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Straining of magnetic fields by large-scale shear flow, which is generally assumed to lead to intensification and generation of small scales, is reexamined in light of the persistent observation of large-scale magnetic fields in astrophysics. It is shown that, in magnetohydrodynamic turbulence, unstable shear flows have the unexpected effect of sequestering magnetic energy at large scales due to counteracting straining motion of nonlinearly excited large-scale stable eigenmodes. This effect is quantified via dissipation rates, energy transfer rates, and visualizations of magnetic field evolution by artificially removing the stable modes. These analyses show that predictions based upon physics of the linear instability alone miss substantial dynamics, including those of magnetic fluctuations.
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Observations of turbulence and mean flow in the low-energy hypolimnetic boundary layer of a large lake: Deep water BBL flow and turbulence in a large lake
- Award ID(s):
- 1658156
- PAR ID:
- 10072771
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Limnology and Oceanography
- Volume:
- 63
- Issue:
- 6
- ISSN:
- 0024-3590
- Page Range / eLocation ID:
- p. 2762-2776
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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