The Solar Polar Field The Solar Polar Field Reversal Observed By Reversal Observed By

SOHO/MDISOHO/MDI

Yang Liu, J. Todd Hoeksema, X-P Yang Liu, J. Todd Hoeksema, X-P Zhao – Stanford UniversityZhao – Stanford University

yliu@solar.stanford.eduyliu@solar.stanford.edu

Outline Outline

Show reversal of polar field Show reversal of polar field based on observational data;based on observational data;

Show evolution of large-scale Show evolution of large-scale magnetic field during solar magnetic field during solar cycle, especially in the period cycle, especially in the period of polar field reversal;of polar field reversal;

Discuss change of the Discuss change of the heliospheric magnetic field heliospheric magnetic field during polar field reversal.during polar field reversal.

Magnetic field viewed from Magnetic field viewed from north polenorth pole

Magnetic field viewed from Magnetic field viewed from south polesouth pole

Polar field reversal Polar field reversal (?)(?)

Modeling polar fieldModeling polar field

è8

sinpolarBrB ×=Polar field model:

Solar minimum

Solar maximum

Heliospheric field Heliospheric field

CR1960 (02/2000-03/2000)CR1975 (04/2001-05/2001)

Coronal/Heliospheric Coronal/Heliospheric fieldsfields

Coronal/Heliospheric fields

Coronal field during Coronal field during solar cyclesolar cycle

Interplanetary Magnetic Field Interplanetary Magnetic Field (model & obs)(model & obs)

Summary Summary

Polar field reversal of cycle Polar field reversal of cycle 23 occurred in 2001. The 23 occurred in 2001. The southern polar field reversed southern polar field reversed 10 month later than that of 10 month later than that of north polar field.north polar field.