Comparison of electric fields and density structures seen in simulations and satellite observations

There are now clear observations of large parallel electric fields (E ∥ ) from Polar and FAST in the auroral u pward‐ c urrent r egion ( UCR ). Such fields in some events are associated with large perpendicular electric fields (E ⊥ ) and density cavities while in others they could occur without them. The observed features of the fields and density are found to be compatible with the spatial structures seen in a simulated U‐shaped p otential s tructure ( PS ) using a 2.5D electrostatic code. The spatial and temporal evolution of the U ‐ s haped PS ( USPS ) including its upward and downward motions and its striations into thin long potential structures suggest a variety of signatures in the satellite detection of E ∥ and E ⊥ .