On the origin of the prolate solar chromosphere

A simple geometric model is proposed to explain the recently reported effec t of the prolateness of the solar chromosphere. We assume that a specific d ynamical part of the solar atmosphere above the 2 Mm level, being a mixture of moving up and down jets of chromospheric matter with the coronal plasma between them, is responsible for the solar prolateness. Due to the dynamic nature of this layer, the magnetic field is considered to play a very impo rtant role in the density distribution with the height, guiding the mass fl ows along the field lines. The difference of the magnetic field topology in the polar and the equatorial regions leads to different heights of the chr omospheric limb. Calculations show a satisfactory coincidence with observat ions when the mean separation between opposite polarity concentrations is a bout 9 Mm. The possible observational signature of this network in low phot ospheric and chromospheric layers is discussed.