Wave motion in the Earth’s core and the axial dipole field

COLLOQUIUM TALK

Title: Wave motion in the Earth’s core and the axial dipole field

Abstract: The Earth’s magnetic field is generated by a convection-driven dynamo operating in its fluid outer core. The Earth has a large-scale dipole-dominated field, a fact of historical importance because of the role of the magnetic compass in the exploration of our planet. A long-standing question in dynamo theory is whether the preference for the axial dipole field is due to a purely hydrodynamic process influenced by planetary rotation or due to a magnetohydrodynamic process influenced by both rotation and the self-generated magnetic field. In a nonlinear dynamo, a class of quasi-linear waves known as magnetostrophic waves arise from localized balances between the magnetic, buoyancy and Coriolis (MAC) forces. These waves are thought to be essential for the formation of the axial dipole field. Polarity reversals in the dynamo may occur when these waves disappear under strong buoyant forcing. In this talk, I shall discuss the significant developments that shaped our understanding of dipole formation, and in turn, reversals.

Speaker Bio: Professor Binod Sreenivasan is the Chair of the Centre for Earth Sciences, Indian Institute of Science, Bangalore. He completed his Ph.D. at the University of Cambridge, and his M.S. at the Indian Institute of Technology, Madras. He is a Fellow of the Indian Academy of Sciences and is the recipient of the Doornbos Memorial Prize, the Swarnajayanti Fellowship, the Leverhulme Research Fellowship, and the CNRS Research Fellowship. He has also been recognized with multiple scholarships, such as the Cambridge-Nehru, Chevening, and Overseas Research Scholarships. His research interests span several fields, including dynamo theory and models, planetary magnetism, magneto-hydrodynamics, and vortex dynamics.