Photometric studies of the great red aurora March 13 and 14, 1989

Extended photometric coverage of the great red aurora of March 13–14, 1989 was obtained at the Rabbit Lake observatory located in northern Saskatchewan, at an eccentric dipole latitude of 65.3°. The red aurora first appeared there about 0311 UT on March 13 and appeared to have run its course by about 0700 UT on March 14. During much of the two nights the observatory was near the poleward edge of the display; the aurora was active much of the time and its brightenings were accompanied by poleward expansions to as far north as the observatory. Combining these observations with those at low latitudes suggest a large auroral expanse from an equatorward edge of about 30° to a poleward edge of about 65° magnetic latitude. One key value of the optical data was the semicontinuous monitoring of major auroral emission intensities. The 01D emission at 630 nm reached 130 kR intensity shortly after onset, at about 0347 UT on March 13. Its intensity the following night was typically 35 kR or below. A HILAT satellite pass around 0415 UT March 14 indicated an electron influx of average energies varying between 150 and 800 eV. The excitation efficiency for the 630 nm emission, neglecting any collisional deactivation, was approximately 1 kR per erg cm−2 s−1 (1 erg = 10−7 J) of precipitating electron energy. These measurements along with related worldwide observations will assist in gaining a better understanding of the magnetospheric conditions producing such major widespread auroras.