da Silva Invariants

Note

This package provides tools for radiation belt physicists to calculate the adiabiatic invariants K and L* from gridded models of Earth’s magnetic field. This package supports the T96 and TS05 empirical Tsyganenko magnetic field models, SWMF and LFM MHD simulation output, and data on an arbitrary structured grid.

[Paper] [Poster]

Table of Contents

Installing

To use this module, install the conda environment file (or copy it into your own), which will also install the module. The ability to compile fortran files is required.

$ conda env create -f environment.yml
$ conda activate dasilva-invariants

Brief Tour

Calculating L* from TS05

Below is code which calculates L* using the magnetic fields obtain from TS05 and placed on a regular grid, for a particle observated with a pitch angle of 60° observed at (-6.6, 0, 0) R E (SM coordinate system).

from dasilva_invariants import models, invariants
from datetime import datetime
import numpy as np

# Get TS05 model input parameters
time = datetime(2015, 10, 2)
url = "http://mag.gmu.edu/ftp/QinDenton/5min/merged/latest/WGparameters5min-latest.d.zip",
params = models.get_tsyganenko_params(time, url)

# Evaluate TS05 model on regular grid
axis = np.arange(-10, 10, 0.15)
x, y, z = np.meshgrid(axis, axis, axis)
model = models.get_tsyganenko(
    "TS05", params, time,
    x_re_sm_grid=x,
    y_re_sm_grid=y,
    z_re_sm_grid=z,
    inner_boundary=1
)

# Calculate L*
result = invariants.calculate_LStar(
    model,
    starting_point=(-6.6, 0, 0),
    starting_pitch_angle=60
)

print(f"L* = {result.LStar}")

Calculating K from SWMF

This code calculates the second adiabatic invariant K for a particle bouncing through (-6.6, 0, 0) R E (SM coordinate system) and mirroring at at 50° magnetic latitude, using magnetic fields from SWMF simulation output in CDF format (as obtained from the CCMC).

from dasilva_invariants import models, invariants

model = models.get_model(
    "SWMF_CDF",
    "3d__var_1_e20151221-001700-014.out.cdf"
)

result = invariants.calculate_K(
    model,
    starting_point=(-6.6, 0, 0),
    mirror_latitude=50
)

print(f"K = {result.K}")