LWS TR&T Focus Teams:

Atmosphere-Ionosphere Coupling During Stratospheric Sudden Warmings

Team Leader: Larisa Goncharenko (MIT Haystack Observatory)
Team Research Plan:
Next Team Meeting: TBD
Team-Maintained Web Site: TBD
Team Publications: TBD
Team Members:
Qian Wu (NCAR/HAO)
Ruth Lieberman (GATS-Inc)
David Ortland (NorthWest Research Associates)
S. Irfan Azeem (ASTRA LLC)
Alan Burms (University Corporation for Atmospheric Research)
Astrid Maute (University Corporation for Atmospheric Research)
Raymond Plumb (Massachusetts Institute of Technology)
Lawrence Coy (Naval Research Laboratory)

Target Description: Over the last three years our understanding of the relationship between the neutral atmosphere and ionosphere has been dramatically altered due to research focused on Sudden Stratospheric Warmings (SSW). SSW represent a compelling manifestation of the complex coupling of the troposphere-stratosphere-mesosphere-ionosphere system. SSW events are large-scale, well-defined, long-lasting phenomena, with predictable short term (several day) behavior and post-event duration. Recent studies suggest that a SSW couples all atmospheric layers from the ground to the thermosphere and from the poles to the equator, and leads to significant perturbation in ionospheric electron density in excess of 50% from the mean state. Understanding the forcing mechanisms for SSW events, including wave-wave interactions in the neutral atmosphere and neutral/plasma coupling has the potential to significantly improve understanding of the drivers of ionospheric variability, and improve forecasting of ionospheric space weather.

While the occurrence of the initial SSW forcing is predictable, the subsequent effects of the forcing across the entire atmosphere-ionosphere system are not understood. Disturbances in the lower and middle atmosphere appear related to planetary wave anomalies, their coupling to upper atmospheric layers as well as the combined roles of planetary waves, atmospheric tides, and gravity waves are less clear. Not much is known about the characteristics of nonlinear wave-wave interactions, which require careful analysis to deduce from observational data. A full understanding of SSW coupling into the ionosphere requires studies that bring together simultaneous observations in a variety of neutral and ionosphere parameters and models that fully account for neutral/plasma coupling and dynamics. Other uncertainties to be resolved are the degree of influence on SSW events from solar variability and solar proton fluxes, and the links that SSW processes may have on the modification of planetary wave propagation in the stratosphere, mesosphere, and ionosphere.

Large space-based data sets (observations from EOS, TIMED SABER, Aura MLS, COSMIC, C/NOFS, NCEP and EMCWF global stratospheric maps) along with ground-based data sets (lidars, MF and meteor radars in the MLT region, incoherent scatter radars, magnetometers, GPS TEC maps) are available to address the problem in a mesoscale format. Comprehensive modeling tools (WACCM, NOGAPS, WAM) can be forced with assimilated troposphere and stratosphere data to recreate SSW events and analyze mesospheric-thermospheric responses. Coupled whole atmosphere models can be used to interpret the observations and assess impacts of driving processes on the MLT region and ionosphere.

Goals and Measures of Success: The goal of this Focused Science Topic is to advance our understanding of the dynamical coupling processes between the middle and upper atmospheres in both a theoretical and quantitative manner, and to lay the groundwork for future predictive capabilities in space weather and ionospheric variability through the study of SSW events. Success of this team will be measured by:

• Improved understanding of dynamo processes and energy transport from the lower atmosphere into geospace and from geospace to the lower atmosphere during SSW events.
• Characterization of spatio-temporal variations in wave activity associated with SSW events (planetary waves, atmospheric tides, gravity waves). Determination of the tidal modes modulated during SSW events (solar/lunar, migrating/non-migrating, diurnal/semidiurnal/terdiurnal), planetary and gravity wave fluxes.
• Improved theoretical and observational understanding of key factors affecting the efficiency of the atmosphere-ionosphere coupling (e.g. amplitudes of planetary waves, changes in zonal mean flow) responsible for SSW events.
• Improved theoretical and observational understanding of the relative impacts of gravity waves and planetary waves in driving the atmospheric and ionospheric response to planetary waves originating in the stratosphere during SSW events.
• Characterization of electrodynamic and ionospheric signatures associated with SSW and improved understanding of key mechanisms responsible for these signatures.

Types of Investigations:

• • Observational investigations of planetary wave activity, tidal activity, and gravity wave activity in the stratosphere-mesosphere-ionosphere before, during, and after SSW.
  • Observational investigations of changes in the dynamics in the stratosphere, mesosphere, and upper thermosphere and electrodynamics in the ionosphere-thermosphere system (e.g., electric field) associated with SSW.
  • Modeling studies of interactions during SSW between planetary waves, tides, and gravity waves, planetary waves and zonal mean flow, and their effects on the ionosphere; effects of solar variability on the ionosphere-thermosphere response to these dynamical drivers of lower and middle atmospheric origin.
  • Observational and modeling studies of the temporal development of the mesospheric and ionospheric response to SSW and recovery from SSW.