Storm-time variations of atomic nitrogen 149.3 nm emission

Net radiances of atomic nitrogen emission line (N-149.3 nm) from the thermosphere are extracted from the FUV spectra observed by TIMED/GUVI on dayside at sunlit latitudes. During geomagnetic storms, the N-149.3 nm intensity is clearly enhanced in the locations where O/N2 depletion and nitric oxide (NO) enhancement are observed. The N-149.3 nm intensity is linearly and tightly correlated with N2 LBHS (140-150 nm) radiance with a fixed LBHS/149.3 nm ratio of ∼4.5, suggesting that dissociation of N2 is the dominant source of the N-149.3 nm emission. In the regions without storm disturbances, the N-149.3 nm intensities are closely correlated with solar EUV flux.