Proceedings with Extended Abstracts (single PDF file) - Radio ...

altitude). In Figure 5 there is an example of the typical range-time intensity (RTI) plot, usedby most radars, of nighttime E region irregularities (left) and an image for the time indicatedby the vertical red line (right). The image shows the structures inside the illuminated beam.Doppler velocity is color coded where pure colors represent very narrow spectral widths (red:away from the radar, green: around zero, blue: towards the radar) while whitish colorsrepresent very wide spectral widths. The intensity is proportional to the SNR. This is a newway of looking at irregularities, so major efforts are being conducted to improve theunderstanding of the scattering mechanisms and to extract state parameters (e.g., winds,electric fields)Figure 3. Examples of spectrograms from oblique observations of EEJ using wide beams (top) and narrowbeams (bottom). The type I and type II Doppler shifts are indicated with yellow and black curves, respectively.3. JULIA observationsAs we mentioned in the Introduction, the observations of field-aligned irregularities,E-region irregularities in particular, are being performed more frequently at Jicamarca byusing small transmitter units and small antenna arrays (JULIA concept). Figure 6, shows anexample of the latest observing modes using the JULIA system. Between 1830 and 0600 Eand F region irregularities are observed in interferometer mode (range scale on the left).Using the range scale on the right, oblique modes are used between 0600 and 0900 andbetween 1600 and 1830 using narrow (top) and wide (bottom) beams. Between 0900 and1600 a narrow oblique beam mode (top) is used for observing the EEJ, while the mainJicamarca antenna is used for observing the 150-km echoes [e.g., Kudeki and Fawcett, 1993](bottom).Besides getting the day-to-day as well as seasonal variability of these irregularities,the main products of these observations can be summarized a follows: vertical and zonal79