Premium
Nonlinear evolution of high frequency R‐mode waves excited by water group ions near comets: Computer experiments
Author(s) -
Kojima H.,
Matsumoto H.,
Omura Y.,
Tsurutani B. T.
Publication year - 1989
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl016i001p00009
Subject(s) - physics , excited state , atomic physics , wavenumber , instability , ion , beam (structure) , longitudinal mode , cyclotron , longitudinal wave , wave propagation , wavelength , computational physics , optics , mechanics , quantum mechanics
An ion beam resonates with R‐mode waves at two frequency bands. These are a high frequency RH mode (ω » Ω p ) and a low frequency RL mode (ω ∼ Ω H 2 O + ), where Ω p and Ω H 2 O + are cyclotron frequencies of protons and water ions, respectively. We study the nonlinear evolution of beam‐generated RH waves by one‐dimensional hybrid computer experiments. Both wave‐particle and subsequent wave‐;wave interactions are examined. We find that the RH waves through the interaction with an ion beam formed by pick‐up heavy ions near comets, grow to a level of B w /B o ∼ 0.23. The waves saturate by wave‐wave interactions (via the decay instability) supplying energy to backward travelling daughter R‐mode waves with slightly lower k (and hence lower ω) as well as forward travelling longitudinal waves. The backward travelling daughter R‐mode waves decay further to granddaughter waves with still lower k . We show that this inverse cascading process occurs faster than the growth of the RL mode instability and produces a wide band wave spectrum which extends from the wavenumber of beam‐excited RH mode to much lower k . The nonlinearly excited longitudinal sound waves play a role in heating solar wind protons.