Impact of Recent Laboratory N$_2$ Data to our Understanding of Thermospheric Nitric Oxide (NO)

In spite of its status as a minor species, NO plays key roles in many upper atmospheric processes. As the only heteronuclear molecule, its fundamental, $\Delta$v=1 emission cools the thermosphere (z$>$100 km). Its low ionization potential ensures that NO$^+$ is the end product of the ion-neutral chemistry in the ionospheric E-region. And in the presence of excess atomic oxygen, NO will catalytically destroy ozone. The production of NO is initiated when N$_2$ is ionized, dissociated, or excited by the solar EUV irradiance ($\lambda <$100 nm). In the mesosphere and lower thermosphere (MLT), much of the irradiance is contained in the highly variable soft x-ray region (1$<\lambda <$20 nm). The resulting photoelectrons produce additional ionization as well as excitation of metastable, chemically-reactive species like the first electronically excited N$_2$ state, N$_2$(A$^3\Sigma_u^+$). This talk will incorporate recent laboratory data on the N$_2$ photoabsorption and electron-impact cross-sections into a 1D photochemical reaction-diffusion model of the thermosphere. It is shown that spin-forbidden ($\Delta$S=1) excitation to the N$_2$ triplet manifold enables neutral N$_2$ to participate in the NO production. Additional physical and chemical uncertainties relevant to NO production and loss are also presented.