Effects of ‘Seeing’ on Vector Magnetograph Measurements |
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Authors: | Leka KD Rangarajan KE |
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Institution: | (1) Colorado Research Associates Division, NorthWest Research Associates, Inc, Boulder, CO , 80301, U.S.A |
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Abstract: | We present a study of the effects of atmospheric seeing on quantities derived from observations of solar polarized light –
specifically, the vector magnetic flux and quantities derived from its magnitude and direction. Data from the Imaging Vector
Magnetograph (‘IVM’) at the U. Hawaii/Mees Solar Observatory, are degraded by various degrees by applying a blur function
to the ‘incoming light’, simulating a range of seeing conditions. A quantitative study of the resulting effects on derived
quantities including total magnetic flux, vertical electric current density and magnetic shear angles, are discussed as a
function of the imposed degradation. The generality of the seeing effects is explored by comparing the results from two different
active regions; we find that the results are comparable for those quantities directly computed from the magnetic flux vector
(e.g., summed, as in total flux) but less so for those quantities involving higher-order calculations (e.g., derivatives,
as in vertical currents). We suggest that for temporal series data from any instrument, a method such as that which we outline
here, be applied in order to model the uncertainties imposed on the data (in addition to instrumental uncertainties, etc.)
due to seeing variations. |
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Keywords: | |
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