SA32A-01 INVITED
Extended High Latitude Incoherent Scatter Radar Observations during the IPY
The high-latitude incoherent scatter radar community has made an unprecedented effort to raise the availability of ionospheric measurements dramatically during the IPY. The EISCAT Svalbard Radar and the new Poker Flat Radar in Alaska have provided the most comprehensive coverage, with substantial contributions from other radars at Sondrestromfjord, Greenland, Millstone Hill, Massachusetts, and Irkutsk, Russia. This presentation will review the scientific and operational impact of the IPY operation using examples of the scientific highlights as well as indications of the future potential of the accumulated data sets. In particular, the application of these unique data sets in testing and developing ionospheric models will be discussed.
SA32A-02 INVITED
High Latitude Thermosphere-Ionosphere Variability During the Solar Minimum IPY Period
The Thermosphere-Ionosphere Mesosphere Electrodynamics General Circulation Model (TIMEGCM) driven by high latitude inputs from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) algorithm represents a true space-weather model that captures much of the variability in the global thermosphere and ionosphere. This coupled model has been run for the entire IPY period at solar minimum, and the ability of the model to reproduce thermosphere-ionosphere climate and weather at various locations has been quantified using incoherent scatter radar data and GUVI composition measurements. The differences between the model and the measurements provide insight into how the model might be improved in the future. Analysis of the AMIE results themselves also provides insight into the variability of the high latitude drivers during solar minimum conditions.
SA32A-03
Investigating the effect of thermospheric parameterization on the ionosphere during the IPY using the Global Ionosphere-Thermosphere Model.
Ionospheric observations made during the IPY provide an excellent opportunity to study the long-term behavior of the ionosphere-thermosphere system and perform statistical comparisons between upper atmospheric models. While the IPY took place during solar minimum, in reality, observations indicate a large range of atmospheric conditions. Simulating these variations during such a long-term observational campaign provides a challenge to modelers because of the relatively high dependence on the parameterization of subgrid-scale features such as Eddy-diffusion and other relatively unknown quantities such as reaction rates within the upper atmosphere. In this study, results from the Global Ionosphere- Thermosphere Model (GITM) are used to investigate the uncertainty associated with this parameterization, specifically of thermospheric properties, and the consequences for the ionospheric solution.
SA32A-04 INVITED
A one-year Statistical Comparison of CTIPe and ISR Data
The International Polar Year (IPY) has made quality high-latitude ionospheric data available in unprecedented quantities. The existence of a year-long continuous high-latitude data base of incoherent scatter radar (ISR) observations of the ionosphere provides an unprecedented opportunity for model/data comparisons. In the past, physics-based ionospheric models have usually only been compared with observations over restricted one or two day events or against climatological averages. In this study, using the ISR observations, the daily space weather, day-to-day variability, and year-long climatology of the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model have been simultaneously addressed to identify modeling shortcomings and successes. The goal of the study was to capitalize on the unique opportunity represented by the huge increase in data availability during solar minimum conditions to dramatically improve the quality of the model, and the underlying physical understanding, and in particular to develop CTIPe's capabilities in now- and fore-casting.
SA32A-05
Heating Events in the Polar Ionosphere-Thermosphere During the IPY
The first 12 months of the IPY campaign occurred during solar minimum conditions. These conditions were not geomagnetically quiet. During the year solar coronal holes produced fast solar wind streams that led to magnetospheric activity. Indications of this activity are found in the planetary geomagnetic activity index, Kp, which has recurrent multi-day periods of Kp values exceeding 3. The nature of these magnetospheric events is under extensive study since they are not viewed as geomagnetic storms or classical substorms. However, the magnetosphere is coupled to the high latitude ionosphere and hence, energy is expected to be deposited in the ionosphere-thermosphere (I-T) system during these events. Where and how much energy are outstanding questions. During this IPY period two incoherent scatter radars (ISR) operated in the polar cap and auroral oval. Both ISRs measured the local altitude profiles electron density, ion temperature, electron temperature, and line-of- sight velocity along their respective magnetic field line. The measurements have a cadence of at least 10 minutes and the ISRs have over 70 percent coverage during the first IPY year. The EISCAT Svalbard Radar (ESR) operated in the polar cap region at Longyearbyne, Svalbard and the NSF Poker Flat ISR (PFISR) operated in the auroral region at Poker Flat, Alaska. At both locations the observed ion temperature shows strong heating correlations with the occurrence of enhanced Kp events. The quiet time solar minimum temperatures at 300 km are observed to range from 800 to 900 K in both the auroral and polar cap regions. During the heating events these temperatures, at both locations, increase. The increase ranges from 50 to 200 K. These observations are presented and discussed in the context of the sustained I-T heating events and their source characteristics. The multiple day sustained heating events are quite different from a few hour substorm heating event or the dynamic fluctuations observed during storm heating.
SA32A-06
Coupling between the Arctic Middle and Upper Atmosphere during the IPY 2007-2008 Winter
Rayleigh lidars at Chatanika, Alaska (65N, 147W) and Kangerlussuaq, Greenland (67N, 51W) have
measured the middle atmospheric density and temperature structure during the 2007-2008 winter. These
lidars are part of the Arctic Observing Network during the fourth International Polar Year (IPY). The lidar
observations have yielded measurements of mean profiles and the gravity wave activity in the upper
stratosphere and mesosphere. TIMED-SABER satellite geopotential data are used to quantify the planetary
wave activity in the middle atmosphere. UKMO and GEOS reanalysis data are used to describe the structure
and evolution of the Arctic stratospheric-mesospheric vortex and Aleutian anticyclone. The lidars sampled
both inside and outside the vortex and anticyclone characterizing the gravity wave activity under different
synoptic regimes. A stratospheric warming occurred in late February 2008. A TIME-GCM simulation (with a
model lower boundary specified by ECMWF) has been conducted for the November 2007-March 2008
period. This study allows us to characterize the planetary and gravity wave activity in the Arctic middle
atmosphere during the IPY. These measurements and analyses will be compared with the TIME-GCM
simulations to study the wave coupling between the middle and upper atmosphere and the expected
response of the high latitude ionosphere to a stratospheric warming during the IPY.
http://research.iarc.uaf.edu/IPY-
CTSM/
SA32A-07
High Latitude Meospheric and Lower Thermospheric Tide Observed from Ground-based and Spaceborne instruments
We used ground-based mesospheric and lower thermospheric (MLT) neutral wind instruments (Fabry-Perot interferometer and meteor radar) and spaceborne FPI to study northern high latitude (75N) tides. The ground based instruments are located at same latitudes and different longitudes. The FPI at Resolute, Canada (74.68N, 94.87W) measures the neutral winds at 87 km (OH emission) and 97 km (O emission) and meteor radar at Bear Island, Norway (74.44N, 19.08 E) measures neutral winds from 78 to 108 km with varying degree coverage. The ground based instruments provide coverage for all local times. The two stations have large longitudinal difference to allow determination of zonal wavenumber of the dominant tide. The TIMED TIDI instrument provides neutral winds from 80 to 110 km globally. The TIMED TIDI instrument, however, has limited local time coverage of 15 longitudes during a day. Hence, it requires a long period (60 days) to accumulate all 24 hour local times coverage. We intend to combine these two types of measurement to study both short term and long term variations of the MLT tide in the high latitudes.
SA32A-08
Gravity wave impacts on mesospheric forcing during Stratospheric Sudden Warming studied with a parameterization scheme
Mesospheric cooling during Stratospheric Sudden Warming (SSW) has been observed by instruments and simulated by various models. While TIME-GCM successfully simulates the cooling effect, the simulated cooling layer thickness is larger than observed. Gravity waves are considered as the primary contributor to the mesospheric cooling and the lower thermosphere warming during SSW through changing the meridional circulation. The aforementioned discrepancies could be caused by the unrealistic gravity wave parameterization. To improve the parameterization for TIME-GCM, we use a gravity wave parameterization model (the Lindzen scheme) to investigate how the mesospheric and lower-thermospheric forcing response to different gravity wave parameters. The background temperature and wind profiles are taken from the NCAR TIME-GCM simulation of the 2008 SSW in Northern Hemisphere. By varying gravity wave spectrum shape, horizontal wavelength, and amplitude as the input to the Lindzen scheme, the mesospheric forcing during the 2008 SSW will be quantified and the gravity wave impacts on the meridional circulation will be assessed.
SA32A-09
Spatial and Temporal Response of Auroral and Subauroral Plasma Convection to High- Latitude Drivers of Geomagnetic Activity
During the IPY, the second of two lower-latitude SuperDARN radars was put into operation in the eastern U.S. Located at Blackstone, VA and directed toward central Canada, it extends the coverage of the preexisting Wallops Island radar to more than 4 hours of magnetic local time and covers 50-70 degrees geomagnetic latitude providing coverage of ionospheric plasma convection and electric fields on magnetic field lines connected to the inner boundary of the plasmasheet, ring current and plasmapause. Although initial measurements with this coordinated pair of radars were made at a time of low geomagnetic activity, there have been many opportunities to examine both the spatial and temporal response of low-latitude auroral and subauroral plasma convection and its associated electric field to a variety of high-latitude magnetospheric drivers including dayside reconnection and midnight sector substorms. In this paper, we discuss the dynamical response of these flows to both dayside reconnection and substorms. We specifically examine the timing, location, spatial extent and intensity of these flow enhancements versus the nature and strength of the driver.
SA32A-10
Evidence That IMF Fluctuations During High-Speed Solar Wind Steams Substantially Affect the Strength of Dayside Ionospheric Convection
The orientation and magnitude of the interplanetary magnetic field (IMF) and solar wind dynamic pressure are known to affect the strength of ionospheric convection. However, the high-speed solar wind streams during the IPY have provided the opportunity to investigate whether the ULF waves of the IMF during high- speed streams can have a substantial contribution to the strength of convection. We have examined ionospheric convection in the dayside polar cap measured by the Sondrestrom radar under various solar wind conditions. Using an extensive radar data set, we find that ULF power in the IMF is closely associated with the strength of dayside ionospheric convection. Convection flows during periods of large north-south IMF fluctuations are observed to be as strong as for steady and large southward IMF periods. Enhanced convection can be also observed even for northward IMF intervals, but only if the interplanetary magnetic field exhibits high ULF power. These observations thus suggest that IMF wave activity can significantly influence ionospheric convection. Comparisons with events with substantial ULF power not occurring during high-speed streams indicate that the ULF power is effective, independent of any direct affect from the solar wind speed. We speculate that resonance between IMF fluctuations and natural magnetospheric oscillation frequencies might be responsible for the connection between ionospheric convection and IMF ULF power. We have also found some evidence for a connection between the ULF power in the solar wind density and the strength of convection.