Time-variation of solar influence on tropospheric circulation

Abstract

The influence of large geomagnetic disturbances and solar magnetic sector structure on Vorticity Area Index (VAI) at 500 mb is studied by subdividing the data of 1946-1978 into 15 blocks, each of five years with three years overlapping in successive blocks. Results clearly show marked time-variation in the amplitude of solar-induced signal in VAI in association with the sector boundary passage as well as with large geomagnetic disturbances. These time-variations bear a close parallelism with those of the absolute value of VAI. It is inferred that the initial intrinsic state of the atmosphere is an important factor in controlling the ensuing sun-weather effect. If the variation of VAI with time is taken into account, varying effects reported by earlier workers can be fairly explained.