Struct

`space::irbem::PathTraceOptions`

cheatah-space v0.1.0-alpha — Biome Standard 0.6.5-alpha

Tuning for the path-returning traces.

Defaults match lstar.hpp's TraceOptions where the two overlap, so a Bmin from find_magequator and a Bmin from trace_invariant are the same number computed on the same grid rather than two resolutions of the same idea.

Constants & variables

var double r0 #

The reference surface the trace terminates on, Earth radii — IRBEM's R0.

Values below 1 are legal and meaningful: a drift-loss-cone study wants the line followed below the surface.

var double steps_per_l #

Steps per unit L, as TraceOptions::steps_per_l.

ds = L/steps_per_l, with L the start point's dipole L — see lstar.hpp's brief on why the step is proportional to L.

var double step_size #

An ABSOLUTE step in Earth radii, overriding steps_per_l when positive.

This is what IRBEM's TRACE_FIELD_LINE_TOWARD_EARTH takes as its ds, and the only reason it exists: a caller who wants uniform sampling for a plot should not have to work backwards from L.

var int max_steps #

The cap on RK4 steps in ONE direction. Reaching it is Status::OpenFieldLine.

var int refine_iterations #

Regula-falsi iterations inside the final step, for every sub-step refinement here.

Eight takes the residual below the fp64 noise of the field evaluation itself; the cost is eight field evaluations against a trace's several hundred.