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- Title
A Parametric Study of Oxygen Ion Cyclotron Harmonic Wave Excitation and Polarization by an Oxygen Ring Distribution.
- Authors
Liu, Xu; Chen, Lunjin; Sun, Jicheng; Wang, Xueyi; Usanova, Maria E.
- Abstract
Oxygen ion cyclotron harmonic (OCH) waves are electromagnetic emissions with frequencies near the harmonics of the oxygen ion cyclotron frequency. These waves can be excited by an energetic O+ ring distribution. Here, we perform a parametric study of OCH waves by an O+ ring distribution. We investigate the effects of ring concentration (ηho), velocity (vr), temperature (Tr), total O+ concentration (ηo), and wave normal angles (WNAs) on the wave growth rate and polarization. We find that four‐wave modes are related to OCH waves. The growth rates and frequency range increase with ηho and ηo and decrease with Tr. The peak growth rate roughly follows the first peak of Jn2 ${J}_{n}^{2}$ (square of the Bessel function corresponding to the O+ ring) or cold plasma wave modes, which can be used to explain the vr and WNA dependences. OCH waves shift from the transverse mode to the compressional mode as vr increases. Plain Language Summary: Oxygen ion cyclotron harmonic (OCH) waves are electromagnetic emissions with frequencies near the harmonics of the oxygen ion gyrofrequency. These waves can be excited by energetic oxygen ions. In this study, we perform a parametric analysis of the OCH wave dispersion relation, growth rate, and polarization using different oxygen ion ring parameters. We investigate the effects of the concentration, velocity, and temperature of the oxygen ion ring, total oxygen ion concentration, and wave normal angles (WNAs). We find that OCH waves are oxygen ion Bernstein mode waves that are coupled with three cold plasma wave modes (magnetosonic and H+ and O+ band electromagnetic ion cyclotron wave modes). The growth rate increases with oxygen ion ring and total oxygen ion concentrations and decreases with ring temperature. The wave mode and polarization shift once the ring velocity and WNA change. This study shows the dependences of the OCH wave frequency, growth rates, and polarization on various oxygen parameters, and thus, significantly advances our understanding of the excitation characteristics of OCH waves. Key Points: Oxygen ion cyclotron harmonic (OCH) waves shift from the transverse mode to the compressional mode as the O+ ring velocity increasesThe growth rates and frequency range of OCH waves increase with both O+ ring and total O+ concentrations and decrease with O+ ring temperatureThe dependences of the wave frequency and wavenumber of the peak growth rates on plasma parameters are explained
- Subjects
CYCLOTRONS; PLASMA waves; PLASMA instabilities; ELECTROMAGNETIC waves; LOW temperature plasmas; ION acoustic waves
- Publication
Journal of Geophysical Research. Space Physics, 2022, Vol 127, Issue 11, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2022JA030828