheric characteristics of Indonesia. I suggest using the ionospheric average from the ionosonde instead of the IRI model.
line 340: What are the acoustic gravity wave characteristics observed during the eclipse? The problem is the authors did not comment on the origin and generation of TIDs during the eclipse. Therefore, It is out of scope and I suggest removing AGW from the text.
Line 349: Why is the laplacian the better approach to capture the inhomogeneity? the authors have to give to read more details about the technic and explain the vantages and disadvantages of this technic to study these differences in data.
Line 407: I suggest discussing the present results with results observed over the South American sector. See resende et al. (2021) ttps://doi.org/10.5194/angeo-2021-61
Line 482: Which is the physical mechanism that may explain these phenomena?
Citation: https://doi.org/10.5194/egusphere-2022-909-RC2 -
AC2: 'Reply on RC2', Rezy Pradipta, 09 Dec 2022
We thank the referee for providing many useful suggestions and questions. Below are our item-by-item responses to the referee’s comments.
In the TEC calculation, the cutoff for the elevation angle was 20 degrees. In the revised manuscript, we are adding this additional information.
The typographical error in Line 192 will be fixed (i.e. “eclipse”) in the revised manuscript.
Regarding the baseline curves in Figures 5-7, we are going to follow the suggestions given by the referee. In the revised manuscript, we will be using the average values from ionosonde observations to form the baseline curves. The performance of IRI model over the Southeast Asian region, more specifically over the Indonesian region, turned out to be less than optimal. More detailed quantification on the IRI model performance over this geographic region may also be investigated further in future research.
Following the suggestion, here (in Line 340) we will skip mentioning the AGW due to limited information on wave parameters.
The main advantage of the Laplacian operator for capturing inhomogeneity in the form of sharp discontinuity in 2-D data is its low computational cost. In addition, the Laplacian operator has the same properties in each direction (i.e. isotropic), which simplifies the interpretation of results. Unfortunately, the edge direction is unavailable, which is its disadvantage. Nevertheless, edge direction is not very important in our situation, and our analysis was not impacted. In the revised manuscript, we are going to include more detailed explanation and foundational references regarding the use of Laplacian technique.
In the revised manuscript, we will be including some additional discussion of the present results in relation to results that had been obtained over the South American sector.
Regarding the “shallow TEC valley” (Line 482 of the manuscript), at this stage we do not know the precise physical mechanism that may have caused the phenomena for certain. What we have done was to eliminate as much as possible various scenarios involving instrumental artefact and geographical distribution of ground-based observing stations, which could conceivably lead to such a “shallow TEC valley”. One scenario under consideration was a systematic/correlated shift in the TEC bias for a group of nearby receiver stations. However, each receiver device is operating independently (even when their spatial distances are quite close), which makes it unlikely for their hardware biases to be linked electronically. Another scenario under consideration was slant factors that may be quite extreme (due to low elevation angles) for IPPs that are located over ocean region unpopulated by receiver stations. However, it turned out that this latter scenario predicts that the “shallow TEC valley” would instead have happened over the ocean region (opposite to the observed fact that the “shallow TEC valley” actually occurred over land mass region populated with receiver stations). Hence, we can rule out this possibility as well. Therefore, the exact physical mechanism for the occurrence of this “shallow TEC valley” is still an open scientific question for the community. Nevertheless, some possible instrumental effects have been ruled out in our considerations.
Citation: https://doi.org/10.5194/egusphere-2022-909-AC2
-
AC2: 'Reply on RC2', Rezy Pradipta, 09 Dec 2022
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-909', Anonymous Referee #1, 10 Nov 2022
The authors present evidence of the effect of the 26 December 2019 solar eclipse on the ionosphere. They showed this using Total Electron Content (TEC) data from Global Navigation Satellite System (GNSS) receivers over the Indonesian region. Also, ionosonde data from Canadian Advanced Digital Ionosonde (CADI) in two locations were used to complement the TEC observation. Using the Solar Dynamics Observatory (SDO), they tracked the umbra of the eclipse spatiotemporally. Their investigation methods are clear. The authors gave much emphasis to the effect of the eclipse on the ionosphere particularly the reduction in the TEC and Ionosonde observations as well as the time delay. This current work contributes to literature by showing how this type of eclipse affects the ionosphere in the Indonesian region. However, the structure of the paper needs to be improved, especially the methodology and the results. Also, there are quite a number of repetitions of some sentences (please kindly rephrase). I, therefore, recommend the work be published after the implementation of the comments and corrections.
Major comments:
Introduction:
Kindly mention clearly what is the new findings of this work.
Figures:
The resolution of some of the labels of some Figures needs to increase, they appear blurred.
Methodology and Results:
Please improve the methodology. I suggest you give more details on how the TEC was estimated with some equations and references. Similarly, the methodology of the keogram should be elaborated in detail. I would like to encourage the authors not to assume, the readers are already familiar with the techniques.
Specific comments:
Figure 2, if it is possible I will suggest the authors improve the resolution.
For the Figures with subpanels, please label them for easy identification. E.g., Figure 14(a(i)).
Minor comments and technical correctionsAbstract:
#1. Line 10: Kindly rewrite this sentence for clarity.
#2. Line 18: Put "of" before “some”.
Introduction:
#1. Line 36: Change “solar local time” to “local solar time”.
#2. Lines 45-48: Please kindly rewrite “For many decades ... ; ...Hairston et al., 2018)
Instrumentation and Methodology:
#1. Line 73: Please remove “Relatively”.
#2. Lines 92 - 93: Change (x.xx°S yyy.yy°E) and anywhere in the text to (x.xx°S, yyy.yy°E).
#3. Line 128: Kindly rephrase the sentence “Further in the analysis, TEC data detrending was also performed”.
#4. Lines 128 - 130: Change “Two types of data detrending were performed: one to derive âTEC (general deviations from the normal condition) and another to derive TECP (wavelike perturbations with much smaller 130 amplitudes and finer structures)” to “Two types of data detrending were performed: (1) to derive âTEC (general deviations from the normal condition) and (2) to derive TECP (wavelike perturbations with much smaller 130 amplitudes and finer structures)”.
#5. Lines 133 - 134: Kindly rephrase the sentence “Only after completing the detrending process on the IPPs did we spatially map the TECP values onto fixed grid point(s) for data display.”
Observation Results:
Ionosonde Observations
#1. Lines 144 - 145: Rewrite as ……….: one in the southeast of the solar disk and the other in the northwest of the solar disk.
#2. Lines 188 - 190: Please rephrase as: The recovery phase occurred over a duration of 155 minutes, starting at 06:20 UTC (13:20 LT) until 08:55 UTC (15:55 LT) with an increase in foF2 by 1.23 MHz (from 5.44 MHz to 6.67 MHz).
#3. Lines 195 - 196: change “……. while that over Pontianak was 83 minutes” to “……. whereas that over Pontianak was 83 minutes”.
#4. Line 235: …… climb …… to ……. ascent…. .
#5. Line 242: …… climb …… to ……. ascent…. .
GPS TEC Observations
#1. I will suggest the authors “change keogram” plot to “keogram”.
#2. Line 293: Kindly change “…… since at this time of day, …….. maximum level.” to “…… since at this time of the day, …….. maximum level.”
#3. Line 303 - 304: Please rephrase this sentence - “Not until nearing the maximum eclipse did âTEC started to drop, which eventually reached approximately -6 TECU at its lowest”.
#4. Line 342 -343: Change to: “The further away the striped patterns were from the alignment with the C1/max/C4 epoch lines, the more likely they are to be associated with AGW/TID.”
Solar EUV Illumination Variability
#1. Line 370: Please change “Further,……” to “Furthermore, …”
Discussion
#1. Line 404: I suggest you change “…… 97 minutes and 83 minutes.” to “…… 97 and 83 minutes.”
#2. Line 408-409: Please insert “e.g.,” in the citation as (e.g., Farges et al., 2001; Adeniyi et al., 2007; Goncharenko et al., 2018), …. .
#3. Line 417: Same as comment #1, line 404.
#4. Line 438 - 440: This overshoot might have been caused by an inward shift of the EIA crest position during the post-eclipse period, after an outward shift that happened earlier during the eclipse (Aa et al., 2020). Please have done any analysis to prove this point in this study?
#5. Line 469: Please put a colon after “includes” as … includes: (1) ….
Citation: https://doi.org/10.5194/egusphere-2022-909-RC1 -
AC1: 'Reply on RC1', Rezy Pradipta, 09 Dec 2022
We thank the referee for many useful comments (including suggestions and questions) on the material presented in the manuscript. Below are our item-by-item responses to the referee's comments.
As suggested by the referee, we are going to emphasize the mention of new findings from this investigation in the Introduction section of the revised manuscript.
In the revision, we are going to enhance the resolution of figure labels that appear blurred in the preprint.
As part of the revision, we are going to include some additional details regarding the TEC calculation, including fundamental equations and related references. Similarly, we are also going to include a more detailed description on the methodology surrounding the keograms.
More specifically regarding Figures 2, we are going to enhance the resolution of the figure labels which presently appear blurred. For Figures 12-15 which contain multiple subpanels (in rows and columns), we are going to add additional labeling with roman numerals (i-iv) in addition to the letters (a, b, c) for ease of identification.
Based on the suggested technical corrections by the referee, we are making the following changes to the manuscript.
The sentence in Line 10 will be modified in order to improve clarity.
In Line 18, we will change “some” into “of some”
In Line 36, we will change “solar local time” into “local solar time”
The sentence in Lines 45-48 will be modified in order to make it simpler and easier to understand by the readers.
We will remove the word “relatively” in Line 73 of the manuscript.
We will modify the format of geographic coordinates used throughout the manuscript.
We will restructure the sentence in Line 128 to make it clearer and more coherent.
In Lines 128-130 of the manuscript, we are modifying the sentence based on the suggestion given by the referee.
We will restructure the sentence in Lines 133-134 in order to improve its clarity.
We will rewrite the sentence in Lines 144-145 following the given suggestion.
We will rephrase the sentence in Lines 188-190 based on the suggested sentence structure.
We will modify the sentence in Lines 195-196 following the suggested wording.
In Lines 235 and 242, we will modify the vocabulary/wording of “climb” into “ascent”
We will change the phrase “keogram plot” into “keogram”
We will rephrase the sentence in Line 293 following the given suggestion.
We will rephrase the sentence in Lines 303-304 in order to make it simpler and easier to understand by the readers.
We will modify the sentence in Lines 342-343 following the given suggestion.
We will rephrase Line 370 following the suggestion.
We will modify Lines 404 and 417 following the suggestion in order to make them more compact.
In Lines 408-409, we will add “e.g.” based on the suggestion.
Regarding the overshoot phenomenon during recovery (Lines 438-440), a more detailed description and chain of logic are as follows. In a past research work reported by Aa et al. (2020) <https://doi.org/10.1029/2020JA028296> on the same solar eclipse event, there was an outward shift of the EIA crest during the eclipse based on TEC and satellite measurement data. This outward shift was explained in terms of enhanced eastward polarization electric field during the eclipse which strengthened the equatorial fountain, making the fountain flow landed over the greater |MLAT| locations. In the analysis of our processed TEC data, we confirmed that the maximum TEC in the EIA zone during the eclipse was located farther away from the geomagnetic equator line, compared to pre-eclipse. Further, we also found that several hours after the eclipse had ended, the EIA crest configuration was back to normal, just like EIA configuration on regular days. This is consistent with the fountain returning to normal strength as the enhanced polarization electric field diminished. Thus, we conclude that the calming of the fountain effect must have acted as a restoring process to reverse the outward shift of the EIA crest from earlier stage, which would mean an inward shift of the EIA crest as part of the recovery toward the end of the eclipse. In the manuscript revision, we are expanding the discussion with this additional set of information in order to fill the gap in the overall chain of logic and analysis.
We will modify Line 469 in the manuscript following the suggestion.
Citation: https://doi.org/10.5194/egusphere-2022-909-AC1
-
AC1: 'Reply on RC1', Rezy Pradipta, 09 Dec 2022
-
RC2: 'Comment on egusphere-2022-909', Anonymous Referee #2, 11 Nov 2022
Review report of “Ionosonde and GPS Total Electron Content Observations during the 26 December 2019 Annular Solar Eclipse over Indonesia” by Harjosuwito et al.
The main goal of this paper is to present the ionospheric effects of the annular solar eclipse on 26 December 2019 using ionosonde and GNSS receivers and models. The analysis is sound and their results are important to the scientific community. However, the manuscript needs minor improvements.
Line 121: I suggest including information about elevation angles used in TEC calculation.
Line 192: Correct the word "ecipse" to eclipse.
Figures 5-7: It is clear that IRI does not represent the ionospheric characteristics of Indonesia. I suggest using the ionospheric average from the ionosonde instead of the IRI model.
line 340: What are the acoustic gravity wave characteristics observed during the eclipse? The problem is the authors did not comment on the origin and generation of TIDs during the eclipse. Therefore, It is out of scope and I suggest removing AGW from the text.
Line 349: Why is the laplacian the better approach to capture the inhomogeneity? the authors have to give to read more details about the technic and explain the vantages and disadvantages of this technic to study these differences in data.
Line 407: I suggest discussing the present results with results observed over the South American sector. See resende et al. (2021) ttps://doi.org/10.5194/angeo-2021-61
Line 482: Which is the physical mechanism that may explain these phenomena?
Citation: https://doi.org/10.5194/egusphere-2022-909-RC2 -
AC2: 'Reply on RC2', Rezy Pradipta, 09 Dec 2022
We thank the referee for providing many useful suggestions and questions. Below are our item-by-item responses to the referee’s comments.
In the TEC calculation, the cutoff for the elevation angle was 20 degrees. In the revised manuscript, we are adding this additional information.
The typographical error in Line 192 will be fixed (i.e. “eclipse”) in the revised manuscript.
Regarding the baseline curves in Figures 5-7, we are going to follow the suggestions given by the referee. In the revised manuscript, we will be using the average values from ionosonde observations to form the baseline curves. The performance of IRI model over the Southeast Asian region, more specifically over the Indonesian region, turned out to be less than optimal. More detailed quantification on the IRI model performance over this geographic region may also be investigated further in future research.
Following the suggestion, here (in Line 340) we will skip mentioning the AGW due to limited information on wave parameters.
The main advantage of the Laplacian operator for capturing inhomogeneity in the form of sharp discontinuity in 2-D data is its low computational cost. In addition, the Laplacian operator has the same properties in each direction (i.e. isotropic), which simplifies the interpretation of results. Unfortunately, the edge direction is unavailable, which is its disadvantage. Nevertheless, edge direction is not very important in our situation, and our analysis was not impacted. In the revised manuscript, we are going to include more detailed explanation and foundational references regarding the use of Laplacian technique.
In the revised manuscript, we will be including some additional discussion of the present results in relation to results that had been obtained over the South American sector.
Regarding the “shallow TEC valley” (Line 482 of the manuscript), at this stage we do not know the precise physical mechanism that may have caused the phenomena for certain. What we have done was to eliminate as much as possible various scenarios involving instrumental artefact and geographical distribution of ground-based observing stations, which could conceivably lead to such a “shallow TEC valley”. One scenario under consideration was a systematic/correlated shift in the TEC bias for a group of nearby receiver stations. However, each receiver device is operating independently (even when their spatial distances are quite close), which makes it unlikely for their hardware biases to be linked electronically. Another scenario under consideration was slant factors that may be quite extreme (due to low elevation angles) for IPPs that are located over ocean region unpopulated by receiver stations. However, it turned out that this latter scenario predicts that the “shallow TEC valley” would instead have happened over the ocean region (opposite to the observed fact that the “shallow TEC valley” actually occurred over land mass region populated with receiver stations). Hence, we can rule out this possibility as well. Therefore, the exact physical mechanism for the occurrence of this “shallow TEC valley” is still an open scientific question for the community. Nevertheless, some possible instrumental effects have been ruled out in our considerations.
Citation: https://doi.org/10.5194/egusphere-2022-909-AC2
-
AC2: 'Reply on RC2', Rezy Pradipta, 09 Dec 2022
Peer review completion
Journal article(s) based on this preprint
Data sets
Scaled Ionogram Parameters and Processed GPS TEC Data Jiyo Harjosuwito https://doi.org/10.7910/DVN/ZUXCCK
Video supplement
Masked Solar Images and 2-D Regional GPS TEC Maps Jiyo Harjowusito https://doi.org/10.7910/DVN/ZUXCCK
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(5268 KB) - Metadata XML
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Supplement
(700 KB) - BibTeX
- EndNote
- Final revised paper