caa a22 4500 445346671 CHVBK 20180317142831.0 cr unu---uuuuu 170323e20110401xx s 000 0 eng 10.1007/s11207-010-9699-9 doi (NATIONALLICENCE)springer-10.1007/s11207-010-9699-9 Coronal Field Opens at Lower Height During the Solar Cycles 22 and 23 Minimum Periods: IMF Comparison Suggests the Source Surface Should Be Lowered [Elektronische Daten] [C. Lee, J. Luhmann, J. Hoeksema, X. Sun, C. Arge, I. de Pater] The solar cycle 23 minimum period has been characterized by a weaker solar and interplanetary magnetic field. This provides an ideal time to study how the strength of the photospheric field affects the interplanetary magnetic flux and, in particular, how much the observed interplanetary fields of different cycle minima can be understood simply from differences in the areas of the coronal holes, as opposed to differences in the surface fields within them. In this study, we invoke smaller source surface radii in the potential-field source-surface (PFSS) model to construct a consistent picture of the observed coronal holes and the near-Earth interplanetary field strength as well as polarity measurements for the cycles 23 and 22 minimum periods. Although the source surface value of 2.5R ⊙ is typically used in PFSS applications, earlier studies have shown that using smaller source surface heights generates results that better match observations during low solar activity periods. We use photospheric field synoptic maps from Mount Wilson Observatory (MWO) and find that the values of ≈ 1.9 R ⊙ and ≈ 1.8 R ⊙ for the cycles22 and 23 minimum periods, respectively, produce the best results. The larger coronal holes obtained for the smaller source surface radius of cycle 23 somewhat offsets the interplanetary consequences of the lower magnetic field at their photospheric footpoints. For comparison, we also use observations from the Michelson Doppler Imager (MDI) and find that the source surface radius of ≈ 1.5 R ⊙ produces better results for cycle 23, rather than ≈ 1.8 R ⊙ as suggested from MWO observations. Despite this difference, our results obtained from MWO and MDI observations show a qualitative consistency regarding the origins of the interplanetary field and suggest that users of PFSS models may want to consider using these smaller values for their source surface heights as long as the solar activity is low. The Author(s), 2011 Corona, models nationallicence Coronal holes nationallicence Magnetic field, interplanetary nationallicence Magnetic field, observations nationallicence Solar cycle, observations nationallicence Lee C. Space Sciences Laboratory, University of California, Berkeley, CA, USA aut Luhmann J. Space Sciences Laboratory, University of California, Berkeley, CA, USA aut Hoeksema J. W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA aut Sun X. W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA aut Arge C. Air Force Research Laboratory/Space Vehicles Directorate, Kirtland Air Force Base, NM, USA aut de Pater I. Department of Earth and Planetary Science, University of California, Berkeley, CA, USA aut Solar Physics Springer Netherlands 269/2(2011-04-01), 367-388 0038-0938 269:2<367 2011 269 11207 https://doi.org/10.1007/s11207-010-9699-9 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11207-010-9699-9 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Lee C. Space Sciences Laboratory, University of California, Berkeley, CA, USA aut NATIONALLICENCE 700 1- Luhmann J. Space Sciences Laboratory, University of California, Berkeley, CA, USA aut NATIONALLICENCE 700 1- Hoeksema J. W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA aut NATIONALLICENCE 700 1- Sun X. W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA aut NATIONALLICENCE 700 1- Arge C. Air Force Research Laboratory/Space Vehicles Directorate, Kirtland Air Force Base, NM, USA aut NATIONALLICENCE 700 1- de Pater I. Department of Earth and Planetary Science, University of California, Berkeley, CA, USA aut NATIONALLICENCE 773 0- Solar Physics Springer Netherlands 269/2(2011-04-01), 367-388 0038-0938 269:2<367 2011 269 11207 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer