Formation of Magnetic Fields on Grand Scale Distances Involving Anisotropic Electron Distributions*

The emergence of significant magnetic fields in cosmic plasmas over large scale distances is an important issue to deal with and is still unresolved. One of the difficulties is that known and potentially applicable theories, such as those based on the Weibel instability, suffer from involving unrealistically small distances (in particular, $c/omega_{pe}$). The presently proposed theory starts from considering the electron density and temperature fluctuations [1] which can be excited in circumbinary disks sustained by pairs of black holes. These low frequency fluctuations can drive a “magneto-thermal alternator” of the kind introduced in Ref. [2] which can produce a slowly varying and sheared magnetic field structure. The shearing component of this field can then be amplified by a magneto-thermal reconnection process [2,3] up to substantial amplitudes following the emergence of electron populations with non-thermal distributions in momentum space and significant (spatial) gradients. The simplest case treated is that of an electron population with anisotropic temperatures. An important feature of magneto-thermal reconnection is that the width of the layer where reconnection takes place remains significant relative to the involved macroscopic distances [2] unlike the case of the weakly collisional tearing mode identified in Ref. [4]. *Sponsored in part by the Kavli Foundation (MIT) and by CNR of Italy.

1. B. Coppi, Fundamental Pl. Phys., 100007 (2023).

2. B. Coppi, and B. Basu, Phys. Lett. A, 397, 127265 (2021).

3. B.Coppi,J.Mark,G.Bertin and L.Sugiyama,Ann.Phys.119,370(1979)

4. B. Coppi, Phys. Fluids (1964).