Theoretical study of the formation mechanism of the topside ionosphere nighttime mid-latitudinal ionization peak on equinox using SAMI2
Recent observations have shown that there is an ionization density peak in the nighttime mid-latitudinal ionosphere,but the formation mechanism of the nighttime mid-latitudinal ionization peak(MIP)structure is not perfect.Using Swarm-A satellite observation data,this paper firstly counts the spatial distribution of the ionization density in the nighttime mid-and low-latitudinal ionosphere on the equinox months under the geomagnetic quiet activity,and the results show that the nighttime MIP structure is most prominent after midnight and under low solar activity,which mainly occurs around the magnetic latitude±40°.Then,for the first time,using SAMI2 model,we successfully reproduced the nighttime MIP structure on spring equinox under low solar activity and geomagnetic quiet activity.Simulation shows that the MIP structure is most prominent after midnight and at topside ionosphere-plasmasphere.The reconstruction of the ionosphere ionization density continuity equation of SAMI2 model reveals the contribution of various physical processes for the nighttime MIP structure of 450 km height topside ionosphere.Before and after sunset,the eastern Pacific sector ionosphere firstly formed the MIP structure in the southern hemisphere,and the long-lasting sunlight at the mid-latitudinal ionosphere,the equatorward neutral wind induced by the eastward magnetic declination and the weaker PRE electric field are all conducive to its formation.The formation mechanism of late-night MIP structure is mainly the inward EX B drift induced by the westward zonal electric field,which forms the MIP structure by rapidly reducing the ionization density of the low-latitudinal ionosphere.The simulation results also show that the contribution of the neutral wind to the nighttime MIP structure depends on the local time-latitudinal distribution of its effecftive vertical wind.
Mid-latitudinal ionization peakSwarm-A satelliteSAMI2 modelTheoretical study
万方数据
维普
