Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

Understand

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz.

• Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy.
• A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement.
• The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers.