Contribution of chemical processes to infrared emissions from nitric oxide in the thermosphere

Abstract

Infrared emissions from nitric oxide (NO) are the dominant source of radiative cooling between 120 and 200 km and play an important role in determining the energy budget of the Earth's upper atmosphere. The emission arises as a consequence of producing vibrationally excited NO, either by collisions with energetic atomic oxygen or via the reaction of atomic nitrogen with molecular oxygen. The latter process is a potentially important source of cooling, as it can excite the higher vibrational levels (v ≥ 2) of nitric oxide, resulting in the emission of multiple photons. This chemiluminescent emission has been modeled by calculating the level populations of NO(v ≤ 10) considering production from the reaction of N(2D) and N(4S) with O2, along with interlevel cascade due to radiative deexcitation and collisional quenching. We integrate this model into the NCAR TIE‐GCM (Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model) to calculate the contribution of chemiluminescence to infrared emissions from NO in the thermosphere. For day 80 of 2003, it is shown that chemiluminescence accounts for 15–30% of the total column emissions from NO in the sunlit thermosphere between ±50° latitude. More than 60% of the chemiluminescence is produced from v ≥ 3, indicating that these vibrational levels are an important source of thermospheric cooling. Model calculations of the first overtone emission (Δv = 2) are shown to be in agreement with measurements by the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS‐1A) experiment. A computationally inexpensive parameterization which calculates the chemiluminescence from v ≤ 10 within 5% of the full calculation is also presented.

A Numerical Study of the Thermospheric Overcooling During the Recovery Phases of the October 2003 Storms

“…The details are given in the appendix. As shown in Figure A1, the higher vibrational levels (v ≥ 2) of NO and the N 2 (A) have important contribution to the NO emission during quiet time, which is consistent with previous studies (Venkataramani et al, 2016;Yonker, 2013). However, they contribute little to the NO production during storm time and the thermosphere recovery in this event.…”

“…Besides collisions with oxygen atom, the excited NO also can be generated from reactions (R1) and (R2) in higher vibrational levels(v ≥ 2), which would radiate 5.3-μm emission and 2.7-μm overtone emission (Miquel et al, 2003;Sultanov & Balakrishnan, 2006). Venkataramani et al (2016) integrated the chemiluminescence, which resulted from chemical excitation NO, into the TIEGCM and demonstrated that the contribution of chemiluminescence constituted 30% of total NO emissions during quiet time.…”

“…Due to the great contribution of chemiluminescence and N 2 (A) during quiet time, we conducted two additional simulations, which are similar to Run 2 but consider the contribution of either chemiluminescence or N 2 (A) to the NO production. The calculation method for chemiluminescence was described by Venkataramani et al (2016). For the calculation of N 2 (A), we adopted a simplified way as suggested by Yonker (2013).…”

“…Yonker (2013) demonstrated that the electronically excited state of molecular nitrogen, N 2 (A), contributes to the NO production effectively. Venkataramani et al (2016) integrated the high vibration level of NO from chemical processes into the TIEGCM and suggested that the chemical excitation has significant influence on the NO emission. Sheng et al (2017) investigated the density recovery time scale using the TIEGCM with the temperature-dependent reaction rate from Duff et al (2003) Duff et al (2003) is applied in the simulation.…”

Thermospheric nitric oxide response to shock‐led storms

“…Recently, Venkataramani et al . [] modeled low‐latitude NO emission by calculating the populations of NO ( υ ≤ 10) given the reaction of N( 2 D) or N( 4 S) with O and O 2 . They found that for geomagnetic quiet conditions vibrationally ‐excited NO produced by N( 2 D) is the dominant source of the emission in the sunlit thermosphere, contributing on average ~85% of the emission between 100 and 200 km.…”