16:45 〜 17:00
[PEM13-17] Decay of ionospheric irregularity due to auroral particle impact
キーワード：ロケット、電離圏擾乱、オーロラ
Ionospheric irregularities have been systematically investigated during the last four decades. The combination of in-situ and ground based observation enables the investigation of the irregularity associated with the auroral particle precipitation and whether the irregularity was decayed due to the conductance increasing in the E-region. Therefore, the purpose of this presentation is to investigate the potential relationship between auroral particle precipitation and F-region plasma irregularity formation and decay by using rocket in-situ and ground based measurements.
The VISIONS-2 35.039 sounding rocket was launched from Ny-Ålesund, Svalbard, on 7 December 2018 at 11:06 UT, and traveled overhead of the cusp aurora. The payload reached an apogee of 806.6 km and provided measurements of the electric field (E) and electron density (Ne) with a high sampling rate of 6250 Hz. The high sampling data allows to estimate the horizontal structure of E and Ne from meters to kilometers scale.
The horizontal variation for the electron density and electric field (ΔNe/Ne and ΔE) and integrated power spectral density of Ne and E (ΣPNe and ΣPE) for 1-10, 10-100, and 100-1000 Hz range were derived. Those values were compared with the 557.7 and 630.0 nm emission intensity obtained from an 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. ΔNe/Ne, ΔE, ΣPNe, and ΣPE 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 showed indications of decay when the 557.7 nm emission intensities enhanced above 4.5 kR. This may suggest that particle impact ionization created sufficient Pedersen conductance in the E-region to short the F-region current. Thus, the irregularity in the F-region and rocket altitude was likely to decay. This mechanism efficiently affects damping of the 10 m scale irregularities.
The VISIONS-2 35.039 sounding rocket was launched from Ny-Ålesund, Svalbard, on 7 December 2018 at 11:06 UT, and traveled overhead of the cusp aurora. The payload reached an apogee of 806.6 km and provided measurements of the electric field (E) and electron density (Ne) with a high sampling rate of 6250 Hz. The high sampling data allows to estimate the horizontal structure of E and Ne from meters to kilometers scale.
The horizontal variation for the electron density and electric field (ΔNe/Ne and ΔE) and integrated power spectral density of Ne and E (ΣPNe and ΣPE) for 1-10, 10-100, and 100-1000 Hz range were derived. Those values were compared with the 557.7 and 630.0 nm emission intensity obtained from an 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. ΔNe/Ne, ΔE, ΣPNe, and ΣPE 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 showed indications of decay when the 557.7 nm emission intensities enhanced above 4.5 kR. This may suggest that particle impact ionization created sufficient Pedersen conductance in the E-region to short the F-region current. Thus, the irregularity in the F-region and rocket altitude was likely to decay. This mechanism efficiently affects damping of the 10 m scale irregularities.