Le guidage des whistlers par le champ magnetique

In this paper the question is examined of how the v.l.f. radio-waves are guided along the magnetic field. Energy passes through the magnetic field under two sets of conditions. Corresponding to the “nose-whistlers” explained by Helliwell, the first one occurs when the wave-normal itself is in the direction of the magnetic field. This does not happen in the second case when the remarkable property is also shown that all frequencies are propagated at the same velocity V₀ = cƒ_H/2ƒ₀ (ƒ_H gyrofrequency, ƒ₀ frequency of the plasma). Considerations of energy point out that, if such a propagation is not easily observable in the case of an isotropic emission, it is not the same thing for an emission produced by erenkov effect, which is able to produce all energy by this mode of propagation, provided the particle's velocity has a low fixed value (˜ 10,000 km/sec in the exosphere). All frequencies being emitted at the same time and following the same path wtih the same velocity, we can explain the broadband noise observed during the reception of whistlers. The required velocity of particles is exactly the velocity V₀. This coincidence is explained in an appendix, and extended to other anisotropic media.