Methods for Detecting Cyclotron Maser Radio Emissions from Stars and Exoplanets

The Cyclotron Maser Instability (CMI) is a well-known mechanism responsible for auroral radio emissions from the Earth, Jupiter, Saturn, Uranus, and Neptune. These emissions occur at frequencies near or equal to the local electron cyclotron frequency, which is directly related to the local magnetic field strength. Detecting CMI radio emissions from exoplanets would provide direct evidence of planetary magnetic fields, offering a unique method to identify such fields. This approach is particularly valuable since techniques like Zeeman Doppler Imaging are ineffective for exoplanets due to their weak magnetic fields, which are insufficient to produce a detectable Zeeman effect. Jupiter, often regarded as a miniature exoplanetary analog, serves as a valuable benchmark for testing detection methods. In this presentation, we will introduce two techniques for identifying these weak radio signals using observations from the Nançay Decameter Array and NenuFAR ground-based radio telescopes, employing both high and low time and frequency resolutions. Additionally, we will showcase an example of CMI stellar radio emission from the red dwarf AD Leonis, detected by the FAST Chinese radio telescope. This detection highlights the ability to constrain in situ parameters, such as source locations and the energy of the electrons responsible for these emissions.