North-south aligned equatorial airglow depletions


  • E. J. Weber,

  • J. Buchau,

  • R. H. Eather,

  • S. B. Mende


A new instrument for all-sky spectrophotometric imaging of aurora and airglow has been installed in the Air Force Geophysics Laboratory's Airborne ionospheric Observatory. Initial observations of equatorial and near-equatorial 6300-Å O I airglow show the existence of north-south aligned regions of airglow depletion. These dark bands often extend more than 1200 km in the north-south direction and 50–200 km in the east-west direction. They are observed to drift toward the east during the evening-midnight hours, with one observation of westward drift after local midnight. Airglow fine structure associated with the boundaries of the dark bands has been observed down to the 2.5-km resolution limit of the instrument. Simultaneous airborne ionospheric soundings indicate that these regions of airglow depletion are characterized by an increase in the virtual height of the F layer. A simple model of field-aligned electron density depletion in the bottomside of the F layer explains both the airglow observations and the ionospheric soundings.