The Liquid Sodium Dynamo Experiment at New Mexico Tech is designed to demonstrate how naturally occurring flows in planets, stars, and Active Galactic Nuclei (AGN) accretion disks can generate the magnetic fields of these bodies. The scientific question of the research is whether driven plumes, necessary for coherent helicity generation in a conducting fluid will create so much turbulent resistivity as to prevent the necessary orthogonal omega or shear gain and thus prevent exponential dynamo gain. Educationally, the project offers research opportunities for undergraduates.
The standard belief is that turbulence in a conducting fluid will make a dynamo in astrophysical circumstances regardless of the randomness of the motions. This experiment is designed to prove the contrary. A low turbulent shear flow in liquid sodium (this experiment) has already demonstrated an omega gain of a factor of eight. The experimental question is whether helicity injection of approximately one-eighth the shear flow can recreate the original poloidal field without reducing the omega gain by turbulent resistivity below threshold.
A dynamo is a physical system that generates a magnetic field from scratch, without wires or a battery. There is a natural dynamo inside the Earth that generates the Earth'smagnetic field, and there are dynamos inside all of the planets of the Solar System that have liquid metal cores. There is a dynamo inside the Sun, and a dynamo at the center of our Milky Way galaxy. We no not know in detail how dynamos work. A laboratory dynamo is a physicsl system that amplifies and changes the geometry of a pre-existing magnetic field. The purpose of a laboratory dynamo is to investigate how natural dynamos work. Laboratory dynamos operate by rotating a conducting fluid using as few constraints as possible. The New Mexico Dynamo operates by rotating liquid sodium metal. The sodium is constrained to flow between two cylinders that can rotate independently, at different speeds. A pre-existing magnetic field is applied acting from the right to the left in the figure. The action of the dynamo twists the pre-existing magnetic field into a vertical torus, or donut, about the horizontal axis of the dynamo, and amplifies it by a factor of eight. This is the highest performance of any laboratory dynamo to date. Other laboratory dynamos have succeeded in twisting the geometry of a pre-existing magnetic field, but have not amplified it as much. This dynamo work has resulted in the publication of seven scientific papers during the funding period, three of which are refereed.
