Thermospheric NO Cooling During 2003 October “Halloween Storm”: Revisited

Abstract

AbstractThe Nitric Oxide (NO) emission at 5.3 μm wavelength is a well‐known coolant above 100 km. It effectively regulates thermospheric temperature during space weather events. We studied NO cooling emission over Tromsø (geographic:69.59°N, 19.22°E; cgm:66.58°,102.94°), Norway by using the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) simulation driven by both Heelis and Weimer models as sources of geomagnetic forcing during October–November 2003 storm. The Weimer driven TIEGCM significantly overestimates thermospheric Nitric Oxide and Atomic Oxygen densities and underestimates temperature as compared to the Heelis driven simulation. The density ratio between the Weimer and Heelis driven estimations decreases with increasing altitude for both NO and atomic oxygen densities. The Heelis driven Joule heating rate agrees very well with the European incoherent scatter (EISCAT) radar measurements. It peaks during the main phase of the storm with magnitude about 4–5 times higher than that driven by Weimer model which peaks during the recovery phase. The difference in Joule heating rates between the Heelis and Weimer driven models increases with storm intensity, reaching a peak discrepancy of about an order of magnitude during the October‐November 2003 storm. An early and stronger NO cooling enhancement is predicted by Heelis driven TIEGCM simulation. It overestimates NO cooling emission by about 2–3 times as compared to SABER observations and about 4–5 times the Weimer driven calculation. This strong difference between the two models can be attributed to the model calculations of high latitude electric field and convection patterns.