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FREJA Cold Plasma Analyzer

The Swedish satellite FREJA (name pronounced fray-ya) was launched October 6th, 1992 from the Gobi Dessert in Central China. It carried a Canadian Cold Plasma Analyzer (designated F3C), the development of which was led by Dr. Brian Whalen of the Herzberg Institute for Astrophysics in Ottawa and built by COM DEV Ltd. in Cambridge, Ontario. This instrument was designed to measure cold plasma. F3C was able to discern energy per unit charge (E/Q) of ions or electrons in the range 0 < E/Q < 200 Volts and complemented measurements made by the F3H hot plasma experiment. Funding for the construction of F3C was provided by the National Research Council of Canada - Space Division, which later became the Canadian Space Agency. CSA funded final development and operations of the CPA. Support for scientific work was initially generated by the National Research Council's Herzberg Institute and then by the Natural Science and Engineering Research Council of Canada.

Data from F3C were telemetered to receiving stations at Esrange, Sweden, Prince Albert, Saskatchewan, and at the Japanese base SYOWA in Antarctica. CPA operations were handled by Institute for Space and Atmospheric Studies at the University of Saskatchewan in Saskatoon, while the data analysis has been done at the U of C following the arrival in 1995 the CPA's PI for data analysis (David Knudsen) following Dr. Whalen's retirement.

The CPA operated from January 1993 through May 1994, and had two new capabilities that made it unique: 1) True 2-D energy/angle-of-arrival imaging capability and 2) unprecedented spatial resolution. The latter feature has led to observations which show that intense ion heating is often confined within narrow regions of intense, low-frequency electromagnetic perturbations only a few hundred metres across, and which have been identified as solitary kinetic Alfven waves (SKAW's). Future studies using CPA will seek to uncover the exact mechanisms by which SKAW's energize ions, and to characterize the larger-scale plasma environment in which these small-scale particle energization structures are embedded (see Publications below).

Below are two panels of processed data obtained from the Canadian Cold Plasma Analyzer aboard the Swedish FREJA satellite.

The colour panel plots show ion flux into the Freja F3C Cold Plasma Analyzer during a pass which traverses the dayside cusp/cleft region and extends back into the evening auroral zone. The top panel shows ion counts as a function of time and arrival angle in the 2-D angle-image plane, and illustrates how the measured ion distribution becomes more isotropic within heating regions. The second panel shows ion counts versus time and energy, from 2 to 21 eV. The red ion heating "hot spots" occur in the polar cleft and auroral zone and are associated with intense ELF (< 1 kHz) plasma waves and soft (< 1 keV) electron precipitation.

The plot shows ion flux integrated over arrival angle and energy at high time resolution, showing how the larger scale heating regions in Figure 1 are comprised of very small-scale bursts of ion flux, each a few hundred meters wide, which have been found to occur within intense, low-frequency electromagnetic perturbations known as Solitary Kinetic Alfven Waves (SKAWs).

CPA-related Publications:

Whalen, B., A., D. J. Knudsen, A. W. Yau, A. M. Pilon, T. A. Cameron, J. F. Sebesta, D. J. McEwan, J. A. Koehler, N. D. Lloyd, G. Pocobelli, J. G. Laframboise, W. Li, R. Lundin, L. Eliasson, S. Watanabe, and G. S. Campbell, The Freja F3C Cold Plasma Analyzer, Space Sci. Rev., 70, p.541-561, 1994.

Knudsen, D. J., B. A. Whalen, A. W. Yau, M. J. Greffen, A. I. Eriksson, N. Lloyd, M. Boehm, J. Clemmons, and L. G. Blomberg, Sub-kilometer thermal plasma structure near 1750 km altitude in the polar cusp/cleft, Geophys. Res. Lett., 21, 1907, 1994.

Knudsen, D.J., J.H. Clemmons, and J.-E. Wahlund, Correlation between core ion energization, suprathermal electron bursts, and ELF plasma waves, J. Geophys. Res., 103, 4171, 1998.

Knudsen, D.J., and J.E. Wahlund, Core ion flux bursts within solitary kinetic Alfvén waves, J. Geophys. Res., 103, 4157, 1998.

Knudsen, D.J., P.O. Dovner, A.I. Eriksson, and K.A. Lynch, The effect of lower hybrid cavities on core plasma observed by Freja, J. Geophys. Res., 103, 4241, 1998.

Knudsen, D. J., T. D. Phan, M. D. Gladders, M. Greffen, and B. A. Whalen, Thermal electron temperature measurements from the Freja Cold Plasma Analzyer, AGU Monograph on Measurement Techniques for Space Plasmas, edited by Borovsky, Pfaff, and Young, American Geophysical Union, Washington, D.C., 1998.

Wahlund, J.-E., A.I. Eriksson, B. Holback, M.H. Boehm, J. Bonnell, P.M. Kintner, C.E. Seyler, J.H. Clemmons, L. Eliasson, D.J. Knudsen, P. Norqvist, L.J. Zanetti, Broadband ELF plasma emission during auroral energization, 1, Slow ion acoustic waves, J. Geophys. Res., 103 , 4343, 1998.