Research on the ionospheric diurnal Double-Maxima patterns in Asia-Australian area based on the VTEC observations of BDS geostationary satellites

Ionospheric diurnal double-maxima (DDM) pattern is a special phenomenon of the ionosphere, which shows that ionospheric electron density/total content (TEC) presents two-peak structure during daytime. This paper uses Beidou geostationary (GEO) vertical total (VTEC) data from MGEX tracking stations in Asian-Australian area 2019 to 2020 study DDM phenomenon. The results show occurrence rate roughly symmetrical about magnetic equator, with “W”-shaped distribution. With decreasing latitude, first decreases 58%/73% 7%/17% and then increases equatorial region 30%. Minimum occurs near ± 20°. different latitude regions varies longitude. There no significant variation at low-latitudes (magnetic 15°N ∼ 15°S), while northern hemisphere mid-latitudes (regions north 15°N), longitude observation. southern hemisphere’s south 15°S) east 90°E an increasing trend two peaks one valley mainly occur 10:00–13:00 LT, 14:00–18:00 12:00–15:00 respectively. As decreases, time structures tends be delayed, but there increase usually earlier than hemisphere. months inverted “U” shape appear latest local summer earliest winter. low-latitude regions.