Concentric Secondary Gravity Waves in the Thermosphere and Ionosphere Over the Continental United States on March 25–26, 2015 From Deep Convection

Abstract

AbstractWe examine the total electron content (TEC) from GPS receivers over the United States on March 25–26, 2015. We observe partial to nearly fully concentric rings of traveling ionospheric disturbances (TIDs) with centers close to deep convection. Many of these TIDs have observed horizontal phase speeds cH > 300 m/s, suggesting they are induced by gravity waves (GWs) created in the thermosphere. We investigate the largest‐amplitude concentric TIDs at 23:00 UT on March 25 and 01:20 UT on March 26. We find that cH and the GW period τr increase linearly with radius and the horizontal wavelength, λH, increases quadratically with radius. This is expected if the GWs are excited by point sources. For these GWs, cH = 150–530 m/s, τr ∼ 8–40 min, and λH ∼ 100–500 km. Using reverse ray‐tracing, no GW with cH > 200 m/s propagates below z = 100 km, 73% of the GWs in the first case cannot propagate below z ∼ 100 km, all of the GWs in the second case cannot propagate below z ∼ 100 km, and the inferred thermospheric point sources are ∼2–4° from deep convection. Because the underlying GWs are most likely excited by a point source and most must be created in the thermosphere, we find that these concentric TIDs are most likely induced by GWs generated in the thermosphere, including those with cH = 150–200 m/s. Their close proximity to deep convection and the TEC map asymmetries suggest these TIDs are likely induced by secondary GWs from local horizontal body forces created by the dissipation of primary GWs from deep convection.