Seminar "Unexpected Crossover from Weak to Strong Magnetohydrodynamic Turbulence" by Prof. Mahendra Verma

[Speaker]

Prof. Mahendra Verma
Department of Physics & Kotak School of Sustainability
Indian Institute of Technology Kanpur, India

[Abstract]

The quest for a consistent theory of magnetohydrodynamic (MHD) turbulence has remained one of the most enduring challenges in physics. In this talk, we present a universal crossover between weak and strong turbulence regimes.  We demonstrate that spectral scaling is fundamentally governed by a competition between the external and local magnetic fields. We show that large mean magnetic field yields Iroshnikov–Kraichnan -3/2 scaling due to weak modulation of Alfvén waves, but moderate and weak magnetic fields produce Kolmogorov’s -5/3 scaling driven by strong modulation from the local magnetic field.  I connect the above result to the long-sought physical explanation for the evolution of the solar wind spectral index and corona heating in the quiet and active zones.