## 3 Results
### Correlation Analysis between Radiance and the Dst Index during Auroral Events  
Solar wind is essentially a supersonic stream of charged particles released from the outer atmosphere of the Sun during periods of strong solar activity, consisting mainly of protons and electrons. The solar wind speed, V\({}_{\rm sm}\), is one of the most important parameters reflecting solar activity strength. The AE index is a measure of the strength of auroral electrojet currents derived from data acquired by 12 magnetometers distributed evenly along the auroral zone. On the other hand, the Dst index characterizes the intensity of symmetrical perturbations in the Earth's dipole equator magnetic field. Furthermore, the IMF B\({}_{\rm Z}\), displayed in Figure 1, represents the southward (northward) orientation of the interplanetary magnetic field, and it has a weak correlation with the variation in radiance. The entire radiance process at NO 5.3 \(\upmu\)m (reactions (4)-(7)) is influenced by temperature. Hence, this study focuses on examining the correlation between radiance values measured at a distance of 120 km around 55\({}^{\circ}\)S 160\({}^{\circ}\)W of SABER channel 6 NO 5.3 \(\upmu\)m and variables such as temperature, solar wind speed, AE index, and Dst index during the period of 18-23 November. The findings are illustrated in Figure 7, with the red line representing the fitted curve. Figure 7 depicts a stronger correlation between the Dst index and the NO 5.3 \(\upmu\)m radiance value, with an adjusted R\({}^{2}\) (R\({}^{2}_{\rm adj}\), it constitutes an adjusted version of the coefficient of determination, R\({}^{2}\), incorporating considerations of both the number of independent variables and the sample size to prevent overfitting) of 0.42. This could be due to reaction (4), because reaction (4) is temperature-dependent. Consequently, atmospheric parameters such as thermospheric temperature, and densities of nitric oxide and atomic oxygen dictate the behavior of nitric oxide infrared radiative emission [14; 15]. These physical changes, however, are driven by changes in solar irradiance and geomagnetic conditions [24]. The Dst index directly characterizes the variations in the geomagnetic field. Hence, a significant correlation exists between them, justifying further analysis. The present study identifies the tangent point altitude with the highest correlation for the Dst index and the NO 5.3 \(\upmu\)m radiance, and analyzes the corresponding R\({}^{2}_{\rm adj}\) for radiance values within the 50-200 km altitude range using a 10 km interval. These results are presented in Figures 8 and 9. Figure 7: Correlation between the measured radiance of NO 5.3 \(\upmu\)m at 120 km around 55\({}^{\circ}\)S 160\({}^{\circ}\)W of SABER and temperature, V\({}_{\rm sw}\), AE index, and Dst index during 18–23 November 2003. Based on the above figures, it can be observed that within the altitude range of 50-80 km, the correlation exhibits relative stability, ranging from 0.5 to 0.6, with minimal variation. Nevertheless, the correlation steadily decreases within the range of 80-110 km, reaching its lowest value of 0.41 at 110 km. This can be attributed to the complexity of photochemical reactions occurring around the altitude of 110 km, as the Dst index is derived from global station measurement data. Consequently, the Dst index is unable to be determined by the Dst index. Figure 8: Correlation of Dst index with NO 5.3 \(\upmu\)m radiance at different altitudes around 55\({}^{\circ}\)S 160\({}^{\circ}\)W of SABER during 18–23 November 2003. Figure 9: The adjusted R\({}^{2}\) of the fitting curves corresponding to different altitudes during 18–23 November 2003.  
to capture such fine details, leading to a diminished correlation at an altitude around 110 km. Subsequently, the correlation progressively rises with increasing altitude, reaching its peak of 0.88 at 170 km, denoting the strongest correlation. This high correlation is maintained within the altitude range of 160-200 km, with values around 0.87.