Abstract
Abstract Electrostatic ion-cyclotron wave (EICW) and ion-Bernstein wave 
(IBW) are two typical normal modes of plasma propagating 
vertically to a magnetic field. 
These modes satisfy the extreme conditions 
$\omega \ll k_{\parallel} v_{\rm te}$ and $\omega \gg k_{\parallel} v_{\rm te}$, 
where $\omega$, $k_{\parallel}$, and $v_{\rm te}$ are the wave 
angular frequency, wave number parallel to the magnetic field, 
and the electron thermal speed. Between these extremities, 
there exist IBW-like waves that have not been studied. 
In this paper, the co-excitation of the EICW and IBW-like wave in 
an experiment is presented. It is shown that, in an argon (Ar) 
discharge, the EICW appears in the fundamental and second 
harmonic frequency bands of the ion-cyclotron frequency. 
In contrast, the IBW-like wave appears in the higher 
harmonic frequency bands and in the case of a relatively 
strong magnetic field. In a helium (He) discharge, the IBW-like 
wave is excited in the fundamental frequency band, 
but the wave behaviour becomes complicated in the harmonic 
frequency bands. The measured dispersion relations of the 
excited EICW are in agreement with the results of the fluid and 
kinetic models in some range of frequencies, but those of the 
excited IBW-like wave are only in qualitative agreement with 
the kinetic model of the IBW. 
This study is important for identifying the 
IBW-like mode that may have potential application in plasma 
heating via Landau damping.
Published Version
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