Letter | Published:

Magnetic Storm and Aurora, December 16-17

    Naturevolume 100page344 (1918) | Download Citation



    ON the magnetic traces at Kew Observatory, Richmond, Surrey, there were indications of disturbance shortly after 8h. on December 16, but no striking movements until after 14h. (2 p.m.). Activity was greatest between 16h. and midnight of December 16, but some considerable movements appeared after midnight, and the disturbance did not die down until after 4h. on December 17. The range of declination (D) was about 34′, the ranges of horizontal force (H) and vertical force (V) being respectively about 400y and 250y. The needle reached its extreme westerly position about 14h. 40m., and its extreme easterly position just after 21h. Its largest continuous movement was a swing of 23 to the west, occupying about thirty-five minutes, and ending just after 22h. The highest and lowest values of H occurred about 17h. and 21h. 15m. respectively; between these hours there was a general tendency to fall. A very rapid movement in H ended just before 21h. 15m., the element falling 215y in less than ten minutes. Between the end of this movement and 2h. 25m. on December 17, H rose almost 350 y.

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