A New Look at Nonlinear Evolution of Alfven Waves in Neutron Star Magnetospheres

Yajie Yuan (CCA, Flatiron Institute)

September 27, 2021

–

Abstract: Young and active neutron stars may experience star quakes that can launch kHz Alfven waves into the magnetosphere. An Alfven wave packet propagating along the closed field lines undergoes several interesting nonlinear processes: (1) the Alfven wave can convert to fast magnetosonic waves that leave the magnetosphere; (2) the Alfven wave packet gets sheared due to the different lengths of neighboring field lines, leading to enhanced current that triggers kinetic instabilities; (3) Alfven waves propagating to the outer magnetosphere may break and form plasmoids (closed field loops) that accelerate away from the star. Most interestingly, the third process may be a viable mechanism to produce the simultaneous X-ray bursts and fast radio bursts from the galactic magnetar SGR 1935+2154. In this talk, I will present our systematic study of these processes and discuss their observational consequences.