IGPP Seminar Series 2022: Daria Holdenried-Chernoff

IGPP is pleased to invite you to join its Fall 2022 Seminar Series presentation featuring UC Berkeley's Daria Holdenried-Chernoff. Dr. Holdenried-Chernoff's talk, "Turbulent Diffusivity in the Statistical Kinematic Dynamo" will be available via Zoom on November 8, 2022, starting at 12:00pm. Zoom: https://ucsd.zoom.us/j/98554553248?pwd=cG05UStPRjhZbjJ6TW5DTHlMUWdVdz09 Password: igpp_earth

Time: 12:00 pm, Pacific Time
Location: Revelle 4000 (on-site with a zoom link)

Abstract: Variations in the geomagnetic field occur on a vast range of time scales, from milliseconds to millions of years. The advent of satellite measurements has allowed for detailed studies of the short timescale behaviour of the geomagnetic field, but understanding its long timescale evolution remains challenging due to the sparsity of the paleomagnetic record.

We introduce a field theory framework for studying magnetic field generation as a result of random fluid motions. A stochastic kinematic dynamo model is constructed, where the fluid velocity is taken to act as a random forcing obeying Gaussian statistics. Starting from this model we compute statistical properties of the magnetic field that may be compared to observations from the paleomagnetic record. More specifically, we use the Martin-Siggia-Rose-Janssen-de Dominicis (MSRJD) formalism to compute the average magnetic field response function. From this we obtain an estimate for the turbulent contribution to the magnetic diffusivity and find that it is consistent with results from mean-field dynamo theory. This framework presents much promise for studying the geomagnetic field in a stochastic context.

Making use of mean-field theory results and estimates of the turbulent magnetic diffusivity from paleomagnetic observations, we propose an upper bound for the average flow velocities in the Earth’s outer core.

Nov 8 2022 - 12:00pm