SCIFER‐Height measurements of the midmorning aurora

Abstract

Dual‐site ground‐based optical observations were performed January 25, 1995 in support of the SCIFER rocket campaign (Sounding of the Cleft Ion Foundation Energization Region). Two Meridian Scanning Photometers (MSPs) were operative simultaneously at Ny‐Ålesund (NYA) and Nordlysstasjonen in Adventdalen (LYR) 118 km apart in the geomagnetic meridian. The photometers at each station scanned approximately along the same geomagnetic meridian plane and measured the intensity of auroral wavelengths as a function of zenith angle and time. The principal wavelengths used in the present analysis were the green 5577 Å and the red 6300 Å emission lines of atomic oxygen. For the magnetospheric cleft auroral activity studied here at 10 hr magnetic local time (MLT), the luminosity maximum for the green line varied in altitude between 125 and 160 km. The red line maximum was in the range 200 to 220 km. The absolute intensity ratio and the height‐luminosity profiles obtained using this method were consistent with the near simultaneous rocket measurement of the field‐aligned electrons having a characteristic energy of 230 eV by the SCIFER experiment [Lorentzen, et al., 1996]. Geomagnetic disturbance data obtained during the flight included an example of a magnetic impulse event (MIE) coinciding with a bright, discrete arc. The altitude of this arc was >140 km, and it is doubtful that it produced an increase of conductivity in the E Region or developed a current system which could be associated with the MIE. It is proposed that the transient magnetic events were associated with the energetic pulsating aurora which was occurring equatorward of the zenith. In addition, the altitude of three poleward‐moving auroral forms (PMAFs) was measured. Within the error of the observations, the PMAFs do not seem to change in altitude with increasing latitude. The sample is too small for a definitive conclusion, but the method shows promise.