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A comprehensive survey of atmospheric quasi 3 day planetary‐scale waves and their impacts on the day‐to‐day variations of the equatorial ionosphere
Author(s) -
Liu Guiping,
England Scott L.,
Immel Thomas J.,
Frey Harald U.,
Mannucci Anthony J.,
Mitchell Nicholas J.
Publication year - 2015
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020805
Subject(s) - thermosphere , solstice , ionosphere , mesosphere , amplitude , atmospheric sciences , total electron content , atmosphere (unit) , depth sounding , airglow , atmospheric tide , gravity wave , wavelength , tec , physics , latitude , geology , geophysics , geodesy , meteorology , stratosphere , gravitational wave , astronomy , optics , oceanography
This study reports a comprehensive survey of quasi 3 day (2.5–4.5 day period) planetary‐scale waves in the low‐latitude mesosphere and lower thermosphere using the temperature observations from Thermosphere Ionosphere and Mesosphere Electric Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry throughout 2002–2012. Occurrences and properties of the waves, including the eastward propagating zonal wave numbers of 1–3 ( E 1– E 3) and vertical wavelengths, are determined for each case. The impacts of these waves on the equatorial ionosphere are investigated by searching for the corresponding variations with the same periods and wave numbers in total electron content (TEC) from the concurrent observations of the ground‐based GPS network. For a threshold amplitude of 4 K in temperature, a total of 300 waves are identified, of which there are 186 E 1, 63 E 2, and 51 E 3 events. The mean amplitudes and vertical wavelengths of these waves are calculated to be about 7.9 K and 34 km for the E 1, 5.7 K and 29 km for the E 2, and 5.1 K and 27 km for the E 3, having the standard deviations of 1.5 K and 6.5 km, 0.6 K and 5.6 km, and 0.5 K and 6.7 km. Occurrences of the E 1 cases are not observed to depend on season, but the large‐amplitude (>8 K) cases occur more often during solstices than at equinoxes. Similarly, the E 2 and E 3 cases are observed to occur most often in January–February and May–August. Among these waves, 199 cases (66%) are found to have the corresponding variations in the equatorial ionosphere with amplitudes ≥4.2% relative to the mean TEC values (corresponding to 90th percentile). Most of these waves have long vertical wavelengths and large amplitudes (∼3 times more than short vertical wavelength and small‐amplitude waves). Because no seasonal or solar cycle dependence on the frequency at which these waves have corresponding variations in the ionosphere at this TEC perturbation threshold is observed, we conclude that there is no seasonal and solar cycle dependence on the propagation of such waves from the mesopause region to higher altitudes. We also identify that only 28 cases (19%) of the E 1 TEC variations do not correspond to any E 1 waves, which is consistent with the hypothesis that E 1 waves are the primary cause of E 1 TEC variations. Conditions that are favorable for 3 day waves to create ionospheric variations are present approximately two thirds of the time. This study quantifies the importance and frequency of atmospheric quasi 3 day planetary‐scale waves on the day‐to‐day variations of the equatorial ionosphere using a statistical rather than case study approach.