NPG Nonlinear Processes in Geophysics NPG Nonlin. Processes Geophys. 1607-7946 Copernicus Publications Göttingen, Germany 10.5194/npg-6-235-1999 Energetic particle cross-field diffusion: Interaction with Magnetic Decreases (MDs) Tsurutani B. T. 1 Lakhina G. S. 2 Winterhalter D. 1 Arballo J. K. 1 Galvan C. 1 Sukurai R. 1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA Indian Institute of Geomagnetism, Colaba, Mumbai/Bamobay, India 31 12 1999 6 3/4 235 242 Copyright: © 1999 B. T. Tsurutani et al. 1999 This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Generic License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-nc-sa/2.5/ This article is available from https://npg.copernicus.org/articles/6/235/1999/npg-6-235-1999.html The full text article is available as a PDF file from https://npg.copernicus.org/articles/6/235/1999/npg-6-235-1999.pdf

Magnetic field Decreases (MDs) are detected in the heliospheric polar regions. The MDs have minimum spatial scales sizes of 25 proton thermal gyroradii, and are typically bounded by tangential or rotational discontinuities. The distribution of the magnitudes of the decreases within AIDs is a continuum, with the smallest decreases being most frequent in occurrence. The largest decreases can be 80% of the ambient field. The thickness distribution is also a continuum, and is shown to be independent of the field magnitude decrease. Charged particle interactions with the MDs lead to particle guiding center displacements and hence particle cross-held diffusion. We develop a diffusion model to apply to energetic ion interactions with MDs 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 extremely rapid due to such interactions.