Custom field and MHD grid

Dictionary: custom_field_params · Class: CustomFieldParams

Used by: all functions

Custom internal field (Gauss coefficients) and MHD grid configuration.

Key	Type	Default	Description
g	list or None	None	Custom Gauss g coefficients. Required when internalmag="Custom Gauss".
h	list or None	None	Custom Gauss h coefficients. Required when internalmag="Custom Gauss".
max_degree	int	13	Maximum spherical harmonic degree/order used when expanding the internal field from Gauss coefficients. Higher = more accurate near Earth but more computation; capped at the underlying coefficient table's degree (IGRF: 13; "Dipole" is forced to degree 1 regardless of this value).
MHDfile	str or None	None	Path to an MHD simulation output file. Required when externalmag="MHD"; OTSO validates the file exists before running.
MHDcoordsys	str or None	None	Coordinate system the MHD file's grid positions and field components are given in (any of OTSO's Cartesian systems, e.g. "GSM", "GEO"). OTSO rotates positions into this frame and the interpolated field back, so it can be combined with any internalmag.
MHDgridtype	str	"auto"	How grid cells are found: "auto" detects per-axis spacing, "uniform" forces the fast fixed-spacing lookup (only correct if every axis is evenly spaced), "stretched" forces the general lookup for grids whose spacing varies (e.g. finer near Earth).
MHDinterpolation	str	"trilinear"	How the field is reconstructed between grid points: "trilinear" (fast, kinked gradients at cell faces), "tricubic" (smooth, much more accurate in smooth regions, can overshoot near sharp features), "monotonic" (tricubic with overshoot limiting; recommended), "divfree" (curl of an interpolated vector potential; exactly divergence-free, for long quasi-trapped trajectories, less point-wise accurate). Works on uniform and stretched grids. See MHD input.