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Next: 6 Jan/9517:03 - Up: Morphology during a Complete Previous: SuperDARN Maps of Double-peaked

1 Jan/95, 16:21 - 16:23 UT

During the period of the event, WIND measured a solar plasma speed of 310-320 km/s and very quiet IMF conditions. The tex2html_wrap_inline4540 component was within 2 nT of zero and mainly negative from 15:00 to 17:00 UT. IMP8 data were not available. The tex2html_wrap_inline4548 index at the time of the event was 1.0 and rising.

The morphology map of Figure 5.16 shows a moderate amount of backscatter. Clearly visible is an area of missing backscatter from tex2html_wrap_inline5318 E to tex2html_wrap_inline5320 E and tex2html_wrap_inline5322 N to tex2html_wrap_inline5324 N latitude for both radars. Just beyond that region at higher latitudes double-peaks can be found in the spectrum, forming a banded region centered around tex2html_wrap_inline5326 N. Both radars observe the spectral features.

Figure 5.16: Map of spectral findings from the Saskatoon and Kapuskasing radars: 1 Jan/95

As indicated in Figure 5.17, the satellite passes through the region where spectral features can be seen from tex2html_wrap_inline5328 - tex2html_wrap_inline5330 and through the blank region where the radars do not detect echoes from tex2html_wrap_inline5330 - tex2html_wrap_inline5334 .

Figure 5.17: Peak-map with overlaid flight path of the DMSP F12 satellite: 1 Jan/95

The energy and fluxes shown in Figure 5.18 correlate with the radar measurements of the double peaked spectra. The flux increases past a value of tex2html_wrap_inline5336 at tex2html_wrap_inline5338 while average energies are at or below tex2html_wrap_inline5340 and quite variable. There is a sharp increase in both the flux and characteristic energy at tex2html_wrap_inline5330 , after which the average electron energy remains steady at about tex2html_wrap_inline5344 . The flux then drops below tex2html_wrap_inline5346 at tex2html_wrap_inline5348 while the characteristic energy remains at about tex2html_wrap_inline5344 until the satellite leaves the field of view of the radars.

Figure 5.18: Average electron energy and flux determined from SSJ/4 instrument measurements: 1 Jan/95

Figure 5.19 shows, as expected, a high F-layer ionization rate when there was a large flux of soft electrons with characteristic energy around tex2html_wrap_inline5340 . This interval corresponds exactly with the occurrence of the double-peaked spectra from tex2html_wrap_inline5338 to tex2html_wrap_inline5356 . Similarly, the high energy fluxes measured later produce a high ionization in the E-layer from tex2html_wrap_inline5330 to tex2html_wrap_inline5360 , corresponding to the region of missing backscatter in the radar data.

Figure 5.19: Estimated ionization rates at E- and F-layer heights determined from electron spectra measurements: 1 Jan/95

Figure 5.20 shows a sharp conductivity increase starting at tex2html_wrap_inline5330 . If the satellite speed is taken as tex2html_wrap_inline5364 , the sharp increase in the Pedersen conductivity corresponds to a conductivity gradient along the satellite track of tex2html_wrap_inline5366 , centered at tex2html_wrap_inline5368 .

Figure 5.20: Estimated E-layer conductivities from the Robinson model: 1 Jan/95

The velocity map for the event, as shown in Figure 5.21, indicates a relatively steady flow northward of the region where double-peaked spectra were found. In the region around tex2html_wrap_inline5370 E and tex2html_wrap_inline5326 N the flow vectors are of low velocity and variable in direction. This quasi-turbulent behaviour of the velocity vectors is consistent with the assumption that the double-peaks are caused by Kelvin-Helmholtz instability driven turbulence.

Figure 5.21: SuperDARN velocity map: 1 Jan/95

next up previous
Next: 6 Jan/9517:03 - Up: Morphology during a Complete Previous: SuperDARN Maps of Double-peaked

Andreas Schiffler
Wed Oct 9 10:05:17 CST 1996