Climatological features of the maximum electron density of the ionospheric F2 layer (NmF2) in polar regions

Climatological features of NmF2 are investigated and compared using long-term observations among the Arctic and Antarctic stations of Tromso (69.6N, 19.2E; CGM:66.7N, 102.2E), Longyearbyen (78.2N, 16.0E; CGM: 75.4N, 110.7E) and Zhongshan (69.4S, 76.4E; CGM:74.7S, 96.9E). Interesting results are presented as follows: The maximum value of NmF2 mainly occurs at local noon (LN) at the auroral latitude station Tromso, but at magnetic noon (MN) at the cusp latitude station Longyearbyen and between local noon and magnetic noon at Zhongshan. There is another peak just before magnetic midnight at Longyearbyen in winter during solar maximum years. An enhancement of NmF2 is also detected during 21-01 UT in winter at Tromso. There are semi-annual anomaly at Tromso and normal variability at both Longyerabyen and Zhongshan during solar minimum years. During solar maximum years there is semi-annual anomaly for all three stations. The winter anomaly is evident at Tromso and Zhongshan, but does not exist at Longyearbyen. It is demonstrated that in addition to the solar radiation the magnetosphere-ionosphere coupling processes, such as particle precipitation and plasma convection, play a significant role in the high latitude ionosphere.