Abstract
The effect of an ionospheric dynamo electric field on the electron density and total electron content (TEC) perturbations in the F layer (150–600 km altitudes) is investigated at two arbitrarily selected locations (noted as 29° N and 60° N in latitudes) in the presence of seismic tsunami-excited gravity waves propagating in a stratified, nondissipative atmosphere where vertical gradients of atmospheric properties are taken into consideration. Generalized ion momentum and continuity equations are solved, followed by an analysis of the dynamo electric field (E). The E -strength is within several mV/m, determined by the zonal neutral wind and meridional geomagnetic field. It is found that, at the mid-latitude location, n0 e is dominated by the atmospheric meridional wind when E = 0, while it is determined by the zonal wind when E ≠ 0. The perturbed TEC over its unperturbed magnitude lies in around 10% at all altitudes for E = 0, while it keeps the same percentage at most altitudes for E ≠ 0, except a jump to >25% in the F2-peak layer (300–340 km in height). By contrast, at the low-latitude location, the TEC jump is eliminated by the locally enhanced background electron density.
Highlights
Tsunamis have been a significant threat to humans living in coastal regions throughout recorded history
From as early as the 1970s, modeling results have demonstrated that the ionospheric signature of an ocean tsunami can potentially be detected as traveling ionospheric disturbances (TIDs) produced by internal gravity waves propagating upward in the upper atmosphere in periods of 10–30 min, horizontal wavelengths and phase speeds of several hundreds of km and ∼200 m/s, respectively, and vertical speeds of the order of 50 m/s (e.g., [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]), and these tsunami-driven TIDs have been identified in ionospheric total electron content (TEC) data, the vertical integration of the ionospheric electron density, as measured from ground-based GPS radio signals (e.g., [19,20]) or satellite altimeter radar [21]
The rest of the paper is as follows: Section 2 exhibits tsunami-driven disturbance at the sea surface and its upward propagation in atmosphere; Section 3 discusses ionospheric plasma properties in the upper atmosphere; Section 4 introduces the ionospheric dynamo electric field and its effects on plasma momentum and continuity equations; Section 5 estimates the electron density and TEC perturbations driven by tsunami-excited gravity waves in both the absence and presence of the dynamo electric field
Summary
Tsunamis have been a significant threat to humans living in coastal regions throughout recorded history. For example, Cole’s model exposed a magnitude of |E| ∼ a few mV/m drives ions away from Maxwellian substantially due to the E × B drift (where B = Bb is the local geomagnetic field and b is the unit vector along magnetic field lines), the magnitude of which is larger than the local thermal speeds of neutrals These abundant theoretical and experimental studies demonstrated that the electric field effect is more conspicuous at high latitude (seldom relevant to tsunami-related applications); whenever E exists anywhere, including regions at mid- or low latitudes, plasma properties are modulated . Because the displacement is due to the sum of all the waves in the the bandwidth of spectrum, the final value of w(kh ) turns out to be 1.17 × 10−4 m/s [11]
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