<p> MAGNETIC OBSERVATORIES IN ANTARCTICA</p><p>Some historical landmarks</p><p>The magnetic measurement history in Antarctica and surrounding oceans traces back to the expeditions aiming at South magnetic pole tracking (see Fogg, 1992 for a review). Until the turn of the nineteen/twentieth century, all measurements were performed at sea, with instruments steadily improved, including Gauss (E. Drygalski expedition, 1901-1903) and </p><p>Discovery (first R.F. Scott expedition, 1901-1904), both ships being equipped with a magnetic observatory (Lüdecke, 2003). The first confirmed landing (although certainly not really the first one), is to be credited to C. Borchgrevink’s expedition (1893-1895) whose party reached Cape Adare and did there some magnetic measurements (Fogg, 1992). The first significantly long lasting records were performed at the observatory of Orcadas del Sur (South</p><p>Orkneys, IAGA code ORC ) founded by R.C. Mossman in 1903, during the expedition led by </p><p>W.S. Bruce, 1902-1904, (Moneta 1951). Most annual means of the magnetic elements are available there since 1905 up to now. Other observatories had a rather short life time: Hut </p><p>Point (Discovery bay) set up by the first R.F. Scott expedition (1902-1903), Cape Evans </p><p>(1911-1912) opened during the tragic second expedition headed by R.F. Scott, Cape Denison </p><p>(1912-1913) opened by D. Mawson, Little America (May 1929 - February 1930; February </p><p>1934-February 1935). Thus, during the first half of the twentieth century, apart from the long lasting ORC observatory, the efforts were scarce and ephemeral. Things changed after the second world war. It seems that P.N. Mayaud pioneered this new era with the observatory of </p><p>Port Martin built in 1951 (Mayaud, 1953). Unfortunately, the station burned down two years later. Whereas the first International Polar Year (1882-1883) which came to early for </p><p>Antarctica, and the second IPY (1932-1933) launched in an economically depressed context, did not give rise to scientific activities in Antarctica, the very start of magnetic observations in</p><p>1 Antarctica was given by the first International Geophysical Year (1957) which boosted the opening of a noticeable number of observatories, jumping from 4 to 14. All of the observatories recorded field variations on analog photographic magnetograms, according to common practice in use before the advent of digital records in the nineteen seventies (the first reported digital records were performed at Dumont d’Urville in 1969).</p><p>Situation at the beginning of the 21th century</p><p>The present day more or less permanent sites may be divided into three types: standard observatories, with or without regular absolute measurements, unmanned magnetometer chains devoted to external field studies and repeat stations, the two latter being beyond the scope of this review. According to J.L. Rasson (2001), altogether 44 observatories opened during various time spans at geographic latitudes higher than 60° S, which we have retained as limit of the area. Figure 1 displays the location of the observatories and magnetometer chains with respect to geographic and geomagnetic coordinates, including in addition two </p><p>Japanese observatories (Mizuho and Dome Fuji). It shows that 8 observatories were located on the ice cap, away from possible crustal field contamination. Vostok is the only survival of this on-land group not taking into account the new base currently opening at DomeC (French-</p><p>Italian Concordia station). Regarding the time span covered by the records, ORC is the only observatory, opened before the first IPY, which continues its activity nowadays. If we restrict our analysis to the observatories set up around the first IPY, the time span they cover is highly variable, ranging from one year or so to nearly the full range 1957-2004. Mawson (IAGA code MAW) is the observatory yielding the most complete set of data (Hopgood, 2002). Since the start up initiated by the first IPY, the number of open observatories has remained stable around 14. In 2005, thirteen are still running. All of them yield relative records complemented</p><p>2 by base line control afforded by absolute measurements. The quality of this control is variable. It ranges from episodical measurements performed during summer campaigns to full year range in the bases staffed during winter and hosting qualified observers (AIA, CSY, </p><p>DRV, MAW, MIR, NVL, ORC, SBA, SYO, VOS), the most accurately controlled base line being yielded by the Intermagnet observatories (AIA, DRV, SBA) and MAW.</p><p>The history of the magnetic observatories in Antarctica closely reflects the history of the discovery of this mysterious and hardly accessible continent and development of its human knowledge. From the beginning to nowadays, the concerns dealt with main field description as well as with solar-terrestrial science. In both topics, the magnetic observatories played and still continue to play a prominent role.</p><p>Acknowledgements</p><p>Updated information were provided by A. Kadokura, (N.IC.T., Japan), V.O. Papitashvili </p><p>(University of Michigan, Ann Arbor), P. Crosthwaite, Geoscience Australia, and A. </p><p>Eckstaller, Alfred Wegener Institute, Bremen, Germany.</p><p>Jean-Jacques Schott, Jean Rasson</p><p>References</p><p>Fogg, G.E., 1992. A history of Antarctic science. Cambridge University Press.</p><p>Hopgood, P.A., 2004. Australian Geomagnetism Report 2002, 50, pp. 79:81.</p><p>Lüdecke, C., 2003. Scientific collaboration in Antarctica (1901-04) : a challenge in times of </p><p> political rivalry. Polar Record, 39, 35-48.</p><p>Mayaud, P.N., 1953. Champ magnétique moyen et variation séculaire en Terre Adélie au 1er </p><p> janvier 1952. C.R. Acad. Sci. Paris, 256, 954-956.</p><p>3 Moneta J.M., 1951. Cuatro Años en las Orcadas del Sur. Peuser : Buenos Aires.</p><p>Rasson, J.L., 2001. The status of the world-wide network of magnetic observatories, their location and instrumentation. In Proceedings IXth IAGA Workshop, 2000. Contributions to </p><p>Geophysics and Geodesy, 31, pp. 427-454</p><p>Cross references</p><p>History of geomagnetism</p><p>IAGA</p><p>Magnetometers</p><p>Observatories, global network</p><p>4 5 Figure 1. Location of the magnetic observatories in Antarctica. Large full triangles: open; stars: Intermagnet observatories; small open squares: closed. Dotted lines: geomagnetic coordinates according to the 2005 IGRF model.</p><p>6</p>