Near‐Earth plasma sheet azimuthal pressure gradient and associated auroral development soon before substorm onset

The azimuthal plasma pressure gradient in the near‐Earth plasma sheet makes crucial contributions to field‐aligned current (FAC) formation. Numerical simulations and statistical observations have shown that a plasma pressure peak tends to build up in the premidnight region of the near‐Earth plasma sheet during the substorm growth phase owing to enhanced magnetic drift. This leads to azimuthal pressure gradients in this region. The temporal …