Comparison of Inferred and Observed Interplanetary Magnetic Field Polarities

The inferred polarity (toward or away from the sun) of the interplanetary magnetic field at earth using polar observations of the geomagnetic field has been compared with spacecraft observations. A list published by Svalgaard (1974) of the inferred field polarities during 1970-1972 isfound to be correct on 82 % of the days. A near real time (same day) method of inferring the polarity of the interplanetary magnetic field using geomagnetic observations at Vostok and Thule is in use at the NOAA Space Environ-ment Laboratory, Boulder, Colorado. During 1972 this method is found to be correct on 87 % of the days. A list of 'well-defined ' sector boundaries at earth during 1970-1972 is given. A method of inferring the polarity (toward or away from the sun) of the interplanetary magnetic field at earth has been dis-covered by St•algaard [1968] and Mansurot • [1969]. This method uses observations of the geomagnetic field obtained at polar observatories such as Thule and Vostok and has been described by St•algaard [1972] (see also Wilcox [1972]). Friis-Christensen et al. [1971] have analyzed the success of this method during the year 1969. Russell and Rosenberg [1974