Simulations of dynamo action in slowly rotating M dwarfs: Dependence on dimensionless parameters
| Autor: | Ortiz-Rodríguez, C. A., Käpylä, P. J., Navarrete, F. H., Schleicher, D. R. G, Mennickent, R. E., Hidalgo, J. P., Toro, B. |
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| Rok vydání: | 2023 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | The aim of this study is to explore the magnetic and flow properties of fully convective M dwarfs as a function of rotation period Prot and magnetic Reynolds ReM and Prandlt numbers PrM. We performed three-dimensional simulations of fully convective stars using a star-in-a-box setup. This setup allows global dynamo simulations in a sphere embedded in a Cartesian cube. The equations of non-ideal magnetohydrodynamics were solved with the Pencil Code. We used the stellar parameters of an M5 dwarf with 0.21M_odot at three rotation rates corresponding to rotation periods (Prot): 43, 61 and 90 days, and varied the magnetic Prandtl number in the range from 0.1 to 10. We found systematic differences in the behaviour of the large-scale magnetic field as functions of rotation and PrM. For the simulations with Prot = 43 days and PrM <= 2, we found cyclic large-scale magnetic fields. For PrM > 2 the cycles vanish and field shows irregular reversals. In simulations with Prot = 61 days for PrM <= 2 the cycles are less clear and the reversal are less periodic. In the higher-PrM cases, the axisymmetric mean field shows irregular variations. For the slowest rotation case with Prot = 90 days, the field has an important dipolar component for PrM <= 5. For the highest PrM the large-scale magnetic field is predominantly irregular at mid-latitudes, with quasi-stationary fields near the poles. For the simulations with cycles, the cycle period length slightly increases with increasing ReM. Comment: 11 pages, 12 figures, submitted to A&A |
| Databáze: | arXiv |
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