Ion acoustic waves and related plasma observations in the solar wind

The paper presents a study of the relationship between the interplanetary ion acoustic waves detected by Helios and the macroscopic and microscopic characteristics of the solar wind plasma. Two major mechanisms, an electron heat flux instability and a double-ion beam instability, are considered for generating the ion-acoustic-like waves observed in the solar wind. The results provide support to both mechanisms for generating the solar wind ion acoustic waves, although each mechanism has problems under certain conditions.