09 Feb 2021
09 Feb 2021
Role of Eddy Diffusion in the Delayed Ionospheric Response to Solar Flux Changes
- 1Leipzig Institute for Meteorology, Universität Leipzig, Stephanstr. 3, 04103 Leipzig, Germany
- 2German Aerospace Center, Kalkhorstweg 53, 17235 Neustrelitz, Germany
- 3Space Weather Prediction Centre, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA
- 1Leipzig Institute for Meteorology, Universität Leipzig, Stephanstr. 3, 04103 Leipzig, Germany
- 2German Aerospace Center, Kalkhorstweg 53, 17235 Neustrelitz, Germany
- 3Space Weather Prediction Centre, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA
Abstract. Simulations of the ionospheric response to solar flux changes driven by the twenty-seven days solar rotation have been performed using the global 3-D Coupled Thermosphere/Ionosphere Plasmasphere electrodynamics (CTIPe) physics- based numerical model. Using the F10.7 index as a proxy for solar EUV variations in the model, the ionospheric delay at the solar rotation period is well reproduced and amounts to about 1 day, which is consistent with satellite and in-situ measurements. From mechanistic CTIPe studies with reduced and increased eddy diffusion, we conclude that the eddy diffusion is a primary factor that influences the delay of the ionospheric total electron content (TEC). We observed the peak response time of atomic oxygen to the molecular nitrogen ratio to solar EUV flux changes quickly during the increased eddy diffusion compared with weaker eddy diffusion. These results suggest that an increase in the eddy diffusion leads to faster transport processes and an increased loss rates resulting in a decrease of the ionospheric time delay. Furthermore, we found that an increase in solar activity leads to an enhanced ionospheric delay. At low latitudes, the influence of solar activity is stronger, as EUV radiation drives ionization processes that lead to composition changes. Hence, the combined effect of eddy diffusion and solar activity lead to longer delay in the low and mid latitude region.
Rajesh Vaishnav et al.
Status: open (until 11 Apr 2021)
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RC1: 'Comment on angeo-2021-12', Anonymous Referee #1, 14 Feb 2021
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Comments on the manuscript “Role of Eddy Diffusion in the Delayed Ionospheric Response to Solar Flux Changes” by Rajesh Vaishnav et al.
This study focused on the contributions from the eddy diffusion to the ionospheric delay, which is an interesting topic and worthy of investigation. The authors showed that the increased eddy diffusion can contribute to decreasing the delay of the ionosphere. The results are not surprising but this work helps to improve our understanding of the ionospheric delayed response to the periodic variation of solar activity to some degree. There are some issues which should be addressed before the possible publication
- The authors mentioned “…the eddy diffusion is a primary factor that influences the delay of the ionospheric total electron content (TEC)” in many places. It should be noted that the root mechanism that responsible for the ionospheric delay is the imbalance between the production and loss of the electrons. The eddy diffusion can alter the general circulation, which thus impact the thermospheric neutral species. Whereas, the thermospheric circulation is controlled by not only eddy diffusion, but also temperature, pressure, neutral species, et al. All of them are affected by solar flux changes. Thus, it is not true to say that the eddy diffusion is the “primary factor”. The author should clarify this statement throughout the paper.
- Different eddy diffusion coefficients can result in different ionospheric time delay. However, the eddy diffusion at a given location and time interval should NOT change much. The eddy diffusion could contribute to the long-term change of ionospheric time delay, for instance, the seasonal variation of time delay.
- It seems that the authors did not show the results for the first day and 27th day in Figures 1 and 8-9. I suggest them to plot the results during the whole 27-day interval. In addition, it should be better to draw the vertical line at 13.5 days instead of the 14th day.
- There are two relevant papers which can be cited in this work. (1) Schmölter, E., Berdermann, J., & Codrescu, M. (2021). The delayed ionospheric response to the 27âday solar rotation period analyzed with GOLD and IGS TEC data. Journal of Geophysical Research: Space Physics, 126, e2020JA028861. https://doi.org/10.1029/2020JA02886 (2) Ren, D., Lei, J., Wang, W., Burns, A., & Luan, X. (2021). Observations and simulations of the peak response time of thermospheric mass density to the 27âday solar EUV flux variation. Journal of Geophysical Research: Space Physics, 126, e2020JA028756. https://doi.org/10.1029/2020JA028756
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AC1: 'Reply on RC1', RAJESH VAISHNAV, 25 Feb 2021
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The comment was uploaded in the form of a supplement: https://angeo.copernicus.org/preprints/angeo-2021-12/angeo-2021-12-AC1-supplement.pdf
Rajesh Vaishnav et al.
Rajesh Vaishnav et al.
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