Observations of small-scale solar magnetic fields

Abstract

Spectrograms, obtained during moments of good seeing with the high spatial resolution afforded by the 80-cm solar image at the Kitt Peak National Observatory, show the following:

• (1) Magnetic fields of several hundred gauss occur in tiny areas easily as small as 500 km in extent in regions of the solar surface sometimes well removed from areas of sunspot activity.

• (2) In these tiny areas of magnetic field, many Fraunhofer lines seem to be weakened, appearing on spectrograms as discontinuities or gaps in the absorption lines.

• (3) Although the small-scale magnetic fields are manifested by local weakenings of many absorption lines, these fields often correspond to local darkenings in the continuum, suggesting that the small-scale fields often occur in the dark lanes and pores of the granulation.

• (4) These tiny areas of relatively strong magnetic field correspond to regions of bright Ca⁺ K₂₃₂ emission, not to the so-called K_2V bright points seen on spectroheliograms.

It is implied that these relatively strong fields associated with the weakenings or gaps in Fraunhofer lines are precisely the fields detected using Leighton's photographic technique.