Effects of the Weak Polar Fields of Solar Cycle 23: Investigation Using OMNI for the STEREO Mission Period

The current solar cycle minimum seems to have unusual properties that appear to be related to weak solar polar magnetic fields. We investigate signatures of this unusual polar field in the ecliptic near–Earth interplanetary magnetic field (IMF) for the STEREO period of observations. Using 1 AU OMNI data, we find that for the current solar cycle declining phase to minimum period the peak of the distribution for the values of the ecliptic IMF magnitude is lower compared to a similar phase of the previous solar cycle. We investigate the sources of these weak fields. Our results suggest that they are related to the solar wind stream structure, which is enhanced by the weak polar fields. The direct role of the solar field is therefore complicated by this effect, which redistributes the solar magnetic flux at 1 AU nonuniformly at low–to–mid heliolatitudes. 1 Space Sciences Laboratory, University of California, Berkeley, California, USA email: [email protected] 2 Department of Earth and Planetary Science, University of California, Berkeley, California, USA 3 Space Sciences Laboratory, University of California, Berkeley, California, USA email: [email protected] 4 W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, USA email: [email protected] 5 W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, USA email: [email protected] 6 Predictive Science, Inc., San Diego, California, USA email: [email protected] 7 Air Force Research Laboratory/Space Vehicles Directorate, Kirtland Air Force Base, New Mexico, USA email: [email protected] 8 Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California, USA email: [email protected] 9 Department of Earth and Planetary Science, University of California, Berkeley, California, USA email: [email protected] SOLA: cleelowbfinal.tex; 24 March 2009; 3:01; p. 1 Manuscript Click here to download Manuscript: CLeeLowBFinal.tex