"G3: Low latitude ionosphere effects on systems and radio propagation" 6 p., incluye PPT.

Diapositivas presentadas en: CEDAR Workshop 2009 del 28 de junio al 2 de julio de 2009 en Santa Fe, Nuevo México, USA.

Resumen.

In this work, I examine various techniques for measuring wind velocities using clear-air radars. Special emphasis has been given to the vertical wind measurements. All the observations were obtained in the lower atmosphere (below 20 km) using the Jicamarca 50 MHz radar system near Lima, Peru. I have concentrated my efforts on: (a) examining: different radar techniques for horizontal wind estimation, (b) improving the understanding of angle-of-arrival radar measurements, and (c) comparing a number of techniques for the measurement of the vertical wind velocities. I have measured horizontal wind velocities by a variety of both time- and frequency-domain spaced antenna (SA) techniques. Comparisons of these techniques for both zonal and meridional components have been carried out in a statistical sense. Two sets of data were analyzed under both "quiet" (low wind, low variability) and "active...

Diapositivas de una presentación oral realizada en la University de Nagoya, Japan en el año 2010.

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...

Diapositivas presentadas en la universidad de Piura el 4 de septiembre del 2009.

Jicamarca radar observations of a new class of large-scale plasma waves in the equatorial electrojet (EEJ) are presented and characterized. The study is based on long-term (204 days), single-baseline interferometry observations made in 2003 using a low-power radar mode, also known as JULIA mode, along with a few hours of observations made in an aperture synthesis imaging mode. The large-scale waves are found to occur at high altitudes in the E-region, mainly between 120 and 140km, around twilight (between 18:30 and 20:00 LT), with durations of a few minutes to an hour. In our long-term observations, these large-scale waves occur very often (between 1 and 5 out 10 nights), drift westward (~70 ms–1), exhibit very narrow spectral widths, and have both positive and negative Doppler shifts. The imaging results show that the large-scale waves occur along tilted bands that sweep westward and ...

Diapositivas de una presentación oral realizada en Arecibo, Puerto Rico, en el año 2010.

Diapositivas presentadas en la conferencia organizada por la Stanford University, in June 30, 2010).

Ronald F. Woodman Pollit: Científico, Ingeniero/Inventor, Mentor, Deportista. Diapositivas presentadas en el Encuentro Científico Internacional, ECI-2010, celebrado en Lima, Perú.

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

Diapositivas presentadas en Nagoya University, Japan, March 24 2010.

Diapositivas presentadas en: CEDAR Workshop 2009 del 28 de junio al 2 de julio de 2009 en Santa Fe, Nuevo México, USA.

We compare two types of VHF vertical velocity measurement techniques using a special configuration of the Jicamarca 50-MHz radar antenna. Zenith (vertically directed single-beam) techniques and spaced antenna (SA) techniques are compared using a 54-hour concurrent data set. We compare two different zenith techniques using different antenna beam widths (0.85° and 3.5°). In addition, we compare vertical velocities measured by a “quasi” Doppler beam swinging (QDBS) technique and a SA approach that incorporate either “inferred” or “corrected” vertical velocities. All of the results are compared in terms of statistical basis. Results are presented for both quiet (low wind, low variability) and active (high wind, high variability) conditions. We use the results of the narrow-beam zenith technique as a reference profile and discuss its validity as a reference. Our comparisons show...

Doppler 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.

We present a summary ofthe characteristics of echoes from ionospheric (E and F region) field-aligned irregularities obtained with the Piura VHF radar (~7.0° dip latitude, outside the equatorial electrojet region). Our results are based on (1) intermittent monostatic observations made between 1991 and 1999, (2) continuous monostatic observations made between January 2000 and June 2001, and (3) intermittent interferometric observations since August 2001. Among other important results, we have found that the E-region echoes are stronger and occur more frequently during local summer. In addition, we have observed that the seasonal and daily occurrences of Piura F-region irregularities are similar to the occurrence oftopside ESF irregularities over Jicamarca.

Diapositivas presentadas en el 2010 CEDAR Workshop, University of Colorado, Boulder, CO, 20-25 June 2010.

On the basis of scattering theory, we present four different contributions to angle-of-arrival (AOA) measurements using spaced antenna (SA) radar systems. We show that the measurement of the scattering parameters is needed to estimate most AOA contributions (e.g., tilt angle of layers). We analyze a general SA system (i.e., receiving antennas not necessarily symmetrically placed about the transmitter) and show, theoretically, that such systems can be used for vertical velocity corrections without explicitly knowing the scattering parameters (e.g., correlation lengths). The theoretical AOA expressions are compared with lower atmospheric data (3–21 km) obtained with the Jicamarca VHF radar system in Perú. We compare the AOAs obtained by a time and a frequency domain method, giving both methods essentially the same information. While the results are comparable, frequency domain AOAs tend...

Conference organized by Stanford Research Institute (SRI), Menlo Park, Califormia, USA in June 15, 2010.