The Importance to Solar-Terrestrial Physics of Amundsen’s and Scott’s Conjugate Observations of the Earth’s Magnetic Field

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• Alv Egeland (Department of Physics, University of Oslo)
• Wednesday 15 October 2014, 16:30-17:30
• Scott Polar Research Institute, main lecture theatre.

If you have a question about this talk, please contact Poul Christoffersen.

The ships Gjøa and Discovery sailed to the opposite ends of the Earth during the years 1902-06. Among the scientific goals of the two expeditions, was that of documenting the nature of the high latitude geomagnetic field and especially the location of the respective north and south magnetic dip poles (MDP). Both expeditions overwintered within 200 km of their respective poles, and, unwittingly, at nearly the same geomagnetic longitude, 240°. Thus, they were camped at opposite ends of the same geomagnetic field line. Their unique magnetic observations at Gjøahavn and Cape Armitage more than 100 years ago were at the same local geomagnetic time, but they were separated in local solar time by ~6 hours because of the tilt of the geomagnetic axis with respect to the geographic axis. This is important to the interpretation of the data, especially when the relationship of the high latitude geomagnetic field to the interplanetary magnetic field (IMF), is examined.

Indeed, the combined observations offer a glimpse of the solar wind fifty years before it was known to exist. After a brief review of the characteristics of the Earth’s magnetic field, the main facts found on diurnal and seasonal variations of the field at Gjøahavn will be compared with similar observations at Cape Armitage. These are unique observations of the geomagnetic field in the polar-regions decades before modern polar observatories were established. After comparing the data sets of the two expeditions and subjecting the data to modern analysis, we reached the following conclusions:

Amundsen and Scott were the first to demonstrate that the north and south magnetic dip-poles do not have a permanent location, but move their position in a regular manner on average. The activity was more intense in the local summer than in the local winter. The wavelike, diurnal variation in the field at Cape Armitage mimics the Gjøahavn data almost exactly.

The quality of these magnetic observations may be shown 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 interplanetary magnetic field in the solar wind called the .Svalgard-Mansurov effect (SME). From this comparison, we found that the solar wind and its temporal variations were similar to what we observe today. For stations near 80 degrees magnetic latitude we conclude that the SME is not a UT effect, but maximizes near magnetic noon.

Our motivation for this study has been to illuminate the contributions of Amundsen and Scott as scientists. Their contributions are important to the world-wide survey of the Earth’s magnetic field in the early 20th century.

This talk is part of the Scott Polar Research Institute - Polar Physical Sciences Seminar series.

This talk is included in these lists:

• AUB_Cambridge Seminars
• Climate Science Seminars within Cambridge
• Department of Geography
• Scott Polar Research Institute - Polar Physical Sciences Seminar
• Scott Polar Research Institute, main lecture theatre
• seminars

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