Communication to : 12th international conference on methods of aerophysical research (ICMAR 2004), Novosibirsk (Russie), 28 Juin - 1 Juillet 2004Available from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.2004 n.230 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc