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

• Published in: Solar physics Vol. 256; no. 1-2; pp. 345 - 363
• Main Authors: Lee, C. O., Luhmann, J. G., Zhao, X. P., Liu, Y., Riley, P., Arge, C. N., Russell, C. T., de Pater, I.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-05-2009; Springer Nature B.V
• Subjects: Astrophysics and Astroparticles; Atmospheric Sciences; Magnetic fields; Physics; Physics and Astronomy; Solar physics; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Stereo Science Results at Solar Minimum; Magnetic fields, interplanetary; STEREO mission; Solar cycle, observations; Solar cycle, models; Magnetic fields, observations; Solar wind
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/s11207-009-9345-6

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.