Table 3 A summary of spectral characteristics of OH (3,1) and \(\text {N}_2^+\) (1,2) bands for the two aurora events observed by the NIRAS

Aurora morphology

Aurora breakup

Isolated aurora arc intensification

NIRAS FWHM

2.5 nm

3.3 nm

OH temperature (nightly mean)

215.8 K

210.9 K

Wavelength: \(\text {P}_1(2)\), OH (3,1) band

1521.2–1525.7 nm

1520.8–1526.3 nm

Intensity of OH (3,1) band

24.6 kR

37.1 kR

Intensity of \(\text {N}_2^+\) (1,2) band

35.5 kR

41.8 kR

Ratio \(\text {N}_2^+\) (1,2) / OH (3,1)

1.4

1.1

Wavelength: \(\text {P}_1(4)\), OH (3,1) band

1540.1–1544.6 nm

1540.7–1545.2 nm

Intensity of OH (3,1) band

21.2 kR

27.3 kR

Intensity of \(\text {N}_2^+\) (1,2) band

15.9 kR

18.5 kR

Ratio \(\text {N}_2^+\) (1,2) / OH (3,1)

0.75

0.67

Contaminated OH temperature

178.8 K

172.0 K