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Browsing Pósters by Author "Chau Chong Shing, Jorge Luis"
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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 Development of the new Jicamarca Acquisition Radar System: JARS(Instituto Geofísico del Perú, 2010) Abad, Rita; Inoñán, M.; Yanque, R.; Chau Chong Shing, Jorge LuisThe need for high-precision radar measurements of the upper atmosphere has motivated the development of new acquisition systems at the Jicamarca Radio Observatory (JRO). Digital receivers have replaced the old analog receivers, providing higher dynamic range, faster sampling rates, and more flexibility in configuration. At JRO, off-the-shelf Digitals Receivers (Echotek GC214) are used, but they are not as flexible as we need, so we decided to develop our own digital receiver system. The first prototype we built was a two-channel data acquisition system (REX-2X). The system was finished in 2008 and it has been used to modernize the SOUSY radar at Jicamarca. In 2009, after the experience gained from REX-2X, a new project was started. An eight-channel acquisition system named JARS (Jicamarca Acquisition Radar System) was designed.Item Open Access Equatorial zonal electric fields during the 2002-2003 sudden stratospheric warming event(Instituto Geofísico del Perú, 2009) Olson, Michael E.; Fejer, B. G.; Stolle, C.; Chau Chong Shing, Jorge Luis; Goncharenko, L. P.For nearly fifty years, the Jicamarca Radio Observatory (11.95°S, 76.87°W, 2°N dip latitude) near Lima, Peru, has measured ionospheric plasma drifts. Over the last ten years, measurements of plasma drift velocities have also been measured using radar observations of the equatorial 150 km altitude región (Kudeki and Fawcett, 1993; Chau and Woodman, 2004).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 Ionospheric effects of recent stratospheric sudden warmings(Instituto Geofísico del Perú, 2011) Goncharenko, L.; Coster, A.; Chau Chong Shing, Jorge Luis; Valladares, C. E.Recent studies have shown large variations in low-latitude ionospheric parameters occurring after stratospheric sudden warming events. We use observations of vertical ion drift from Jicamarca ISR and GPS total electron content data in the Western Hemisphere for winters of 2008-2009 and 2009-2010 to illustrate main features of ionospheric changes related to stratospheric sudden warmings. The common feature in all events is the increase in the electron density during the morning hours and the decrease in the afternoon, related to amplification of 12-hour signature in low-latitude vertical ion drifts. This feature persists for several days after the peak in stratospheric temperature. The observed phenomena is related to quasistationary planetary waves, which have a high amplitude level prior to the stratospheric warmings. Non-linear interaction of planetary waves with tides leading to increase in tidal amplitudes in the low latitude lower thermosphere and modulation of E-region electric field with subsequent mapping to the F-region is thought to be the primary mechanism responsible for the observed ionospheric response. We investigate the characteristics of ionospheric oscillations with planetary wave periods between 2 and 30 days and in a wide range of latitudes in context of variations in stratospheric parameters.Item Open Access Ionospheric variations during January 2009 stratospheric sudden warming(Instituto Geofísico del Perú, 2009) Goncharenko, L.; Coster, A.; Rideout, W.; Chau Chong Shing, Jorge Luis; Liu, H. -L.; Valladares, C. E.The stratospheric sudden warming peaking in January 2009 was the strongest and most prolonged on record. We report significant ionospheric variations is association with this event, which are especially pronounced at low latitudes. Large increase in the vertical drifts is observed at Jicamarca, displaying 12-hour signature with upward drifts in the morning hours and downward drifts in the afternoon hours, with pattern persisting for several days. Analysis of GPS TEC data indicates that variations in electron density are observed in a large range of longitudes and latitudes. The entire daytime ionosphere is affected, with morning increase in low-latitude TEC exceeding 100% of the mean value, and afternoon decrease in TEC approaching ~50% of the mean value. These variations are consistent with ionospheric disturbances observed during other stratospheric warming events. We suggest the observed phenomena is related to planetary waves, which have a high amplitude level prior to the stratospheric warmings. Interaction of planetary waves with tides and modulation of tides can lead to changes in the low-latitude electric field through the wind dynamo process, which in turn is responsible for a largescale redistribution of ionospheric electron density.Item Open Access Modos de observación en el espacio cercano con el radar de Jicamarca(Instituto Geofísico del Perú, 2010) Kuyeng, K.; Castillo, O.; Condori, L.; Chau Chong Shing, Jorge LuisEl Radio Observatorio de Jicamarca (ROJ) es la principal estación ecuatorial de la cadena de radio observatorios de dispersión incoherente (cuyas siglas en inglés es ISR) del hemisferio oeste que se extienden desde Lima - Perú hasta Søndre Strømfjord, Groelandia y la más importante en el mundo para estudiar la ionósfera ecuatorial. Esta compuesto de tres transmisores de 1.5 MW y un arreglo de antenas de 18,432 dipolos, cubriendo un área aproximada de 85,000 m2. El estudio de la ionósfera ecuatorial ha adquirido mayor importancia debido, en gran parte,a las contribuciones hechas por el Radio Observatorio de Jicamarca. El Observatorio se ubica a media hora de viaje en automóvil hacía el este de Lima y a 10 kms de la Carretera Central (latitud 11.95°Sur, longitud 76.87° Oeste).Item Open Access Perpendicular and off-perpendicular to B observations of 150-km echoes: evidence of meridional modulation and structure(Instituto Geofísico del Perú, 2009) Chau Chong Shing, Jorge Luis; Woodman Pollitt, Ronald Francisco; Milla, MarcoAlthough discovered more than 40 years ago [Balsley, 1964], there is still no physical mechanism that explains the occurrence of coherent echoes from altitudes around 150 kms (the so called 150-km echoes). East-West oblique beam [Fawcett, 1999] as well as wide beam imaging observations at Jicamarca, indicates that temporal variability of 150-km echoes (the pearls in the necklace) is not due to structuring and/or modulation in the zonal direction. These results point to a meridional modulation [E. Kudeki, personal communication]. Recently Chau [2004] reported the observations of echoes from off-perpendicular to B angles, implying that the aspect sensitivity (i.e., the North-South angular brightness) is not a narrow Gaussian as originally thought…Item Open Access The LISN database: description and initial results(Instituto Geofísico del Perú, 2009) De la Jara, César; Chau Chong Shing, Jorge Luis; Espinoza, J. C.; Veliz, Oscar; Valladares, C.; Bullet, T.The heavy volume of data that GPS, ionosondes and magnetometers are continuously collecting is stored in the LISN server and managed using a set of rules that are intended to provide an efficiently way to manipulate the large data sets and also implement an adequate method to systematically transform all this information into knowledge. LISN integrates multiple data sources and should provide security, integrity and availability in a multi-user environment. Data from the remote stations arrives to the server continuously and is stored, processed and distributed. This data is easily available and in some cases freely accessible to the community promoting research and encouraging collaboration between users.Item Open Access Using JULIA long dataset to find preconditioning evidence of ESF in bottom-type layers(Instituto Geofísico del Perú, 2008) Pinedo, H.; Chau Chong Shing, Jorge Luis; Hysell, D.Recently Hysell et al. [2005] has suggested that the periodic structuring observed in the bottomtype (BT) scattering layers might be used to determine the occurrence or not of full-blown equatorial spread F (ESF) on a given day. The seed or precursor waves may be generated by a collisional shear instability. Preliminary observations at Jicamarca and AL TAIR have shown that such structures present wavelengths of the order of tens or hundreds of kilometers. At Jicamarca periodic structures have been observed using in-beam radar imaging techniques, however such observations are limited to few days in the last five years. On the other hand, routine observations using the JULIA system at Jicamarca have been done since 1996 on approximately 100 days per year on average, using interferometric and dual-beam observations with very narrow beams. Since the bottom-type irregularities drift ata relatively constant speed in the westward direction, using the JULIA narrow beams (～1o), the spatial periodicities might be observed as temporal periodicities in typical range-time intensity maps. In this initial work we present the statistics of the observed bottom-type periodicities and the occurrence of ESF plumes as detected with the JULIA system for years 2006-2008. Besides we presenta time occurrence statistics of a weak bottom-type layer that took place previously to bottom-type layers.Item Open Access Using non-spectacular radar meteor echoes to monitor lower thermosphere wind profiles(Instituto Geofísico del Perú, 2009) Oppenheim, Meers; Sugar, Glenn; Bass, Elizabeth; Slowey, Nick; Chau Chong Shing, Jorge Luis; Close, SigridWe present a new method of measuring lower thermospheric wind velocity profiles by tracking non‐specular meteor echoes in time. This approach relies on having a radar following plasma irregularities as they are dragged by the neutral wind. This requires a VHF radar with interferometric capability able to point close to perpendicular to the geomagnetic field. Using a small sample of data from the Jicamarca Radio Observatory, we calculated wind speeds and directions between 90 and 110\ km with a range resolution of a few hundred meters. The measurements taken show speeds reaching 150m/s and someAmes changing by as much as 100m/s over a 6km altitude range. With some refinement of the data collection and analysis techniques, we expect that one could obtain high resolution images of lower thermospheric winds as they change in both altitude and time. We will discuss these results, the physics underlying these measurements, and the limitations.Item Open Access Wide-beam forming using binary phase coding(Instituto Geofísico del Perú, Radio Observatorio de Jicamarca, 2000) Woodman Pollitt, Ronald Francisco; Chau Chong Shing, Jorge LuisIn imaging work, it is desirable to have the transmitting beam width matched to the receiving one. One possibility to do this at Jicamarca, when single receiving modules are employed, is using one antenna module as the transmitting array (the whole Jicamarca array consists of 8 by 8 modules). However, with this solution one cannot transmit the high peak power available at Jicamarca (～2 MW). A second solution, where high transmission power is possible, consist on transmitting with ali the antenna modules, but using 4 different sets ofbinary cedes (0 or 180 phase delays), i.e., a two-dimensional complementary phase code. After the decoding process, the information obtained is equivalent to what one would obtain if the high power were transmitted on a single antenna module. The wide beam information is synthesized by adding the second-order statistics obtained with each set of codes. We have tested this idea at Jicamarca to get three-dimensional images of the tropopause and lower stratosphere. For transmission we have used four sets of codes, where each code consists of 4 by 4 elements.