Crossing of Plasma Structures by Spacecraft: A Path Calculator

When spacecraft (s=c) missions probe plasma structures (PS) the relative location of the s=c with respect to the PS is unknown. This information is however needed to mea sure the geometrical features of the PS (orientation and thickness) and to understand the physical processes underlying the PS dynamics. Methods to determine the s=c location exist but they need strong assumptions to be satis ed (stationarity and special spatial dependencies). This reduces the number of treatable cases, aects severely the results and demands the assumptions to be valid for the entire PS. These methods are not so able to discriminate the local variations of the PS features during the s=c crossing. In this paper we present new methods to compute the s=c trajectory through weakly stationary PSs allowing one to avoid such limitations. The methods are tested both on arti cial and real data, the latter provided by the Magnetospheric MultiScale (MMS) mission probing the Earth's magnetopause (MP). 1D and 2D trajectories of the MMSare found that can be used as an initial step for future reconstruction studies. Advanced minimization procedures to optimize the results are discussed.