Roald Amundsen's contributions to our knowledge of the magnetic fields of the Earth and the Sun
Abstract. Roald Amundsen (1872–1928) was known as one of the premier polar explorers in the golden age of polar exploration. His accomplishments clearly document that he has contributed to knowledge in fields as diverse as ethnography, meteorology and geophysics. In this paper we will concentrate on his studies of the Earth's magnetic field. With his unique observations at the polar station Gjøahavn (geographic coordinates 68°37'10'' N; 95°53'25'' W), Amundsen was first to demonstrate, without doubt, that the north magnetic dip-pole does not have a permanent location, but steadily moves its position in a regular manner. In addition, his carefully calibrated measurements at high latitudes were the first and only observations of the Earth's magnetic field in the polar regions for decades until modern polar observatories were established. After a short review of earlier measurements of the geomagnetic field, we tabulate the facts regarding his measurements at the observatories and the eight field stations associated with the Gjøa expedition. The quality of his magnetic observations may be seen to be equal to that of the late 20th century observations by subjecting them to analytical techniques showing the newly discovered relationship between the diurnal variation of high latitude magnetic observations and the direction of the horizontal component of the interplanetary magnetic field (IMF By). Indeed, the observations at Gjøahavn offer a glimpse of the character of the solar wind 50 yr before it was known to exist. Our motivation for this paper is to illuminate the contributions of Amundsen as a scientist and to celebrate his attainment of the South Pole as an explorer 100 yr ago.