[P-EM14] Study of coupling processes in solar-terrestrial system

[PEM14-P01] A Statistical Survey of Polar Cap Cold and Hot Patches in the Southern Hemisphere Using a DMSP Satellite

*Duan Zhang¹, Qinghe Zhang^1,2, Kjellmar Oksavik^3,4, Zanyang Xing², L. R. Lyons⁵, Huigen Yang^6,2, Tong Xu⁷, Marc Hairston⁸, Xiangyu Wang², Yuzhang Ma², Guojun Li⁹, Sheng Lu², Jin Wang¹ (1.National Space Science Center, CAS, 2.Shandong University, 3.University of Bergen, 4.University Centre in Svalbard, 5.University of California, 6.Polar Research Institute of China, 7.China Research Institute of Radiowave Propagation, 8.University of Texas at Dallas, 9.Chongqing University of Posts and Telecommunications)

Keywords:polar ionosphere, polar cap patch, statistical survey, southern hemisphere

This paper is a statistical survey of Southern Hemisphere cold and hot polar cap patches in relation to the interplanetary magnetic field (IMF) and ionospheric convection geometry. A total of 11,946 patch events were identified by DMSP F16 during the years 2011-2022. A temperature ratio of Ti/Te < 0.68 is recommended to define a hot patch in the Southern Hemisphere, otherwise it is a cold patch. The cold and hot patches have different dependencies on IMF clock angle, while dependencies on IMF cone angle are similar. Both cold and hot patches appear more on the duskside, and the distribution of cold patches gradually decreases from the dayside to the nightside, while hot patches have a higher occurrence rate near 14 and 21 magnetic local time (MLT). Moreover, we compared the key plasma characteristics of polar cap cold and hot patches in the Southern and Northern Hemispheres. The intensity of the duskside upward field-aligned current of patches in the Southern Hemisphere is stronger than that in the Northern Hemisphere, which may be due to the discrepancy of the conductivities between two hemispheres caused by the dipole tilted. The downward soft-electron energy flux of the dawnside patches is significantly greater than that of the duskside patches in both hemispheres.