{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "# Hollweg Dispersion Solver\n", "\n", "[hollweg]: ../../api/plasmapy.dispersion.numerical.hollweg_.hollweg.rst\n", "[bellan2012]: https://doi.org/10.1029/2012JA017856\n", "[hollweg1999]: https://doi.org/10.1029/1998JA900132\n", "\n", "This notebook details the functionality of the [hollweg()][hollweg] function. This function computes the wave frequencies for given wavenumbers and plasma parameters based on the solution to the two fluid dispersion relation presented by [Hollweg 1999][hollweg1999], and further summarized by [Bellan 2012][bellan2012]. In his derivation Hollweg assumed a uniform magnetic field, zero D.C electric field, quasi-neutrality, and low-frequency waves ($\\omega \\ll \\omega_{ci}$), which yielded the following expression\n", "\n", "$$\n", " \\left( \\frac{\\omega^2}{{k_z}^2 {v_A}^2} - 1 \\right)\n", " \\left[\\omega^2\n", " \\left(\\omega^2 - k^2 {v_A}^2 \\right)\n", " - \\beta k^2 {v_A}^2 \\left( \\omega^2 - {k_z}^2 {v_A}^2 \\right)\n", " \\right] \\\\\n", " = \\omega^2 \\left(\\omega^2 - k^2 {v_A}^2 \\right) {k_x}^2 \\left(\n", " \\frac{{c_s}^2}{{\\omega_{ci}}^2} - \\frac{c^2}{{\\omega_{pe}}^2}\n", " \\frac{\\omega^2}{{k_z}^2 {v_A}^2} \\right)\n", "$$\n", "\n", "where\n", "\n", "$$\\beta = c_{s}^2 / v_{A}^2$$\n", "\n", "$$k_{x} = k \\sin \\theta$$\n", "\n", "$$k_{z} = k \\cos \\theta$$\n", "\n", "$$\\mathbf{B_{o}} = B_{o} \\mathbf{\\hat{z}}$$\n", "\n", "$\\omega$ is the wave frequency, $k$ is the wavenumber\n", ", $v_{A}$ is the Alfvén velocity, $c_{s}$ is the ion\n", "sound speed, $\\omega_{ci}$ is the ion gyrofrequency, and\n", "$\\omega_{pe}$ is the electron plasma frequency.\n", "\n", "