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Abstract This work investigates mesoscale structures in the northern high‐latitude thermosphere using an ascending‐descending accelerometry (ADA) technique to determine whether observed in‐track acceleration perturbations are influenced by in‐track winds. The ADA technique is applied to accelerometer measurements from the Challenging Minisatellite Payload mission between 2003 and 2006 during quiet geomagnetic activity, revealing a climatological view of regularly occurring acceleration perturbation structures. The ADA technique reveals a structured acceleration enhancement on the dayside with a strong signature of density dominance confined to a spatial envelope ranging from 8:00 to 17:00 magnetic local time (MLT) and between 72° and 82° magnetic latitude, aligning with past observations of the cusp density enhancement. Additionally, this sector displays a wind perturbation structure with a reversal in direction that coincides with the center of the enhancement. The premidnight quadrant shows strong evidence of wind influence in the acceleration perturbations from 18:00 to 24:00 MLT between 70° and 90° magnetic latitude associated with southward wind perturbations. This suggests that past analyses of this region could have misidentified this structure as a density enhancement by neglecting in‐track wind influences in accelerometry‐derived mass density data sets. The early morning quadrant consists of negative acceleration perturbations attributed to density depletions, with signatures of southward wind perturbations. These mass density perturbations, in conjunction with in‐track wind perturbations, suggest that the coupled ionosphere‐thermosphere mechanisms responsible for the high‐latitude density structure also influence the wind structure. This work is supplemented with TIEGCM simulations to verify the accuracy of ADA and highlight discrepancies between the simulations and observations.
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Distinguishing Density and Wind Perturbations in the Equatorial Thermosphere Anomaly
Abstract In this paper, the equatorial thermosphere anomaly (ETA) is investigated using accelerometer measurements to determine whether the feature is density‐dominated, wind‐dominated, or some combination of the two. An ascending‐descending accelerometry (ADA) technique is introduced to address the density‐wind ambiguity that appears when interpreting the ETA in atmospheric drag acceleration analyses. This technique separates ascending and descending acceleration measurements to determine if a wind's directionality influences the interpretation of the observed ETA feature. The ADA technique is applied to accelerometer measurements taken from the Challenging Minisatellite Payload mission and has revealed that the ETA is primarily density‐dominated from 9:00 to 16:00 local time (LT) near 400 km altitude, with the acceleration perturbations behaving similarly between 2003 and 2004 across all seasons. This finding suggests that the perturbations in the acceleration due to in‐track wind perturbations are small compared to the perturbations due to mass density, while indicating that the formation mechanisms across these local times are similar and persistent. The results also revealed that in the terminator region at 18:00 LT the acceleration perturbations deviate appreciably between ascending and descending passes, indicating different or multiple processes occurring at this local time compared to the 9:00–16:00 LT ascribed to the ETA. These results help constrain ETA formation theories to specific local times and thermospheric property responses without the use of supplemental wind measurements, while also indicating regions where in‐track winds cannot always be neglected.
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- Award ID(s):
- 1936665
- PAR ID:
- 10511224
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 129
- Issue:
- 6
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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