Science questions What is the source of the SAV variation, the amplitude variation over the solar cycle, and the reason for the phase modulation? How does the seasonal/latitude, solar cycle, and storm-time variation in radiative cooling impact global neutral density structure? What is the cause of the phase lag in the neutral density response to solar UV radiation? What is the temporal response of neutral density to flares, substorms, and storms? What is the impact of T-I coupling on the neutral density structure? Goal Capture the improved physical understanding in the next generation hybrid empirical/physical models. Focus Area II: Internal Processes and Thermosphere-Ionosphere Coupling Fuller-Rowell, Forbes, Thayer, Codrescu, Crowley, Solomon, Richmond Relationship between  and N e - from CHAMP

“Internal” Processes Wave propagation Neutral wind response to geomagnetic activity Semi-annual variation Thermosphere-ionosphere coupling - ETWA Midnight temperature maximum (MTM) Radiative processes - NO cooling (Geoff Crowley) Response and recovery timescales - EUV, UV, storms (Stan Solomon)

Sources of Semi-Annual Variation in Neutral Density Thermospheric “spoon” - solar cycle variation - CTIPe/TIEGCM Variation in turbulent mixing and/or turbopause height from lower atmosphere sources - IDEA Seasonal variation in geomagnetic heating - CTIPe/GGCM simulations Seasonal variation in NO cooling - TIEGCM/CTIPe, IDEA, SABER

Solstice composition structure controlled by balance between solar and magnetospheric forcing Kp~3 Strickland et al., 2004: GUVI obs. Ratio of the height-integrated O and N 2 above a reference level ~130km

Magnitude of Semi-Annual Variation in Neutral and Ion Density Global circulation at solstice mixes the thermosphere like a spoon Increase in molecular species at higher altitudes decreases scale height, RT/mg Atmosphere more contracted at solstice reducing neutral density at a given height Semi-annual variation in neutral density, composition, and ion density

Solar activity variation of semi-annual oscillation - implication for global circulation courtesy Bruce Bowman Implies strength of global circulation increases with solar activity, or Seasonal variation in geomagnetic energy input increases with solar activity Note that the lower atmosphere atmosphere forcing/mixing less likely to have solar cycle variation

EIA and neutral density Liu et al Peaks in neutral density associated with the EIA

ETWA Equatorial Temperature and Wind Anomaly Ragavarao 1991 Several theories have been suggested: Adiabatic heating and cooling Horizontal (zonal) transport Joule dissipation Ionospheric recombination

Evidence of multi-day planetary wave periodicities in the upper atmosphere Dayside electrodynamics during 2001: day-to-day changes Electrodynamics drives plasma transport 5-day wave - possible signature of tropospheric planetary modulation of upper atmosphere Periodogram

Impact of parallel ion drag: increased latitude structure Maruyama et al.

Solar cycle variation of midnight temperature maximum Diurnal, Semi-Diurnal, and Ter-diurnal Variation at Low Latitude Observations and modeling indicates MTM comparable to dayside peak at low solar activity High solar activityLow solar activity

Internal Processes Radiative processes - NO cooling (Geoff Crowley)

Thermospheric Density and Nitric Oxide G Crowley University of Texas at San Antonio (UTSA) Density Structure Temperature Structure Energy Balance

Energy equation Mol and therm conduction Radiation Advection Adiab. Other Many terms

Heating Terms in TIMEGCM QEUVEUV ( Å) (EUVEFF= 5%) QSRCO 2 -Schumann-Runge continuum ( Å) QSRBO 2 -Schumann-Runge bands ( Å) QO3O 3 - Lyman a ( Å) O 3 - Hartley, Huggins and Chappuis ( nm) QO2O 2 - Lyman a ( Å) O 2 Herzberg ( Å) QNCExothermic neutral-neutral chemistry (NOX, HOX, OX, CH4, O(1D) quench, CLX) Atomic O recombination Heating from O( 1 D) quenching QICExothermic ion-neutral chemistry QANon-Maxwellian auroral electrons (AUREFF= 5%) QPPhotoelectrons (X-rays, EUV, and Night) (EFF=5%) QEICollisions between e -, ions and neutrals QDH 4 th order diffusion heating QGW Gravity Waves QM Viscous Dissipation QJ Joule heating QTTotal Heating Cooling Terms O( 3 P) 63  m O( 3 P) fine structure NO 5.3  m Nitric Oxide CO 2 15  m Carbon Dioxide O  m Ozone Km Molecular Conduction DIFKT Eddy Diffusion Cooling Dynamical terms Adiabatic cooling Horizontal Advection Vertical Advection

Cooling Terms O( 3 P) 63  m O( 3 P) fine structure NO 5.3  m Nitric Oxide CO 2 15  m Carbon Dioxide O  m Ozone Km Molecular Conduction DIFKT Eddy Diffusion Cooling Dynamical terms Adiabatic cooling Horizontal Advection Vertical Advection Heating Terms in TIMEGCM QEUVEUV ( Å) (EUVEFF= 5%) QSRCO 2 -Schumann-Runge continuum ( Å) QSRBO 2 -Schumann-Runge bands ( Å) QO3O 3 - Lyman a ( Å) O 3 - Hartley, Huggins and Chappuis ( nm) QO2O 2 - Lyman a ( Å) O 2 Herzberg ( Å) QNCExothermic neutral-neutral chemistry (NOX, HOX, OX, CH4, O(1D) quench, CLX) Atomic O recombination Heating from O( 1 D) quenching QICExothermic ion-neutral chemistry QANon-Maxwellian auroral electrons (AUREFF= 5%) QPPhotoelectrons (X-rays, EUV, and Night) (EFF=5%) QEICollisions between e -, ions and neutrals QDH 4 th order diffusion heating QGW Gravity Waves QM Viscous Dissipation QJ Joule heating QTTotal Heating

Heating Terms in TIMEGCM QEUVEUV ( Å) (EUVEFF= 5%) QSRCO 2 -Schumann-Runge continuum ( Å) QSRBO 2 -Schumann-Runge bands ( Å) QO3O 3 - Lyman a ( Å) O 3 - Hartley, Huggins and Chappuis ( nm) QO2O 2 - Lyman a ( Å) O 2 Herzberg ( Å) QNCExothermic neutral-neutral chemistry (NOX, HOX, OX, CH4, O(1D) quench, CLX) Atomic O recombination Heating from O( 1 D) quenching QICExothermic ion-neutral chemistry QANon-Maxwellian auroral electrons (AUREFF= 5%) QPPhotoelectrons (X-rays, EUV, and Night) (EFF=5%) QEICollisions between e -, ions and neutrals QDH 4 th order diffusion heating QGW Gravity Waves QM Viscous Dissipation QJ Joule heating QTTotal Heating Cooling Terms O( 3 P) 63  m O( 3 P) fine structure NO 5.3  m Nitric Oxide CO 2 15  m Carbon Dioxide O  m Ozone Km Molecular Conduction DIFKT Eddy Diffusion Cooling Dynamical terms Adiabatic cooling Horizontal Advection Vertical Advection

Effect of Solar Cycle on Cooling (Equinox) SMINSMAX SMINSMAX K/day450 K/day

Effect of Solar Cycle on Heating (Equinox) SMAX SMIN SMIN

NITRIC OXIDE S MAX S MIN 5.3  m cooling + TN

Effect of Solar Flare on NO Cooling How does this affect neutral density?

Effect of Storms on NO Cooling (December Solstice) 12-hr Storm How does this affect neutral density?

Conclusions We expect a relationship between density and energy input into the atmosphere Energy content is not fixed and stable Using global models we can examine the energy budget Nitric oxide is a highly variable component of the energy budget Expect NO will influence thermospheric density response Need to study magnitude of response for Smin and Smax Need to study timescale of NO response and how it relates to density response Density Structure Temperature Structure Energy Balance

Internal Processes Response and recovery timescales - EUV, UV, storms (Stan Solomon)

Response of the Thermosphere to Solar Irradiance: Model Results and the Lag Effect Stan Solomon and Liying Qian High Altitude Observatory National Center for Atmospheric Research with thanks to Bruce Bowman Air Force Space Command NADIR MURI Kickoff CU/LASP 27 November 2007

Energy Deposition in the Upper Atmosphere

Ionization Processes and Atmospheric Heating Photon flux enters the atmosphere Ionization processes convert photon energy to chemical potential energy Dissociative recombination converts ionization energy to dissociation products and kinetic energy i.e., heat

Model & Measurement of Thermosphere Solar Cycle Variation

Model-Data Comparison for 2003

Average Model-to-Data Ratio for 2003 MSIS-00TIE-GCM Mean Std. Dev

Evidence for a “Lag” in Solar Forcing of the Thermosphere MSIS and other empirical models have traditionally used a solar index (e.g., F 10.7 ) from the previous day to describe thermospheric densities/temperatures for the current day. Common sense dictates that it will take some finite time for the thermosphere to respond to a change in forcing. Bruce Bowman reports incrementally improved correlations between satellite-drag measurements of thermospheric density and empirical models when a component of the proxy set includes solar measurement data in the far-ultraviolet, with a lag of about 6 days. These improved correlations also occur when a solar chromospheric index (e.g., Mg II core-to-wing ratio) is used instead of direct measurements, with a ~6-day lag. But keep in mind that all solar activity indices are highly mutually correlated.

Temperature/Density Response to Impulsive Solar Forcing

The Thermospheric Energy Chain — “Catch and Release” Highly simplified description of important chemical pathways Consider EUV v. FUV 30.4 nm photon: Deposits energy ~150~200 km h + N 2  N e* e* + N 2  N e* e* + N 2  N + N + KE (~1 eV) N e  N + N + KE (~6 eV) N O  NO + + N + KE (~3 eV) NO + + e  N + O + KE (~3 eV) N + O 2  NO + O + KE (~1 eV) NO + N  N 2 + O + KE (~4 eV) 150 nm photon: Deposits energy ~100~150 km h + O 2  O + O + KE (~3 eV) O + O + M  O 2 * + M + KE (~1 eV) O 2 * + M  O 2 + KE (~4 eV) O 2 *  O 2 + h but this recombination can only happen below ~100 km!

Atomic Oxygen Changes following Impulsive FUV Input

Validating this Theory — Work in Progress Demonstrate lag effects with 3D model Investigate vertical transport timescales with 3D model Investigate atomic/molecular oxygen change/interchange Calculate atomic oxygen recombination energetics Compare with data using increased methodological rigor