Search for: All records

Abstract The high latitude ionospheric evolution of the May 10‐11, 2024, geomagnetic storm is investigated in terms of Total Electron Content and contextualized with Incoherent Scatter Radar and ionosonde observations. Substantial plasma lifting is observed within the initial Storm Enhanced Density plume with ionospheric peak heights increasing by 150–300 km, reaching levels of up to 630 km. Scintillation is observed within the cusp during the initial expansion phase of the storm, spreading across the auroral oval thereafter. Patch transport into the polar cap produces broad regions of scintillation that are rapidly cleared from the region after a strong Interplanetary Magnetic Field reversal at 2230UT. Strong heating and composition changes result in the complete absence of the F2‐layer on the eleventh, suffocating high latitude convection from dense plasma necessary for Tongue of Ionization and patch formation, ultimately resulting in a suppression of polar cap scintillation on the eleventh. 

Abstract The structure, variability, and mean‐flow interactions of the quasi‐2‐day wave (Q2DW) in the mesosphere and lower thermosphere during January 2015 were studied employing meteor and medium‐frequency radar winds at eight sites from 23°S to 76°S and Microwave Limb Sounder (MLS) temperature and geopotential height measurements from 30°S to 80°S. The event had a duration of ~20–25 days, dominant periods of ~44–52 hr, temperature amplitudes as large as ~16 K, and zonal and meridional wind amplitudes as high as ~40 and 80 m/s, respectively, at middle and lower latitudes. MLS measurements enabled definition of balance winds that agreed well with radar wind amplitudes and phases at middle latitudes where amplitudes were large and quantification of the various Q2DW modes contributing to the full wave field. The Q2DW event was composed primarily of the westward zonal wavenumber 3 (W3) mode but also had measurable amplitudes in other westward modes W1, W2, and W4; eastward modes E1 and E2; and stationary mode S0. Of the secondary modes, W1, W2, and E2 had the larger amplitudes. Inferred MLS balance winds enabled estimates of the Eliassen‐Palm fluxes for each mode, and cumulative zonal accelerations that were found to be in reasonable agreement with radar estimates from ~35°S to 70°S at the lower altitudes at which radar winds were available.