NSEE Yielding Electron Temperature Measurements at the Arecibo Observatory

Abstract

Narrowband stimulated electromagnetic emissions (NSEE), a component of radio emissions created during high‐frequency (HF) radiowave ionospheric modification experiments, occur within 1 kHz of the HF pump frequency. NSEE was observed and studied for the first time at the HAARP (High Frequency Active Auroral Research Program) facility in Alaska (Norin et al., 2009, https://doi.org/10.1103/PhysRevLett.102.065003; Bernhardt et al., 2010, https://doi.org/10.1103/PhysRevLett.104.165004). Magnetized stimulated Brillouin scatter (MSBS) is a component of NSEE, which was also first observed at HAARP (Norin et al., 2009, https://doi.org/10.1103/PhysRevLett.102.065003; Bernhardt et al., 2010, https://doi.org/10.1103/PhysRevLett.104.165004) and later at European Incoherent Scatter Scientific Association (Fu et al., 2015, https://doi.org/10.5194/angeo-33-983-2015). Ion‐acoustic and electrostatic ion cyclotron modes are the daughter products of MSBS and can be used for the determination of the electron temperature and of the presence of minor ion species, respectively, in the HF‐modified ionosphere. Here we present the first observations of the MSBS process at magnetic midlatitudes, excited during radio wave ionospheric modification experiments at the Arecibo Observatory. The NSEE observations, in combination with a theoretical model and the wave matching conditions, are used to estimate background ionospheric parameters. A qualitative comparison of the MSBS component of the NSEE spectrum with the thermal ion line measured by incoherent scatter radar is presented.

Electron Temperature Inversion by Stimulated Brillouin Scattering During Electron Gyroharmonic Heating at EISCAT

“…Mahmoudian, Senior, et al (2019) observed IA and EIC emissions due to MSBS near 4f ce . At Arecibo, SBS emissions including IA and EIC have also been observed by Djuth et al (2018) and Mahmoudian, Nossa, et al (2019). Meanwhile, the correlation…”

“…Mahmoudian, Senior, et al (2019) observed IA and EIC emissions due to MSBS near 4 f ce . At Arecibo, SBS emissions including IA and EIC have also been observed by Djuth et al (2018) and Mahmoudian, Nossa, et al (2019). Meanwhile, the correlation between SEE with electron temperature, plasma irregularities, HF‐induced plasma, and ion lines has also been investigated at EISCAT (Honary et al, 1995) and HAARP (Fu et al, 2018; Mahmoudian et al, 2016).…”

A Stimulated Emission Diagnostic Technique for Electron Temperature of the High Power Radio Wave Modified Ionosphere

“…The descending layer in the white dashed box in Figure 3b starts from the resonance height when the heater turns on and then descends downwards producing discrete enhanced N r which is in consistent with observations of the BUM in Figure 3d and plasma lines in Figure 3e within the dashed white lines. The descending raw electron density near 3$${f}_{\mathrm{ce}}$$ in Figure 3b shows similar descending raw electron density for 4 f ce (Mahmoudian, Nossa, et al., 2019; Mahmoudian, Senior, et al., 2019) at EISCAT.…”

Controlled beat-wave Brillouin scattering in the ionosphere

“…Therefore it would be of interest to carry out a beat-wave experiment near an electron gyroharmonic to investigate whether significant power can be transferred from the pump to the probe through the SBS-1 process. The ionacoustic wave is used as part of a diagnostic of the electron temperature in the ionosphere during ionospheric heating experiments 34,36,75 , using the dependence of the dispersion of the mode on the ion-acoustic speed. There are also observations of electromagnetic sidebands where the separation was close to ion gyroharmonics [37][38][39][40][41][42][43][44][45][46][47] which gives information about the local magnetic field and ion composition.…”