1. Mike Ruohoniemi (Space@VT)OGIS 2012VT SuperDARN Remote Sensing of the Ionosphere and Earth’s Surface with HF Radar J. Michael Ruohoniemi and Joseph Baker Nathaniel Frissell, Sebastien de Larquier, and Evan Thomas Center For Space Science and Engineering Research (Space@VT) Bradley Department of Electrical and Computer Engineering Virginia Tech April 13, 2012

2. OGIS 2012Mike Ruohoniemi (Space@VT)VT SuperDARN Primer on Remote Sensing with HF Radar High Frequency (HF) radars operate at ~10 MHz (wavelengths of ~30 m) An early success of HF radar as a remote sensing device was the discovery of the ionosphere (from reflections) The ionosphere is the layer of the atmosphere that contains weakly ionized plasma and extends upwards from about 90 km HF rays are bent, or refracted, by the ionosphere and can propagate to great distances leading to:  Short wave radio propagation  Over-The-Horizon (OTH) radar An HF radar can detect scatter from blobs, or irregularities, in the ionosphere and from structure on Earth’s surface

3. Propagation and Reflection of HF Signal Primer on HF Radar Ionospheric plasma irregularities B F-Region Ground Scatter HF rays are refracted in the ionosphere as they encounter gradients in electron density. Transmitted signals can be reflected back to the radar by: 1) Ionospheric plasma irregularities OR 2) Earth’s surface Information about the reflectors is carried in the returned signal, e.g., Doppler velocity ~ 300 km altitude HF radar

4. Example of an HF Radar Map of Backscattered Power Primer on HF Radar Field-of-view plot of backscattered power from the Goose Bay radar for a single two-minute scan (October 15 th, 2000,15:00-15:02 UT).

5. OGIS 2012Mike Ruohoniemi (Space@VT)VT SuperDARN Virginia Tech SuperDARN HF Radars Kapuskasing, Ontario, Canada Fort Hays, Kansas, USABlackstone, Virginia, USA Goose Bay, Newfoundland and Labrador, Canada

6. OGIS 2012Mike Ruohoniemi (Space@VT)VT SuperDARN Coverage by the SuperDARN radars

7. OGIS 2012Mike Ruohoniemi (Space@VT)VT SuperDARN Remote Sensing with the SuperDARN HF Radars The SuperDARN group at Virginia Tech operates HF radars as part of an international research collaboration (10 countries) SuperDARN: Super Dual Auroral Radar Network With these radars we remotely sense:  Motion of ionospheric plasma due to coupling from the solar wind (‘Space Weather’)  Passage of large-scale waves in the atmosphere  Roughness at the Earth’ surface including ocean waves and ice cover  Winds in the atmosphere at 90 km altitude (meteor trails)  Unusual clouds in the upper atmosphere (Polar Mesopheric Clouds)

8. Coherent ionospheric scatter SuperDARN Conditions required to observe ionospheric scatter with SuperDARN radars EM backscatter generated by free electrons in the ionosphere accelerated by a transmitted signal. Backscatter is amplified under Bragg conditions by density fluctuations with scale sizes on the order of half the transmitted wavelength. Orthogonality of the transmitted signal with the background magnetic field (aspect condition) guarantees maximum returned power.

9. OGIS 2012Mike Ruohoniemi (Space@VT)VT SuperDARN Mapping Plasma Motion in the Ionosphere Common-volume line-of-sight velocities measured by radars in Oregon and Kansas

10. OGIS 2012Mike Ruohoniemi (Space@VT)VT SuperDARN Mapping Plasma Motion in the Ionosphere Map of merged two-dimensional plasma velocity vectors

11. OGIS 2012Mike Ruohoniemi (Space@VT)VT SuperDARN Mapping Plasma Motion in the Ionosphere Twenty-minute movie of ionospheric plasma ‘winds’

12. OGIS 2012Mike Ruohoniemi (Space@VT)VT SuperDARN Mapping Plasma Motion in the Ionosphere Global map of ionospheric plasma circulation (Northern Hemisphere)

13. Waves in Earth’s Atmosphere Atmospheric Gravity Waves Time lapse of gravity wave action from the Tama, Iowa KCCI-TV webcam on 6 May 2007. [http://www.youtube.com/watch?v=yXnkzeCU3bE]

14. HF Ray Paths during Gravity Wave Events Atmospheric Gravity Waves [Bristow et al., 1994] Gravity Wave Causes Moving Ionospheric Concavities Concavities focus radar beams, therefore resulting in stronger backscatter at these locations.

15. HF Radar Observations of Atmospheric Gravity Waves Atmospheric Gravity Waves Goose Bay Radar (GBR) 19 November 2010

16. Total Electron Content of the Ionosphere with GPS Map of the ionosphere obtained from analysis of GPS signal

17. Total Electron Content of the Ionosphere with GPS Mid-latitude SuperDARN radars observed high-speed flows associated with a subauroral polarization stream (SAPS) in the TEC trough region. Comparison with SuperDARN observations of irregularity backscatter

18. Map of Line-of-Sight Velocities for 08:40 UT, March 9 th, 2011 NSF MSI SuperDARN MSI SuperDARN: First Extended, Instantaneous Image of a SAPS Flow Channel First extended, instantaneous image of a SAPS event recorded on March 9 th, 2011 at 08:40 UT. Line-of-sight velocities are shown. Christmas Valley, ORHays, KS

19. Map of Line-of-Sight Velocities for 08:40 UT, March 9 th, 2011 NSF MSI SuperDARN MSI SuperDARN: First Extended, Instantaneous Image of a SAPS Flow Channel First extended, instantaneous image of a SAPS event recorded on March 9 th, 2011 at 08:40 UT. Line-of-sight velocities are shown. Christmas Valley, ORHays, KS

20. Mapping the Roughness of Earth’s Surface Field-of-view plot of backscattered power from the Goose Bay radar for a single two-minute scan (October 15 th, 2000,15:00-15:02 UT). The scatter from the ground is most intense from water-covered areas and almost extinguished over the ice cap of central Greenland Detection of ocean wave activity and ice cover

21. SuperDARN: mid-latitude ionosphere science results Furthest extent of sea ice cover during month of October 2000 (National Snow and Ice Data Center, Boulder, CO). Ground scatter occurrence rate observed by the radar at Goose Bay during daytime over the month of October 2000. Mapping the Roughness of Earth’s Surface Comparison of sea ice cover and HF radar observations