An X‐ray detector has been flown on‐board a NASA F‐106 jet into thunderstorms. We have concluded that significant quantities of 3 to >12 keV X‐rays are produced within thunderstorm clouds which support lightning discharge activity. It is inferred that the X‐rays are the bremsstrahlung radiation emitted from energetic electrons which have been accelerated through run‐away processes. It is suggested and supported that the structures responsible for the acceleration are strong double‐layers which are supported by the very high current densities attributed to lightning discharges.

A rocket‐borne experiment consisting of a vector magnetometer system and energetic charged particle detectors was launched from Fort Churchill, Canada, over a stable IBC II auroral arc at 2000 LT on February 26, 1969. Vector magnetic field profiles and energetic particle flux profiles are presented which indicate the existence of geomagnetically aligned sheet currents associated with the visible auroral arc. In particular, evidence is shown that suggests that precipitated energetic electrons in the range 2 to 18 kev carry a significant fraction of the total upward field‐aligned current, but that energetic particles in this range are apparently unimportant in providing the downward return current. The spatial relation of the precipitated particle structure and the auroral current configuration are discussed.

A rocket‐borne auroral particles experiment was fired from Fort Churchill, Canada, over a homogeneous arc at 2000 local time on February 26, 1969. Detectors measured the pitch‐angle distribution of the fluxes of electrons with energies of 2–18 and <50 kev, and of protons with energies of 2–18 and 80–1000 kev. The downward (zero pitch angle) electron flux in the 2‐ to 18‐kev interval reached ∼3×108/cm2 sec ster kev as the rocket passed over the visible arc at 135 km altitude. The total backscattered flux was about 20% of the downward flux in the same energy range. No protons in the 2‐ to 18‐kev range, or any higher energy particles, were found in significant quantities. The north‐to‐south electron flux profile of the arc was roughly gaussian with a 10% intensity width of 10 km and a smaller secondary maximum to the north of the central maximum. Integration of the electron flux over pitch angle showed that the maximum net current density due to 2‐ to 18‐kev electrons was 1.5×10−5 amp/m2. The current density integrated across the arc width was equivalent to a sheet current of 0.08 amp/m. A vector magnetometer aboard the rocket indicated an upward current of 0.16 amp/m in the region of the downward electron flux. Comparison of these measurements shows that the energetic (>2 kev) auroral electrons carry a substantial part of the Birkeland current. The intensity and location of the electron fluxes were in reasonable agreement with measurements by ground‐based photometers and all‐sky cameras. The arc extended at least 1500 km in an east‐west direction and was not associated with substorm activity.

This paper reports on electron spectra associated with two aurorae observed by ground‐based television. One auroral arc was observed to flicker, large variations in the precipitated electron energy occurring on a time scale of 114 ms. The major variations occur at the higher energies of the 0.5–20 keV range covered by the detectors. Changes in the particle flux occur primarily in the pitch angle range 0° to 60°. Analysis of the video data shows a larger variation in intensity along the lower border of the arc in keeping with the results of the electron spectra. The second arc was not observed to flicker, and the associated electron spectra and video data show no large variations in precipitated electron energy or video intensity modulation. While pitch angle distributions tend to be field‐aligned in the first arc, the distributions in the second arc are nearly isotropic or peaked from 60° to 90° in the downward hemisphere.