Atmospheric Density Response to a Severe Magnetic Storm Detected by the 520 km Altitude Spherical Satellite
, Dan Du 5, Aibing Zhang 1,2,3,4, Xinchun Tang 6, Feng Yan 6, Yueqiang Sun 1,2,3,4, Xianguo Zhang 1,2,3,4, Bowen Wang 1,2,3,4 and Yuerong Cai 1,2,3,4
Round 1
Reviewer 1 Report
1) The data you used should be described in detail, including its web site and if it is available freely.
2) You stated that “The disadvantage is that the limited sampling rate leads to lower sensitivity, and also the limitation of the inversion algorithm to the calculation results. ” you should also give the information of the sampling rate specifically.
3) There is no difference between the equation (1) and (2).
4) Since the results gained by POD, the models and strategies of POD should be listed.
5) In part 2 of 3.3.1, if the description is showed in table, it will be improve the readability.
Author Response
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Reviewer 2 Report
This paper presents the atmospheric density data at 520 km observed by the polar-orbiting spherical experimental satellite of China. The density changes with solar activity and a geomagnetic storm are considered. The observations have been able to reproduce the general mechanism of atmospheric density variations and align with simulations.
This paper uses the new data. It is well written and presents informative figures. The abstract adequately shows the obtained in the paper results. As a consequence, I recommend its publication almost in its present form. I have only two very minor comments/questions that need to be clarified.
Comments：
1. The new data are just compared with the simulations. To increase the reliability of the results and the credibility of the conclusions, It is better to also compare with other satellite observations.
2. Figure 3 only shows the correlation and error distribution between different simulations and observations during storm time, it would be interesting to show the statistical results over a long period.
3. Is the GPOD observations at different latitudes similar to simulations? Please give the most credible region for GPOD density data.
4. What are the physical processes that lead to the observed storm time density changes at low and middle latitudes? Joule heating occurs at high latitudes, so I am willing to see a short discussion about the heating at high latitudes leading to the density enhancement at low latitudes. As Li et al. (2018, 2019) discussed, the storm-enhanced electric fields drive a strong ion motion at high latitudes. The large differential motion between the ions and neutrals cause enhanced Joule heating and ion drag, which then drive large changes in Tn and winds in the upper thermosphere. Large latitudinal pressure gradient caused by Tn increases drives a large equatorward meridional circulation at higher altitudes. When high-latitude wind circulation is modulated by a storm and the wind disturbance is transmitted toward lower latitudes, vertical winds in the lower latitudes are changed and can be more downward/upward.
References:
1) Li, J. Y., W. B. Wang, J. Y. Lu, et al., on the responses of mesosphere and lower thermosphere temperatures to geomagnetic storms at low and middle latitutdes, Geophys. Res. Lett., 45(19), 10128-10137, doi:10.1029/2018GL078968, 2018
2) Li, J. Y., W. B. Wang, J. Y. Lu, J Yue, AG Burns, T Yuan, XT Chen, WJ Dong, A theoretical study of the responses of mesosphere and lower thermosphere winds to geomagnetic storms at middle latitudes, J. Geophys. Res. Space Physics,124(5), 3666-3680. 24 April 2019. DOI: 10.1029/2018JA026533
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