6533b855fe1ef96bd12b1ba3

RESEARCH PRODUCT

Centre-to-limb variation of photospheric facular radiance and image resolution

A. OrtizVicente DomingoI. CabelloBlai Sanahuja

subject

PhysicsAtmospheric ScienceLine-of-sightPixelbusiness.industryAerospace EngineeringAstronomy and AstrophysicsSolar atmosphereSolar irradianceMagnetic fieldGeophysicsOpticsSpace and Planetary ScienceRadianceGeneral Earth and Planetary SciencesbusinessImage resolution

description

Abstract We study the effect of the angular resolution on the determination of the angular properties of the facular radiance. We analyze photospheric intensity in the continuum, around the Ni 676.8 nm line, and longitudinal magnetic field along the line of sight, measured by the MDI instrument aboard SOHO with two spatial resolutions, 4″ and 1.2″ (2″ and 0.6″ 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. Our study of the high-resolution data shows that intensity contrast of magnetic features between 80 and 600 Gauss increases from centre to limb up to a maximum that occurs at higher heliocentric angles (θ) when obtained with higher resolution data than for lower resolution data. There is a suggestion that at heliocentric angles below about 75° there is only a monotonic increase in the contrast as one goes from cos (θ) = 1 to cos (θ) = 0.2.

yearjournalcountryeditionlanguage
2005-01-01Advances in Space Research
https://doi.org/10.1016/j.asr.2005.01.083