3-DIMENSIONAL GEOMETRY OF PLANAR MAGNETIC-STRUCTURE IN THE CORONA

The coronal magnetic field (CMF) during Carrington rotation 1870 is in ferred by using the so-called 'potential model' with the photospheric magnetic field observed at Kitt Peak. Magnetic field lines starting at areas restricted (90 degrees +/- 30 degrees in longitude and 0 degree s + 20 degrees in latitude) in both the photosphere and the source sur face of 2.5 solar radii are traced to examine fine geometrical structu res of the CMF. We found a well-ordered planar magnetic structure (PMS ) near 90 degrees Carrington longitude in the corona. The PMS consists of magnetic flux of negative polarity emanating from several small ar eas in the photosphere. The magnetic flux expands into a wide longitud inal angle in the source surface making a planar magnetic structure.