Browsing by Author "Huba, J.D."

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    Full profile incoherent scatter analysis at Jicamarca
    (European Geosciences Union (EGU), 2008-02-04) Hysell, D.L.; Rodrígues, F.S.; Chau Chong Shing, Jorge Luis; Huba, J.D.
    Incoherent scatter data from a hybrid longpulse/double-pulse experiment at Jicamarca are analyzed using a full-profile analysis similar to the one implemented by Holt et al. (1992). In this case, plasma density, electron and ion temperatures, and light ion composition profiles in the topside are estimated simultaneously. Full-profile analysis is crucial at Jicamarca, since the long correlation time of the incoherent scatter signal at 50 MHz invalidates conventional gated analysis. Results for a 24 h interval in April of 2006 are presented, covering altitudes through 1600 km with 10 min time resolution, and compared with results from the NRL ionospheric model SAMI2. The analysis provides the first comprehensive assessment of ionospheric conditions over Jicamarca at sunrise as well as the first 24-h record of helium ion layers. Possible refinements to the experiment and the algorithm are discussed.
    Palabras clave:IonosphereEquatorial ionosphereIon chemistry and composition
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    The lifetime of a depression in the plasma density over Jicamarca produced by space shuttle exhaust in the ionosphere
    (Editor no identificado, 2001) Bernhardt, P.A.; Huba, J.D.; Kudeki, E.; Woodman Pollitt, Ronald Francisco; Chau Chong Shing, Jorge Luis; Sarango, M.F.
    When the Space Shuttle Orbiting Maneuver Subsystem (OMS) engines bum in the ionosphere, a plasma density depression or "hole" is produced. Charge exchange between the exhaust molecules and the ambient o+-ions yields molecular ions beams that eventually recombine with electrons. The resulting plasma hole in the ionosphere can be studied with ground based, incoherent-scatter radars (ISR' s ). This type of ionospheric modification is being studied during the Shuttle Ionospheric Modification with Pulsed Localized Exhaust (SIMPLEX) series of experiments over ISR systerns located around the globe. The SIMPLEX I experiment occurred over Jicamara, Peru in the aftemoon on 4 October 1997 during the Shuttle Mission STS-86. An electron density depression was produced at 359-km altitude on the rnid-point of a magnetic field line. The experiment was scheduled when there were no zonal drifts of the plasma so the modified field-line remained fixed over the 50 MHz, Jicamarca radar. The density depression was filled in by plasma flowing along the magnetic field line with a time constant of 4.5 minutes. The density perturbation has completely vanished 20 minutes after the engine bum. The experimental measurements were compared with two models: (1) SAMI2 a fully numerical model of the F­region, and (2) an analytic representation of field-aligned transport by arnbipolar diffusion. The computed recovery time from each model is much longer than the observed recovery time. The theory of arnbipolar diffusion currently used in ionospheric models seems to be inadequate to describe the SIMPLEX I observations. Several possible sources for this discrepancy are discussed. The SIMPLEX I active experiment is shown to have the potential for testing selected processes in ionospheric models.
    Palabras clave:Plasma densityIonosphereSpace shuttle