Interplanetary Magnetic Sector Polarity from Polar Geomagnetic Field Observations

Abstract

IT has recently been reported1,2 that the interplanetary magnetic sector polarity has an influence on the diurnal variation of the polar geomagnetic field. Briefly, for an interplanetary sector with polarity away from the Sun, the effect is most prominent as a broad minimum for a few hours near local noon in the vertical component of a station near the northern pole such as Thule (corrected geomagnetic latitude 86.8° N), and as an increase in the horizontal component of a lower latitude station such as Godhavn (corrected geomagnetic latitude 77.5° N). For a sector with polarity toward the Sun, the vertical component at Thule has a corresponding maximum, and the horizontal component at Godhavn is decreased. The effect seems to exist over the entire polar cap, but disappears at latitudes a few degrees below Godhavn. In the southern hemisphere the effects corresponding to a given interplanetary polarity are systematically reversed.