plot of open field lines as viewed 4 days ahead of 11 May 99 (using CR1949 source surface model coefficients from WSO)

plot of open field lines as above, but only those mapping to the source surface equator at 2.5 Rs (note in the central meridian region the solar wind source switches from the North to South hemisphere)

Carrington map of open field regions on photosphere and projected open field lines as above (note the central meridian on the day of interest-4 days before the event- is at about 270 deg Carrington longitude)

Carrington map of polarity boundary on source surface at 2.5 Rs (note the 270 deg longitude spot is also a sector boundary)