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.

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

We present here the first Jicamarca observations of incoherent scatter radar (ISR) spectra detected from E- and D-region altitudes. In the past such observations have not been possible at Jicamarca due a combined effect of strong equatorial electrojet (EEJ) clutter and hardware limitations in the receiving system. The observations presented here were made during weak EEJ conditions (i.e., almost zero zonal electric field) using an improved digital receiving system with a wide dynamic range and a high data throughput.

The observed ISR spectra from E- and D-region altitudes are, as expected, narrow and get even narrower with decreasing altitude due to increasing ion-neutral collision frequencies. Therefore, it was possible to obtain accurate spectral measurements using a pulse-to-pulse data analysis. At lower altitudes in the D-region where signal correlation...

We show here that VHF signals scattered from the 150 km region above Jicamaca exhibit two distinct types of features. In one type (type A), the Doppler spectral width increases with the echo strength and the corresponding signal-to-noise ratio (SNR). A second type (type B) of higher SNR echoes exhibits SNR-independent Doppler spectral widths that are much narrower than those observed in the first type. The type A echo population is by far the dominant population. Comparisons with earlier data sets collected at Jicamarca and elsewhere suggest that the type A and type B are likely to be associated with a naturally enhanced incoherent scattering (NEIS) process and the unstable growth of field-aligned irregularities (FAIs), respectively. We conjecture that small radar systems operated near the geomagnetic equator that have reported 150 km echo observations detected FAI echoes and that the NE...

In this work we summarize the statistics of the socalled 150-km echoes obtained with a low-power VHF radar operation at the Jicamarca Radio Observatory (11.97◦ S, 76.87◦ W, and 1.3 ◦ dip angle at 150-km altitude) in Peru. Our results are based on almost four years of observations between August 2001 and July 2005 (approximately 150 days per year). The majority of the observations have been conducted between 08:00 and 17:00 LT. We present the statistics of occurrence of the echoes for each of the four seasons as a function of time of day and altitude. The occurrence frequency of the echoes is ∼75% around noon and start decreasing after 15:00 LT and disappear after 17:00 LT in all seasons. As shown in previous campaign observations, the 150-echoes appear at a higher altitude (>150 km) in narrow layers in the morning, reaching lower altitudes (∼135 km) around noon, and disappear a...

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

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

Vertical shear in the zonal plasma drift speed is apparent in incoherent and coherent scatter radar observations of the bottomside F region ionosphere made at Jicamarca from about 1600–2200 LT. The relative importance of the factors controlling the shear, which include competition between the E and F region dynamos as well as vertical currents driven in the E and F regions at the dip equator, is presently unknown. Bottom-type scattering layers arise in strata where the neutral and plasma drifts differ widely, and periodic structuring of irregularities within the layers is telltale of intermediate-scale waves in the bottomside. These precursor waves appear to be able to seed ionospheric interchange instabilities and initiate full-blown equatorial spread F. The seed or precursor waves may be generated by a collisional shear instability. However, assessing the viability of shear instabili...

We use Jicamarca incoherent scatter radar measurements to study for the first time the altitudinal variations of late afternoon and early night equatorial F region vertical plasma drifts. We also present the initial vertical drift measurements over the altitudinal range from about 200 to 2000 km. These data show that the afternoon drifts decrease weakly with altitude. Near their evening prereversal enhancements, the vertical drifts generally increase with altitude below about the F layer peak, decrease with height near the F layer peak and above, and are nearly height independent in the (solar flux dependent) topside ionosphere. The transition altitudes from height‐decreasing to height‐independent evening upward drifts decrease with altitude from solar maximum to solar minimum. After their reversal to downward, the vertical drifts do not change much with height. The altitudinal dep...

In October 1997 and July 1999 during the STS-86 and STS-93 flights of the Space Shuttle, the crew performed experiments with controlled ion injections over the incoherent scatter radar (ISR) facilities located at Arecibo, Puerto Rico; Jicamarca, Perú; and Kwajalein, Marshall Islands. Ion beams were formed by charge exchange in the ionosphere of the high velocity neutral molecules exhausted by the Orbital Maneuver Subsystem (OMS) engines on the Space Shuttle. Pick-up ions were produced with energies between 2 and 10 eV depending on the orientation of the OMS engines relative to the vehicle orbit. The ions eventually recombined with electrons yielding electrón density depressions or holes.

Diapositivas presentadas en 2009 Joint Assembly. The Meeting of the Americas. 24-27 May 2009. Toronto, Ontario, Canada.

Correlation studies performed on data from recent mesospheric experiments conducted with the 50-MHz Jicamarca radar in May 2003 and July 2004 are reported. The study is based on signals detected from a combination of vertical and off-vertical beams. The nominal height resolution was 150 m and spectral estimates were obtained after ~1 min integration. Spectral widths and backscattered power generally show positive correlations at upper mesospheric heights in agreement with earlier findings (e.g., Fukao et al., 1980) that upper mesospheric echoes are dominated by isotropic Bragg scatter. In many instances in the upper mesosphere, a weakening of positive correlation away from layer centers (towards top and bottom boundaries) was observed with the aid of improved height resolution. This finding supports the idea that layer edges are dominated by anisotropic turbulence. The data also suggests...

During the Condor campaign a number of instruments were set up in Peru to support the rocket experiments. In this series of papers we report on the results of the experiments designed to study the equatorial F region. In this overview paper we summarize the main results as well as report upon the macroscopic developments of spread F as evidenced by data from backscatter radars, from scintillation observations, and from digital ionosonde meaurements. In this latter regard, we argue here that at least two factors other than the classical gravitational Rayleigh-Taylor plasma instability process must operate to yield the longest-scale horizontal organization of spread F structures. The horizontal scale typical of plume separation distances can be explained by invoking the effect of a shear in the plasma flow, although detailed comparison with theory seems to require shear frequencies a bit h...