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The Spatial Distribution of Rapid Geomagnetic Fluctuations: Part II |
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| Abstract: | i A detailed examination has been made of some examples of rapid irregular magnetic field changes which occurred during a typical geomagnetic storm, selected from 180mm/h recordings. The following points were noted: 1. At a number of different times of day, the rapid irregular changes at a given observing station were extremely various. They varied widely in form, and loops ranged in shape from nearly linear ones to crude circles. 2. During a chosen interval, the rapid irregular changes at neighbouring stations were very similar, and between mid-latitude stations 1200 km apart there was still a strong relationship between the changes occurring during defined time intervals. 3. Phase differences between stations, during the chosen interval, were very small. The average phase gradient North to South was less than 0.5 ～ 10– 4. Vector diagrams of increments between selected times indicated large scale patterns in which the horizontal vectors tended to converge, the points of convergence being variable in position. To this extent, the changes examined cannot be distinguished either from micropulsations or from slow irregular variations. 5. Some of the evidence suggested a type of current circulation which either travelled eastwards as a whole, or spread in extent, while pulsating in amplitude. 6. The average phase gradient East to West and the suggestion of an eastward moving current circulation, both referring to daylight hemisphere changes, are reminiscent of a deduction by Dungey concerning propagation of waves on the Chapman-Ferraro surface. |
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