PHYSICAL-MECHANISMS OF MAN-MADE INFLUENCES ON THE MAGNETOSPHERE

Since the discovery of the Luxembourg effect in the 1930s, it is clear that man-made activities can perturb the ionosphere and the magnetosp here. The anthropogenic effects are mainly due to different kinds of w aves coming from the Earth's surface. Acoustic gravity waves are gener ated by large explosions, spacecraft launches, or fight of supersonic planes. Electromagnetic waves are active in different frequency ranges . Power line harmonic radiation which is radiated in the ELF range by electrical power systems can be observed over industrial areas. At VLF and HF, the ground-based transmitters used for communications or radi o-navigation heat the ionosphere and change the natural parameters. A large variety of phenomena is observed: wave-particle interaction, pre cipitation of radiation belt electrons, parametric coupling of EM whis tler waves, trigger ed emissions, frequency shift, and whistler spectr um broadening. This paper will review the different physical mechanism s which are relevant to such perturbations, The possibility of direct chemical pollution in the ionosphere due to gas releases is also discu ssed.