AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 94. Quiet Sun Magnetic Fields
Display, Thursday, June 3, 1999, 9:20am-4:00pm, Southeast Exhibit Hall

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[94.05] Measuring Local Short-Term Changes in the Global Solar Magnetic Field

J.T. Hoeksema, X.P. Zhao, K.-C. Chu, P.H. Scherrer (HEPL, Stanford Univ.)

Global evolution of the solar magnetic field is driven by local magnetic flux changes. We have systematically measured the small-scale magnetic field on the visible surface over an extended time interval. The MDI instrument on SOHO has made 2" full-disk observations of the photospheric field every 96 minutes since May 1996, except for a several-month gap in 1998 and early 1999 caused by problems with the SOHO spacecraft. We are now developing tools to characterize the local variations and relate them to their global effects. MDI magnetograms compare well with KPNO and WSO observations at higher and lower resolution. Several MDI magnetograms are available in near real time each day. MDI daily synoptic charts show the evolution of large-scale coronal structures. Daily updates and archival records of individual magnetograms and synoptic charts can be found on the www at http://soi.stanford.edu.

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