code: def calc_gs_eta(b, ne, delta, sinth, nu):
      
      s = nu / calc_nu_b(b)
      return (b * ne *
              3.3e-24 *
              10**(-0.52 * delta) *
              sinth**(-0.43 + 0.65 * delta) *
              s**(1.22 - 0.90 * delta))
docs: Calculate the gyrosynchrotron emission coefficient η_ν.
  
      This is Dulk (1985) equation 35, 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 emission coefficient (AKA "emissivity"), in units
      of ``erg s^-1 Hz^-1 cm^-3 sr^-1``.
  
      No complaints are raised if you attempt to use the equation outside of its
      range of validity.