Auroral NO⁺ 4.3 μm emission observed from the Midcourse Space Experiment: Multiplatform observations of 9 February 1997

Abstract

[1] The Spatial Infrared Imaging Telescope III (SPIRIT III) radiometer on the Midcourse Space Experiment satellite (MSX), observed enhanced 4.3 mm emission from a very well characterized aurora over the Barents Sea on 9 February 1997, in conjunction with observations by the POLAR and FAST satellites, the Loparskaya ground site, and ultraviolet and visible spectrometers aboard MSX. Measurements of the auroral location, form, spatial extent and dosing conditions were applied to specify the component of auroral 4.3 mm radiance due to the slowly produced and optically thick CO 2 n 3 (001-000) transition. An analysis based on the Auroral Atmospheric Radiance Code (AARC) indicates: (1) the emission originates near and beyond the tangent point; (2) the optically thick CO 2 n 3 radiation is largely self absorbed by the intervening atmosphere; and (3) the auroral enhancement is predominantly due to NO + Dv = 1 vibrational state transitions. In addition, the analysis indicates that the previously reported laboratory result for the NO + v ! 1 vibrational yield from the reaction, N + + O 2, is insufficient to account for the observed 4.3 mm emission. In order to explain the current results, we propose that there is additional production from the reaction, N 2 + + O, forming NO + in vibrational levels 0, 1, and 2 with relative populations of approximately 0.25, 0.5, and 0.25, respectively. The combined production processes yield an energetic electron induced efficiency of 0.56 ± 0.18 photons per auroral ion pair for NO + Dv = 1 emission at altitudes equal to or greater than 112 km.

Polar mesospheric clouds: Infrared measurements from the Midcourse Space Experiment

“…The MSX program objectives, sensors and experiments are described by Mill et al [1994] and O'Neil et al [1994]. The characterization of high latitude infrared emissions from aurora [ Sharma et al , 2001; O'Neil et al , 2007] and PMCs was part of the MSX Earth limb background measurements program. Polar mesospheric cloud observations by the MSX ultraviolet and visible (UVISI) sensors are described by Carbary et al [1999, 2001, 2002, 2003].…”

Observations of 4.26 μm CO2 Auroral Emissions From AIRS Nadir Sounder Measurements

“…Additionally, the 4.26 μm emission itself is susceptible to enhancements due to energetic particle precipitation during geomagnetic disturbances. This emission enhancement is known for both NO + (Mertens, Fernandez, et al., 2008; Mertens, Winick, et al., 2008; O’Neil et al., 2007) and CO 2 (Kalogerakis et al., 2016; Kumer, 1977; Sharma et al., 2015; Winick et al., 1987). The CO 2 auroral excitation results in NLTE, and has previously been discussed with regards to the Cross‐track Infrared Sounder (CrIS) NLTE observations in comparison to modeled NLTE radiances, which do not capture the full contribution to NLTE due to aurora (Z. Li et al., 2020), as models have assumed NLTE conditions that occur during the daytime.…”

Spatial and Temporal Variation Patterns of NO 5.3 µm Infrared Radiation during Two Consecutive Auroral Disturbances

“…The cooling process occurs due to the conversion of kinetic energy into radiative energy, which is then released into space and the lower atmosphere [14,15]. Based on satellite observations and auroral infrared detection experiments [25][26][27][28], it has been found that during the auroral disturbance, 5.3 µm radiation mainly derives from the ∆v = 1 band of NO, as shown in reaction (4):…”