Association of Extreme-Ultraviolet Imaging Telescope (EIT) Polar Plumes with Mixed-Polarity Magnetic Network

SOHO EIT spectroheliograms showing the polar coronal holes during the present sunspot minimum are compared with National Solar Observatory (Kitt Peak) magnetograms taken in Fe I lambda 8688 and Ca II lambda 8542. The chromospheric lambda 8542 magnetograms, obtained on a routine, near-daily basis since 1996 June, reveal the Sun's strong polar fields with remarkable clarity. We find that the Fe IX lambda 171 polar plumes occur where minority-polarity flux is in contact with flux of the dominant polarity inside each polar hole. Moreover, the locations of "plume haze" coincide approximately with the patterns of brightened He II lambda 304 network within the coronal hole. The observations appear to be consistent with mechanisms of plume formation involving magnetic reconnection between unipolar flux concentrations and nearby bipoles. The fact that minority-polarity fields constitute only a small fraction of the total magnetic flux within the polar holes suggests that plumes are not the main source of the high-speed polar wind.