Ionospheric ripples excited by superimposed wave fronts associated with Rayleigh waves in the thermosphere

Abstract

[1] Coseismic ionospheric disturbances (CIDs) associated with the 2011 Tohoku earthquake off the Pacific coast (M w 9.0, Tohoku EQ) were examined using total electron content and seismic wave data. A faster CID propagated at~3.0 km/s only in the west-southwest, while a slower CID propagated concentrically at 1.2 km/s or slower from the tsunami source area. Taking the propagation speed and oscillation cycle into account, the faster CID was associated with a Rayleigh wave, but the slower CID was associated with an acoustic or gravity wave. The north-south asymmetry of the CID associated with the Rayleigh wave suggests that the Rayleigh wave did not act as a point source of the acoustic wave because a point source propagating in all directions must produce symmetric CID in all directions. Therefore, a superimposed wave front of acoustic waves was excited by the Rayleigh wave and produced the north-south asymmetry of the faster CID due to the magnetic inclination effect, which is different from a well-known north-south asymmetry of CID excited at the epicenter. On the other hand, above and south of the tsunami source area, the CID with a period of 4 min was excited by a point source located at the tsunami source area because atmospheric waves propagating from a point source produce north-south asymmetry in the resulting CID.

Ionospheric disturbances induced by a missile launched from North Korea on 12 December 2012

“…These data were obtained at Japan, Taiwan, and South Korea. The frequency of ionospheric disturbance seen in TEC variation in this event was slower than those observed after earthquakes [e.g., Calais and Bernard Minster , ; Choosakul et al ., ; Kamogawa et al ., ; Kakinami et al ., ]. In the figure, the ionospheric point (IP) where the raypath from the GPS satellite pierced the ionosphere was assumed to be 425 km.…”

“…A dense GPS array is a good 2‐D monitoring tool for the ionosphere. By using a dense GPS array, medium‐scale traveling ionospheric disturbances [e.g., Saito et al ., ], storm enhanced density [e.g., Foster et al ., ], earthquake‐related disturbances [e.g., Ducic et al ., ; Heki and Ping , ; Kakinami et al ., ], tsunami‐related disturbances [e.g., Rolland et al ., ; Kakinami et al ., ], and volcano‐explosion‐related disturbances [e.g., Dautermann et al ., ] have been revealed. Here we report on ionospheric disturbances possibly related to a missile launched from North Korea on 12 December 2012.…”

Coseismic Traveling Ionospheric Disturbances during the Mw 7.8 Gorkha, Nepal, Earthquake on 25 April 2015 From Ground and Spaceborne Observations

“…The perturbations in ionospheric plasma density during large earthquakes have been widely reported in the literature using both ground‐based and spaceborne observations (Astafyeva et al, ; Calais & Minster, ; Coisson et al, ; Liu et al, ; Otsuka et al, ; Tsugawa et al, , and references therein). The ionospheric total electron content (TEC) observations from the ground‐based GPS (Global Positioning Systems) receivers are most commonly used because of their accurate and time continuous observations at high temporal resolution as well as the availability of spatially dense and distributed networks (Astafyeva et al, ; Dučić et al, ; Heki & Ping, ; Kakinami et al, ; Otsuka et al, ; Saito et al, , and references therein).…”

Vertical midscale ionospheric disturbances caused by surface seismic waves based on Irkutsk chirp ionosonde data in 2011–2016

“…One of these phenomena is generation of midscale ionospheric irregularities directly by shock wave from the supersonic seismic source propagating over the surface [ Maruyama et al , ; Liu et al , ; Rolland , ; Kakinami et al , ; Maruyama and Shinagawa , ; Berngardt et al , ; Maruyama et al , , ; Kherani et al , ; Chum et al , ; Liu et al , ]. These irregularities are observed at ionograms as fast changes of the trace over frequency and time (initially smooth and slow changing) and known as multicusp effect [ Maruyama et al , ].…”