Polar and tropical auroræ: And the isoauroral diagram
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After describing theisochasmic diagrams of Fritz and Vestine, which map the distribution of frequency of auroralvisibility from any point on the earth, it is pointed out that there is a need for a new type ofisoauroral diagram, showingisoaurores or lines of equal frequency ofoccurrence above any terrestrial point. The nature and “enumeration” of the isoaurores is discussed.
The few auroræ which have been reported as visible from India are discussed: namely (1) one reported from Benares on 1847 November 11, (2) one reported by J. D. Hooker as seen on 1848 Feb. 14, from a point on the Soane River at 24° 52′ N., 84° 22′ E.,—the validity of both these reports has been questioned—and (3) the undoubted case of the aurora of 1872 Feb. 4, seen as far south as Bombay, and from many more northerly points in India and elsewhere.
An appeal is made for a search by Indian scientists for material relating to Indian observations of these and possibly other auroræ.
KeywordsMagnetic Storm Geomagnetic Latitude Auroral Zone Geomagnetic Equator Auroral Visibility
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