欧洲地区电离层峰值电子密度逐日变化的相关距离研究

本文采用欧洲22个台站的电离层F^₂层峰值电子密度N_mF^₂，分析了其逐日变化分量的相关距离S，着重研究了S的周日变化、季节变化及其随太阳活动和地磁活动的变化.首先用指数型函数模式来拟合任意两站间电离层逐日变化的相关系数R随间距d的变化，由此估算出逐日变化的相关距离S.详细研究了S在不同的季节（春季、夏季、秋季和冬季），不同的地磁活动（平静和扰动）及不同的太阳活动（低、中和高）随世界时的变化（周日变化）.结果表明：（１）S的范围一般为400～1600 km；（２）S值在白天比夜间大；（３）S值具有季节变化，夏季最大，冬季最小，春秋季差异不大；（４）S值在地磁扰动时比平静时大；（５）当太阳活动低时，S值在日落到正午间要比太阳活动中或高时明显偏小，而在正午到日落间则与太阳活动中或高时差异不大.根据以上结果，我们认为：（１） 太阳辐射对电离层逐日变化的影响是大尺度的，并在白天和太阳活动高时大于晚上和太阳活动低时；（２） 地磁活动的影响也是大尺度的；（３）气象活动的影响是相对小尺度的，且逐日变化具有季节性.本文从相关尺度分析的角度，证实了电离层逐日变化来源于太阳辐射、地磁活动和气象活动因素的论断.

A study of correlation distance of the day to day variability of F2 layer peak electron density over Europe

In order to study the correlation distance S of the ionospheric day-to-day variability,especially the diurnal and seasonal variation of S and how it changes with solar and geomagnetic activities,we adopted the ionospheric F_2-layer peak electron density,N_mF_2,obtained from 22 European stations.We first used an exponential function to describe how the correlation coefficient R of the ionospheric day-to-day variability between any two stations changes with its distance d,and then from that computed the correlation distance S. We then studied the diurnal variation of correlation distance S versus universal time for different seasons(spring,summer,autumn and winter),different geomagnetic activity levels(quiet and disturbed),and different solar activity levels(low,medium and high).We found that:(1) The ranges of S are confined from 400 up to 1600 km;(2) The values of S are larger at daytime than nighttime;(3)There are seasonal trends of S,generally,the S values are largest in summer,smallest in winter,and the differences between it in spring and autumn are quite small.(4) When the geomagnetic activity level is disturbed,the S values are larger than when quiet.(5) From sundown to noon of next day the S values are distinctly smaller when the solar activity level is low,than those when the solar activity level is medium or high,but from noon to just before sundown,the S values change little with the solar activity levels.Based on the above results,we conclude that:(1) The influences of solar radiation on the ionospheric day-to-day variability are of large-scale,and are larger at daytime and when the solar activity level is high than at nighttime and when the solar activity level is low.(2) The influences of geomagnetic activity are also of large-scale.(3) The meteorological influences are relatively of small-scale and the day-to-day variability has seasonal trends.From the standpoint of the correlation scales,we validated the known conclusion that the sources of ionospheric day-to-day variability include the solar radiation,the disturbances from the geomagnetic and meteorological activities.