A balloon-borne x-ray pinhole camera has been developed to detect and image auroral x rays in the energy range 20 to 120 keV. We have flown this camera on four different occasions and have imaged bremsstrahlung x rays from precipitated energetic electrons in the auroral zone and from a circumpolar navigating balloon in Antarctica. The images, which include several dynamic precipitation temporal forms, show that auroral x rays persistently include small spatial structures of ≈2O km (at ionospheric heights). The x-ray energy spectral information as a function of space and time shows that electron precipitation often includes two energy components that can be fit by exponential functions. Typical e-folding energies of these spectra are a few kilo-electron-volts and several tens of kilo-electron-volts. The x-ray camera remote senses characteristics of energetic electron sources in the distant magnetosphere that cannot be achieved by any other means.
George K. Parks,
Scott H. Werden,
Michael Patrick McCarthy,
"Pinhole x-ray cameras for imaging small-scaled auroral structures," Optical Engineering 32(12), (1 December 1993). http://dx.doi.org/10.1117/12.149185