[1] Airglow production at various beam positions relative to the magnetic field was investigated as part of an optics campaign at HAARP in February 2002. Strong emissions up to several hundred Rayleigh at 630.0 nm and more than 50 R at 557.7 nm were produced in a small spot approximately 6°in diameter located near the magnetic zenith when the transmitter beam was directed up the magnetic field. This effect was observed hundreds of times over a wide range of frequencies and ionospheric conditions. The spot at HAARP appears on average just equatorward of the nominal magnetic field direction, deflects somewhat toward the beam center when the beam is scanned, and varies slightly in size with transmitter frequency. Red-to-green ratios as low as 3 were observed, with both wavelengths showing significant onset delay. Identifiable enhancements in red-line emission were produced down to 2 MW ERP in a power ramp experiment.

Abstract. An ordinary mode electromagnetic wave can decay into an ion acoustic wave and a scattered electromagnetic wave by a process called stimulated Brillouin scatter (SBS). The first detection of this process during ionospheric modification with high power radio waves was reported by Norin et al. (2009) using the HAARP transmitter in Alaska. Subsequent experiments have provided additional verification of this process and quantitative interpretation of the scattered wave frequency offsets to yield measurements of the electron temperatures in the heated ionosphere. Using the SBS technique, electron temperatures between 3000 and 4000 K were measured over the HAARP facility. The matching conditions for decay of the high frequency pump wave show that in addition to the production of an ion-acoustic wave, an electrostatic ion cyclotron wave may also be produced by the generalized SBS processes. Based on the matching condition theory, the first profiles of the scattered wave amplitude are produced using the stimulated Brillouin scatter (SBS) matching conditions. These profiles are consistent with maximum ionospheric interactions at the upper-hybrid resonance height and at a region just below the plasma resonance altitude where the pump wave electric fields reach their maximum values.

High power electromagnetic waves transmitted from the HAARP facility in Alaska can excite low-frequency electrostatic waves by magnetized stimulated Brillouin scatter. Either an ion-acoustic wave with a frequency less than the ion cyclotron frequency (f(CI)) or an electrostatic ion cyclotron (EIC) wave just above f(CI) can be produced. The coupled equations describing the magnetized stimulated Brillouin scatter instability show that the production of both ion-acoustic and EIC waves is strongly influenced by the wave propagation relative to the background magnetic field. Experimental observations of stimulated electromagnetic emissions using the HAARP transmitter have confirmed that only ion-acoustic waves are excited for propagation along the magnetic zenith and that EIC waves can only be detected with oblique propagation angles. The ion composition can be obtained from the measured EIC frequency.

On-orbit firings of both liquid and solid rocket motors provide localized disturbances to the plasma in the upper atmosphere. Large amounts of energy are deposited to ionosphere in the form of expanding exhaust vapors which change the composition and flow velocity. Charge exchange between the neutral exhaust molecules and the background ions (mainly O + ) yields energetic ion beams. The rapidly moving pickup ions excite plasma instabilities and yield optical emissions after dissociative recombination with ambient electrons. Line-of-sight techniques for remote measurements rocket burn effects include direct observation of plume optical emissions with ground and satellite cameras, and plume scatter with UHF and higher frequency radars. Long range detection with HF radars is possible if the burns occur in the dense part of the ionosphere. The exhaust vapors initiate plasma turbulence in the ionosphere that can scatter HF radar waves launched from ground transmitters. Solid rocket motors provide particulates that become charged in the ionosphere and may excite dusty plasma instabilities. Hypersonic exhaust flow Manuscript

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