Excitation of the ionized nitrogen molecule in the aurora

Abstract

An understanding of the excitation mechanism of the ionospheric molecules during auroral activity is of vital importance for the overall ionospheric understanding including its interaction with the magnetosphere. In this thesis we study two emissions originating from the excited nitrogen molecule ion. The first negative (0,1) emission at 4278 Å originating from the B state, and Meinel (2,0) emission at 7852 Å originating from the A state during moderate to strong aurora have been observed with an imaging spectrograph at Poker Flat, Alaska. The B state has a short lifetime compared to the inverse collision frequency at auroral altitudes, while the A state can be deactivated during collisions at altitudes near 95 km. The B state can be populated by an up-welling of N₂ into sunlit regions. Both processes are expected to depend on auroral activity. If none of the processes are present we expect a constant ratio between the two emissions. Data for three nights have been studied and a constant ratio was found at all times. Thus neither deactivation of the A state or up-welling of the ion seem to appear during the observations presented here. The values of the ratio for the three nights are 2.53 plus-minus 0.38, 3.05 plus minus 0.22, and 3.40 plus minus 1.10, respectively.