A Case Study of Pc1 Waves Observed at the Polar Cap Associated with Proton Precipitation at Subauroral Latitudes
In the present work, we present a case study of an EMIC/Pc1 event simultaneously observed at DMC in Antarctica and by the LEO CSES-01 spacecraft at L = 6.7 on 30 March 2021. The event was also observed in the northern hemisphere at the highest-latitude station in the Finnish pulsation magnetometer network. These data suggest a possible source region for the pulsations in the evening/L~6.7 magnetosphere, and provide further evidence of the wave propagation in the ionospheric waveguide up to the polar cap. In addition, the availability of measurements of precipitating particles and auroral radiance observations also allows to observe proton precipitation upon the wave event, accompanied by the corresponding occurrence of an IPA.
2. Materials and Methods
Both magnetometers provide variations in the geomagnetic H (northward), D (eastward), and Z (vertically downward) field components at a 5 Hz sampling rate.
It is worth noting that, in the present investigation, we have resampled geomagnetic signals at 5 Hz, in order to have the same sampling frequency as for southern observatories.
Auroral activity has been additionally monitored from the ground, exploiting the all-sky images taken by the white-light cameras at the Antarctic Syowa Station, which is the mother station of the Japanese Antarctic Research Expedition (JARE), established in 1957.
That said, we suggest that the EMIC waves propagated from their magnetospheric source along the magnetic field lines both southward and northward; after their injection into the northern ionosphere, they were transmitted to KEV ground station (probably close to the injection region); while in the southern ionosphere, they arrived at the CSES satellite, located near to the injection region, then propagating up to the field line with footprint at DMC polar station.
The timing of the Pc1 event, when compared to LEO satellite observations of sudden and localized proton precipitation, is considered a strong point in favor of an associated resonant wave–particle interaction.
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