Variations of ionospheric ionization and related solar fluxes during an intense solar cycle
Variations of ionospheric ionization and related solar fluxes during an intense solar cycle
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DOI：
10.1029/93ja02099
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发表时间：
1994-02
影响因子：
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通讯作者：
N. Balan;G. J. Bailey;B. Jenkins;P. Rao;R. Moffett
中科院分区：
文献类型：
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作者：
N. Balan;G. J. Bailey;B. Jenkins;P. Rao;R. Moffett
研究了强太阳活动21周期间电离层电子含量（IEC）和相关太阳辐射通量随10.7厘米太阳辐射通量指数（F10.7）的变化，F10.7高达367。本文利用1980-1985年在几个台站收集的IEC资料、由EUV 91太阳EUV通量模型得到的太阳EUV（50-1050 A）通量、莱曼α（1216 A）通量和He I（10，830 A）等效宽度（EW）的实测值进行了研究。结果表明，当F10.7（或其81天的运行平均值）超过一个阈值（约160-200），这稍微取决于季节和纬度的日最大IEC（IECmax）饱和（保持不变）。太阳EUV通量模式值的变化表明，当F10.7超过阈值时：（1）积分太阳EUV（50-1050 A）通量以很低的速率增加;（2）重要的（对热层加热）色球层线和间隔的通量一般饱和（保持不变），而日冕线和间隔的通量以减小的速率增加。当F10.7超过阈值时，作为太阳EUV通量模型输入数据的莱曼α通量和He I EW也以很低的速率增加。在最近的三个太阳活动周19-21期间，观测到的电离层电离饱和是由于太阳EUV和莱曼α通量随F10.7的非线性变化。IECmax随太阳EUV积分通量、莱曼α通量和He I EW的增加而线性增加。
Variations of ionospheric ionization (represented by ionospheric electron content (IEC)) and related solar fluxes with the 10.7-cm solar flux index (F10.7) are studied for the intense solar cycle 21 when F10.7 was as high as 367. The IEC data collected at several stations during 1980-1985, the solar EUV (50-1050 A) fluxes obtained from the EUV91 solar EUV flux model, and the measured values of Lyman α (1216 A) flux and He I (10,830 A) equivalent width (EW) are used for the study. It is shown that daily values of diurnal maximum IEC (IECmax) saturate (remain constant) when F10.7 (or its 81-day running average) exceeds a threshold (approximately 160-200) which depends slightly on season and latitude. Variations of the model values of the solar EUV fluxes reveal that when F10.7 exceeds the threshold: (1) the integrated solar EUV (50-1050 A) flux increases at a very low rate, and (2) the fluxes of the important (for thermospheric heating) chromospheric lines and intervals generally saturate (remain constant), while those of the coronal lines and intervals increase at a reduced rate. Lyman α flux and He I EW, which are used as input data in the solar EUV flux model, also increase at a very low rate when F10.7 exceeds the threshold. The saturation of ionospheric ionization, observed for high values of F10.7 during the last three solar cycles 19-21, is the result of the nonlinear variation of the solar EUV and Lyman α fluxes with F10.7. IECmax increases linearly with the integrated solar EUV flux, Lyman α flux and He I EW.