The Magnetic Storm and Solar Disturbance of June 17, 1915

Abstract

THE magnetic storm described in NATURE of June 24 by the Rev. A. L. Cortie seems to have been larger at Stonyhurst than at Kew. The extreme westerly position of the declination needle at Kew occurred about 1.30 p.m., and the extreme easterly position about 5.37 p.m., the total range being about 72â. Between 5 and 6 p.m. the movements had a range of 61′. I am not clear which of the two corresponds to the 91.5â mentioned by Father Cortie, but either is substantially less, even allowing for the fact that the strength of the horizontal field is about 6 per cent, higher at Kew than at Stonyhurst. This is, of course, quite in accordance with the usual tendency for disturbance to be greater in higher latitudes, but it helps to illustrate the fact that whatever the ultimate source may be, terrestrial position counts for a good deal. The total range shown by the horizontal force at Kew was about 460η (Iη = 1 × 10^â5 C.G.S.), the maximum occurring about 5.42 p.m., and the minimum about 9.30 a.m.