Observed emission rates in sprite streamer heads

Sprite observations at 10,000 fps have shown tendrils and branches to be formed by bright streamer heads moving at ∼10 7 m/s. The streamer heads typically brighten as they move up or down, often saturating the detector. We present here inferred emission rates. The streamer heads are presumably smaller than our 140 m spatial resolution and, therefore, they have to be treated as point sources. The optical emissions are assumed to be dominated by the N 2 1P band and comparing with stars in the images we find total emission rates in individual streamer heads ranging from 4 10 21 to 3 10 24 photons/s. For a 25 m streamer head the range of average brightness would be 9 10 8 –5 10 11 R. Alternatively, using a volume emission rate of 8 10 11 photons/cm 3 /s the size range would be 10 to 100 m.