Conjunction ground triangulation of auroral rays and magnetospheric processes observed by the Van Allen Probe satellite near 6 Re

The presented data from simultaneous ground-based and satellite observations in magnetically conjugated regions in the ionosphere and magnetosphere provide evidence for the relationship between electron fluxes that generate auroral rays and the processes of wave–electron interaction in the magnetosphere at 6 Re. Various types of wave modes are known to be responsible for auroral precipitation. In recent years, special attention has been given to high-intensity nonlinear broadband electrostatic waves, which have been detected in the inner magnetosphere near the equator on the Van Allen Probe A satellites (VAP-A), as in the case being considered. Using the triangulation of the aurora observations, we determined the precipitating electron energies for rays in the weak aurora during the 17 March 2015 event in the time interval 19:22–19:25 UT. We found that the main contribution to the energy spectrum of electrons comes from a peak with an energy of 50–400 eV, with an additional contribution at energies of a few tens of eV, which extends the profile to higher altitudes. The largest increase in the electron flux was recorded on the conjugate satellite VAP-A at the same time when the rays were observed in the aurora. Comparing the spectra of precipitating electrons in the raised structures of the aurora with measurements of electrons in the equatorial region aboard the VAP-A satellite, in combination with observations of the aurora, showed qualitative agreement. First, during the registration of the aurora, the electron fluxes on the satellite inside and near the loss cone increased by E ~ (10–400) eV, which corresponds to the electron energy range determined in the rays of the aurora. Second, the spectrum of precipitating electrons on a satellite contains two populations: electrons with E < 50 eV, whose fluxes decrease with increasing energy, and more energetic electrons with local peaks at E ~ 50–400 eV. It is shown that the intensification of the aurora was concomitant with broadband electrostatic waves with a maximum amplitude at frequencies <100 Hz, which were detected by the VAP-A satellite in the conjugate region near the equator. Since only broadband electrostatic fluctuations were observed on the satellite during the coincidence of the aurora and waves, we assume that broadband electrostatic waves cause electron precipitation that produces rayed structures in the aurora.
This research was funded by the Russian Science Foundation (grant no. 22-12-20017).