VARIATIONS IN EXOSPHERIC DENSITY DURING 1967-8, AS REVEALED BY ECHO 2.
ROYAL AIRCRAFT ESTABLISHMENT FARNBOROUGH (ENGLAND)
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Values of atmospheric density at heights near 1000 km have been obtained from the orbit of Echo 2 during 1967 and 1968. The results clearly show the existence in the exosphere of 27-day variations associated with the rotation of the sun and also correlation with geomagnetic disturbances. The semi-annual variation in the exosphere is again apparent, and has now been traced from before solar minimum in 1964 up to and probably past the current solar maximum the magnitude of the semi-annual density variation shows no definite dependence on the level of solar activity. The irregular year-to-year variations in the effect are similar to those at lower heights, being large at all heights at the same time. The variation in the exosphere exceeds the magnitude expected on the basis of variations at lower heights at dates before July 1966 and after April 1968, but is of the expected magnitude between these dates. Author
- Atmospheric Physics