grplinst

grplinst (“group–plasma instabilities”) is an extension for the CRPropa 3 propagation code. It models the energy losses that plasma instabilities induced by interactions of cascade electron–positron pairs interacting with the intergalactic medium (IGM).

The module supplies:

• a family of PlasmaInstability* modules that plug straight into a CRPropa ModuleList, each implementing a different literature prescription for the instability cooling time;
• Flow classes that describe the pair-beam density the cascade drives into the IGM;
• MediumDensity and MediumTemperature classes that describe the ambient plasma;
• helper functions such as plasmaFrequency and maximumLinearGrowthFrequency;
• full Python bindings through SWIG, so every component can be configured, sub-classed, and combined from Python.

A word of caution. Plasma instabilities in a dilute relativistic pair beam are a genuinely hard kinetic problem. grplinst does not solve it from first principles; it wraps a set of effective cooling prescriptions taken from the literature and lets you compare them within the same cascade simulation. A fully self-consistent treatment requires particle-in-cell (PIC) methods. Please read the Physics Background page before drawing quantitative conclusions.

Where to go next

A thirty-second example

from crpropa import *
from grplinst import *

# ambient intergalactic medium and pair beam
temperature = MediumTemperatureHomogeneous(1e4) # K
density = MediumDensityHomogeneous(0.1) # m^-3
beam = FlowHomogeneous(1e38, Vector3d(0, 0, 0)) # source luminosity in W

# one instability prescription, ready to drop into a ModuleList
plinst = PlasmaInstabilityBroderick2012(beam, density, temperature)

sim = ModuleList()
sim.add(SimplePropagation(1e-3 * kpc, 10 * Mpc))
sim.add(Redshift())
sim.add(plinst)

A complete, physically meaningful pipeline (with pair production and inverse-Compton scattering) is given on the Usage page and in examples/testPlugin.py.

Citing grplinst

If grplinst contributes to your work, please cite the method paper:

“Simulations of Electromagnetic Cascades in the Intergalactic Medium with Plasma Instabilities: the grplinst code”
R. Alves Batista, A. Saveliev
[doi] || [arXiv]

See References for the full bibliography, including the origin of each instability model.