Triggered ion acoustic waves in the solar wind. (arXiv:2108.07802v1 [physics.space-ph])
<a href="http://arxiv.org/find/physics/1/au:+Mozer_F/0/1/0/all/0/1">Forrest S. Mozer</a>, <a href="http://arxiv.org/find/physics/1/au:+Vasko_I/0/1/0/all/0/1">Ivan .Y. Vasko</a>, <a href="http://arxiv.org/find/physics/1/au:+Verniero_J/0/1/0/all/0/1">J. L. Verniero</a>
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.
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.
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