biMaxwellian
BiMaxwellian is a term used in plasma physics to describe a velocity distribution of particles in a magnetized plasma where the distribution is Maxwellian in both directions, but with different temperatures parallel and perpendicular to the magnetic field. This anisotropy reflects different heating or cooling processes along and across magnetic field lines and is common in magnetized environments such as the solar wind, planetary magnetospheres, and tokamak edge plasmas.
The BiMaxwellian distribution function, oriented with the magnetic field along the z-axis, can be written as
f(v) = n / (π^(3/2) v_th_perp^2 v_th_para) × exp[-(v_x^2 + v_y^2)/v_th_perp^2 - v_z^2/v_th_para^2],
where v_perp^2 = v_x^2 + v_y^2, v_para = v_z, and v_th_perp = sqrt(2 k_B T_perp / m), v_th_para = sqrt(2 k_B T_para
Physically, the BiMaxwellian implies a pressure tensor with P_perp = n k_B T_perp and P_para = n k_B
Applications include modeling and fitting observed particle distributions in space plasmas, informing kinetic theory and Vlasov