Large TEC Variations Between Mars and Earth: Simulation and Observation Comparisons

Large total electron content (TEC) variations along the line from Mars to Earth have been demonstrated by analyzing the ground received Tianwen-1 differential one-way range (DOR) signals when corona mass ejections (CMEs) and co-rotating interaction regions (CIRs) pass through the signal path. Here, the TEC variations along the line from Mars to Earth are calculated from the Wang-Sheeley-Arge (WSA)-Enlil space weather forecast model. The results are compared with the Tianwen-1 line of sight (LOS) observations as well as the STEREO-A in situ solar wind density measurements. It is found that the TEC variations calculated from the WSA-Enlil model are usually much smaller in amplitude, especially in the cases of CIRs passing through the signal path. In addition, the timings of CMEs and CIRs passing through the DOR signal path in the WSA-Enlil model can be half a day earlier or later than the observed ones. In comparison with in situ solar wind measurements, the ground received Tianwen-1 DOR signals carry solar wind density information over a large spatial region along the signal path. Such remote sensing measurement can be valuable for constraining and improving global solar wind forecast models. Space weather forecast is important for ground-based and space-borne technology, including power grids, satellite navigation, and satellite radio communication. Wang-Sheeley-Arge (WSA)-Enlil is one of the current advanced models to predict the space weather. We calculate the amount of charged particles along the line from Mars to Earth from the model, and compare it with the observed one by remote sensing method. Significant differences exist between the two results. It is, therefore, suggested that space weather forecast models should incorporate those remote sensing measurements, which may make the space weather forecast more accurate. TEC variations along the line from Mars to Earth in the cases of CMEs and CIRs passing through are calculated from the WSA-Enlil model In comparison with the TEC variations obtained from the Tianwen-1 DOR signals, the WSA-Enlil model results are far from realistic The Tianwen-1 DOR signals carry solar wind density information along the signal path and can help to constrain solar wind forecast models