The study of low-frequency waves in the solar wind by the RPW/TDS instrument onboard Solar Orbiter

The Time Domain Sampler (TDS) receiver is a part of the Radio and Plasma Wave instrument (RPW) onboard Solar Orbiter, sampling three electric and one magnetic field components at frequencies up to 524 kHz. The RPW instrument has been operating almost continuously during the commissioning phase of the mission and through the first perihelion in June 2020, covering an interval of heliocentric distances between 0.5 AU to 1 AU. The most common plasma phenomena observed by TDS are low-frequency electrostatic waves at frequencies between hundreds of Hertz and 10 kHz. These are interpreted as strongly Doppler-shifted ion-acoustic waves, generated by solar wind ion beams and often accompanying large scale solar wind structures. In this initial study, we performed a statistical investigation of the waves, studying their modulation and polarization.