Interplanetary magnetic clouds: Statistical patterns and radial variations Original Research Article

Pioneer Venus IMF data have been used to study the correlation between the structure of magnetic clouds in the inner heliosphere and the evolution of solar magnetic fields in the course of the solar cycle. We find that the leading polarity of these magnetic clouds follows the global polarity of the sunʹs magnetic field. In addition if we interpret the polarity structure of the clouds in terms of twisted magnetic fields, we find that the axes of these twisted ropes must vary greatly over the course of the solar cycle. The helicity of the ropes show no obvious pattern of behavior. Case studies of flux ropes seen at both Earth and the NEAR spacecraft are used to test a new technique for determining the radial variation of flux rope speeds.