Igoshev, Andrei, Moraga, Nicol\u00e1s A., Reisenegger, Andreas, Skene, Calum S. and Hollerbach, Rainer<\/p>\n\n\n\n
Magnetic field evolution in neutron star cores is not fully understood. We describe the field evolution both for one barotropic fluid as well as two collisionally coupled barotropic fluids with different density profiles using the anelastic approximation and the Navier\u2013Stokes equations, to simulate the evolution in three dimensions. In the one-fluid case, a single fluid describes the motion of the charged particles. In the two-fluid model, the neutral fluid is coupled to the electrically conductive fluid by collisions, the latter being dragged by the magnetic field. In this model, both fluids have distinct density profiles. This forces them to move at slightly different velocities, resulting in a relative motion between the two barotropic fluids\u2014ambipolar diffusion. We develop a code based on Dedalus and study the evolution of simple poloidal dipolar and toroidal magnetic fields. Unlike previous 2D studies that found poloidal magnetic fields evolving towards a stable Grad\u2013Shafranov equilibrium, in our 3D simulations, we find an instability. The fastest growing azimuthal harmonics are m=4 and m=6 for Re=2, and m=2 for Re=0.1, which might be more relevant for neutron star core conditions. The instability grows on Alfv\u00e9n timescale. After the instability saturates, a highly nonlinear Lorentz force introduces small-scale fluid motion that leads to turbulence, development of a cascade and significant, non-axially symmetric changes in the magnetic field configuration. Fluid viscosity plays an essential role in regularizing the small-scale fluid motion, providing an energy drain.<\/p>\n\n\n\n
Paper in ApJ<\/a><\/p>\n\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" Igoshev, Andrei, Moraga, Nicol\u00e1s A., Reisenegger, Andreas, Skene, Calum S. and Hollerbach, Rainer Magnetic field evolution in neutron star cores is not fully understood. We describe the field evolution both for one barotropic fluid as well as two collisionally coupled barotropic fluids with different density profiles using the anelastic approximation and the Navier\u2013Stokes equations, to … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-223","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"http:\/\/www.pulsars.info\/wordpress\/wp-json\/wp\/v2\/posts\/223","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.pulsars.info\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.pulsars.info\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.pulsars.info\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.pulsars.info\/wordpress\/wp-json\/wp\/v2\/comments?post=223"}],"version-history":[{"count":1,"href":"http:\/\/www.pulsars.info\/wordpress\/wp-json\/wp\/v2\/posts\/223\/revisions"}],"predecessor-version":[{"id":224,"href":"http:\/\/www.pulsars.info\/wordpress\/wp-json\/wp\/v2\/posts\/223\/revisions\/224"}],"wp:attachment":[{"href":"http:\/\/www.pulsars.info\/wordpress\/wp-json\/wp\/v2\/media?parent=223"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.pulsars.info\/wordpress\/wp-json\/wp\/v2\/categories?post=223"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.pulsars.info\/wordpress\/wp-json\/wp\/v2\/tags?post=223"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}