极区电离层F_2层峰值电子浓度对太阳活动依赖性的共轭研究

Comparative studies on solar activity variations of N_mF_2 at the Arctic and Antarctic Stations

本文利用南极中山站(ZHS),以及北极与其地理共轭的Tromso站(TRO)、地磁共轭的Longyearbyen站(LYB)各自约一个太阳活动周的观测数据,对比分析了极区电离层F2层峰值电子浓度(NmF2)对太阳活动的依赖性.结果表明,三个台站NmF2月中值随修正太阳10.7cm通量指数F10.7P(简称P)增大在总体上呈线性增长,这说明在这三个台站,太阳辐射仍是其F2层主要电离源.其中TRO站NmF2与P线性关系最好,ZHS站的次之,LYB站的最差.在日变化中,TRO站NmF2对太阳活动响应最为敏感的时刻出现在地方时中午附近,LYB站出现在磁中午,ZHS站则出现在地方时中午和磁地方时中午之间.这主要是由地理/地磁纬度差异引起的不同强度的光致电离与极区等离子体对流共同作用的结果.在年变化中,TRO站NmF2随太阳活动变化上升最快的季节出现在冬季,夏季上升最慢.在ZHS站与LYB站,NmF2对太阳活动变化的响应都在两分季最为敏感.这种季节上的差异则是由于三个台站光致电离与中性大气成分R[O/N2]的不同所致.

Solar activity dependences of the ionospheric F2 peak electron density （NmF2） are investigated and compared based on long-term observations at the Arctic and Antarctic stations of Tromso, Longyearbyen, and Zhongshan. It is found that NmF2 increases linearly with solar activity indices at most of the time at all three stations, illustrating that the solar radiation is the primary factor in the formation of the ionosphere. Also, there exits an apparent ＂saturation effect＂ at Zhongshan in the Southern Hemisphere summer, but exits an ＂amplification effect＂ atTromso and Longyearbyen in the Northern Hemisphere winter. The linear relationship between NmF2 and solar activity indices F10.7P is the strongest at Tromso, and it is the weakest at Longyearbyen. For the diurnal variations, NmF2 is the most sensitive to solar activity variations around local noon at Tromso, around magnetic noon at Longyearbyen, and between the two at Zhongshan. It is mainly subjected to the different proportion of photoioni2ation and plasma convection between the three stations, which is controlled by their geographic latitude and geomagnetic latitude. For its annual variations, NmF2 is the most sensitive to solar activity variations in winter at Tromso, and it is more sensitive in equinoxes than in summer. At Zhongshan and Longyearbyen, NmF2 is the most sensitive to solar activity in equinoxes. The sensitivity is the lowest in summer at Zhongshan, but the lowest in winter at Longyearbyen. The annual variations of sensitivity of NmF2 to the solar activity are mainly due to the differences in photoioni2ation and chemical compositions at the three stations. At magnetic midnight in winter of both Tromso and Zhongshan, NmF2 has the lowest sensitivity to solar activity and the linear relationship between NmF2 and F10.7P is the worst. And so is it during 12-16UT at Zhongshan in winter. Different from the other two stations, NmF2 still has a strong sensitivity to solar activity before magnetic midnight in winter at gongyearbyen, which is attributed to the transpolar transport of EUV ioni2ation from day to night.