We proposed for the first time that the angle between the projection of the magnetic field line and the sunrise line (AMFS) is a crucial factor controlling predawn heating. Then, we quantitatively investigated the relationship between the predawn heating effect and the AMFS depending on the model results and examined the influence of the length of the magnetic field line (LMF). The results indicate that the predawn heating is influenced by the combined effect of the AMFS and the LMF. Our study suggests that the increase of AMFS promotes predawn heating, while the increase of LMF blocks predawn heating. Finally, we found that when the LMF is about 4000 km and the AMFS is around 30 degrees, the combined effect of the AMFS and the LMF on the predawn heating effect reaches its maximum, exceeding 400K, while the influence of both AMFS and LMF exhibit saturation effects.

Based on nearly 4.6 million radio occultation ionospheric profile data from COSMIC satellites in 2006-2020, a global three-dimensional ionospheric electron density model was constructed by a new concept. The global 3D ionosphere structure was divided into total 338,661 grids with longitude intervals of 10 degrees, latitude intervals of 2 degrees, and height intervals of 5 km. Each individual grid model is first constructed, and then all grid models are combined to form a global ionospheric model. Each grid model has 21 coefficient for modeling solar activity, geomagnetic activity, local time, and season variation.This method makes full use of all ionospheric electron density data without any spatial smoothing, and can effectively model the fine ionospheric spatial structure like longitudinal wavenumber-4 structure in low latitudes. The model also takes into account the influence of both solar and geomagnetic activities on the ionosphere. It can give the climatological variation of ionospheric electron density with geomagnetic activity. In addition, by combined with the International Reference Ionospheric electron density results of E layer below 140km, the problem of three-peak error of occultation data below peak height of F2 layer in middle and low latitude region is effectively solved, and accurate low-altitude profile data can be obtained. Compared with other data sources such as ZH01 and ROCSAT-1, the simulation ability of the model in fine spatial structure is verified.

Based on the data of Maven's NGISM neutral composition and Langmuir probe electron density and temperature, we statistically analyzed the climatic variations of the Martian thermosphere and ionosphere, and found significant north-south asymmetry. In winter and summer, it mainly comes from the north-south asymmetry of solar zenith Angle. The observational data still show significant north-south asymmetry in equinox seasons. Under low solar EUV radiation, the thermosphere density in the northern hemisphere is higher than that in the southern hemisphere. With solar radiation increase, the thermosphere density in the southern hemisphere gradually exceeds that in the northern hemisphere. In addition, the southern hemisphere increases non-linearly with the increase of solar radiation, while the northern hemisphere increases linearly. The electron density in Martian ionosphere also shows significant north-south asymmetry in seasons. The electron density in the southern hemisphere is higher than that in the northern, and the electron temperature in the southern hemisphere is lower than that in the northern. The asymmetries in the ionosphere and thermosphere between the northern and southern hemispheres are likely related to significant differences in Mars' north-south topography or to north-south asymmetries in the residual magnetic field. After preliminary analysis, we found that the north-south asymmetry of Mars' remaining magnetic field would intensify the hemispheric asymmetry of the ionospheric electron density, but have no effect on the thermospheric neutral density. The hemispheric asymmetry may be mainly related to the significant difference in Mars' north-south topography.