Evaluating single spacecraft observations of planetary magnetotails with simple Monte Carlo simulations: 2. Magnetic flux rope signature selection effects

A Monte Carlo method of investigating the effects of placing selection criteria on themagnetic signature of in situ encounters with flux ropes is presented. The technique is applied to two recentflux rope surveys of MESSENGER data within the Hermean magnetotail. It is found that the different criteriaplaced upon the signatures will preferentially identify slightly different subsets of the underlying population.Quantifying the selection biases first allows the distributions of flux rope parameters to be corrected,allowing a more accurate estimation of the intrinsic distributions. This is shown with regard to thedistribution of flux rope radii observed. When accounting for the selection criteria, the mean radius ofHermean magnetotail quasi-force-free flux ropes is found to be589+273−269km. Second, it is possible toweight the known identifications in order to determine a rate of recurrence that accounts for the presenceof the structures that will not be identified. In the case of the Hermean magnetotail, the average rateof quasi-force-free flux ropes is found to 0.12 min−1when selection effects are accounted for (up from0.05 min−1previously inferred from observations).