Inversion studies of magnetic cloud structure at 0.7 AU: Solar cycle variation

Pioneer Venus observations from 1979-1988 have revealed the solar cycle evo lution of magnetic clouds in the inner heliosphere. Non-force-free magnetic rope models, fit to 44 magnetic clouds, allow us to determine the structur es of these clouds and compare their properties with potential field maps o f their solar source regions. The leading magnetic polarity in these clouds is correlated with the polarity of the sun's global field. The axis of sym metry of the clouds varies with the inclination of the magnetic streamer be lt. At 0.72 AU, the median radius of a magnetic flux rope is 0.10 AU. The m edian rope contains 11 TWb and carries 0.5 GAmps of parallel electric curre nt. The occurrence frequency of different handedness of the ropes is equall y left and right throughout the solar cycle and shows no correlation with o ther modeled parameters.