Virginia TechSamimi, A.Scales, Wayne A.Bernhardt, P. A.Briczinski, S. J.Selcher, C. A.McCarrick, M. J.2014-06-092014-06-092012Samimi, A., Scales, W. A., Bernhardt, P. A., Briczinski, S. J., Selcher, C. A., and McCarrick, M. J.: On ion gyro-harmonic structuring in the stimulated electromagnetic emission spectrum during second electron gyro-harmonic heating, Ann. Geophys., 30, 1587-1594, doi:10.5194/angeo-30-1587-2012, 2012.0992-7689http://hdl.handle.net/10919/48604Recent observations show that, during ionospheric heating experiments at frequencies near the second electron gyro-harmonic, discrete spectral lines separated by harmonics of the ion-gyro frequency appear in the stimulated electromagnetic emission (SEE) spectrum within 1 kHz of the pump frequency. In addition to the ion gyro-harmonic structures, on occasion, a broadband downshifted emission is observed simultaneously with these spectral lines. Parametric decay of the pump field into upper hybrid/electron Bernstein (UH/EB) and low-frequency ion Bernstein (IB) and oblique ion acoustic (IA) modes is considered responsible for generation of these spectral features. Guided by predictions of an analytical model, a two-dimensional particle-in-cell (PIC) computational model is employed to study the nonlinear processes during such heating experiments. The critical parameters that affect the spectrum, such as whether discrete gyroharmonic on broadband structures is observed, include angle of the pump field relative to the background magnetic field, pump field strength, and proximity of the pump frequency to the gyro-harmonic. Significant electron heating along the magnetic field is observed in the parameter regimes considered.application/pdfenIn CopyrightIonosphereActive experimentsPlasma waves and instabilitiesDownshifted peakUpper hybridIonosphereFrequencyInstabilityWavesAstronomy & astrophysicsGeosciences, multidisciplinaryMeteorologyAtmospheric sciencesArticlehttp://www.ann-geophys.net/30/1587/2012/angeo-30-1587-2012.htmlhttps://doi.org/10.5194/angeo-30-1587-2012