Development and validation of observational and modeling tools for ground-based studies of the upper atmosphere and ionosphere

We report recent progress on ground-based studies of optical emissions from airglow and aurora. We used a state-of-the-art hyperspectral imager to collect airglow and auroral data, which were analyzed using updated optical data analysis and modeling tools.

The observations were made by the High Throughput and Multislit Imaging Spectrograph (HiT&MIS), a moderate resolution (λ/Δλ ~15,000) spectrograph with a field of view of 0.1° × 40°.  The instrument can be customized for a scientific study by choosing selected spectral bands within the visible to near infrared regime. For the studies reported here, it simultaneously recorded prominent airglow and auroral features such as OI (557.7 nm, 630.0 nm, 777.4 nm), N₂⁺ (427.8 nm), OH (784.1 nm, 786.0 nm, 655.3 nm), as well as the Hα (656.3 nm) and Hβ (486.1 nm) emissions.

For nightglow studies, HiT&MIS collected spectral images between late January to early March in 2022 from Lowell, Massachusetts, USA (42.6° N, 71.3° W). Due to its physical location, zenith observations were not possible, and we developed a 2-D framework for the GLOW model (GLOW-2D). We also updated older versions of the neutral atmosphere, ionosphere, and magnetic field models previously used in GLOW by incorporating NRLMSIS-2.1, IRI-2020 and IGRF-14, respectively. In addition, simultaneous Vertical TEC data provided by the GNSS network and digisonde data from nearby Millstone Hill Observatory were used to derive the GLOW-2D model predictions while comparing against the observed optical measurements.

HiT&MIS was deployed in Kiruna, Sweden (67.8° N, 20.2° E) to support two Oxygen and its Role In Generating and Influencing Nightglow (ORIGIN) sounding rocket missions in January and December 2025, respectively. The characteristic energy and flux of the precipitating electrons in several nighttime auroras were obtained from the measured green and red line intensities constrained by the GLOW-2D model. Currently, we are incorporating other emissions to further refine the model results and preparing a HiT&MIS data processing pipeline to analyze round-the-clock auroral spectroscopic data.