Survival of discrete structures in the solar wind

Survival time scales are estimated for structures ejected from the sun into the solar wind, which are subject to decay processes during their transit from the sun to the earth. With the assumption that the structures are magnetic, MHD estimates are made to determine the time scales for reconnection into the ambient magnetic field. It is found that for structures smaller than a few tens of Mm at the sun, the probability of surviving the transit to the earth is low. The transition in size between structures that survive the sun-earth transit and those that do not (20-30 Mm at the sun) corresponds to scales of (4-6) x 10 to the 11th cm at the earth orbit (assuming radial expansion).