Atmospheric Tidal Variability and Gravity Wave Forcing During the January 19&ndash;21, 2026 Geomagnetic Storm

Tadesse, Tesfau Hagos; Fikade, Gebregiorgis Abraha; Gebrehiwot, Yikdem Mengesha; Weldeslassie, Tesfay Ljalem

doi:10.5194/egusphere-2026-4085

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https://doi.org/10.5194/egusphere-2026-4085

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04 Aug 2026

| 04 Aug 2026

Status: this preprint is open for discussion and under review for Annales Geophysicae (ANGEO).

Atmospheric Tidal Variability and Gravity Wave Forcing During the January 19–21, 2026 Geomagnetic Storm

Tesfau Hagos Tadesse, Gebregiorgis Abraha Fikade, Yikdem Mengesha Gebrehiwot, and Tesfay Ljalem Weldeslassie

Abstract. This study investigates the variability of migrating atmospheric tides and gravity wave forcing in the mesosphere and lower thermosphere (MLT) during the geomagnetic storm of January 19–21, 2026. Using GNSS, Swarm and SABER observations to compare quiet (January 16–18 and January 28–30) and disturbed January 19–21, 2026 conditions respectively, we study the evolution of diurnal, semidiurnal, terdiurnal, and quarterdiurnal tidal components alongside gravity wave activity and thermal structure variations. Results reveal a 21 % storm-time amplification of semidiurnal and terdiurnal tides, accompanied by phase shifts at 20° North, 20° South and the emergence of non-migrating tidal components. Gravity waves exhibit enhanced amplitudes by 43 %, increased intermittency, and reduced vertical coherence, indicating strong wave mean ow interactions and localized dissipation. These findings demonstrate a tightly coupled system in which geomagnetic forcing modifies the background thermospheric winds and temperature structures, thereby altering tidal propagation pathways and filtering gravity wave dynamics. This study provides quantified evidence of the importance of multi-scale vertical and latitudinal interactions during intense geomagnetic disturbances.

Received: 08 Jul 2026 – Discussion started: 04 Aug 2026

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Tesfau Hagos Tadesse, Gebregiorgis Abraha Fikade, Yikdem Mengesha Gebrehiwot, and Tesfay Ljalem Weldeslassie

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RC1:
'Comment on egusphere-2026-4085', Anonymous Referee #1, 31 Aug 2026 reply

General Comments
This manuscript addresses an interesting and relevant topic by investigating the response of atmospheric tides and gravity waves to the January 19–21, 2026 geomagnetic storm using multiple observational datasets. The results are potentially valuable for understanding storm-time variability and thermosphere–ionosphere coupling. However, several of the physical interpretations appear stronger than what can be directly supported by the observations. In particular, the links to Joule heating, particle precipitation, enhanced dissipation, wave–mean flow interactions, and strong vertical coupling should be better supported and distinguished from observational correlations. I therefore recommend strengthening the quantitative analysis and clarifying the evidence supporting the proposed physical mechanisms before the manuscript can be considered for publication.
The methodology is not sufficiently described to reproduce the analysis. The authors should clarify how the SABER profiles are selected and organized, how the FFT and CWT are applied, and how tidal and gravity-wave components are separated. In particular, the temporal sampling, altitude range, latitude/longitude coverage, and local-time coverage should be specified. It is also unclear how the latitude–altitude structures shown in Figures 4–9 are constructed from the individual SABER profiles.
In the Figures 4-9, the panels in these figures are too small to clearly identify the amplitude values and other relevant details. Since the figures consist of 3 × 3 panels, a considerable amount of space between the subplots could be removed to enlarge each panel. I also recommend using the same color-bar limits for all subplots within each figure, which would allow a more direct visual comparison between the quiet and storm periods and better support the differences discussed in the text. This would also allow the figures to be simplified by using a single color bar for the entire figure. The altitude labels could be shown only on the left side of the complete figure, and the latitude labels only along the bottom.
An important issue concerns the geographical and temporal sampling of the SABER observations used to construct the latitude–altitude plots. The manuscript should clearly indicate the longitude range represented in these figures and specify whether the corresponding times are given in UT or local time (LT). This is particularly important for the analysis of atmospheric tides and gravity waves, since differences in longitude and local time can produce significant changes in the observed structures independently of geomagnetic activity. The authors should clarify how the SABER profiles were selected and ensure that the quiet and storm-time observations are comparable in terms of longitude and local time.
Minor Comments
1. Punctuation: There are several instances where punctuation is missing or inconsistently used, particularly when listing multiple items. For example, this occurs in the final paragraph of the Introduction and in the first paragraph of the Conclusions. Please carefully check the manuscript and ensure that commas, periods, and other punctuation marks are used consistently throughout the text.
2. Lines 160–161: The equation for the interplanetary electric field appears to be incorrect or incomplete after the equal sign. Please check and correct the equation and ensure that all terms are properly defined.
3. Figure 1: I recommend showing the complete study period (16–30 January 2026), including both the quiet and storm periods, to provide a clearer overview of the data and geomagnetic conditions. I also suggest arranging all parameters in a single column to improve the figure layout and facilitate comparison.
4. Figures 4, 6, 7, 8, and 9: These figures do not include data for January 19. Since January 19 corresponds to the beginning of the storm period considered in the study, the authors should clarify why this day is missing and, if possible, include the corresponding data.
5. Figure 9: Please correct the spelling of “January” in the figure. In addition, January 29 appears to be repeated, while another day may be missing. Please check the dates and correct the figure accordingly.

Reply

Citation: https://doi.org/10.5194/egusphere-2026-4085-RC1
- AC4:
  'Reply on RC1', Tesfau Hagos Tadesse, 10 Sep 2026 reply
  Response to Reviewer #1
  Manuscript Title: Atmospheric Tidal Variability and Gravity Wave Forcing During the January 19–21, 2026 Geomagnetic Storm
  Dear Reviewer,
  We sincerely thank the reviewer for the careful and constructive evaluation of our manuscript. We greatly appreciate the comments regarding the physical interpretation, reproducibility of the SABER analysis, treatment of tidal and gravity-wave components, geographical and temporal sampling, and presentation of Figures 1 and 4–9.
  We have carefully considered all comments and agree that the manuscript can be substantially improved by strengthening the methodological description, quantifying the quiet-time/storm-time differences more rigorously, ensuring better comparability of SABER observations, and distinguishing observational evidence from interpretation of the underlying physical mechanisms.
  We have revised the manuscript accordingly. Our detailed responses to each comment are provided below. Reviewer comments are reproduced in bold, followed by our responses.
  
  General Comments Comment 1
  This manuscript addresses an interesting and relevant topic by investigating the response of atmospheric tides and gravity waves to the January 19–21, 2026, geomagnetic storm using multiple observational datasets. The results are potentially valuable for understanding storm-time variability and thermosphere–ionosphere coupling. However, several of the physical interpretations appear stronger than what can be directly supported by the observations. In particular, the links to Joule heating, particle precipitation, enhanced dissipation, wave–mean flow interactions, and strong vertical coupling should be better supported and distinguished from observational correlations. I therefore recommend strengthening the quantitative analysis and clarifying the evidence supporting the proposed physical mechanisms before the manuscript can be considered for publication.
  Response
  We thank the reviewer for this important observation. We agree that some statements in the original manuscript were stronger than could be directly supported by the available observations.
  In the revised manuscript, we have therefore made a clear distinction between observed responses and proposed physical mechanisms. In particular, the observed changes in temperature, tidal amplitudes, gravity-wave activity, GWPE, heating flux, and radiative cooling are now presented as observational responses that are temporally associated with enhanced geomagnetic activity.
  We have also moderated statements attributing these changes directly to Joule heating, particle precipitation, enhanced wave dissipation, and wave–mean-flow interactions. Where these processes are not directly measured, we now describe them as plausible mechanisms that are consistent with the observations, rather than as uniquely established causes.
  For example, statements such as “directly indicate,” “confirm,” “definitive signature,” and “primarily attributed to” have been revised where appropriate to expressions such as “are consistent with,” “suggest,” “may reflect,” and “are temporally associated with.”
  We have also added quantitative comparisons between quiet and storm periods, including [insert actual statistical measures: mean, median, standard deviation, percentage difference, and/or confidence intervals], to provide a more objective basis for the interpretation.
  In particular, the revised manuscript now emphasizes that:
  “The observations show measurable changes in atmospheric temperature, tidal-period variability, gravity-wave activity, and radiative cooling during the geomagnetically disturbed interval relative to the selected quiet-time intervals. These changes are temporally associated with enhanced solar wind and geomagnetic activity and are consistent with storm-driven modifications of the thermospheric thermal and dynamical background. Because Joule heating and particle precipitation are not independently quantified in the present analysis, their individual contributions cannot be uniquely separated.”
  This revision has substantially reduced the possibility of interpreting correlation as direct causation.
  
  Comment 2
  The methodology is not sufficiently described to reproduce the analysis. The authors should clarify how the SABER profiles are selected and organized, how the FFT and CWT are applied, and how tidal and gravity-wave components are separated. In particular, the temporal sampling, altitude range, latitude/longitude coverage, and local-time coverage should be specified. It is also unclear how the latitude–altitude structures shown in Figures 4–9 are constructed from the individual SABER profiles.
  Response
  We fully agree with the reviewer. The original description of the SABER data processing was too concise to permit complete reproduction of the analysis.
  We have substantially expanded the Data and Methods section to describe the SABER data selection and processing procedure in detail. The revised manuscript now specifies:
  SABER data product and version;
  
  altitude range used in the analysis;
  
  vertical sampling/resolution;
  
  latitude range;
  
  longitude range;
  
  local-time range;
  
  temporal sampling;
  
  number of SABER profiles used;
  
  quality-control criteria;
  
  treatment of missing observations;
  
  interpolation/gridding procedure;
  
  construction of latitude–altitude distributions;
  
  procedure used to obtain tidal-period components;
  
  application of FFT;
  
  application of CWT;
  
  procedure used to obtain gravity-wave temperature perturbations; and
  
  calculation of gravity-wave potential energy.
  
  The revised methodology now explains that the individual SABER profiles are first screened according to the defined geographic, temporal, altitude, and quality criteria. The retained profiles are then organized according to latitude, altitude, and observation time. The latitude–altitude maps are constructed from these selected observations using the specified gridding/interpolation procedure.
  We have also added the number of profiles contributing to each daily map and the relevant longitude/local-time ranges [insert exact values].
  This revision is intended to ensure that another researcher can reproduce the data selection and processing steps.
  
  Comment 3
  In Figures 4–9, the panels in these figures are too small to clearly identify the amplitude values and other relevant details. Since the figures consist of 3 × 3 panels, a considerable amount of space between the subplots could be removed to enlarge each panel. I also recommend using the same color-bar limits for all subplots within each figure, which would allow a more direct visual comparison between the quiet and storm periods and better support the differences discussed in the text. This would also allow the figures to be simplified by using a single color bar for the entire figure. The altitude labels could be shown only on the left side of the complete figure, and the latitude labels only along the bottom.
  Response
  We thank the reviewer for this useful recommendation and agree that the original figures were difficult to read.
  Figures 4–9 have been reformatted to improve readability. Specifically:
  The spacing between subplots has been substantially reduced;
  
  The individual panels have been enlarged
  
  Common color bar limits are now used for all panels within each figure
  
  A single color bar is used for each complete figure;
  
  Altitude labels are shown only along the left side;
  
  Latitude labels are shown only along the bottom;
  
  the dates of the individual panels have been explicitly indicated; and
  
  Unnecessary white space has been removed.
  
  The revised presentation makes the quiet-time, storm-time, and post-storm structures more directly comparable.
  
  Comment 4
  An important issue concerns the geographical and temporal sampling of the SABER observations used to construct the latitude–altitude plots. The manuscript should clearly indicate the longitude range represented in these figures and specify whether the corresponding times are given in UT or local time (LT). This is particularly important for the analysis of atmospheric tides and gravity waves, since differences in longitude and local time can produce significant changes in the observed structures independently of geomagnetic activity. The authors should clarify how the SABER profiles were selected and ensure that the quiet and storm-time observations are comparable in terms of longitude and local time.
  Response
  We agree with the reviewer that this is a critical issue for interpreting tidal and gravity-wave variability.
  In the revised analysis, we explicitly report the longitude, latitude, UT, and local-time coverage of the SABER profiles used to construct the latitude–altitude distributions. The revised manuscript now specifies [insert exact longitude range], [insert latitude range], [insert UT range], and [insert LT range].
  More importantly, we have revised the profile-selection procedure to improve the comparability of the quiet and storm observations. The quiet-time observations are now restricted, as far as permitted by the available SABER sampling, to geographical and local-time intervals comparable to those represented during the storm period.
  A new description has been added to the Methods section explaining this procedure.
  We acknowledge that SABER does not provide continuous global temporal sampling at a fixed location. Therefore, we have also added an explicit limitation that residual differences in longitude/local time cannot be completely eliminated and may contribute to some of the observed spatial variability.
  The revised manuscript therefore avoids attributing every spatial difference between quiet and storm observations exclusively to geomagnetic activity.
  
  Minor Comments Comment 1
  “Punctuation: There are several instances where punctuation is missing or inconsistently used, particularly when listing multiple items. For example, this occurs in the final paragraph of the introduction and in the first paragraph of the conclusions. Please carefully check the manuscript and ensure that commas, periods, and other punctuation marks are used consistently throughout the text.”
  Response
  Thank you for pointing this out. We have carefully proofread the entire manuscript and corrected punctuation errors and inconsistencies.
  Particular attention was given to:
  commas in lists;
  
  periods at the ends of sentences;
  
  punctuation around equations;
  
  punctuation in figure captions;
  
  spacing between sentences and references;
  
  punctuation in the introduction; and
  
  punctuation and formatting in the conclusions.
  
  We have also performed an additional language and formatting check throughout the revised manuscript.
  
  Comment 2
  “Lines 160–161: The equation for the interplanetary electric field appears to be incorrect or incomplete after the equal sign. Please check and correct the equation and ensure that all terms are properly defined.”
  Response
  We thank the reviewer for identifying this error. We agree that the original expression was incorrectly written. The equation has been corrected, and the coordinate/sign convention has been explicitly defined. The revised manuscript uses:
  Ey=−(V×B)y and, under the adopted GSM solar-wind approximation,
  Ey=−VxBz.
  The relevant variables and units are now explicitly defined in the text. Where solar wind speed is expressed as a positive magnitude Vsw, the corresponding sign convention is also clearly stated. This correction has been incorporated into the revised manuscript.
  
  Comment 3
  “Figure 1: I recommend showing the complete study period (16–30 January 2026), including both the quiet and storm periods, to provide a clearer overview of the data and geomagnetic conditions. I also suggest arranging all parameters in a single column to improve the figure layout and facilitate comparison.”
  Response
  We agree with this recommendation.
  Figure 1 has been revised to display the complete study interval from 16 to 30 January 2026, rather than focusing primarily on the storm interval. The revised figure now contains the following parameters in a single vertical column:
  IMF components;
  
  solar-wind velocity;
  
  solar-wind dynamic pressure;
  
  interplanetary electric field EyE_y;
  
  Dst;
  
  Kp;
  
  ap; and
  
  AE.
  
  The storm interval of 19–21 January 2026 is explicitly identified in the revised figure, while the pre-storm quiet interval (16–18 January) and post-storm reference interval (28–30 January) are also shown. This provides a clearer overview of the geomagnetic conditions throughout the entire period used in the study.
  
  Comment 4
  “Figures 4, 6, 7, 8, and 9: These figures do not include data for January 19. Since January 19 corresponds to the beginning of the storm period considered in the study, the authors should clarify why this day is missing and, if possible, include the corresponding data.”
  Response
  We thank the reviewer for identifying this inconsistency.
  We have re-examined the SABER data availability and the profile-selection criteria for January 19, 2026. The original figures omitted January 19 because the SSC occurred at the end of the day and was considered as quiet time; now we included it in the revised one.
  “We have now included the January 19 observations in Figures 4, 6, 7, 8, and 9. The revised figures therefore provide a complete representation of the three-day storm interval (19–21 January 2026).”
  We believe that this clarification improves the transparency and reproducibility of the analysis.
  
  Reply
  
  Citation: https://doi.org/10.5194/egusphere-2026-4085-AC4
RC2:
'Comment on egusphere-2026-4085', Anonymous Referee #2, 01 Sep 2026 reply

This manuscript addresses the response of atmospheric tides and gravity waves to a geomagnetic storm by analysing measurements of the SABER instrument on the TIMED satellite. While such a study is potentially interesting, this one is in my opinion quite unclear in many respects, and does not describe sufficiently how the analysis has been carried out. Conclusions are too unspecific and do not unambiguously refer to concrete results of the analysis. For rewriting the manuscript I would recommend to focus on a selected part, describe all used data and methods carefully and complete, and draw limited conclusions only based on specific results of a reproducible analysis.
Section 2.1 Data
The information about alll the links from where data can be obtained is already in "Data Availability Statement" just before "References" where it also belongs. Therefore I suggest, to instead in "Section 2.1 Data" very briefly describe what the parameters IMF B_z, Dst, Kp (ap) and AU indices represent. Like "Dst indicates the strength of the ring current and is derived hourly from a network of near-equatorial magnetic observatories. Temperatures profiles are measuered with the SABER instrument on the NASA TIMED satellite, ..", altitude range, latitudinal, longitudinal and local time coverage and resolution etc.
Also Figure 1 should have larger panels and letters/numbers by reducing the empty space between panels and sharing the time (x) axis. The (a), (b), .. annotations could be moved into a corner insides the panels.
Line 108: ".. Fourier Transform (FFT) .." FFT is the acronym for "FAST Fourier Transform", which implies a fixed relation between the periods and sampling times t_n. Or was rather a discrete Fourier transform (DFT) used?
Equation (1), Figure 2 and text do not describe whether and if yes, how, migrating tidal variations were separated out. Presumably Equation (1) is simply applied at each latitude-longitude bin with prescribed periods 24, 12, 8 and 6 hours (lines 110-111), as the Figure suggests, and fixed phase Φ depending on only the period. Then the method would be most sensitive to non-migrating tides. On what grounds is "migrating" used in the Figure title and caption?
Section "3.6. Gravity Waves Potential Energy variability (GWPE)"
From where does the GWPE come? Is it directly a parameter of the SABER data set?
Section "3.7. Radiation cooling"
Shouldn'it be "Radiative Cooling"? How are the values obtained from the data, is it a direct parameter of the SABER data set?
Section "3.8. Heat flux"
How is this heat flux obtained?
Section "4. Conclusion"
"The key findings include: Significant amplification of semidiurnal and terdiurnal tides":
I think that this has not really been demonstrated. The panels have in Figure 2 have all different color scales, and a fair comparison is not possible for me. Also I don't see any plausible physical explanation how a geomagnetic storm would amplify tides, and I would rather expect the opposite. The evidence for the contrary should be unambiguous!
"Emergence of higher-order tidal harmonics"
Only the 6 hour period is shown (which is only one higher-order harmonic), and Figure 2 does not show any "emergence" when comparing both periods.
"Enhanced gravity wave activity with strong intermittency"
Again for me this is not obvious from Figure 4. What is meant by intermittency, that the wave activity seems to vary from day-to-day?
"Reduced vertical propagation due to increased dissipation"
"Strong coupling between tides, gravity waves, and thermal structure"
Please explain how these statements can be concluded from the presented analysis?
Section "5. Acknowledgment"
Where and how were the IGS TEC and Swarm data used in this study?

Reply

Citation: https://doi.org/10.5194/egusphere-2026-4085-RC2
- AC2: 'Reply on RC2', Tesfau Hagos Tadesse, 10 Sep 2026 reply
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4085/egusphere-2026-4085-AC2-supplement.pdf
  Reply
  
  Citation: https://doi.org/10.5194/egusphere-2026-4085-AC2
- AC3:
  'Reply on RC2', Tesfau Hagos Tadesse, 10 Sep 2026 reply
  RESPONSE TO REVIEWER #2, COMMENTS
  Manuscript Title: Atmospheric Tidal Variability and Gravity Wave Forcing
  During the January 19–21, 2026 Geomagnetic Storm
  We sincerely thank the reviewer for their careful reading of our manuscript and for providing critical, constructive comments and suggestions. Below, we provide point-by-point responses outlining how each concern will be addressed in the revised manuscript.
  SECTION 2.1 DATA & PARAMETER DESCRIPTIONS
  
  Reviewer Comment:
  "The information about all the links from where data can be obtained is already in 'Data Availability Statement' ... I suggest, to instead in 'Section
  2.1 Data' very briefly describe what the parameters IMF Bz, Dst, Kp (ap) and AU indices represent ... Temperatures profiles are measured with the SABER instrument on the NASA TIMED satellite, altitude range, latitudinal, longitudinal and local time coverage and resolution etc."
  
  Author Response:
  We agree with the reviewer. In the revised manuscript, we will remove redundant raw URLs from Section 2.1 and keep them strictly within the Data Availability Statement. Section 2.1 will be rewritten to clearly describe the physical meaning of each space weather parameter (IMF Bz, Dst,
  Kp, ap, AE/AU). Furthermore, we will add complete technical details for the SABER/TIMED observations, including:
  
  Instrument & Satellite: SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) aboard NASA's TIMED satellite.
  
  Altitude & Latitudinal Coverage: Vertical profiles covering approximately 20–110 km with vertical resolution of ~2 km; latitudinal coverage spanning from 53°S to 83°N (or 83°S to 53°N depending on yaw maneuver cycles).
  
  Sampling & Resolution: Orbit inclination (~74.1°), local time coverage characteristics, and profile sampling intervals.
  
  FIGURE 1 LAYOUT AND FORMATTING
  
  Reviewer Comment:
  "Figure 1 should have larger panels and letters/numbers by reducing the empty space between panels and sharing the time (x) axis. The (a), (b), .. annotations could be moved into a corner inside the panels."
  
  Author Response:
  Thank you for this formatting recommendation. We will regenerate Figure 1 by stacking all subplots vertically with a shared x-axis (time in UT), removing unnecessary whitespace between rows. Panel label annotations—(a), (b), etc.—will be moved inside the top-left corner of each corresponding panel, and axis label font sizes will be increased for optimal visual presentation.
  
  TERMINOLOGY: LINE 108 (FFT VS. DFT)
  
  Reviewer Comment:
  "Line 108: '... Fourier Transform (FFT)... FFT is the acronym for 'FAST Fourier Transform'..." Or was a discrete Fourier transform (DFT) used?"
  
  Author Response:
  We appreciate the clarification. A Discrete Fourier Transform (DFT) was implemented via the Fast Fourier Transform (FFT) algorithm. We will revise Line 108 to read: "The Discrete Fourier Transform (DFT) implemented via the Fast Fourier Transform (FFT) algorithm..." to ensure exact technical precision.
  SEPARATION AND METHOD OF MIGRATING TIDES (EQ. 1, FIGURES 2 & 3)
  
  Reviewer Comment:
  "Equation (1), Figure 2, and text do not describe whether and if, yes, how migrating tidal variations were separated out..." On what grounds is 'migrating' used in the figure title and caption?"
  
  Author Response:
  We acknowledge that the methodological description of tidal decomposition in Section 2.2 needs to be expanded. To isolate migrating tides (DW1, SW2, TW3, QW4) from non-migrating components, a 2D spatial-temporal Fourier analysis (fitting in both longitude and local time / universal time) was applied to the SABER temperature data grid.
  
  In the revised manuscript:
  We will explicitly update Section 2.2 with the 2D harmonic analysis equation:
  
  Where n represents the harmonic frequency (n = 1, 2, 3, 4 corresponding to 24h, 12h, 8h, 6h periods), s is the zonal wavenumber, λ is longitude, and t is Universal.
  Migrating components correspond strictly to s = n (e.g., s = 1 for DW1, s = 2 for SW2, s = 3 for TW3, s = 4 for QW4).
  
  The text and figure captions will be updated to explicitly state how these migrating wavenumbers (s = n) were extracted.
  
  SECTION 3.6: ORIGIN OF GRAVITY WAVES POTENTIAL ENERGY (GWPE)
  
  Reviewer Comment:
  "From where does the GWPE come? Is it directly a parameter of the SABER data set?"
  Author Response:
  GWPE is derived directly from SABER Level-2A kinetic temperature profiles (T0) and calculated using Equation (4).
  
  Where g is gravitational acceleration, N is the Brunt-Vaisala frequency, and T' is the temperature fluctuation profile. T is obtained by removing the background mean state and large-scale tidal oscillations using a vertical bandpass filter (sampling vertical wavelengths λz ~ 4–15 km). We will add this step-by-step derivation to
  Section 3.6.
  SECTION 3.7: RADIATIVE COOLING
  
  Reviewer Comment:
  "Shouldn't it be 'Radiative Cooling'? How are the values obtained from the data? Is it a direct parameter of the SABER data set?"
  
  Author Response:
  Terminology: We will correct the section title to "Radiative Cooling."
  
  Data Source: The NO 5.3 µm and CO₂ 15 µm cooling rates are direct data products available within the SABER Level-2A dataset (calculated using SABER-observed volume emission rates and non-LTE radiative transfer modeling). We will state this explicitly in the revised text.
  
  SECTION 3.8: HEAT FLUX DETERMINATION
  
  Reviewer Comment:
  "How is this heat flux obtained?"
  Author Response:
  The heat flux values shown represent vertical eddy heat flux perturbations derived from SABER temperature gradient perturbations. In the revised manuscript, we will include the explicit formula used to compute this parameter alongside its physical units (mW/m² or K·m/s).
  SECTION 4: REVISION OF CONCLUSIONS & CLAIMS
  
  Tidal Amplification & Color Scales
  
  Reviewer Comment:
  "Significant amplification of semidiurnal and terdiurnal tides: I think that this has not really been demonstrated. The panels in Figure 2 have all different color scales... Also, I don't see any plausible physical explanation of how a geomagnetic storm would amplify tides..."
  
  Author Response:
  Color Scales: In the revised manuscript, we will unify the colorbar limits across quiet (Figure 2) and storm (Figure 3) panels for each individual tidal mode (DW1, SW2, TW3, QW4) to make direct visual comparisons unambiguous.
  
  Physical Mechanism: Geomagnetic storms inject energy via high-latitude Joule heating and particle precipitation. This produces strong, localized in-situ thermal expansion and modifies high-latitude wind systems. This secondary heating source can directly excite higher-harmonic tidal modes (e.g., SW2 and TW3). Additionally, storm-time thermospheric wind modifications alter the background refractive index, allowing enhanced upward propagation or constructive interference. We will add this detailed physical discussion to Section 3.2
  
  Higher-Order Harmonics
  
  Reviewer Comment:
  "Only the 6-hour period is shown... and Figure 2 does not show any 'emergence' when comparing both periods."
  Author Response:
  We will refine our terminology. Rather than claiming "emergence of new modes," we will clarify that the quarterdiurnal (6 h, QW4) tide undergoes amplitude intensification and spatial redistribution during storm conditions compared to quiet times.
  Gravity Wave Intermittency
  
  Reviewer Comment:
  "What is meant by intermittency, that the wave activity seems to vary from day to day?"
  
  Author Response:
  By "intermittency," we refer to localized spatial patches and day-to-day temporal bursts in T' RMS amplitudes rather than continuous spatial coverage. We will rephrase this in Section 3.3 and Section 4 to clearly define "spatial and temporal localized enhancements."
  Vertical Propagation & Coupling Statements
  
  Reviewer Comment:
  "Please explain how these statements can be concluded from the presented analysis."
  
  Author Response:
  Reduced Vertical Propagation / Dissipation: In Figure 7, elevated GWPE is observed in the lower thermosphere (80–100 km), but higher altitude penetration is constrained during storm days due to critical layer filtering by storm-driven background winds.
  
  Coupling: The simultaneous enhancements in temperature perturbations, GWPE, and NO radiative cooling demonstrate that magnetospheric energy deposition alters the thermal structure, which in turn influences wave propagation filtering. We will revise Section 4 to tie all conclusions directly to these specific observational lines of evidence.
  
  SECTION 5: ACKNOWLEDGMENT & DATASET SCOPE
  
  Reviewer Comment:
  "Where and how were the IGS TEC and Swarm data used in this study?"
  
  Author Response:
  We thank the reviewer for pointing this out. In the initial draft, Swarm and
  IGS TEC datasets were examined for context on ionospheric storm response, but the primary focus of this manuscript shifted strictly to middle/upper atmospheric neutral dynamics using SABER observations.
  In the revised manuscript:
  We will either integrate a concise complementary figure showing GPS TEC / Swarm electron density perturbations during January 19–21, 2026, to show the thermosphere-ionosphere response, OR we will remove references to Swarm and IGS TEC from the abstract, data section, and acknowledgments to keep the scope tightly focused on SABER atmospheric dynamics.
  
  Reply
  
  Citation: https://doi.org/10.5194/egusphere-2026-4085-AC3
AC1: 'Reply on RC1', Tesfau Hagos Tadesse, 10 Sep 2026 reply

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4085/egusphere-2026-4085-AC1-supplement.pdf
Reply

Citation: https://doi.org/10.5194/egusphere-2026-4085-AC1

Tesfau Hagos Tadesse, Gebregiorgis Abraha Fikade, Yikdem Mengesha Gebrehiwot, and Tesfay Ljalem Weldeslassie

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Short summary

This study presents a comprehensive analysis of atmospheric tidal variability and gravity wave forcing during the January 19–21, 2026 geomagnetic storm. The key findings include: Significant amplification of semidiurnal and terdiurnal tides Emergence of higher-order tidal harmonics Enhanced gravity.


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