Peculiar features of some high-latitude magnetic impulse events
Similarities and dissimilarities of magnetic impuels (MIE) recorded at the chain of six northernmost stations of IMAGE magnetometer array and visualized in forms of (a) stacked magnetograms, (b) sequences of equivalent overhead currents (OC) for these stations, and (c) sequences of elements of time-dependent covariance matrics (TCM) are analysed. Ad hoc MIE types - one "ordinary", and three "strange" - are discerned as a result of this analysis. The existence of these types, as well as of the MIE features not utilized to separate the types, leads to the conclusion that three is a great, hitherto depreciated influence of horizontal irregularities in ionospheric Hall (sigma)H and Pedersen (sigma)P integrated conductivities in the behaviour of geomagnetic phenomena of small and middle scale. One of these "strange" MIE types, for which a minimum in magnetic variations amplitude is visible at the station under the MIE's center trace, gets a simple explanation using the assumption of a small-scale irregularity of (sigma)H over this station and nearby area, when compared with other stations. Somewhat more complicated explanations will probably be needed for two other "strange" types. It seems, however, that they will also be possible using proper assumptions on distributions of (sigma)H and/or (sigma)P over the array of magnetometer stations. An additional substantial conclusion resulting from the evident great role of (sigma)H- irregularities is that the localization of MIE's (centers)according to maximum amplitude of magnetic variations, as done in some paper, may result in large errors.
Bibliogr. 11 poz.