Search for: All records

The 2022 Tongan volcanic eruption released significant energy into the atmosphere. Tropospheric satellite images show that the eruption generated pressure waves that traveled globally. The Global Observation of the Limb and Disk (GOLD) mission observed significant wave‐like thermospheric temperature perturbations (>100 K) from 12 to 16 UT. These temperature perturbations' spatial curvatures and arrival times are initially similar to the tropospheric wave‐fronts but differ significantly with eastward propagation. The perturbations had a phase speed of ∼300–400 m/s and wavelengths greater than 2,400 km. Near‐concurrent Ionospheric Connection Explorer neutral wind measurements suggest that the eruption's effects reversed the direction of the prevailing thermospheric zonal winds around the perturbed regions. The eruption's global and whole atmospheric effects provide a unique opportunity to study how different atmospheric layers exchange energy and momentum during explosive events. GOLD's synoptic observations are uniquely positioned to study these effects in the middle thermosphere.

This paper discusses the solar cycle variation of the DE3 and DE2 nonmigrating tides in the nitric oxide (NO) 5.3 μm and carbon dioxide (CO₂) 15 μm infrared cooling between 100 and 150 km altitude and ±40° latitude. Tidal diagnostics of SABER NO and CO₂cooling rate data (2002–2013) indicate DE3 (DE2) amplitudes during solar maximum are on the order of 1 (0.5) nW/m³in NO near 125 km, and on the order of 60 (30) nW/m³in CO₂at 100 km, which translates into roughly 15–30% relative to the monthly zonal mean. The NO cooling shows a pronounced (factor of 10) solar cycle dependence (lower during solar minimum) while the CO₂cooling does not vary much from solar min to solar max. Photochemical modeling reproduces the observed solar cycle variability and allows one to delineate the physical reasons for the observed solar flux dependence of the tides in the infrared cooling, particularly in terms of warmer/colder background temperature versus smaller/larger tidal temperatures during solar max/min, in addition to cooling rate variations due to vertical tidal advection and tidal density variations. Our results suggest that (i) tides caused by tropospheric weather impose a substantial—and in the NO 5.3 μm case solar cycle dependent—modulation of the infrared cooling, mainly due to tidal temperature, and (ii) observed tides in the infrared cooling are a suitable proxy for tidal activity including its solar cycle dependence in a part of Earth's atmosphere where direct global temperature observations are lacking.