太阳活动对EUV辐射在大气中吸收过程的影响

本文利用A-E卫星在太阳活动21周峰年间观测到的EUV辐射资料,高层大气成分的吸收截面,以及MSIS-86热层大气模式,研究了EUV辐射在大气中的吸收过程;在透射比为1/e和0.1/100时分别计算了透射高度随波长及太阳活动的变化。在波长范围50—1050内对37个波段分别求出了透射高度随太阳天顶角的变化。结果表明,当太阳活动增强时各波段的透射高度均升高,而且透射比越大则透射高度随太阳活动的变化也越剧烈。当透射比为一定时,太阳天顶角越大则透射高度随太阳活动的变化也越大。除此之外还存在一个相反效应,即太阳活动会使Chapman函数变小,这反过来又促使透射高度降低。这两种效应的综合作用结果可较好地解释某些电离层观测中的日没效应。

EFFECTS OF SOLAR ACTIVITY ON EUV ABSORPTION PROCESSES IN THE UPPER ATMOSPHERE

Using a set of aeronomical parameters,such as absorption cross sections for the dominant thermospheric constituents,EUV flux data from the Atmosphere Explorer Satellites and Hedin's MSIS-87 neutral thermospheric model,the variations of penetration heights of solar EUV radiation with maximum and minimum solar activities are numerically calculated.For transmit-tance being l/e and 0.1/100,the variations of panetration height of EUV radiation in wavelength range 50-1050 A divided in 37 wavebands are also obtained.The results indicate the penetration heights are obviously controlled by solar activities,and the larger the transmittan-ce is,the closer the correlative relation of penetration height with solar activity is.At the solar zenith angles near normal astronomical sunset,the solar activity leads to increasing the penetration heights on one hand,and to decreasing the Chapman's function,which reduces the penetration height on the other.These effects could physically explain some ionospheric phenomena observed at local sunset.