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Small-scale dynamo magnetism as the driver for heating the solar atmosphere
Tahar Amari1, Jean-François Luciani1, Jean-Jacques Aly2
1Centre de Physique Théorique, Ecole Polytechnique, CNRS, F-91128 Palaiseau Cedex, France.
Nature
|June 12, 2015
Summary
Solar atmosphere heating is explained by new models showing small eruptions in the chromosphere heat plasma. These eruptions can reach the low corona, while Alfvén waves heat the upper corona.
Area of Science:
- Solar physics
- Plasma physics
- Astrophysics
Background:
- The solar atmosphere's heating mechanism remains a long-standing problem.
- Previous studies highlighted magnetic reconnection and waves, emphasizing chromosphere-corona interaction.
- A fully consistent model explaining coronal heating by chromospheric phenomena is still lacking.
Purpose of the Study:
- To model the heating of the quiet Sun's atmosphere.
- To investigate the role of subphotospheric magnetic field generation and chromospheric eruptions.
- To understand the contribution of Alfvén waves to coronal heating.
Main Methods:
- Developed a model of magnetic field generation via a subphotospheric fluid dynamo linked to granulation.
- Simulated magnetic field expansion into the chromosphere and subsequent plasma heating.
- Incorporated the effect of vertical network magnetic fields and Alfvén wave dissipation.
Main Results:
- The model reproduces chromospheric plasma heating (4,500 W/m²) through small-scale eruptions releasing magnetic energy and driving sonic motions.
- Energetic eruptions were observed to reach heights of 10 million meters, impacting the low corona.
- Alfvén waves generated in the chromosphere carry the required energy flux (300 W/m²) for coronal heating.
- The model predicts a complex surface magnetic field (160 gauss) and features resembling spicules, blinkers, and solar tornadoes.
Conclusions:
- Small-scale chromospheric eruptions are crucial for heating the chromosphere and can influence the low corona.
- Alfvén waves originating in the chromosphere provide a viable mechanism for heating the corona.
- The model offers a consistent framework for understanding solar atmospheric heating, integrating subphotospheric processes with chromospheric and coronal phenomena.
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