A basal contribution from p-modes to the Alfvénic wave flux in the Sun’s corona

• Published in: Nature astronomy Vol. 3; no. 3; pp. 223 - 229
• Main Authors: Morton, R. J., Weberg, M. J., McLaughlin, J. A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.03.2019; Nature Publishing Group
• Subjects: 639/766/34; 639/766/34/867; Acoustics; Astronomy; Astrophysics and Cosmology; Corona; Energy balance; Energy transfer; Fluctuations; Letter; Magnetic fields; Physics; Physics and Astronomy; Solar cycle; Wave energy
• ISSN: 2397-3366; 2397-3366
• DOI: 10.1038/s41550-018-0668-9

Many cool stars possess complex magnetic fields 1 that are considered to undertake a central role in the structuring and energizing of their atmospheres 2 . Alfvénic waves are thought to make a critical contribution to energy transfer along these magnetic fields, with the potential to heat plasma and accelerate stellar winds 3 – 5 . Despite Alfvénic waves having been identified in the Sun’s atmosphere, the nature of the basal wave energy flux is poorly understood. It is generally assumed that the associated Poynting flux is generated solely in the photosphere and propagates into the corona, typically through the continuous buffeting of magnetic fields by turbulent convective cells 4 , 6 , 7 . Here, we provide evidence that the Sun’s internal acoustic modes also contribute to the basal flux of Alfvénic waves, delivering a spatially ubiquitous input to the coronal energy balance that is sustained over the solar cycle. Alfvénic waves are thus a fundamental feature of the Sun’s corona. Acknowledging that internal acoustic modes have a key role in injecting additional Poynting flux into the upper atmospheres of Sun-like stars has potentially significant consequences for the modelling of stellar coronae and winds. A spatially ubiquitous energy flux from the interior of the Sun reaches the corona through Alfvénic waves generated by internal acoustic modes. Such flux persists for the whole solar cycle and contributes significantly to the energy in the corona.