Jens Mahlmann

Different phases of the fast magnetosonic (fms) pulse current sheet interaction in a large system. The pulse propagates upwards into the upstream. We display the current density (bottom panel), as well as out-of-plane electric field of the emerging fast wave signal (top panel). The compression triggers reconnection in the otherwise stable current sheet. Small plasmoids appear and merge to form hierarchically larger ones under the emission of a firework of high-frequency fms waves.

An initially linear Alfvénic perturbation propagates along magnetic field lines in the magnetar magnetospheres. Interaction with the curved magnetic field lines converts part of the Alfvén wave energy into fast magnetosonic modes propagating across field lines. Alfvén waves are strongly sheared due to the different lengths of magnetic field lines and bounce in the inner magnetosphere after reflection from the stellar surface. The fast wave amplitude relative to the magnetic field becomes significant as the generated pulses propagate outwards. Electric zones can develop (green contour).

3D visualization of field line dynamics in the magnetar magnetosphere. A constant twist is induced in the twisting region centered at θ = 55° with an extension of 0.1π. Subsequent eruptions open up the magnetosphere on a global scale. Volume-filling colors denote the conserved parallel current. Inset plots represent poloidal (field lines) and toroidal (color) magnetic fields in a meridional slice centered on the induced twist.

3D current structure emerging during the interaction of continuously overlapping Alfvén waves. Current structures stabilize over time and extend across the full length of the domain. The sheets ripple as they are stretched between elongated eddies and eventually break up into smaller (turbulent) structures.

Three-dimensional visualizations of interacting binary magnetospheres for aligned companion. We display the field-aligned force-free current λ (left panel) and the relative strength of the electric field E/B (right panel). The right panels show regions of strong electric fields throughout the volume and colorized faces (grayscale) of the cube.

Currents during the evolution of a flux tube with both ends tied to conducting surfaces (α = 1, p0 = 0.75, L/r0 = 14). During the evolution, structures characteristic of the asymmetric m = 1 (kink) mode as well as the m = 2 (fluting) mode arise. The m = 2 mode has shorter wavelengths than the m = 1 mode. In the relaxed state, some currents remain.

During each collision of the primary Alfvén wave packets, the energy in the (1,1) mediator mode grows. The (1,1) mode can be decomposed into Alfvén wave packets and fast waves. Such fast waves effectively propagate as spherical waves in a periodic domain. They continuously interact with Alfvén waves and other fast waves.