ITM SYSTEM.

Current Paradigm

• Solar interactions with the lower atmosphere (deep convection, HO and O radiation absorption, etc.) excite a wide spectrum of waves that dissipate in the ITM system.
• Dissipating waves deposit net momentum and heat, altering the mean circulation and temperature structures.
• Wave instabilities generate turbulence (eddy mixing) which affects the distributions of chemical constitutents.
• Solar radiation absorption WITHIN the ITM system initiates an extensive photchemical chain that redistributes this energy via exothermic reactions; UV, visible, and IR emissions; collisions; etc.
• E-fields of magnetospheric origin produce Joule heating and neutral gas acceleration via ion-neutral collisions.
• Energetic particles heat the ionospheric plasma, produce localized ionization/conductivity enhancements, and significantly perturb the chemistries of important minor constituents such as NO and O.
• The ITM system responds to magnetospheric forcing through a major global rearrangement of wind patterns, mass transport, and neutral and ion composition changes.
• Quiet solar and "disturbance" winds in the lower ionosphere generate a global pattern of electric fields via the dynamo mechanism; these fields subsequently map to higher levels and redistribute plasma through E B drifts.
• Localized plasma structures evolve within larger scale features to spawn instabilities and plasma irregularities.
• Thermal balance is controlled by a complex combination of dynamical radiation and chemical pathways. Non-local thermodynamic equilibrium (NLTE) cooling is important in lower ITM.

Weaknesses in Current Understanding

• The global distribution of small-scale waves, their connections with turbulence (eddy mixing) and chemical composition changes, the distributions of energy and momentum deposition due to wave dissipation, and the lower atmosphere sources of small-scale waves, remain unknown.
• The global distribution of tidal winds and temperatures is poorly known; the global distribution of tidal variations in chemical composition is unknown.
• The basic physics of how small-scale motions (waves and turbulence) mutually interact with the larger scale dynamics remains essentially unknown. There exists much controversy between existing parameterizations in large-scale circulation models.
• The manner in which energy is redistibuted via chemical and radiative pathways is poorly known.
• The physics underlying the penetration of various planetary waves (Rossby, Kelvin, mixed Rossby-Gravity) into the ITM system, and their overall role in the dynamics, energetics, and electrodynamics of the system remain unknown.
• The chemical pathways which redistribute absorbed solar energy until it is transformed to a state which can be radiated away to space are poorly known.
• The physics underlying the generation and evolution of plasma structures are poorly understood.
• The degree to which anthropogenic changes are occurring in the ITM system due to global changes in CO and CH remains unknown.

Measurement Objectives

• Characterize the global distributions of the basic parameters: temperature, winds, ion and neutral composition, minor constituents, emissions, electric fields.
• Measure the sources: convection electric fields, particle fluxes, EUV radiance, lower atmosphere wave sources.
• Measure the global response to source variations over various scales: diurnal, daily, seasonal, internnual, long-term trends.
• Map the structuring and plasma flows within the lower ionosphere
• Measure directly the radiative consequences of NLTE processes, excitation and relaxation processes.
• Measure characteristics of local structures in the ionosphere and mesosphere/thermosphere (gravity waves, irregularities, small scale winds)

Current Spacecraft

• UARS

Future Missions

• Development pending: TIMED
• "Mission Concepts": Global Electrodynamics Mission , Mesospheric Coupler, ITM Dynamics Mission (multi-satellite), ITM Coupler, Solar Interactions at Mars, Lower Ionosphere Structure

New Technology Requirements

• Whatever it takes to make wind and temperature measurements both day and night over a significant range of altitudes (need help here about the specific technology needed)
• Microsatellites able to make simultaneous measurements in several orbital planes
• Miniaturized in situ sensors for low altitude transition flow regimes
• Tethered satellite technologies
• Improved remote sensing techniques (algorithms, sensors, etc.)
• New cooling systems for long term observations of atmospheric IR outputs
• Satellite-to-satellite GPS dual frequency capability and inversion development

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