First Experimental Characterization of Microwave Emission from Cosmic Ray Air Showers

Area of Science:

• Cosmic-ray physics
• Astrophysics
• Radio astronomy

Background:

• Extensive air showers (EAS) are cascades of secondary particles produced by high-energy cosmic rays interacting with Earth's atmosphere.
• Understanding the characteristics of EAS is crucial for determining the origin and nature of high-energy cosmic rays.
• Previous studies have primarily focused on radio emission from EAS in lower frequency ranges.

Purpose of the Study:

• To directly measure and characterize microwave radio emission from extensive air showers.
• To investigate the feasibility of using microwave emission as a new method for studying high-energy air showers.
• To explore the properties of GHz frequency radio emission from EAS.

Main Methods:

• Utilizing the KASCADE-Grande air shower array for triggering.
• Employing the Cosmic-Ray Observation via Microwave Emission (CROME) experiment's microwave antennas for signal detection.
• Analyzing GHz frequency signals for signatures of radio emission from EAS.

Main Results:

• Detection of microwave signals from over 30 air showers with energies exceeding 3x10^16 eV.
• Observations are consistent with a predominantly forward-directed emission pattern.
• Evidence suggests the microwave emission is polarized.
• The detected signals fall within the GHz frequency range.

Conclusions:

• Microwave radio emission is a measurable phenomenon from extensive air showers.
• The characteristics observed (forward-directed, polarized) provide new insights into EAS processes.
• Microwave radiation presents a novel and promising tool for studying air showers at energies of 10^17 eV and above.