Magnetic Field Generation in Stars

Abstract

Enormous progress has been made on observing stellar magnetism in stars from the main sequence through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence,in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Thus we maybe at the dawn of a new era of exciting discoveries in compact star magnetism driven by the opening of a new, non-electromagnetic observational window. We also review recent advances in the theory and computation of magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo theory. These advances offer insight into the action of stellar dynamos as well as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field generation in stars to appear in Space Science Reviews, Springe

Generation of strong magnetic fields in hybrid and quark stars driven by the electroweak interaction of quarks

“…For T 0 = 10 8 K in figures 1(a) and 1(b), B sat ≈ 1.1 × 10 14 G; and for T 0 = 10 9 K in figures 1(c) and 1(d), B sat ≈ 1.1 × 10 15 G. However, unlike [9][10][11], B sat in figure 1 is defined entirely by T 0 . The obtained B sat is close to the magnetic field strength predicted in magnetars [1], especially if T 0 = 10 9 K.…”

“…The origin of strong magnetic fields B ∼ 10 15 G in magnetars [1] is a puzzle for modern astrophysics. Despite the existence of multiple models describing the generation of such magnetic fields, which are based on magnetohydrodynamics of stellar plasmas, none of them can satisfactory describe the observational data.…”

Magnetic fields in isolated and interacting white dwarfs

“…The second is that fields are generated in convective dynamos when two stars, one of which with a degenerate core, merge (see the various merging scenarios proposed by Tout et al, 2008;Nordhaus et al, 2011;García-Berro et al, 2012;. In the following sections we will review the work done on the origin of magnetic fields in WDs and the pros and cons of the two different generation theories noting that a full review on field generation in all stars can be found in Ferrario et al (2015b).…”

The impact of the environment of white dwarf mergers on fast radio bursts

“…Interestingly, Dessart et al (2007) find that the explosion energy immediately after bounce is also much higher (about 10 51 erg) than in models in which the presence of fields is neglected. They also find that despite the extraction of angular momentum by magnetic fields, the proto-neutron star would still be rotating at ∼ 1 ms period so that a magnetic field of a few 10 15 G is likely to be generated in the process, following the α − Ω mechanism (Duncan & Thompson 1992;Thompson & Duncan 1993;Ferrario et al 2015;Wickramasinghe et al 2014).…”