Abstract

Magnetic observatory data from St. John's, on the Atlantic seaboard of Canada, and Victoria, near the Pacific seaboard, are analysed for coast effects at diurnal periods by comparison with similar records from inland observatories. The five international quiet days of August 1968 are studied. When resolved to geographic coordinates and adjusted to local solar time, the horizontal components of the daily variation are spatially uniform across the continent, but the vertical components vary greatly. Subtracting the vertical signal recorded at Ottawa (inland) from that recorded at St. John's demonstrates a long-period coast effect, with an anomalous vertical component leading the cross-shore horizontal component in phase by about an eighth of a cycle. Subtracting the vertical signal at Newport (inland) from that at Victoria demonstrates a similar but lesser effect. These results are consistent with the diurnal coast effect observed for two coasts of the Australian continent and for California. A Parkinson-type coast effect is interpreted to occur at the long periods of the daily variation, in addition to the substorm periods at which it has traditionally been observed.Separate from the coast effect, there is a substantial difference in the daily-variation vertical component between the two inland stations of Ottawa and Newport. This difference may be caused by a change in typical source-current configuration from one station to the other or it may indicate a contrast in electrical conductivity between the two inland regions of the continent. In the latter case the indication would be of higher conductivity to the east and lower conductivity to the west, the reverse of many currently accepted models.

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