Inclined Inhomogeneities in the Solar Atmosphere.
Abstract
Good spectrograms of undisturbed regions on the sun show a pattern of lengthwise threads representing granulation. I have measured the x positions (perpendicular to dispersion) of threads as a function of X distance from the center of the strong line Fe4383.6 from AX=0.2 A to the continuum, and at the centers of other lines nearby. The standard deviation of a single measure corresponds to +20 to +40 km on the sun for sharp or fuzzy threads. Inspection of many spectrograms showed that many threads are visible curved, as though the positions of the corresponding granules along the slit varied with A~. The measurements on one spectrogram covering 135 000 km on the sun showed the following thread characteristics: (a) The x displacements are symmetrical, having the same sign and magnitude on the blue and violet sides of the line. The sign of the displacement is quite random. (b) Of the 58 bright threads visible in the spectrogram, the x displacements of 39 were >~160 km; of 4, >~970 km; and the rms for all was 500 km. (c) The displacements are present in all Fraunhofer lines and are very strongly correlated with line strength for any single thread. (d) There is no systematic tendency for threads to become fuzzy in their curved portions. My interpretation of this behavior is that a curved thread represents a columnar inhomogeneity which is sharply inclined to the vertical along the slit direction. At different AX's (or at the centers of weaker lines) we see cross sections of the column at a series of different heights, and hence at different apparent x positions. Allowing a very liberal 500 km for the total height range, the statistics show that high inclinations of 45o are the normal thing for bright inhomogeneities. This ignores the uncomfortable fact that the observed displacements occur between 5 and 20 Doppler widths from the line core, where we might expect a very small height range, and little height discrimination.
- Publication:
-
The Astronomical Journal
- Pub Date:
- 1964
- DOI:
- 10.1086/109447
- Bibcode:
- 1964AJ.....69R.541E