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Volume 24, issue 12
Ann. Geophys., 24, 3313–3327, 2006
https://doi.org/10.5194/angeo-24-3313-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 24, 3313–3327, 2006
https://doi.org/10.5194/angeo-24-3313-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.

  21 Dec 2006

21 Dec 2006

Sun-Earth System Interaction studies over Vietnam: an international cooperative project

C. Amory-Mazaudier1, M. Le Huy2, Y. Cohen3, V. Doumbia4,*, A. Bourdillon5, R. Fleury6, B. Fontaine7, C. Ha Duyen2, A. Kobea4, P. Laroche8, P. Lassudrie-Duchesne6, H. Le Viet2, T. Le Truong2, H. Luu Viet2, M. Menvielle1, T. Nguyen Chien2, A. Nguyen Xuan2, F. Ouattara9, M. Petitdidier1, H. Pham Thi Thu2, T. Pham Xuan2, N. Philippon**, L. Tran Thi2, H. Vu Thien10, and P. Vila1 C. Amory-Mazaudier et al.
  • 1CETP/CNRS, 4 Avenue de Neptune, 94107 Saint-Maur-des-Fossés, France
  • 2Institute of Geophysics, Vietnamese Academy of Science and Technology , 18 Hoang Quoc Viet, Cau Giay, Hanoï, Vietnam
  • 3IPGP, 4 Avenue de Neptune, 94107 Saint-Maur-des-Fossés, France
  • 4Laboratoire de Physique de l'Atmosphère, Université d'Abidjan Cocody 22 B.P. 582, Abidjan 22, Côte d'Ivoire
  • 5Institut d'Electronique et de Télécommunications, Université de Rennes Bât 11D, Campus Beaulieu, 35042 Rennes, cédex, France
  • 6ENST, Université de Bretagne Occidentale, CS 83818, 29288 Brest, cédex 3, France
  • 7CRC , Faculté des Sciences, 6 Boulevard Gabriel, F 21004 Dijon cédex 04, France
  • 8Unité de Recherche Environnement Atmosphérique, ONERA, 92332 Chatillon, cédex, France
  • 9University of Koudougou, Burkina Faso
  • 10Laboratoire signaux et systèmes, CNAM, 292 Rue saint Martin, 75141 Paris cédex 03, France
  • *V. Doumbia previously signed V. Doumouya
  • **affiliation unknown

Abstract. During many past decades, scientists from various countries have studied separately the atmospheric motions in the lower atmosphere, in the Earth's magnetic field, in the magnetospheric currents, etc. All of these separate studies lead today to the global study of the Sun and Earth connections, and as a consequence, new scientific programs (IHY- International Heliophysical Year, CAWSES- Climate and Weather in the Sun-Earth System) are defined, in order to assume this new challenge. In the past, many scientists did not have the possibility to collect data at the same time in the various latitude and longitude sectors. Now, with the progress of geophysical sciences in many developing countries, it is possible to have access to worldwide data sets. This paper presents the particularities of geophysical parameters measured by the Vietnamese instrument networks. It introduces a cooperative Vietnamese-IGRGEA (International Geophysical Research Group Europe Africa) project, and presents, for the first time, to the international community, the geophysical context of Vietnam.

Concerning the ionosphere: since 1963, during four solar cycles, the ionosonde at Phu Thuy (North Vietnam) was operating. The Phu Thuy data exhibits the common features for the ionospheric parameters, previously observed in other longitude and latitude sectors. The critical frequencies of the E, F1 and F2 ionospheric layers follow the variation of the sunspot cycle. F2 and E critical frequencies also exhibit an annual variation. The first maps of TEC made with data from GPS receivers recently installed in Vietnam illustrate the regional equatorial pattern, i.e. two maxima of electronic density at 15° N and 15° S from the magnetic equator and a trough of density at the magnetic equator. These features illustrate the equatorial fountain effect.

Concerning the Earth's magnetic field: a strong amplitude of the equatorial electrojet was first observed by the CHAMP satellite at the height of 400 km in the Vietnamese longitude sector. In this paper we compare the ground magnetic observations of the Indian and Vietnamese magnetometer networks. This comparison highlights the regional structure of the amplitude of the equatorial electrojet, which is stronger in Vietnam than in India.

Concerning the monsoon: Vietnam exhibits a strong monsoon and has mainly one rainy season peaking in August, hence associated with the southwest monsoon flow. But some monsoon variability from one place to another is related to the orography. In the mountainous northern regions of Vietnam, there is an "early" monsoon peaking in July. In the coastal regions between 12° N and 19° N the monsoon season is centered on October.

Concerning lightning: Vietnam is a country of strong atmospheric storms with some areas of very intense lightning in North Vietnam (22,5° N, 105° E) and in South Vietnam (11° N, 107° E). In North Vietnam strong lightning is associated with the most intense rainy region.

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