Magnetic field tubes emerging in the photosphere
Abstract
Magnetic field tubes emerging in the photosphere are the dominant contributors to the solar irradiance variations with time. The knowledge of the radiative properties of the photospheric magnetic field elements is, therefore, of high interest to understand the solar irradiance. A classical way to quantify the angular distribution of their radiative properties is the measurement of the contrast between their radiance and the one from the surrounding photosphere as a function of their heliocentric angle location, known as centre-to-limb-variation (CLV). There are many published measurements of the CLV of photospheric small magnetic elements, mostly faculae, made in different conditions and giving different results. One of the parameters that may be different from one observation to another is the angular resolution. We study the effect of the angular resolution on the determination of the angular properties of the facular radiance, with measurements of photospheric intensity in the continuum, around the Fe 676.8 nm, and of the longitudinal magnetic field, along the line of sight, made with the MDI instrument aboard SOHO with two resolutions, 4 arc seconds and 1.2 arc seconds (2 and 0.6 arc second pixels, respectively) . The effect of the limited photometric sensitivity of the instrument and the limited information on the angular structure of the magnetic field tubes are considered.
- Publication:
-
35th COSPAR Scientific Assembly
- Pub Date:
- 2004
- Bibcode:
- 2004cosp...35.4732D