GITM and Non-hydrostatic processes

Yue Deng Department of Physics

University of Texas, Arlington

Ionosphere/Thermosphere Processes

Courtesy of Joseph Grebowsky, NASA GSFC

Electrodynamics & particleSun

Tides and Gravity Waves

The Global Ionosphere-Thermosphere Model (GITM)The Global Ionosphere-Thermosphere Model (GITM)GITM solves for:GITM solves for: 6 Neutral & 5 Ion Species6 Neutral & 5 Ion Species Neutral windsNeutral winds Ion and Electron Velocities Ion and Electron Velocities Neutral, Ion and Electron TemperaturesNeutral, Ion and Electron Temperatures

Ridley, A., Deng, Y., and Toth, G. (2006), J. Atmos. Solar-Terr. Phys., 68, 839-864.

GITM Features:GITM Features:

Flexible grid resolution Flexible grid resolution Can have non-hydrostatic Can have non-hydrostatic

solutionssolutions CoriolisCoriolis Vertical Ion DragVertical Ion Drag Non-constant GravityNon-constant Gravity Massive heating in auroral Massive heating in auroral

zonezone Runs in 1D and 3DRuns in 1D and 3D Solves in altitude coordinatesSolves in altitude coordinates Vertical winds for each major Vertical winds for each major

species with friction coefficientsspecies with friction coefficients Non-steady state explicit Non-steady state explicit

chemistrychemistry Variety of high-latitude and Solar Variety of high-latitude and Solar

EUV driversEUV drivers Fly satellites through modelFly satellites through model Time step: 2 secondsTime step: 2 seconds

Why Non-hydrostatic?Why Non-hydrostatic? The vertical momentum equation:The vertical momentum equation:

Non-hydrostatic effects (deep convection) have been Non-hydrostatic effects (deep convection) have been investigated in the low atmosphere using WRF. How about its investigated in the low atmosphere using WRF. How about its effect on the upper atmosphere?effect on the upper atmosphere?

Currently, no conclusive interpretation about the observed Currently, no conclusive interpretation about the observed large vertical winds (more than 100 m/s) and density large vertical winds (more than 100 m/s) and density disturbance in thermosphere. [disturbance in thermosphere. [Rees et alRees et al., 1984; ., 1984; Smith et al.,Smith et al., 1995; 1995; Innis et al.,Innis et al., 1999; 1999; Aruliah et al.,Aruliah et al., 2005] 2005]

Offer the opportunity to simulate acoustic waves and give a Offer the opportunity to simulate acoustic waves and give a more realistic description of high-frequency gravity wavesmore realistic description of high-frequency gravity waves

Hydrostatic equilibrium

Study 1: idealized caseStudy 1: idealized case

Vsw=400km/s, IMF(Bz)=-1nT, F10.7=100, HPI=3GWVsw=400km/s, IMF(Bz)=-1nT, F10.7=100, HPI=3GW

00 UT: Bz -1 -20 nT

CPCP: 45 180 kV

Integrated JH increases by 20 times.

After 1 hour, Bz changes back to -1 nT.

Deng, Y., and et. al., GRL (2008)

Temporal variations of the buoyancy Temporal variations of the buoyancy acceleration (300 km)acceleration (300 km) rgr

P

1

Time vs. altitude distribution (77.5Time vs. altitude distribution (77.500S, 22.5S, 22.500E) E) during 15 min:during 15 min:

There is a positive disturbance propagating from low altitudes to high altitudes with increasing amplitude.

Buoyancy~2 m/s2 at 400km, close to 25% of g (8.7m/s2).

Phase speed, direction and frequency show that it is highly likely an acoustic wave.

Buoyancy acceleration

Vertical wind Neutral density

Vertical neutral wind > 100 m/s at 300 km altitude.

Neutral density increase by 100% above 300 km.

Influence on the acoustic-gravity wave propagation: Non-hydrostatic dispersion relation for GW :

[Monin & Obukhov, 1958]

where k and m are horizontal and vertical wave numbers; and are the wave and buoyancy intrinsic frequencies.The last term on RHS vanishes in hydrostatic situation. The conditions for wave to be reflected and ducted are: in the nonhydrostatic

in the hydrostatic cases. [Akmaev, 2011] When , the same wave behaves differently in hydrostatic and non-hydrostatic models.

Study 2: Study 2:

T = 3 minT = 3 min T = 6 minT = 6 min

T = 12 minT = 12 min During the first 12 minutes, acoustic waves are propagating upward

T > 12 minutes, most disturbance is below 200 km, which indicates that the wave got reflected or ducted above that.

• Momentum flux decreases dramatically above 150 km.• Dissipated GW accelerate background neutral wind.• Magnitude and vertical depth of body force are Consistent

with Vadas & Liu, (2009)

Deng, et. al., 2014

Tsunami ImagingTsunami Imaging

March 26, 2014March 26, 2014 Physics Dept Colloquium UT ArlingtonPhysics Dept Colloquium UT Arlington

Courtesy of Attila Komjathy, Xing Meng, JPL

GITM simulationGITM simulation

MarsMars

TitanTitan

Exo-planetsExo-planets

3. Planetary Atmosphere3. Planetary Atmosphere

Discovery rate of exo-Discovery rate of exo-planetsplanets

Exo-planets: habitable Exo-planets: habitable zonezone

Kasting et al. 1993

Atmosphere escape is a hydrodynamic processAtmosphere escape is a hydrodynamic process

Early Martian Upper Atmosphere (Tian, Kasting, & Solomon 2009)

Thank you!Thank you!