Large scale properties of magnetic clouds:: Different approaches to estimate their orientation and impact parameter

Magnetic clouds are the interplanetary manifestation of solar ejecta that present distinctive properties when compared to the typical solar wind. We study a set of 20 magnetic clouds observed by the Wind spacecraft at 1 AU during a solar minimum. Assuming a cylindrical symmetry for the magnetic structure of the cloud, we estimate their (large scale) magnetic helicity content per unit length. For every cloud we analyze the variation of the computed helicity, using different approaches to determine the orientation of the cloud axis and its minimum distance to the spacecraft (i.e., the impact parameter Y-0). We explore different models (force free and non-force free fields) to reconstruct the magnetic structure of the clouds from the observations, which only give information along the (1D) spacecraft trajectory. Estimations of global magnitudes of magnetic clouds are one of the major keys used to link solar and interplanetary events; thus, the results presented here will help to refine the finding of this link from the interplanetary point of view.