Calculate the gyrosynchrotron absorption coefficient κ_ν.

    This is Dulk (1985) equation 36, which is a fitting function assuming a
    power-law electron population. Arguments are:

    b
      Magnetic field strength in Gauss
    ne
      The density of electrons per cubic centimeter with energies greater than 10 keV.
    delta
      The power-law index defining the energy distribution of the electron population,
      with ``n(E) ~ E^(-delta)``. The equation is valid for ``2 <~ delta <~ 7``.
    sinth
      The sine of the angle between the line of sight and the magnetic field direction.
      The equation is valid for θ > 20° or ``sinth > 0.34`` or so.
    nu
      The frequency at which to calculate η, in Hz. The equation is valid for
      ``10 <~ nu/nu_b <~ 100``, which sets a limit on the ratio of ``nu`` and ``b``.

    The return value is the absorption coefficient, in units of ``cm^-1``.

    No complaints are raised if you attempt to use the equation outside of its
    range of validity.

def calc_gs_kappa(b, ne, delta, sinth, nu):
    """Calculate the gyrosynchrotron absorption coefficient κ_ν.

    This is Dulk (1985) equation 36, which is a fitting function assuming a
    power-law electron population. Arguments are:

    b
      Magnetic field strength in Gauss
    ne
      The density of electrons per cubic centimeter with energies greater than 10 keV.
    delta
      The power-law index defining the energy distribution of the electron population,
      with ``n(E) ~ E^(-delta)``. The equation is valid for ``2 <~ delta <~ 7``.
    sinth
      The sine of the angle between the line of sight and the magnetic field direction.
      The equation is valid for θ > 20° or ``sinth > 0.34`` or so.
    nu
      The frequency at which to calculate η, in Hz. The equation is valid for
      ``10 <~ nu/nu_b <~ 100``, which sets a limit on the ratio of ``nu`` and ``b``.

    The return value is the absorption coefficient, in units of ``cm^-1``.

    No complaints are raised if you attempt to use the equation outside of its
    range of validity.

    """
    s = nu / calc_nu_b(b)
    return (ne / b *
            1.4e-9 *
            10**(-0.22 * delta) *
            sinth**(-0.09 + 0.72 * delta) *
            s**(-1.30 - 0.98 * delta))