Generation of superDreicer electric fields in the solar chromosphere

Resumo

The electric field generation at the front of the current pulse, which originates in a coronal magnetic loop owing to the development of the Rayleigh–Taylor magnetic instability at loop footpoints, has been considered. During the τ_A ≈ l/V_A ≈ 5−25 s time (where l is the plasma plume height entering a magnetic loop as a result of the Rayleigh–Taylor instability), a disturbance related to the magnetic field tension B_ϕ(r,t), “escapes” the instability region with the Alfvén velocity in this case. As a result, an electric current pulse I_z(z − V_At), at the front of which an induction magnetic field E_z, which is directed along the magnetic tube axis and can therefore accelerate particles, starts propagating along a magnetic loop with a characteristic scale of Δξ ≈ l. In the case of sufficiently large currents, when B_ϕ²/8π > p, an electric current pulse propagates nonlinearly, and a relatively large longitudinal electric field originates E_z ≈ 2I_z³V_A/c⁴a²B_z²l, which can be larger than the Dreicer field, depending on the electric current value.