Storm-time variations of atomic nitrogen 149.3 nm emission
Introduction
The condition of the thermosphere strongly depends on the energy inputs (solar EUV flux, particle and Joule heating, adiabatic heating, tides and gravity waves from the lower atmosphere), cooling processes (radiative cooling, such as CO2 and NO IR radiation, adiabatic cooling), and transport due to neutral wind. Large neutral disturbances have been observed during geomagnetic storms, such as temperature and total density increase, composition changes (O/N2 decrease, NO enhancement). Bruinsma et al., (2006) reported a 300–800% increase in the thermospheric density around 400–500 km on a global scale based on CHAMP and GRACE measurements during the November 20–21, 2003 superstorm. By analyzing TIMED/GUVI limb data, Meier et al., (2005) found the exospheric temperature was nearly doubled (∼1 000 K versus ∼1800 K) during the 2003 superstorm. Thermospheric O/N2 column density ratios show significant depletion during storms (Zhang et al., 2004) based on TIMED/GUVI imaging data. More recently, TIMED/GUVI spectrograph data have been used to derive O/N2 ratio and NO column density simultaneously (Zhang et al., 2014). In this paper, we report storm-time atomic nitrogen emission (149.3 nm) enhancements at sunlit latitudes that are likely due to storm-time increase in N2 density (major source) and minor contribution from enhanced NO as well as enhanced N transported from the auroral region.
Section snippets
Data
Under an imaging mode, TIMED/GUVI (Paxton et al., 2004; Christensen et al., 2003) measures intensities of thermospheric emissions in five “colors”: 121.6 nm, 130,4 nm, 135.6 nm, LBHS (∼140–150 nm) and LBHL (∼165–180 nm) from 2002 to 2007. Emissions intensities in the “colors’ are useful and have been used to derived O/N2 ratio (Zhang et al., 2004, Strickland et al., 2004, Meier et al., 2005) and auroral particle information (Zhang and Paxton, 2008). However, it is not easy to separate different
Discussion
To understand the variations in the observed N-149.3 nm radiances, it is important to briefly review the key sources of the emission. Meier et al., (1980) listed three major processes that lead to the N-149.3 nm emissions:where equations (1), (2), (3) represent the processes of electron impact on atomic nitrogen, N2 dissociation due to electron impact, and photodissociation of N2, respectively. The electrons in the equations are mostly
Summary
Net N-149.3 nm emission intensities from the thermosphere are determined using the TIMED/GUVI spectrograph data. During geomagnetic storms, the N-149.3 nm radiances at sunlit latitudes were enhanced in the regions with O/N2 depletion and NO enhancement. On the other hand, the N-149.3 nm radiances in the low and equatorial regions (undisturbed by geomagnetic storms) are strongly correlated with solar EUV flux. A close quantitative comparison indicates that the N2 LBHS radiance is proportional to
Acknowledgements
This work is partially supported by NASA grants (NNX14AC13G, NNX14AK74G2 and NNX15AB83G) and NSF grant (1681-206-2009506). The AURIC software was provided by Doug Strickland and Scott Evans of Computational Physics Inc. Discussion with Sam Yee is appreciated.
References (14)
Atmospheric ultraviolet radiance integrated doe (AURIC): theory, software architecture, inputs, and selected results
J. Quant. Spectrosc. Radiat. Transfer
(1999)- et al.
An empirical Kp-dependent global auroral model based on TIEMD/GUVI FUV data
J. Atmos. Sol. Terr. Phys.
(2008) - et al.
Storm-time behaviors of O/N2 and NO variations
J. Atmos. Sol. Terr. Phys.
(2014) - et al.
A model of nitric oxide in the lower thermosphere
J. Geophys. Res.
(2002) - et al.
Thermosphere density response to the 20–21 November 2003 solar and geomagnetic storm from CHAMP and GRACE accelerometer data
J. Geophys. Res.
(2006) Initial observations with the global ultraviolet imager (GUVI) in the NASA TIMED satellite mission
J. Geophys. Res.
(2003)- et al.
The response of thermospheric atomic nitrogen to magnetic storms
J. Geophys. Res.
(1983)
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