Energetic particle cross-field diffusion: Interaction with Magnetic Decreases (MDs)

Magnetic field Decreases (MDs) are detected in the heliospheric polar regio ns. The MDs have minimum spatial scales sizes of 25 proton thermal gyroradi i, and are typically bounded by tangential or rotational discontinuities. T he distribution of the magnitudes of the decreases within MDs is a continuu m, with the smallest decreases being most frequent in occurrence. The large st decreases can be similar to 80% of the ambient field. The thickness dist ribution is also a continuum, and is shown to be independent of the field m agnitude decrease. Charged particle interactions with the MDs lead to parti cle guiding center displacements and hence particle cross-field diffusion. We develop a diffusion model to apply to energetic ion interactions with MD s using the MD properties described in this paper. One specific day of data is used to illustrate that the particle cross-field diffusion will be extr emely rapid due to such interactions.