1. The Super Dual Auroral Radar Network (SuperDARN)
Joseph B. H. Baker
The Center for Space Science and Engineering Research
Virginia Tech

2. What is SuperDARN?
The Super Dual Auroral Radar Network (SuperDARN) is an international network of high-frequency (HF) radars for researching the Earth’s upper atmosphere and ionosphere.
The principle backscatter targets are plasma irregularities with decameter spatial scales.
Each SuperDARN radar has the following characteristics:
Operates between MHz
Transmits ~10 kW of peak power
Uses phased array steering to look in 16 or more beam directions
Uses multi-pulse sequences to simultaneously determine range and Doppler velocity
Has typical range and time resolution of 45 km and 1-2 minutes.
All SuperDARN radars produce identical data products that are routinely combined to produce hemispheric characterizations of ionospheric plasma convection.

3. Northern Hemisphere Radars
King Salmon, AK (Japan)
Kodiak, AK (USA)
Prince George, B.C. (Canada)
Saskatoon, Sask. (Canada)
Kapuskasing, Ont. (USA)
Goose Bay, Lab. (USA)
Stokkseyri, Iceland (France)
Pykkvibaer, Iceland (UK)
Hankasalmi, Finland (UK)

4. SuperDARN PI Institutions
Johns Hopkins University Applied Physics Laboratory (1983)
British Antarctic Survey (1988)
University of Saskatchewan, Canada (1993)
National Center for Scientific Research, France (1994)
National Institute for Polar Research, Japan (1995)
University of Leicester, England (1995)
University of KwaZulu-Natal, South Africa (1997)
University of Alaska (2000)
Communications Research Laboratory, Japan (2001)
La Trobe University, Australia (2001)
Nagoya University, Japan (2006)
Virginia Tech (2008)
Dartmouth College (2010)

5. Collaborative Structure
SuperDARN is an collaboration with minimal hierarchical structure with interactions occurring at the scientist-to-scientist level, rather than between funding agencies.
The foundation for the collaboration is a “PI’s Agreement” which specifies the general principles for sharing data, coordinating scheduling, and other collective interests.
Membership in the collaboration is open to any research group who can gain access to funds to build a radar (~$250 - $500 thousand). By sharing access to their own radar dataset, each PI (and collaborators) gains access to the data from all of the other radars.
All SuperDARN radars conform to a basic design but there can be substantial differences in the hardware. However, the operating software is centrally controlled.
Each year one of the PI institutions hosts a week-long workshop that attracts scientists and engineers to present science results, coordinate planning for the following year, and exchange ideas about analysis techniques and hardware implementation.
The SuperDARN Workshop is being hosted by Dartmouth College next week.

6. Northern Radars Goose Bay Oct 1983 53.328 N , 60.468 W Virginia Tech
RADAR INCEPTION LOCATION PI INSTITUTION
Goose Bay Oct N , W Virginia Tech
Kapuskasing Sep N , W Virginia Tech
Saskatoon Sep N , W University of Saskatchewan
Stokkseyri Aug N , W Universite d’Orleans
Hankasalmi Jun N , E University of Leicester
Pykkvibaer Nov N , W University of Leicester
Kodiak Jan N , W University of Alaska
Prince George Mar N , W University of Saskatchewan
King Salmon Oct N , W NICT, Japan
Wallops Island Jun N , W Johns Hopkins University APL
Rankin Inlet May N , W University of Saskatchewan
Hokkaido Nov N , E Nagoya University
Inuvik Dec N , W University of Saskatchewan
Blackstone Feb N , W Virginia Tech
Hays East Nov N , W Virginia Tech
Hays West Nov N , W Virginia Tech
Oregon East Nov N , W Dartmouth College
Oregon West Nov N , W Dartmouth College

7. Southern Radars RADAR INCEPTION LOCATION PI INSTITUTION
Halley* Jan S , W British Antarctic Survey
Syowa South Feb S , E NIPR, Japan
Sanae Feb S , W University of Kwa-Zulu
Syowa East Feb S , E NIPR, Japan
Kerguelen Jun S , E Universite d’Orleans
TIGER Tasmania Jan S , E La Trobe University
TIGER Unwin Nov S , E La Trobe University
McMurdo Jan S , E University of Alaska
Falklands* Feb S , W British Antarctic Survey

8. Radar Fields Of View

9. Why Operate at HF?
HF signals are refracted in the ionosphere as they traverse gradients in electron density.
The transmitted signals can be reflected back to the radar by:
1) Plasma irregularities if the ray is quasi-perpendicular to the magnetic field
OR 2) The ground
Ionospheric plasma irregularities B
F-Region
Advantages of operation at HF frequencies:
1) Refraction of signals provides access to targets in the F-region ionosphere (~ km)
2) Refraction of signals extends the radar range to > 3500 km.
3) Low power requirements allows for continuous operation.

10. Single Beam Range-Time Plot

11. Single Radar Doppler Map
January 11, :10:00 – 01:11:47 UT

12. Multi-Radar Doppler Map

13. Ionospheric Convection Pattern

14. Conjugate Convection Patterns
09:50 – 09:52 UT on 30th September 2002

15. SuperDARN Science
Hemispheric structure and dynamics of ionospheric convection.
Mesoscale signatures of magnetosphere-ionosphere coupling.
Convection vortices associated with magnetic field-aligned currents.
Ionospheric flow bursts associated with magnetopause reconnection (FTEs).
Inter-hemispheric (i.e. north-south) conjugacy of ionospheric convection.
Convection associated with auroral substorms.
Ionospheric irregularities and high latitude plasma structures (patches).
Electromagnetic waves: MHD, ULF, Magnetic Field Line Resonances.
Neutral atmosphere: Gravity waves, mesospheric winds, planetary waves.
More generally, SuperDARN ionospheric convection patterns have been widely used to interpret localized features identified in other space physics datasets.

16. M-I Coupling

17. Spacecraft Coordination
SuperDARN has a long heritage of coordinating operations with spacecraft missions. In fact, the original concept for SuperDARN evolved during the ISTP era and NASA provided the initial funding to build the Kapuskasing radar in 1993.
In more recent years SuperDARN scientists have continued to be heavily involved in collaborations with the Cluster, THEMIS and Double Star spacecraft communities.
To further facilitate these space-ground collaborations a “Spacecraft Working Group” (SWG) has been formed to facilitate the identification of favourable conjunctions.
Each month the SWG examines predicted orbit files and identifies ~200 hours of conjunctions when spacecraft footpoints pass through the fields-of-view of the SuperDARN radars.
This information is passed to the “Scheduling Working Group” which sets the radar schedule.

18. Radar Scheduling
The PI’s Agreement divides SuperDARN radar operations into three broad categories:
COMMON TIME: Network coordinated operations designed to maximize coverage and resolution of data for ingestion into ionospheric convection patterns. All radars perform 16-beam azimuth scans with 75 range gates and 1-2 minute cadence.
SPECIAL TIME: Network coordinated operations in which some or all of the radars use a customized mode devoted to a very specific science topic (e.g. Rocket launches, ULF pulsations, E-region measurements, satellite conjunctions etc.).
DISCRETIONARY TIME: Radars are allowed to operate independently of each other if there are specific needs of the individual PIs. Common Time is run otherwise.
The PI’s Agreement specifies the following split between the three times:
Common Time: 50% (minimum)
Special Time: 25% (maximum)
Discretionary Time: 25% (maximum)
The “Scheduling Working Group” has responsibility for acting on scheduling requests and drawing up a monthly operations schedule which is approved by the PIs.
The nominal lead time for a scheduling request for special time is 8 weeks.

19. Radar Scheduling 2001/02 2007/08 2002/03 2003/04 2004/05 2005/06
2006/07
Common Time (2-min)
Common Time (1-min)
Discretionary Time
Special Time
Common Time (THEMIS)
2008/09
2009/10
Over the past ten years:
There has been a migration of common time from 2-minute scans to 1-minute scans.
There has been hardly any “Special Time” in the traditional sense.
A special mode designed specifically for the THEMIS mission has become “common”.

20. THEMIS Mode
Beam-7: camping beam data (8-second)
0430 UT
0440 UT
0450 UT
Beam-8: Normal beam data (2-minute)
During THEMIS tail conjunctions SuperDARN radars are running a special “THEMIS mode” to increase temporal resolution for study of substorm expansion phase onsets:
Dwell time reduced from 7 to 4 seconds.
The radar returns to a designated camping-beam between each successive beam.
The THEMIS mode simultaneously provides:
Hemispheric spatial coverage every 2 mins.
Higher temporal resolution on one camped beam per radar (8 secs).

21. Mid-Latitude SuperDARN
First generation SuperDARN radars were built near 60° MLAT for optimal coverage of the auroral zone during weak to moderate levels of geomagnetic activity.
In recent years a second chain has been under construction at middle latitudes to maximize coverage during storms:
Wallops Island, VA (2005)
Hokkaido, Japan (2006)
Blackstone, VA (2008)
Hays, Kansas (x2) (2009)
Christmas Valley, OR (x2) (2010)
These newer SuperDARN radars are ideally located to provide excellent ionospheric context for RBSP measurements.

22. Sub-Auroral Drifts Oksavik et al., GRL 2006
Early measurements with the Wallops radar quickly demonstrated the ability of mid-latitude SuperDARN radars to continuously monitor the temporal dynamics of Sub-Auroral Polarization Streams (SAPS) over extended periods of time.

23. Subauroral Drifts
More recently, we have been able to capture the longitudinal structure of SAPS features with multiple mid-latitude radars. This is a SAPS event on April 9th 2011.

24. Subauroral Irregularities
This figure shows the location of ionospheric irregularities observed during the April 9th SAPS event overlaid on a map of total electron content (TEC) obtained from GPS receivers.
The irregularities are clearly seen to lie inside the mid-latitude ionospheric trough.

25. Plasmasphere Plumes
Combined SuperDARN and GPS TEC measurements can also be used to monitor the evolution of Storm Enhanced Densities (SEDs), which are commonly associated with the ionospheric projection of plasmaspheric plumes.
This figure shows a map of GPS Total Electron Content (TEC) with overlain streamlines of plasma motion obtained from SuperDARN radar measurements and DMSP driftmeter data.
A prominent feature is the tongue of ionization (TOI) which follows the SuperDARN-DMSP streamlines.
In this way, we are able to monitor the evolution of inner magnetosphere electrodynamics and plasmaspheric plumes from the ionosphere.
1730 UT on 20 November 2003
Foster et al., [2005]

26. Penetration Electric Fields
Subauroral electric fields are relatively weak because of shielding by the region-2 field- aligned currents and partial ring current.
However, mid-latitude SuperDARN radars see a considerable amount of dynamics, suggestive of “penetration electric fields” produced by variability in the interplanetary driving conditions and auroral activity.
This figure shows a time-series of subauroral ionospheric convection vectors on May 6th 2010.
Some of the subauroral convection is correlated with auroral activity (AE index) and some of it is more directly related to interplanetary conditions.
This sort of activity is ubiquitous in quiet time mid-latitude SuperDARN measurements.

27. Plasmasphere Subcorotation
The fact that mid-latitude SuperDARN radars see a substantial amount of subauroral plasma drifts, even during quiet periods, suggests that the plasmasphere is not corotating with the Earth.
This figure shows a histogram of the “Corotation Factor” calculated from the plasma drifts seen by mid-latitude SuperDARN radars during quiet conditions (i.e. Kp < 2)
The drift velocities are consistent with the plasmasphere rotating at an average rate that is 88.7% corotational.
This value is consistent with observations of plasmasphere subcorotation obtained by tracking features in IMAGE EUV images [Sandel et al., 2003; Galvan et al., 2010] .
Kp < 2
MEAN=0.887
0.60
1.1
Corotation Factor .
The westward drifts shown on the previous slide imply that, most of the time, the mid-latitude ionosphere is not corotating with the Earth. By extension this would imply that the plasmasphere is probably sub-corotational as well.
We have used the mid-latitude SuperDARN measurements to calculate a corotation factor, which represents the extent to which the mid-latitude ionosphere is corotating.
These panels show distributions for the corotion factor measured by Wallops and Blackstone. Strict corotation corresponds to a factor of one;, represented by this solid line sub-corotation is less than one; super-corotation is greater than one.
The panel on the left shows the distribution for Kp less than or equal to 2. The panel on the right corresponds to Kp larger or equal to 2.
The mean for the distribution on the left is 0.9; the mean for the distribution on the right is closer to 0.85.
These mean values are consistent with studies done using IMAGE spacecraft EUV images to track the rotation velocity of plasmaspheric features.
Furthermore, the results show that subcorotation increases as magnetic activity becomes elevated

28. ULF Pulsations
It is also very easy to find ULF pulsations in mid-latitude SuperDARN data!

29. Mid-Latitude SuperDARN
2009
Hays, KS
2010
Christmas Valley, OR
2011
Aleutian Islands, AK
2012
Azore Islands, Portugal
At RBSP launch the mid-latitude SuperDARN array will be almost complete.
The completed array will provide coverage of the entire Western Hemisphere.

30. Summary
SuperDARN is an international collaborative network of HF radars that is used to study the motion of plasma irregularities in the Earth’s ionosphere at middle to high latitudes.
Currently, there are 18 radars operational in the northern hemisphere and 8 radars operational in the southern hemisphere.
The recent expansion of SuperDARN into middle latitudes has opened up several avenues of new research that have synergies with RBSP science:
Subauroral Polarization Streams during geomagnetic storms
Penetration electric fields during storms and non-storm periods
Structuring and transport of subauroral plasma (cf. plasmaspheric plumes)
Subauroral plasma irregularities (cf. plasmasphere instabilities)
ULF waves and pulsations
More generally, SuperDARN measurements will be useful for providing ionospheric contextual information that will aid in the interpretation of the RBSP spacecraft datasets.