  A time resolved analysis of the emission of HiPIMS plasmas reveals
inhomogeneities in the form of rotating spokes. The shape of these spokes is
very characteristic depending on the target material. The localized enhanced
light emission has been correlated with the ion production. Based on these
data, the peculiar shape of the emission profiles can be explained by the
localized generation of secondary electrons, resulting in an energetic electron
pressure exceeding the magnetic pressure. This general picture is able to
explain the observed emission profile for different target materials including
gas rarefaction and second ionization potential of the sputtered elements.
