Generation of longitudinal flux tube waves in epsilon Eridani

Abstract

The aim of the current study is the computation of wave energy fluxes for longitudinal tube waves generated in the convection zone of the chromospherically active star epsilon Eridani. In our models, we employ a modified theory of turbulence together with the magnetohydrodynamic equations in a time-dependent setting. The wave generation mechanism is given by the interaction between vertically oriented magnetic flux tubes and the convective turbulence. We also use updated values for the effective temperature and surface gravity; additionally, we take different magnetic activity levels into account. Our numerical approach allows for the non-linear effects to be considered. The time-averaged upward propagating energy fluxes range from F-LTW = 4.02 x 10(7) to 2.92 x 10(8) (erg cm(-2) s(-1)) for flux tubes of magnetic field strengths between B-0 = 1830 G and 1445 G, respectively. This increase given as roughly a factor of 7 between the above mentioned values of the magnetic field strengths is attributable to the enhanced rigidity of the magnetic flux tube found for relatively large magnetic field strengths. The current results are highly significant for the construction of theoretical time-dependent model chromospheres.