Fig. 1: Existence of Nodal disks in magnetohydrodynamic plasma.

a Dispersion of the absolute value of eigen frequency ω with \(\omega _c = 2,\,\kappa = 0.4,\,\tau = 2\). Along the k_z axis, the bands are differentiated as right/left handedness circular polarization wave (R/L-wave) and Langmuir wave whose polarization is only in the z-direction. The bands along transverse directions (x-direction) have degeneracies denoted by the red/blue dots. Owing to the rotational symmetry in the plasma system, the dots in a form the loops in b. Akin to the Weyl points, there are two species of Nodal disks in the plasma system with opposite topological charge (+/–1 charge denoted by the red/blue color) that are connect by the spatial inversion operation. c–f Real and imaginary part of the eigen frequency in the k_x−k_z and k_x−k_y plane. Note that in the k_x−k_z plane, real and imaginary parts are simultaneously degenerated at isolated points away from the k_z axis. While in the k_x−k_y plane, the degeneracies form a ring