Magnetic clouds orientations using minimum variance analysis

GULISANO, A.M.; DASSO, S.; MANDRINI, C.H.; DÉMOULIN, P.

Capilla del Monte, Córdoba, Argentina

Congreso; 49 Reunión de la Asociación Argentina de Astronomía; 2006

Magnetic clouds (MCs) at 1 AU present distinctive characteristics from the surrounding solar wind. The minimum variance (MV) technique applied to a temporal series of magnetic  data observed on a satellite trajectory  can find the orientation of the principal axis very well when the distance to the cloud axis (i. e. impact parameter, p) is negligible; when this is not the case the direct application of this technique can be questionable. In this work we generate a set of synthetic clouds with different orientations and p. These clouds are modeled assuming local cylindrical symmetry and a linear force free field for their magnetic configuration. Our goal is to treat the magnetic field values of these synthetic clouds as if they were data observed by a satellite, and estimate the error that the direct application of MV introduces when p is not small. These results are useful to improve the estimations of global magneto-hydrodynamic magnitudes in interplanetary magnetic clouds.