AAS 200th meeting, Albuquerque, NM, June 2002
Session 39. Structure and Dynamics of Chromospheres
Display, Tuesday, June 4, 2002, 10:00am-6:30pm, SW Exhibit Hall

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[39.03] Quantitative measure of quiet photospheric magnetic fields

H. Zirin (Caltech), R. Cameron (Tokyo Science University)

We have analyzed a set of 110 Stokes V spectra of the quiet Sun taken with the spectrovideomagnetograph at BBSO June 23, 2000. The 480x512 pixel spectrograms are bundled into 3 pixel (1 arc sec) spectra, giving 160 distinct spectra on each frame, or 16400 spectra overall. An element of magnetic network was included in each spectrogram, so that actual splitting measurements could be used to check absolute calibration of the field measures. In each case we measured the V signal in both 5250 and 5247 and compared the values. If the ratio was 3:2 as given by the g-factors, the data must represent true measured magnetic fields, since random noise does not understand g-factors.

We find the mean field on each spectrum to range from 3 to 49 gauss in the different frames, and the median absolute field, from 13 to 30 G. In all cases the difference between V(5250) and 1.5xV( 5247) is zero within 1.2 standard errors. To check the popular ``emperor's new clothes" model in which the fields measured are due to invisible spots with kilogauss fields, we calculate the mean value of 1.5xV(5247)/0.78- V(5250), expected to be zero for that model. Rather than zero, that result is typically 3 standard errors from zero, and invariably negative. That result means that the V(5250) is not saturated, as would be expected in the kilogauss model. Thus the emperor, in fact, has no clothes. The fields measured in network elements run from 250 to 700 gauss, and are typically confirmed within 20% by the measured splitting.

The existence of fields of mixed polarity and strength >10 gauss everywhere in the photosphere gives an explanation for the support of the chromosphere, which has a scale height of 1000 Km instead of the expected hydrostatic scale height <200 Km, as well as the filtering out of unionized high-FIP elements, which cannot be supported by the magnetic fields, from the solar wind.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.