To higher energy: Balloon and satellite investigations around the 'knee'
The galactic cosmic radiation spans over 14 decades in energy and follows a power law spectrum in energy which shows two features, a steepening in the power law at a few times 1015 eV - the 'knee' - and a subsequent flattening in the power law at a few times 1018 eV - the 'ankle'. The 'knee' was discovered over 40 years ago through the measurement of cosmic ray initiated air showers, yet its origin and the underlying physics remain largely unknown. Experiments over the past four decades, from both balloon and space platforms, have pressed measurements to ever higher energy and to greater precision. This progression is briefly reviewed with emphasis on the current generation of experiments studying the high-energy regime up to the knee using direct particle-by-particle measurements. Prospects for understanding the 'knee' in terms of the acceleration of the cosmic rays and possible future experiments are included.
Publication Source (Journal or Book title)
Journal of Physics G: Nuclear and Particle Physics
Wefel, J. (2003). To higher energy: Balloon and satellite investigations around the 'knee'. Journal of Physics G: Nuclear and Particle Physics, 29 (5 SPEC. ISS.), 821-830. https://doi.org/10.1088/0954-3899/29/5/304