Earthquake/Tsunami‐Linked Imprints in the Equatorial F Region Zonal Plasma Drifts and Spatial Structures of Plasma Bubbles

Abstract

We report preseismic and postseismic distinct features observed in equatorial ionospheric F region in Indian longitude during two major earthquakes that occurred on 28 March 2005 (Mw=8.6) and 26 December 2004 (Mw=9.1) with epicenters near Sumatra, Indonesia. We used spaced receiver scintillation observations on a 251‐MHz signal transmitted from a geostationary satellite and recorded at dip equatorial station Tirunelveli, which is ≈2,200 km away from the epicenter of these earthquakes. On 28 March 2005, we noticed significant enhancement (≈88.5 m/s) in F region zonal plasma drift as compared to their seasonal quiet time drifts, 20 min prior to the start of earthquake. This implies the presence of additional vertically downward electric field of approximately 3 mV/m, which is linked with the earthquake mechanism. It is unusual because so far we have not encountered such feature on either magnetically quiet or disturbed days. Spatial scales associated with equatorial spread F irregularities generated in the postsunset hours on this earthquake day are considerably smaller. It suggests that the earthquake‐linked electric field influenced the structuring and evolution of equatorial spread F irregularities on this earthquake day. Another earthquake that occurred on 26 December 2004 triggered a tsunami. We noticed that the earthquake‐ and tsunami‐linked effects in the F region plasma drifts are distinctly observed even 18.5 hr after the earthquake.

An Attempt to Analyze a Human Nervous System Algorithm for Sensing Earthquake Precursors

“…In addition, to determine the content of the recovered seismic precursor information, Bayesian posterior probabilities need to be corrected iteratively, and a filtering method similar to Kalman filtering can be used to exclude "noise" and other disturbances of non-seismic precursor signals. The results of earthquake prediction are derived [18] [19] [20] [21].…”

Active (Evolving) Phase of Equatorial Plasma Bubbles Observed Over Tirunelveli

“…Spaced receiver scintillation technique can be used to get the information about average drift speed of ESF irregularity (Bhattacharyya et al, 1989; Ledvina et al, 2004; Valladares et al, 1996) and the dominant spatial scale associated with the ground scintillation pattern (Bhattacharyya et al, 2003; Engavale et al, 2005; Gurram et al, 2019). The ESF irregularities follow a power law spectrum, and the intermediate‐scale irregularities (100 m to 10 km) contribute to amplitude scintillations on VHF signals.…”

The Turkey Earthquake Induced Equatorial Ionospheric Current Disturbances on 6 February 2023

“…Most of the low Earth orbit (LEO) satellites fly in the ionospheric altitudes; thus, the ionosphere plays a crucial role in the near-Earth geospace. Several works have reported that the ionosphere could be remarkably disturbed by lower atmospheric forcing, such as the energy release related to earthquakes, thunderstorms, and volcanic eruptions (e.g., [1][2][3][4][5][6][7][8]). The external driving of the upper atmosphere mainly comes from the energy deposition due to solar wind and magnetosphere coupling (e.g., [9][10][11][12][13][14][15]) and from changes in solar radiation (e.g., [16][17][18][19][20][21][22][23]).…”

“…During an earthquake, a large amount of energy could be released into the atmosphere via the form of acoustic gravity waves and Rayleigh waves, and the ionosphere could be modulated by the generated additional electric field [3,4,31]. During intense earthquakes with a moment magnitude (Mw, a measure of the earthquake's strength based on the seismic moment) larger than 5, acoustic gravity waves could be generated due to the vertical ground displacement and can propagate upward to affect ionospheric electron density [3]. Low-frequency acoustic waves propagate upward and horizontally with the speed of sound.…”

“…An additional vertical electric field directly penetrates into the ionosphere, causing the redistribution of charged particles. For instance, a significant enhancement (~88.5 m/s) in the zonal plasma drifts was observed during a major earthquake on 28 March 2005, inducing a downward electric field of ~3 mV/m [3,33]. Because of the atmospheric resonance, the upper ionosphere/atmosphere could be directly affected as well.…”