A comparison of ground-based hydroxyl airglow temperatures with SABER/TIMED measurements over 23° N, India

Abstract

Abstract. Ground-based observations of OH (6, 2) Meinel band nightglow were carried out at Ranchi (23.3 • N, 85.3 • E), India, during January-March 2011, December 2011-May 2012 and December 2012-March 2013 using an all-sky imaging system. Near the mesopause, OH temperatures were derived from the OH (6, 2) Meinel band intensity information. A limited comparison of OH temperatures (T OH ) with SABER/TIMED measurements in 30 cases was performed by defining almost coincident criterion of ±1.5 • latitude-longitude and ±3 min of the ground-based observations. Using SABER OH 1.6 and 2.0 µm volume emission rate profiles as the weighing function, two sets of OHequivalent temperature (T 1.6 and T 2.0 respectively) were estimated from its kinetic temperature profile for comparison with OH nightglow measurements. Overall, fair agreement existed between ground-based and SABER measurements in the majority of events within the limits of experimental errors. Overall, the mean value of OH-derived temperatures and SABER OH-equivalent temperatures were 197.3 ± 4.6, 192.0 ± 10.8 and 192.7 ± 10.3 K, and the ground-based temperatures were 4-5 K warmer than SABER values. A difference of 8 K or more is noted between two measurements when the peak of the OH emission layer lies in the vicinity of large temperature inversions. A comparison of OH temperatures derived using different sets of Einstein transition probabilities and SABER measurements was also performed; however, OH temperatures derived using Langhoff et al. (1986) transition probabilities were found to compare well.

OH level populations and accuracies of Einstein-<i>A</i> coefficients from hundreds of measured lines

“…two doublets) as a function of the energy of the upper-state E . The distribution of populations displays the well-known pattern of steep population decreases for low N and weaker population gradients for higher N (Pendleton et al, 1989(Pendleton et al, , 1993Cosby and Slanger, 2007;Oliva et al, 2015;Kalogerakis et al, 2018;Noll et al, 2018b). Moreover, it indicates the expected decrease of populations for higher v with a remarkable exception for v = 8 (Cosby and Slanger, 2007;Noll et al, 2015).…”

“…Hence, OH bands with upper-state vibrational levels v up to the highest nascent state can easily be measured. Moreover, the rotational level populations for the different v reveal high overpopulation for high rotational states N compared to the lowest three or four levels under the assumption of a thermal distribution (Pendleton et al, 1989(Pendleton et al, , 1993Dodd et al, 1994;Cosby and Slanger, 2007;Oliva et al, 2015;Noll et al, 2018b). The pseudotemperatures for the high-N populations achieve values up to those found for the v levels (Oliva et al, 2015).…”

OH level populations and accuracies of Einstein-A coefficients from hundreds of measured lines

“…3.3), which is mainly based on the calculations of Goldman et al (1998) for OH. Moreover, we use the coefficients from van der Loo and Groenenboom 2008 Other comparisons used a smaller number of sets (French et al, 2000;Cosby and Slanger, 2007;Noll et al, 2015;Parihar et al, 2017;Noll et al, 2018b). Note that the three oldest sets lack a significant number of the measured 723 Λ doublets.…”

Rare Occurrence of Off‐Equatorial Edge Initiating and Equatorward Surging Plasma Depletions Observed in OI 630‐nm Imaging

“…This f/4 optics‐based imaging system comprises a Mamiya fisheye lens, a shutter unit, the six‐filter wheel assembly, the reimaging optics, and a 512 × 512 pixels back‐illuminated charge‐coupled device as the detector. Parihar et al () have described this imaging system. At OI 630.0‐nm heights (~ 250 km), useful horizontal coverage of this imager was about 1,800 km.…”