A detailed analysis of ion-acoustic waves observed in the solar wind by the Solar Orbiter

<p>Ion-acoustic waves are <span>often </span>observed in the solar wind along the Solar Orbiter&#8217;s orbit. These electrostatic <span>waves</span> are generated via ion-ion or current-driven instabilities below the local proton plasma frequency. <span>D</span>ue to the Doppler shift, they are typically observed in the frequency range between the local electron and proton plasma frequency in the <span>spacecraft </span>frame. Ion-acoustic waves often accompany large-scale solar wind structures and play a role in the energy dissipation in the propagating solar wind. Time Domain Sampler (TDS) receiver, a part of the Radio and Plasma Waves (RPW) instrument, is sampling wave emissions at frequencies below 200 kHz almost continuously from the beginning of the mission. <span>Almost</span> <span>three</span> years of observations allow us to perform a <span>detailed </span>study of ion-acoustic waves in the solar wind under variable plasma conditions. The emission <span>tends </span>to be observed when proton density <span>and</span> temperature are highly perturbed. A detailed analysis of the proton velocity distribution and wave <span>generation</span> using solar wind data from a Proton and Alpha particle Sensor (PAS) of the Solar Wind Analyzer (SWA) <span>is</span> <span>shown</span>.</p>