  Magnetic fields mix axions with photons, allowing for the cyclotron process e
-> e + a by virtue of an intermediate plasmon even if axions do not couple to
electrons at tree level. The axion and longitudinal-plasmon dispersion
relations always cross for a certain wave number, leading to a resonant
enhancement of this process. Even then, however, it cannot quite compete with
the usual nucleon processes in a supernova core. The well-known axion window
10^{-5} eV < m_a < 10^{-2} eV remains open and axions may still constitute the
cosmic dark matter.
