Decay ionospheric irregularity correlate with the green line auroral emission enhancement

Abstract:

The VISION-2 sounding rocket was launched from Ny-Ålesund, Svalbard, on 7 December 2018 at 11:06 UT, and flew overhead of the cusp aurora. The payload reached an apogee of 806.6 km and provided measurements of the electric field and electron density with a high sampling rate of 6250 Hz. The high sampling data allows us to estimate the horizontal structure of the electron density and electric field from meters to km scale.

The horizontal irregularity for the electron density and electric field (∆Ne/Ne0 and ∆E) and integrated power spectra of Ne and E for 1-10, 10-100, 100-1000 Hz were derived. Those values were compared with the 557.7 and 630.0 nm emission intensity obtained from all-sky camera installed in Ny-Ålesund projected at the footprint of the rocket, which was calculated by the tracing Earth’s magnetic field line from the rocket altitude to the emission layer. Both ∆Ne/Ne0 and ∆E irregularity amplitude and integrated power spectra increased with the 630.0 nm emission intensity. Of particular interest is that those values also increased with the 557.7 nm emission intensity up to 4.5 kR, but the plasma irregularities shows indications of decay 557.7 nm emission intensities above 4.5 kR.

The generated irregularities in the F-region coincides with cusp auroral particle precipitation. It remains to be explored whether the particle impact ionization of the electron beams play a direct role on the granulation of plasma irregularities. When the 557.7 nm emission was enhanced above 4.5 kR the plasma irregularities decayed. This indicates that particle impact ionization created sufficient Pedersen conductance in the E-region to shortcut the F-region electron density gradients. This mechanism efficiently affects damping of the 10 m scale irregularities.