HAO Colloquium - Barbara Emery, HAO

Oscillations in Secondary to Primary Polar Crown Polarity Inversion Lines around Solar Maximum over Five Solar Cycles

B. A. Emery (1,2), D. F. Webb (3), S. E. Gibson (1), I. M. Hewins (2), R. H. McFadden (2), T. A. Kuchar (3)

(1) HAO/NCAR, Boulder, CO, (2) Institute for Scientific Research (ISR), Boston College at HAO/NCAR, (3) ISR, Boston College, Chestnut Hill, MA

We undertake a five solar-cycle (SC19-23) ~55-year (December 1954 to August 2009) study of oscillations in the high-latitude polarity inversion lines (PILs) using the recently digitized McIntosh Archive of solar synoptic maps. We look at the latitude evolution of the primary PIL, which is the nearly continuous polar crown ~16° equatorward of the polar coronal hole (CH).  The secondary PIL consists of neutral line segments ~14° equatorward of the primary PIL, which become a nearly continuous line at the end of the rush to the poles before solar maximum when the polar polarity changes with the primary PIL disappearing, and the secondary PIL becoming the primary PIL with the new polarity.  This new primary PIL achieves a maximum poleward latitude of ~±57-58° just after the solar maximum polarity change, where the Northern Hemisphere PIL peaks closer to the polarity change.  The new PIL then relaxes equatorward in oscillations of 2-5 degrees of latitude with periods between ~5-40 Carrington Rotations (CRs).  The presence of the transition PIL poleward peak leads to oscillations ~16 CR, which are not found in the CH boundary that does not experience a transition peak.  Other shared periods are ~25 CR especially in the SH for PILs and CH boundaries, and shorter periods, especially in the NH ~8 CR for PILs and ~11 CR and ~7 CR for the CH boundary.  We found two abrupt equatorward breaks of ~5-10° in 2005 during the descending period of solar cycle 23 that could be manifestations of a deep disturbance traveling ~15°/CR from the southern CH boundary to the northern CH boundary, with ~30-35 CR periodicities before the break and ~20-25 CR after the break in the PILs.

Date and time: 
Wednesday, January 13, 2021 - 2:00pm to 3:00pm