The First Observation of N⁺ Electromagnetic Ion Cyclotron Waves

Abstract

Electromagnetic ion cyclotron waves are predominately left-hand circularly polarized waves with small wave normal angle (WNA), and with frequencies below the proton cyclotron frequency (Horne & Thorne, 1993). EMIC waves are usually generated near the Earth's equator and tend to become more oblique and linearly polarized during their propagation toward higher latitudes. In the inner magnetosphere, EMIC waves are generated preferentially in regions where hot (∼ 10-100 keV) ring current anisotropic ions and cold (∼ few eVs) dense heavy ions spatially overlap (Cornwall, 1965; Jordanova et al., 2001; Kennel & Petschek, 1966). EMIC waves can also be generated in the dayside and nightside magnetosphere during times of enhanced solar wind dynamic pressure, which acts as a source of temperature anisotropy (

Mass Density Inferred From Toroidal Wave Frequencies and Energization of Low‐Energy Helium Ions During H‐Band EMIC Wave Interval

“…Recently, it has been reported that the spectral properties of EMIC waves are also affected by other minor heavy ions such as nitrogen ions (N + ) and doubly charged oxygen ions (O 2+ ) in the terrestrial magnetosphere (Bashir & Ilie, 2018, 2021; Yu et al., 2021). The small fraction of heavy ion concentration changes the EMIC wave properties.…”

First Observations of O2+ Band EMIC Waves in the Terrestrial Magnetosphere

“…Since H + , He + , and O + are the most common ion species observed in the background plasma, EMIC waves are often divided into three usual bands (H + , He + , and O + bands), the wave generation and wave properties of which have been investigated in a great number of studies. The effect of N + on EMIC waves has also been discussed in Bashir and Ilie (2018), and recent studies have reported the occurrence of N + band EMIC waves observed in the inner magnetosphere (Bashir & Ilie, 2021). To the best of our knowledge, however, the effects of O 2+ on EMIC waves and O 2+ band EMIC waves have not been studied yet.…”

“…However, besides He + and O + , other heavy ions exist in the magnetosphere, such as the nitrogen ions (N + ) and doubly charged oxygen ions (O 2+ ; Funsten et al., 2013; Vira et al., 2021; Young et al., 1977, 1982). Recent studies have demonstrated the effect of N + on EMIC waves and observed N + band EMIC waves in the inner magnetosphere (Bashir & Ilie, 2018, 2021). EMIC waves indicating the presence of M / Q = 2 ions in the terrestrial magnetosphere have also been observed (Engebretson et al., 2018; Lee et al., 2019; Miyoshi et al., 2019).…”

On the Impacts of Ions of Ionospheric Origin and Their Composition on Magnetospheric EMIC Waves

“…The propagation of EMIC waves to and across local crossover frequencies in a multi-ion plasma can allow waves to achieve linear or right-handed polarization. Thus, under certain assumptions on wave generation, wave properties from Fourier spectra and the possibility of crossover frequencies enabling mode-conversion during propagation have been used to infer the ion composition or presence of minor ion species in Earth's magnetosphere (Min et al, 2015;Miyoshi et al, 2019;Engebretson et al, 2018;Bashir and Ilie, 2021). Wave modeling and mode conversion at the bi-ion hybrid resonance has also been presented as a method to derive magnetospheric ion composition (E. H. Kim et al, 2015).…”