Results of detailed numerical calculations of some parametric decay effects, arising in a magnetoplasma under the influence of HF, sufficiently strong electric field E↘=E↘p ⋅ cos &ohgr;Et, are given in this paper. The resonance branches and the VLF parametric resonances are calculated in the ionosphere at altitudes Z=200, 300, and 400 km. Calculations in the resonance regions &ohgr;E=s&ohgr;0 (&ohgr;0 is the electron Langmuir frequency, s=1,2,...) were done in the cold plasma and also in the kinetic approximations. It is shown that the angle dependence &ohgr;1(&THgr;, Ep≠0) of the ELF (0<&ohgr;≤&OHgr;B) resonance branch is close to the cosine law. This is in contrast with the earlier published results and with the angle dependence &ohgr;1(&THgr;, E=0). This important effect and the other dependencies given in the paper may be used for the search of the parametric instabilities and of the electric field in the ionosphere and magnetosphere, especially by experiments in situ on satellites. ¿ American Geophysical Union 1995