  The conversion nu_L -> nu_R gamma^* of a neutrino with a magnetic moment is
considered, caused by the additional Wolfenstein energy acquired by a
left-handed neutrino in medium, with an accurate taking account of the photon
\gamma^* dispersion in medium. It is shown that the threshold arises in the
process, caused by the photon (plasmon) effective mass. This threshold leaves
no room for the so-called "neutrino spin light" in the most of astrophysical
situations.
