Atmosphere-Ionosphere Wave Coupling as Revealed in Swarm Plasma Densities and Drifts Jeffrey M. Forbes Department of Aerospace Engineering Sciences, University of Colorado Stephan Buchert Swedish Institute of Space Physics, University of Uppsala David Knudsen and Jonathan Burchill Department of Physics and Astronomy, University of Calgary Atmosphere-ionosphere coupling mechanisms Swarm-CHAMP comparisons Variability of Swarm electron densities and attributions Conclusions

Atmosphere-Ionosphere Coupling by Tides & Planetary Waves Pole Equator Ionosphere-Thermosphere (IT) Lower Atmosphere Mesopause 0 km 500 km Tides Atmosphere-Ionosphere Coupling by Tides & Planetary Waves plasma flow tidal penetration B E tidal dynamo dissipation O3 H2O Atmosphere-Space Interaction Region PWs equatorial anomaly composition changes wind transport Wave Spectrum Gravity Waves 10-100 min 10’s – 1000 km Planetary Waves 2-20 days 1000’s to 10,000 km Tides 24, 12, 8 hours 1000’s to 10,000 km The primary mechanism through which energy and momentum are transferred from the lower atmosphere to the upper atmosphere and ionosphere is through the generation and propagation of waves.

Swarm-CHAMP comparisons – 1 Monthly-mean total [e-] from Langmuir Probe (LP) measurements Plotted in geographic coordinates Swarm: 13-31 Dec 2013 F10.7 = 148 CHAMP: 1-31 Dec 2006 F10.7 = 91 Dec 2005-May 2006, Dec 2013-May 2014 only periods where Swarm-CHAMP local times and months coincide.

Swarm-CHAMP Comparisons – 2 % residuals from longitude mean Moderates differences in F10.7 Moderates latitude differences Temporal variability of the tide-PW spectrum (days, weeks, seasonal, inter-annual) Longitude variability of the tide-PW spectrum Wave-wave interactions within the tide-PW spectrum Solar modulation of ionospheric conductivity in the dynamo region Global magnetic field configuration Complexity due to Atmosphere-Ionosphere Coupling by Tides and Planetary Waves (PW)

Day-to-Day Variability of Swarm Electron Density Residuals – Ionospheric “Weather”

Quantifying the Variability: Periodicities in Time and Longitude distinct peaks eastward- and westward-propagating waves significant differences in latitude and local time

Quantifying the Variability: Separating Responses due to Forcing from “Above” and “Below” Kp and F10.7 spectra for Dec 2013-May 2014 Kp peaks near 6d and 10d also characteristic of PW Kp peaks possibly connected with recurrent geomagnetic activity due to high-speed streams and coronal hole distribution.

closely related to zonal E-field Plasma Drifts from EFI add Additional Guidance and Constraints Concerning Atmosphere-Ionosphere Coupling by Tides and Planetary Waves Vi parallel to B Vi perpendicular to B, meridional plane closely related to neutral wind along B closely related to zonal E-field perpendicular to B Above plotted in geographic coordinates

CONCLUSIONS Swarm reveals significant day-to-day variability, or ionospheric weather, in plasma densities at low to middle latitudes. Much of this variability is due to plasma drifts driven by tidal and planetary wave winds, either indirectly through dynamo generation or directly through collisional transport along B-field lines. Care must be taken to account for variability at PW periods (2-20 days) due to recurrent geomagnetic activity (~7d, 9d, 13.5d) or solar ionizing flux due to rotation of the Sun (~13.5d, 27d). The combined availability of electron densities, plasma drifts, perturbation magnetic fields and neutral densities from Swarm will enable an integrated self-consistent perspective on atmosphere-ionosphere coupling due to tides and PW. The same data will serve to challenge first-principles models of the atmosphere-ionosphere system.