[P-EM11] Exoplanet

[PEM11-P07] Development of data analysis method for auroral radio emissions of exoplanets toward demonstration of their magnetic fields

*Ryusei Morino¹, Tomoki Kimura¹, Philippe Zarka², Laurent Lamy², Hajime Kita³, Yuka Fujii⁴, Fuminori Tsuchiya⁵ (1.Tokyo University of Science, 2.Paris Observatory, 3.Tohoku Institute of Technology, 4.National Astronomical Observatory of Japan, 5.Tohoku University)

Keywords:auroral radio , magnetic fields, atmospheres

Auroral emissions are caused by the planetary magnetosphere-stellar wind interactions, in which the magnetospheric electrons accelerated along the magnetic field by the electric potential difference originating from the stellar wind energy collide with the atmosphere, exciting the auroral emissions from the X-ray to radio wavelength. If we detect the auroras from the exoplanets, we can demonstrate their magnetic fields and atmospheres, which contribute to understanding the habitability of exoplanets. Auroral radio emissions are circularly polarized waves effectively excited by the precipitating auroral electrons (Wu&Lee et al,1979). Therefore they are distinguishable from the stellar radio emissions that are generally not circularly polarized. Detection of auroral radio emissions is a promising way to demonstrate the exoplanetary magnetic fields and atmospheres. Since the frequency of auroral radio emissions depends on the magnetic flux density in the source region (Farrell et al,1999), it is possible to quantify the exoplanetary intrinsic magnetic field from the auroral radio spectrum. The quantified intrinsic magnetic field may constrain the internal convective structure based on the magnetic dynamo theories. The emitted power of auroral radio emission is dependent on the total energy input of the stellar wind to the planetary magnetosphere(Zarka et al., A&A 2018). The auroral radio power tells us about the kinetic energy of the stellar wind and its time variability. The exoplanets have been observed using existing radio telescopes. Only one report claims that the circularly polarized radio emission was possibly detected from an exoplanet (Turner et al,2021). However, the detection of exoplanetary radio emissions is marginal, because sensitivity is less good at very low frequencies (typically below 30-40 MHz)than at 150 MHz, probably in the range of 10s of mJy. Therefore more sensitive observation and data analyzing methods are needed for more significant detection. In this study, we attempt to detect exoplanet auroral radio emissions by applying the analysis method of existing radio telescopes used in Turner et al (2021) to NenuFAR (New Extension in Nancay Upgrading LOFAR), a next-generation low-frequency radio currently under construction and performance evaluation. We applied Turner’s data analysis method to Jupiter observation data to evaluate whether the analysis method is valid for NenuFAR. We successfully detected the auroral radio emission of Jupiter at 18-22MHz with a high statistical significance of *sigma from the background. In the future, we aim to detect exoplanetary auroral radio emissions by improving Turner’s analysis method with higher sensitivities.