IITC IPY Data Descriptions

NorthWest Research Associates (NWRA)
University of Alaska at Fairbanks Geophysical Institute (UAF GI)

This page provides information pertaining to the data available from the tomography chain operated by NorthWest Research Associates (NWRA) and the University of Alaska at Fairbanks Geophysical Institute (UAF GI).

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Mr. James Secan (NWRA)
NorthWest Research Associates, Inc.
2455 E. Speedway Blvd, Suite 204
Tucson, AZ 85719
jim@nwra.com
+00 1 520 319 7773

Two types of data which are of potential interest are available:

1. Tomographic images of ionospheric electron density covering a geographic latitude range of approximately 57° to 73°N (57-76°N geomagnetic latitude) along the 214.5°E longitude meridian (this range is reduced if not all stations in our chain are reporting data for a particular satellite pass).
2. Relative slant-range Total Electron Content (TEC) and intensity and phase scintillation parameters for the receivers that make up the chain from which the tomographic images are created. At present, the locations of receivers in this chain are as follows (note that scintillation data are available only from the four ITS10S receivers):
• Cordova, AK (60.50°N, 214.53°E) (NWRA-operated ITS10S receiver)
• Gakona, AK (62.40°N, 214.84°E) (NWRA-operated ITS10S receiver)
• Delta Junction, AK (63.90°N, 214.76°E) (NWRA-operated ITS10S receiver)
• Fort Yukon, AK (66.56°N, 214.78°E) (UAF-owned CIDR receiver)
• Arctic Village, AK (68.12°N, 214.44°E) (NWRA-operated ITS10S receiver)
• Kaktovik, AK (70.13°N, 216.36°E) (UAF-owned CIDR receiver)

1. From the tomographic images:
• Electron density as a function of geomagnetic latitude and altitude. Standard image provides 20 km spacing in altitude and ~0.11º spacing in latitude.
• Vertical TEC (to 1,000 km altitude), foF2, and hmF2 derived from the electron density profiles, ~0.11º spacing in latitude. Included are estimates of the uncertainty in both TEC and foF2.
• (Note: Alternative atitude and altitude spacing can be provided for individual cases if necessary.)
2. From the receivers:
• Relative slant-range TEC as a function of time, one observation per second.
• (NWRA ITS10S receivers) Intensity (VHF and UHF) and phase scintillation indices, one observation every 10 seconds.

Phase-coherent radio transmissions at VHF and UHF from a set of satellites in low earth orbit (LEO) are monitored whenever a specific satellite is more than 5° above the local horizon. The differential phase between the UHF and VHF signals are used to derive relative slant-range TEC, and the VHF and UHF intensity and the differential phase are processed to generate the intensity and phase scintillation indices.

Tomographic images are generated from all Transit, COSMOS 2407, and DMSP F17 satellites passes which have useable data from at least three of the five stations in the chain and which achieve a minimum elevation of 60° as observed from the Gakona site. These images are generated using a weighted, damped, least-squares (WDLS) inversion technique developed by NorthWest Research Associates (Fremouw, E. J., J. A. Secan, and B. M. Howe, Application of stochastic inverse theory to ionospheric tomography, Radio Sci., 27, 721, 1992).

Processing of the data from the receiver chain, and generation of tomographic images, runs automatically in near real-time.

Tomography Images (4-6 images per day):

• Image files: 150-180 kB per image
• TEC, foF2, and hmF2 files: 10-15 kB per image

Receiver data: Depends on pass length, ranging from 80-150 kB per receiver per pass. We received between 15 and 25 passes per day per station.

Tomography Images

• The electron density profiles are stored in ASCII-format files which include a meta-data header containing information about how the images were created.
• The TEC, foF2, and hmF2 data are in ASCII-format column files.

Receiver data are in netCDF-format files.

Documentation is available for all data files.

Plots of the receiver data, ASCII versions of the receiver data files, and, if generated, plots of tomography images, TEC, and foF2, are posted on the web site operated by the High-latitude Active Auroral Research Program (HAARP).

Data can be made available for ftp or http download upon request. It may also be possible to provide data on CD-ROM, but funds for such activities are limited.

The radio tomography chain of the joint NorthWest Research Associates (NWRA) and University of Alaska Geophysical Institute (UAF-GI) chain, referred to herein as the "NWRA chain", for which details are provided in this form, is part of the project "Radio tomographic imaging of the Arctic ionised atmosphere by the International Ionospheric Tomography Community (IITC)".

Funding for collection and processing of these data is provided by the High-latitude Active Auroral Research Program (HAARP). Rules for release and use of these data have been established between NWRA and HAARP, and all researchers requesting the data described herein will be required to abide by these rules.

Date of last update: 05 December 2006

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