Sentence:  From the brightness of the F component of the solar corona and the brightness of the <WSD>zodiacal</WSD> light , an estimate of the particle sizes , concentrations , and spatial distribution can be derived for regions of space near the ecliptic plane . 
Meaning of the word marked with <WSD> tags:  a luminous tract in the sky; a reflection of sunlight from cosmic dust in the plane of the ecliptic; visible just before sunrise and just after sunset