Switch-on Shock and Nonlinear Kink Alfvén Waves in Solar Coronal-Hole Jets

It is generally accepted that solar coronal-hole jets are generated by fast magnetic reconnection in the low corona, whether driven directly by flux emergence from below or indirectly by instability onset above the photosphere. In either case, twisted flux on closed magnetic field lines reconnects with untwisted flux on neighboring open field lines. Some of that twist is inherited by the newly reconnected open flux, which rapidly relaxes due to magnetic tension forces that transmit the twist impulsively into the outer corona and heliosphere. We suggest that the transfer of twist launches switch-on MHD shock waves, which propagate parallel to the ambient coronal magnetic field ahead of the shock and convect a perpendicular component of magnetic field behind the shock. In the frame moving with the shock front, the post-shock flow is precisely Alfvénic in all three directions, whereas the pre-shock flow is super-Alfvénic along the ambient magnetic field. Consequently, there is a density enhancement across the shock front. Nonlinear kink Alfvén waves are exact solutions of the time-dependent MHD equations in the post-shock region when the ambient corona is uniform and the magnetic field is straight. We report 3D spherical simulations of coronal-hole jets driven by instability onset in the corona. The results are consistent with the generation of MHD switch-on shocks trailed predominantly by incompressible, irrotational, kink Alfvén waves. We will discuss the implications of our results for understanding solar jets and interpreting their heliospheric signatures in light of the new data on S-bends (a.k.a. switchbacks) from Parker Solar Probe. Our research is supported by NASA’s H-ISFM program.