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November 5, 1995

Figure 5 displays PSFR and magnetometer data recorded 2300 UT on November 5 to 0200 UT on November 6, 1995 (1608-1908 MLT), including two periods of dynamic latitude variations in the auroral currents. For reference, the average daily $Kp$ was 3.1 on November 5 and 3.6 on November 6, and the magnetic perturbations of the electrojet varied from $\sim$60 to 1020 nT.

Auroral roar is first detected at Baker Lake (74$^\circ$) near 2300 UT, at which time the poleward boundary of the electrojet is also near 74$^\circ$. At 2315 UT the latitude of the highest emission intensity shifts from Baker Lake (74$^\circ$) to Taloyoak (79$^\circ$), anticipating the sudden poleward shift in the electrojet boundary at 2320 UT. This sudden poleward shift is indicative of a substorm onset similar to those noted during the October 4 event. However, unlike the two substorm onsets on that day, there is no significant increase in the magnitude of the electrojet currents during this poleward shift. The most intense emissions occur at Taloyoak (79$^\circ$) and remain there until $\sim$2337 UT when the emissions completely disappear at all five stations.

Auroral roar is again observed starting at $\sim$0015 UT. The latitude of peak intensity is at Arviat (71$^\circ$) during 0015-0040 UT and then shifts equatorward, fluctuating between Arviat and Churchill (69$^\circ$-71$^\circ$) during 0040-0050 UT. The electrojet boundary is slightly poleward of the peak emissions at 0015 UT and moves gradually equatorward from 73$^\circ$ to 70$^\circ$ during this period, in parallel with the observed equatorward shift of the emissions.

At 0050 UT the poleward electrojet boundary moves rapidly poleward and undulates a bit, reaching 77$^\circ$ at 0105 UT, after which it moves poleward more gradually. The auroral roar intensity mimics this poleward motion, shifting from Churchill (69$^\circ$) at 0047 UT to Arviat (71$^\circ$) at 0047-0055 UT to Baker Lake (74$^\circ$) at 0055-0105 UT to Taloyoak (79$^\circ$) at 0115 UT. The final observations of auroral roar on this day near 0140 UT are most intense at Taloyoak, consistent with the rather extreme poleward location of the electrojet boundary, which even exceeds 80$^\circ$ for short times.

The period from 0045 to 0120 UT is another clear example of a substorm onset like the two examples in the October 4 event. The most intense auroral emissions shift rapidly poleward with the poleward expansion of the electrojet boundary, ceasing at stations equatorward of this boundary, and the intensity of the electrojet increases dramatically from 157 to 1020 nT.


next up previous
Next: May 2, 1997 Up: Data Presentation Previous: October 4, 1995


Simon Shepherd 2002-06-05