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Browsing Pósters by Subject "Atmospheric dispersion"
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Item Open Access Daytime vertical and zonal velocities from 150-km echoes over Jicamarca(Instituto Geofísico del Perú, Radio Observatorio de Jicamarca, 2004-06-27) Chau Chong Shing, Jorge Luis; Woodman Pollitt, Ronald Francisco; Scipión, DannyDoppler velocities of 150-km echoes represents the vertical ExB drift velocities at F region altitudes. 150-km observations represent and excelent mean of monitoring the electric fields at equatorial latitudes. Low power observations of 150-km echoes using the JULIA system have been carried out almost continuosly since August 2001 at Jicamarca [e.g., Anderson et al., 2004]. Most of the observations have been done pointing perpendiculat to the magnetic fiel (B) in the magnetic meridian, allowing the measurement of the vertical component of the ExB drift.Item Open Access Evaluation of topside equatorial spread F spectra estimators using Monte Carlo simulations(Instituto Geofísico del Perú, 2008) Galindo, F. R.; Kuyeng, K. M.; Chau Chong Shing, Jorge Luis; Hysell, D. L.Radar observations typically employ periodic pulses to study any target. This scheme allows a simple processing of the data but the results frequently shows range or frequency aliasing. In order to solve this problem Uppala and Sahr [1] introduced the aperiodic technique (AT) in the radio science community. The AT is based on transmitting pulses at non uniform intervals and allows to study moderately overspread targets. Some equatorial Spread F (ESF) echoes belong to this category, particularly those from the topside. Using this idea Jicamarca Radio Observatory (JRO) has done a couple of experiments to study ESF echoes. Chau et al [2] used the Fast Fourier Transform (FFT) to compute spectra from those experiments and developed some criteria to remove clutter due to the aperiodic sequence. A second scheme of work was introduced by Hysell et al [3] and this scheme uses a Bayesian method to compute the spectra. Continuing this line of research a Monte Carlo simulations of typical echoes from equatorial ionospheric irregularities as well as ground clutter has been done to evaluate different aperiodic pulsing and inversion techniques to estimate the spectra or its corresponding AutoCorrelation Function (ACF). Our main objective is the estimation of the moderately overspread topside equatorial spread F (ESF) spectra. The optimal spectra estimators combined with radar imaging techniques might represent the unique means to estimate the irregularity power and energy spectral density versus wavenumber from the ground.Item Open Access Studies of equatorial spread-F using LISN VIPIR(Instituto Geofísico del Perú, 2009) Gopi Krishna, S.; Valladares, C. E.; Doherty, P.; Bullet, T.; Livingston, R.LISN, the Low Latitude Ionospheric Sensor Network, is a distributed observatory. LISN represents a closely coordinated geophysical instrument set, comprised of GPS receivers providing TEC values and scintillation measurements, magnetometers providing daytime ionospheric electric fields and Vertical Incidence Pulsed Ionospheric Radar (VIPIR) providing ionograms. The LISN Observatory was designed to do continuous measurements using GPS receivers, VIPIR ionosondes and flux gate magnetometers; provide a nowcast of TEC, S4 index, and other derived parameters of the low-latitude ionosphere. The LISN-GPS network of 70 GPS receivers (planned, about 45+ connected now) and 5 VIPIR ionosondes planned in the same field line, will make it possible to address science questions regarding: the effect of E and Es layers on inhibiting ESF, the role of Gravity Waves on seeding plasma bubbles. It will also provide clues to understand the causes of day-to-day variability of the low-latitude ionosphere. The first VIPIR ionosonde has been installed and working temporarily in Jicamarca since October 2008. The VIPIR is able to operate in different modes; we have used high temporal and spatial resolution modes to measure the E and F regions. We carried out a campaign during March 2009 that aimed to measure the effect of gravity waves on the ionospheric densities and to observe the means of gravity waves as a seeding mechanism for spread F. This poster describes the preliminary results on the characteristics of ionospheric density structures, velocities during spread-F conditions from the VIPIR data.