The 50 MHz Jicamarca incoherent scatter radar can be used to make very high precision F-region plasma drift measurements with less than a m/s uncertainty and 5 min/ 15 km time/height resolutions. In such measurements the transmitting antenna beam is pointed perpendicular to the geomagnetic field ~ B [e.g., Kudeki et al. , 1999] and backscattered fields consist of magneto-ionic O- and X- components with unequal phase retardations. Detecting the fields with an orthogonal pair of linear-polarized antennas and fitting the average power and differential- phase of the antenna outputs to an appropriate data model we have succeeded in making F-region electron density measurements with data collected during Jicamarca drifts experiments. This procedure provides Jicamarca with a new capability for simultaneous drifts and density measurements at F-region heights.

Doppler spectra of 50 MHz F-region incoherent backscattered signals detected at Jicamarca will be presented. The measurements were conducted with the Jicamarca radar beams pointed perpendicular to the ambient magnetic field B. Consequently, the Doppler spectra contain a sharp cusplike feature centered about the bulk Ex B velocity of the ionospheric plasma [Kudeki et al. 1999]. The overall shape of the spectrum about the mean Doppler velocity represents a beam weighted superposition of incoherent scatter spectra corresponding to small magnetic aspect angles. Incoherent scatter theory based models for the measured spectra indicate that the spectral width is regulated by the electron temperature Te , However, unless electron Coulomb collisions are included in the model, unrealistically low Te estimates are obtained via model fitting of the measured spectra. The collisions broaden the incohe...

Diapositivas presentadas en URSI General Assembly, August 7-16, 2008, Chicago, Illinois, USA.

The ALTAIR UHF radar was used in an incoherent scatter experiment to observe the low-latitude ionosphere during the Equis 2 rocket campaign. The measurements provided the first high-resolution electron density maps of the low-latitude D- and E-region in the Pacific sector and also extended into the F-region and topside ionosphere. Although the sampling frequency was well below the Nyquist frequency of F-region returns, we were able to estimate Te/Ti ratio and infer unbiased electron density estimates using a regularized inversion technique described here. The technique exploits magnetic aspect angle dependence of ISR cross-section for Te>Ti.

Diapositivas presentadas en: ISEA 12 - 12th International Symposium on Equatorial Aeronomy, May 18-24, 2008. Crete, Greece.

Diapositivas presentadas en 2008 Annual Summer CEDAR Workshop, 16-21 June 2008. Midway, Utah, USA.

Diapositivas presentadas en el XIII Encuentro Científico Internacional, (ECI 2010v), realizado del 5 al 8 de enero de 2010 en la ciudad de Lima, Perú.

Diapositivas presentadas en el XIII Encuentro Científico Internacional, (ECI 2010i), realizado del 2 al 6 de agosto de 2010 en la ciudad de Lima, Perú.

Presentado en MST12 - 12th Workshop on Technical and Scientific Aspects of MST Radars, London, Ontario, Canada, 17-23 May 2009.

Diapositivas presentadas en el II Encuentro Nacional de Radio Científicos e Investigadores Afines 2010 (URSI- PERÚ), llevado a cabo en la Pontificia Universidad Católica del Perú.

The mesosphere-stratosphere-troposphere (MST) radar at Jicamarca, Peru (12S, 77W), made extended (15 day or longer) observations of the horizontal and vertical winds that were used to infer the diurnal and semidiurnal tides. The measurements were made during several months from mid-1997 through mid-1998 and using a higher-power transmitter and finer range resolution during 10 days of August 1998. The three-component winds are used to estimate amplitudes, phases, and momentum fluxes associated with the tides. Thermal forcing of the diurnal tide is also examined with diurnal water vapor heating rates calculated using data from the NASA Water Vapor Project (NVAP). For the region near Jicamarca the calculations from NVAP showed the temporal variability of the diurnal heating to be dominated by an annual cycle with maximum around the summer solstice. When projected into tidal modes, about 25%...

MST (mesosphere, stratosphere, troposphere) radar observations at Jicamarca use four antenna beams, one vertical, others tilted to the east, west, and south, to detect the scattered pulse returns from mesospheric heights (∼55–85 km). Doppler shifts of scattered returns, estimated by fitting the observed signal spectra by generalized Gaussian‐shaped models, are used to estimate mesospheric wind vectors. At some heights two spectral peaks are seen in which case a dual‐peaked model is fitted the spectrum. Dual peaks are more common for returns from the east and west tilted beams with stronger sidelobes. When sidelobe‐caused peaks are dominant and are mistaken for mainlobe peaks, wind errors occur since the estimation algorithm uses the pointing angle of the mainbeam. To avoid such errors we implemented a clustering‐based machine learning procedure to identify and use only the ma...

Range‐time‐intensity (RTI) plots of 50 MHz radar backscatter detected at Jicamarca from the 150‐km region of the equatorial ionosphere exhibit necklace‐shaped multilayered structures first reported by Kudeki and Fawcett (1993, https://doi.org/10.1029/93GL01256). The backscatter layers also exhibit quasi‐periodic intensity fluctuations with periods of about 5–15 min and are separated from adjacent layers by thin and undulating regions of no detectible power returns. A study of the fluctuating backscatter layers and undulating gap regions will be presented using VIPIR ionosonde data taken at the Jicamarca Radio Observatory simultaneously with high‐resolution 50‐MHz radar backscatter data. VIPIR virtual reflection height variations in time are noted to match the RTI gap‐region undulations very closely at selected VIPIR frequencies (or, equivalently, electron densities at r...

A multi-beam incoherent scatter radar technique has been developed at the Jicamarca Radio Observatory in order to maximize the number of ionospheric parameters that can be estimated simultaneously. The technique interleaves radar observations with antenna beams pointing perpendicular and oblique to the Earth's magnetic field. For the estimation of the ionospheric parameters, we have modeled the magnetic aspect angle variations of the signal power and cross-correlation data measured in multiple directions. The data model, formulated in terms of soft-target radar equations, was built based on the theories of incoherent scattering and magneto-ionic propagation. Applying a nonlinear least-squares inversion algorithm, we have succeeded in measuring simultaneously ionospheric electron densities Ne, electronto-ion temperature ratios Te=Ti as well as vertical and zonal plasma drifts. In the past...

Models for the self- and cross-correlation of orthogonal polarized quasi-transverse incoherent scatter returns are presented. The models are used to estimate the F region plasma densities with dual-polarization transverse-beam incoherent scatter data collected at the Jicamarca Radio Observatory using a technique introduced by Kudeki et al. [2003]. The cross-correlation model takes into account magneto-ionic propagation effects associated with quasi-transverse O- and X-modes in an inhomogeneous ionosphere. The phase of the cross-correlation provides the information to convert the measured power data into ionospheric density estimates via a least squares fitting procedure.

Diapositivas presentadas en el Encuentro Científico Internacional, ECI-2010, celebrado en Lima, Perú.

Radar echoes from the daytime lower F region near the magnetic equator, so-called 150-km echoes, have been puzzling researchers for decades. Neither the mechanisms that generate the enhanced backscatter at very high frequencies (typically 30–50 MHz), the sharp lower cutoff height, the intricate layering with multiple echo layers separated by narrow gaps, nor the modulation of the echoes by short-period gravity waves is well understood. Here we focus on the diurnal variation of the echo layers specifically, certain wide gaps in the vertical structure—which apparently descend in the morning, reach their lowest altitude near local noon, and ascend in the afternoon, sometimes described as necklace structure based on the appearance of the layers in range-time-intensity diagrams. Analyzing high-resolution data obtained with the Jicamarca radar between 2005 and 2017, spanning more than one ...

The Jicamarca MST radar was used in two campaigns during June and August 1987 to measure wave influences, flow variability, and mean structure in the equatorial stratosphere and mesosphere. This paper presents observations of motions and momentum fluxes in the mesosphere during each campaign. A companion paper by Hitchman et al. addresses the mean structure and fluxes as well as comparisons with other datasets. Results presented here indicate that the equatorial mesosphere is dynamically very active, with considerable gravity-wave and tidal motions and persuasive evidence of inertial instability and wave-filtering processes. Vertical velocities at high frequencies are comparable to those observed at other locations. Hourly mean horizontal motions and momentum fluxes are Iikewise large and variable, exhibiting enormous vertical shears and strong modulation of the wave spectrum and momentu...