Abstract
The article presents the results of studying novel bursts of ULF emissions within 0.5–2.5 Hz (Pc1 geomagnetic pulsations) with a simultaneous increase (~0.01 Hz/min) and decrease in frequency (~0.01 Hz/min) lagging by ~5÷10 min from the initial mean frequency (~0.6 Hz). From their formal resemblance with the stripes on military officer uniforms, these emissions are called Pc1 chevrons. The bursts were observed during strong short-term geomagnetic disturbances (~1 hour): substorms with high gradient of ionospheric currents+ intensification (dD/dt or dH/dt ~1–1.3 nT/s).
We present the main parameters and couplings of these emissions with substorm geophysical phenomena of 11.02.1985, 06.04.1997 and 18.07.2013 events. Polar satellite observations of auroras are compared with LANL-91, 94 and THEMIS-A observations of charged particle fluxes. Possible mechanisms generating oscillations are also discussed.
Publisher
Mongolian Journals Online
Reference23 articles.
1. Guglielmi, A.V., Troitskaya, V.A. (1973) Geomagnetic pulsations and diagnostics of the magnetosphere. M.: Nauka.
2. Guglielmi, A.V. (1979) MHD waves in near–Earth plasma. М.: Nauka.
3. Kangas, J., Guglielmi, A., Pokhotelov, O. (1998) Morphology and Physics of Short-Period Magnetic Pulsations. (Review). Space Science Reviews, 83: 435-512. http://dx.doi.org/10.1023/A:1005063911643.
4. Fukunishi, H., Toya, T., Koike, K., Kuwashima, M., Kawamura, M. (1981) Classification of hydromagnetic emissions based on frequency-time spectra. J. Geophys. Res., v. 86, No. A11: 9029-9039, https://doi.org/10.1029/JA086iA11p09029.
5. An, Z., Zonca, F., Tao, .X, Chen, L. (2023) Frequency chirping of electromagnetic ion cyclotron waves in Earth’s magnetosphere. arXiv:2303.07799v1 [physics.space-ph].