Physics – Plasma Physics
Scientific paper
Oct 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003aps..dppkm1004c&link_type=abstract
American Physical Society, 45th Annual Meeting of the Division of Plasma Physics, October 27-31, 2003, Albuquerque, New Mexico,
Physics
Plasma Physics
Scientific paper
A liquid metal (sodium) model of an α ω dynamo has been build and initially tested with water. The measured torque confirms the designed stable Couette flow, the required power, and hence the minimum level of turbulence. The experiment is designed to simulate what we believe is the highest gain, e^10^11 and highest power ˜ 3 ot 10^46 ergs/s, dynamo, which presumably occurs in the accretion disk forming the massive black hole, ˜ 10^8 M_&sun;, of every galaxy. The experiment also simulates the fast dynamo gain at the resistivity truncated end of the turbulence spectrum as well as stellar convection driven helicity. In the experiment the Keplerian shear in a conducting fluid is approximated as limiting stable Couette flow in liquid sodium between two cylinders 30 and 15 cm radius rotating at 30 and 120 Hz respectively. The driven plumes are approximated by a pair of forced axial jets driven axially (30 cm length and at ˜ 10 Hz). Numerical simulations and flux rotation arguments both predict positive gain, ˜ 0.2 Ω_0, at the design Couette flow magnetic Reynolds number, Rm = Ω0 R_0^2/ η ≃ 120 and plume Rm ≃ 10. Initially, without the jets, we plan on applying an external quadrupole field which allows us to measure the Ω gain, B_φ≃ Rm/2π ≃ 20 B_r. An axial external field allows us to test for up to six modes of MRI growth. The resulting MRI driven turbulence allows us to test for an MRI dynamo effect at the level of 10-4 of the applied field. Mean-field dynamo theory can be compared to a heuristic coherent flux rotation analysis. Supported by NSF, NMIMT, and LANL.
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