VLA stereoscopy of solar active regions. 2: Altitude, relative motion, and center-to-limb darkening of 20 centimeter emission

Details VLA stereoscopy of solar active regions. 2: Altitude, relative motion, and center-to-limb darkening of 20 centimeter emission VLA stereoscopy of solar active regions. 2: Altitude, relative motion, and center-to-limb darkening of 20 centimeter emission

May 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...426..434a&link_type=abstract

Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 426, no. 1, p. 434-448

Computer Science

Numerical Analysis

33

Altitude, Limb Darkening, Motion Perception, Polarization, Radio Astronomy, Solar Activity, Solar Radio Emission, Stellar Models, Stereoscopy, Astronomical Maps, Brightness Temperature, Image Processing, Numerical Analysis, Very Large Array (Vla)

Scientific paper

A newly developed method of stereoscopic correlation is applied to solar radio maps at a wavelength of 20 cm. On the basis of stereoscopic correlations between radio maps obtained on 6 different days we establish the presence of 66 radio source components associated with 22 active regions. We find the following statistical results for active region source structures at 20 cm: 1. The observed lifetime is consistent with an exponential distribution having an e-folding time scale of greater than 18 days. 2. The average altitude of 20 cm sources is 25 +/- 15 Mm; 90% of the sources are found in heights less than 40 Mm. 3. The average diameter of discrete source structures is 48 +/- 15 Mm, implying a vertical/horizontal aspect ratio of qA approx. = 0.5. 4. No significant source motion has been found with respect to the standard differential rotation rate of Omega = 13.45 deg - ((3 deg (sin2B)). 5. We find a statistical limb darkening, which can be described by the relation (TB(alpha))/TB(0)) = 0.4 + ((0.6(cos2 alpha)) for sources with TB greater than 0.5 MK. 6. The degree of source polarization is 15% +/- 10% and is independent of source location. 7. Bright sources (greater than or approximately equal to 0.5 MK), or equivalently, long-lived sources (greater than or approximately equal to 5 days) show a systematic variation of their altitude as function of the center-limb distance.

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