SMALL-SCALE HORIZONTAL MAGNETIC-FIELDS IN THE SOLAR PHOTOSPHERE

We present recent observations of quiet regions near the center of the solar disk using the Advanced Stokes Polarimeter. These observations reveal a component of the solar magnetic field heretofore unobserved: isolated, small-scale (typically 1 ''-2 '' or smaller), predominantly horizontal magnetic flux structures in the solar photosphere. These fe atures occur in isolation of the well-known, nearly vertical flux conc entrations usually seen in the photospheric ''network.'' Hence we ascr ibe this horizontal flux to the photospheric ''internetwork.'' They re veal themselves by the distinct signature of the Stokes Q and U polari zation profiles, which are symmetric about the line center. The polari zation signals are weak, with peak amplitudes typically similar to 0.1 % - 0.2% of the continuum intensity in the resolved spectral profiles, but they are well above the noise level of these observations (approx imate to 0.05%). Such magnetic fields are weak (significantly less tha n 1000 G) and largely horizontal owing to the absence, or near absence , of accompanying Stokes V polarization when observed at the center of the solar disk. These horizontal field elements are often associated with blueshifted Stokes line profiles, and they often occur between re gions of opposite polarity (but weak) Stokes V profiles. The horizonta l elements are short-lived, typically lasting similar to 5 minutes. Ou r observations suggest that we are viewing the emergence of small, con centrated loops of flux, carried upward either by granular convection or magnetic buoyancy. Even though these entities show weak field stren gths, they also seem to be fairly common, implying that they could car ry the order of 10(24) Mx of magnetic flux to the surface on a daily b asis. However, further observational study is needed to identify the s pecific nature of this phenomenon.