February 17, 1998

Figure 7 displays PSFR and magnetometer data recorded at 2300 UT on February 17 to 0700 UT on February 18, 1998 (1610-0010 MLT). The average daily $Kp$ index is 2.4 on February 17 and 4.1 on February 18, and the magnetic perturbations due to the electrojet currents range from $\sim$60 to 1080 nT.

Auroral roar is detected at all five ground stations beginning near 2330 UT. During 2330-0145 UT the emissions are generally most intense at Churchill (69$^\circ$). From 0145 to 0330 UT the activity shifts mostly to Arviat (71$^\circ$) except for short intervals near 0205 and 0215 UT. The poleward electrojet boundary is consistently equatorward of the latitude of the most intense emissions and is relatively constant between 64$^\circ$ and 67$^\circ$ during this period, implying that the emissions are most intense well poleward of the electrojet boundary by up to 7$^\circ$.

After 0330 UT the latitude of the peak emissions shifts somewhat poleward, fluctuating between Arviat and Baker Lake, except for one brief burst of auroral roar at 0410 UT which is detected strongest at Gillam, $\sim$6$^\circ$ inside of the poleward electrojet boundary. The electrojet boundary also moves poleward from 65$^\circ$ at 0300 UT to 72$^\circ$-77$^\circ$ at 0400-0700 UT. Auroral roar emissions are detected intermittently at the four northernmost stations during this period, peaking poleward of the electrojet boundary at Taloyoak, near the boundary at Baker Lake, and equatorward at Arviat and Churchill.