For more than 12 hours beginning on January 18, 2021, continuous narrowband electrostatic emissions were observed on Parker Solar Probe near 20 solar radii. The observed <1000 Hz frequencies were well below the local ion plasma frequency. Surprisingly, the emissions consisted of electrostatic wave packets with shock-like envelopes, appearing repetitively at a ~1.5 Hz rate. This repetitiveness correlated and was in phase with low frequency electromagnetic fluctuations. The emissions were associated with simultaneously observed ion beams and conditions favorable for ion-acoustic wave excitation, i.e. Te/Ti~5. Based on this information and on their velocity estimates of about 100 km/s, these electrostatic emissions are interpreted as ion-acoustic waves. Their observation demonstrates a new regime of instability and evolution of oblique ion-acoustic waves that have not been reported previously in theory or experiment.
The Damping and Instability of Ion-acoustic Waves in the Solar Wind: Solar Orbiter Observations
Mullard Space Science Laboratory, University College London（伦敦大学学院穆拉德太空科学实验室）；Blackett Laboratory, Imperial College London（帝国理工学院布莱克特实验室）；Lunar and Planetary Laboratory, University of Arizona（亚利桑那大学月球与行星实验室）
On the role of solar wind expansion as a source of whistler waves: scattering of suprathermal electrons and heat flux regulation in the inner heliosphere
A Two-dimensional Numerical Study of Ion-Acoustic Turbulence
Massachusetts Institute of Technology（麻省理工学院）；Department of Defense（国防部）；Princeton Plasma Physics Laboratory（普林斯顿等离子体物理实验室）；Proxima Fusion GmbH（Proxima Fusion有限公司）
Polytropic stellar wind models with strongly localized heating
Ruhr-Universität Bochum（波鸿鲁尔大学）；Ilia State University（伊利亚国立大学）；Evgeni Kharadze Georgian National Astrophysical Observatory（叶夫根尼·哈拉泽格鲁吉亚国家天文台）；Institut für Weltraumforschung, Österreichische Akademie der Wissenschaften（奥地利科学院空间研究所）；Institute of Radio Astronomy, National Academy of Sciences of Ukraine（乌克兰国家科学院无线电天体物理研究所）
