Spatial dependence of electromagnetic ion cyclotron waves triggered by solar wind dynamic pressure enhancements: EMIC Waves Triggered by Dynamic Pressure
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Abstract For more than 12 hr beginning on 2021 January 18, continuous narrowband electrostatic emissions were observed on the 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 kmmore »