A study of the nonlinear response of the upper atmosphere to episodic and stochastic acoustic‐gravity wave forcing

Abstract

Perturbations caused by geophysical and anthropogenic events on the ground have been observed to propagate upward and impact the upper atmosphere. Gravity waves with wavelengths less than 750 km are known to be responsible for the total electron content (TEC) perturbations and to play a significant role in the mass, momentum, and energy budgets of the mesosphere and lower thermosphere. These waves are, however, difficult to continuously measure, globally resolve, and deterministically specify in first‐principle ionosphere‐thermosphere (IT) models. In this study, we investigate IT response to induced acoustic‐gravity waves resulting from strong time‐varying lower atmospheric wave forcing, including a traveling wave packet (TWP) and stochastic gravity wave (SGW) fields using the nonlinear Global Ionosphere Thermosphere Model (GITM) with high‐resolution grids of 0.08° in longitude and latitude. When TWP and SGW forcing occurs concurrently, the induced gravity waves (GWs) cause variation of ±8.8% in neutral, ±6.2% in electron density, and ±1.5% in TEC. The magnitudes decrease by 2.4% (from ±8.8% to ±6.4%) with the SGW effects simulated separately and subtracted; importantly, interactions between TWP and SGW contribute to ±1.4% of the perturbations. On the other hand, the induced acoustic waves (AWs) cause variation of ±13.9% in neutral, ±2.1% in electron density, and ±0.4% in TEC. Furthermore, GWs sustain tens of minutes after the TWP has passed through the lower atmosphere and clear traveling ionospheric disturbances and traveling atmospheric disturbances are developed. We demonstrate that clear wave structures from an episodic event can be isolated even under a ubiquitously and overwhelmingly perturbed atmosphere.

The Effect of Subauroral Polarization Streams on Ionosphere and Thermosphere During the 2015 St. Patrick's Day Storm: Global Ionosphere‐Thermosphere Model Simulations

“…The time step in GITM is relatively small (~2 s), compared with other hydrostatic models. Due to its release of hydrostatic assumption, GITM is capable of simulating acoustic waves (Deng et al, ) and small‐scale gravity waves (Deng & Ridley, ; Lin et al, ). International Geomagnetic Reference Field (Finlay et al, ) under the APEX coordinates (Richmond, ) is applied to represent the magnetic field.…”

Atmospheric Gravity Waves in the Ionosphere and Thermosphere During the 2017 Solar Eclipse

“…Total electron content (TEC) derived from GNSS receivers have captured large-scale and medium-scale traveling disturbances induced from various lower-atmospheric sources, including tsunamis (Galvan et al, 2011;Occhipinti et al, 2006;Saito et al, 2011;Tsugawa et al, 2011) and strong tropical systems in the troposphere (Nishioka et al, 2013;Perwitasari et al, 2015;Yue et al, 2014). Theoretical works have used moving wave packets as forcing to drive lower and upper atmospheric models (Hickey et al, 2009;Lin et al, 2017;Meng et al, 2015;Vadas et al, 2015). Depending on the propagation velocity, moving wave packets in the lower thermosphere induce acoustic or gravity waves.…”

Impacts of Multiscale FACs on the Ionosphere‐Thermosphere System: GITM Simulation

“…In addition, it has flexible options for the grid size. Moreover, one of the primary differences of GITM from other GCMs is that it relaxes the hydrostatic assumption and allows acoustic waves to propagate (e.g., Deng et al, , ; Lin et al, ; Zhu et al, ).…”