Nonmodal analysis of helical magnetorotational instability


Nonmodal analysis of helical magnetorotational instability

Mamatsashvili, G.; Stefani, F.

The helical and azimuthal magnetorotational instabilities (HMRI), relative of standard MRI, has recently received much attention in connection with liquid metal experiments. Its main advantage is that, being governed by Reynolds and Hartmann numbers, persists at very small magnetic Prandtl numbers (Pm) typical to liquid metals, in contrast to standard MRI. However, its applicability to Keplerian astrophysical discs with similarly small Pm is still not settled and controversial; the main hindering factor is the Liu’s criterion. Aiming to resolve this issue, we carry out nonmodal analysis of HMRI, which allows us to capture its growth at intermediate times due to the non-self-adjointness of shear flows, which can occur even when their modal growth would be absent according to Liu’s criterion.

Keywords: magnetorotationa instability; nonmodal growth; nonnormality; astrophysical Keplerian disks; liquid metals

  • Lecture (Conference)
    GdR dynamo meeting, 27.06.-01.07.2016, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-24946
Publ.-Id: 24946