Mie Extinction

Computing Mie Scattering

Although the package <a href=”dustmodel.html”>dust</a> is primarily aimed at modelling emission from interstellar dust at mid/far IR wavelengths it has the facilities to compute both Mie <em>scattering</em> and <em>absorption</em>. The figure below shows the type of output that you will get from the Mie calculation.

Extinction of spherical graphite grain  perpendicular to the planes

Example script

This is a python script which calls the pydust library to compute the Mie absorption and scattering efficiencies:

def MieCalc(wavel,
            radius,
            eps_real,
            eps_imag):
    """
    Calculate absorption and scattering using Mie theory.

    :param wavel: Wavelengh

    :param rad: Radius of the grain (units of wavel and rad must be
    the same but are otherwise not important)

    :param eps_real: Real part of the dielectric constant

    :param eps_imag: Imaginary part of the dielectric constant

    :returns: (Absorption efficiency, scattering efficiency)

    """

    xs=pydust.dust_miexsect()
    pydust.dust_miecalc(wavel,
                        radius,
                        eps_real,
                        eps_imag,
                        xs)
    c= radius**2 * math.pi
    return (xs.Cabs/c,
            xs.Csca/c)

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