Goodness and limitations of minimum variance analysis

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

Mérida

Congreso; VIII Conferencia Latinoamericana de Geofísica Espacial (VIII COLAGE); 2007

Asociación Latinoamericana de Geofísica Espacial

The minimum variance (MV) analysis is one of the methods commonly used to find the orientation of a magnetic cloud; this technique is independent of the model used to describe its structure. It is known that MV gives better estimations for the cloud axis when the distance between the trajectory of the spacecraft and the cloud axis is low respect to the cloud size. We analyze here the goodness and limitations of this technique to find the spatial orientation of magnetic clouds when this distance is not low, and how much it changes the estimations of their global magneto-hydrodynamic magnitudes. Thus, we generate a set of synthetic static and cylindrical clouds with different orientations, and compare the synthetic clouds with the results obtained from applying them the MV method, improving the knowledge of the bias introduced by MV. Then, we analyze a set of observed clouds and compare the results using MV and a method that simultaneously fits of physical and geometrical parameters of the cloud.