Polar Spacecraft Evidence at 2 Re Geocentric Distance for Alfvenic Poynting Flux as an Energy Source for the Quasi-static Parallel Electric Field Acceleration of Auroral Electrons and Up-flowing Ion Beams in the Auroral Acceleration Region

In this paper, we provide evidence obtained during several Polar spacecraft perigee (~2 Re) passes through the auroral acceleration region that the shock-like electric field structures with amplitudes of 0.1- 1V/m responsible for the quasi-static acceleration of auroral electron beams and associated with stationary visible aurora as observed by the UVI and VIS imagers are often associated with intense (4-40 ergs/cm2s) thin (~0.25 deg) sheets of Poynting flux flowing along the ambient magnetic fields towards the Earth. Thus, we provide the first evidence that Poynting flux is the dominant form of energy transfer from higher altitudes which power the quasi-static parallel acceleration of auroral electron beams and may in fact account for nearly all of the power delivered to and dissipated at these structures. The total kinetic energy flux of the auroral electron beam responsible for the aurora as estimated from the UVI images and integrated across the arc is comparable to the Poynting flux integrated across the spatial thickness of the sheets. The electric field structures are associated with upward field-aligned beam-like ions those characteristic energies (300 eV- 5 keV) approximately track the line integral of the electric field along the spacecraft trajectory. This relation relation between the upgoing ions and this integral has been documented in other studies (S3-3, FAST) and is used to argue the ions are accelerated by parallel electric field contours which are the lower altitude closure across field lines of perpendicular electric field equipotential structures. The magnetic field perturbations structures associated with these structures and the Poynting flux are perpendicular to the ambient magnetic field and orthogonal to the direction of the quasi-static electric field structures. The E/B ratio varies from 5000 km/s to 100000 km/s which strongly exceeds the ratio expected for current closure through the ionosphere. Downward Poynting flux strongly dominates over upward or reflected Poynting flux.