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Abstract: We analyze features that resemble type i spicules in two different 3Dnumerical simulations in which we include horizontal magnetic flux emergence ina computational domain spanning the upper layers of the convection zone to thelower corona. The two simulations differ mainly in the preexisting ambientmagnetic field strength and in the properties of the inserted flux tube. We usethe Oslo Staggered Code OSC to solve the full MHD equations with non-grey andnon-LTE radiative transfer and thermal conduction along the magnetic fieldlines. We find a multitude of features that show a spatiotemporal evolutionthat is similar to that observed in type i spicules, which are characterized byparabolic height vs. time profiles, and are dominated by rapid upward motion atspeeds of 10-30 km-s, followed by downward motion at similar velocities. Wemeasured the parameters of the parabolic profile of the spicules and findsimilar correlations between the parameters as those found in observations. Thevalues for height or length and duration of the spicules found in thesimulations are more limited in range than those in the observations. Thespicules found in the simulation with higher preexisting ambient field haveshorter length and smaller velocities. From the simulations, it appears thatthese kinds of spicules can, in principle, be driven by a variety of mechanismsthat include p-modes, collapsing granules, magnetic energy release in thephotosphere and lower chromosphere and convective buffeting of fluxconcentrations.

Author: J. Martinez-Sykora, V. Hansteen, B. De Pontieu, M. Carlsson

Source: https://arxiv.org/

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