1. Earth System Physics Section; The Abdus Salam International Centre for Theoretical Physics; Trieste Italy
2. CEPAMOQ, Faculty of Science; University of Douala; Boulevard de la liberte Douala Cameroon
3. Département de Physique; Université Marien N'gouabi; Brazzaville Republic of Congo
4. AGRHYMET Regional Center; Niamey Niger
5. Faculté des Sciences et Techniques; Université Abdou Moumouni; Niamey Niger