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JULIA (Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere) Coherent Scatter Radar



Contact Persons

The general contact is Jorge (Koki) Chau

Web Pages

The JULIA web page for plots and some data is at and


For the JULIA coherent scatter radar: The Jicamarca Radio Observatory is a facility of the Instituto Geofisico del Peru and is operated with support from the National Science Foundation Cooperative Agreement ATM-0432565 through Cornell University.

Also have Jicamarca ISR and bistatic radar.

Instrument/Model Description

These data are proxy measurements of F-region ExB ion drifts derived from the 150-km echoes measured with the Jicamarca (11.95 S, 76.87 W; 520 m alt) Unattended Long-Term studies of the Ionosphere and Atmosphere (JULIA) system. On day 359 of 2001 at the ground, the apex magnetic lat,lon were (0.58,-5.12) deg. The magnetic inclination and declination angles were 1.145 deg and 0.367 deg. The magnetic local time at 0 UT is ~1835 MLT.

Jicamarca is the site of a 50 MHz incoherent scatter radar (ISR, kinst=10) in operation since the 1960s. The JULIA system is a coherent scatter radar (kinst=840) that uses two low-power 50 MHz transmitters which are phased together to excite the transmission antennas as a single unit. The JULIA system was intended for uninterrupted observations of ionospheric and atmospheric irregularities. JULIA shares the antenna, receiving system, processing, etc. with the ISR, but uses different transmitters. The coherent and incoherent scatter radar transmitters can operate at the same time for intercomparisons [e.g. Chau and Woodman, 2004].

The JULIA data are divided into 3 categories based on their altitude range and local time of occurrance. Observations of the E region electrojet (EEJ) are made between altitudes of 85 and 140 km in the morning and evening. The equatorial spread F (ESF) region irregularities are sampled between 95 and more than 850 km at night. For the valley region and so-called "150 kilometer" echoes, altitudes between 130 and 180 km are sampled during the day. The present 150-km echoes are averages between 140 and 170 km.

JULIA ionospheric irregularity data have been collected beginning in August 1996. Signal-to-noise ratios are shown as intensities. Horizontal zonal drifts are deduced with radar intererometry. Vertical drifts refer to Doppler phase speeds where positive values imply upward phase propagation in the EEJ and ESF modes.

Echoes from 150-km irregularities were first observed in the early 1960's over Jicamarca using the ISR [Balsley, 1964]. These echoes occurr only during the daytime and show very little seasonal dependence. The 150-km echoes have been observed at Jicamarca with the ISR on a campaign basis [e. g., Kudeki and Fawcett, 1993]. Sucessful low power observations of 150-km echoes have been performed since 2001 with the JULIA radar using two different antenna beam configurations (a single vertical beam, and an east-west beam pair). Using the vertical beam, only the vertical ion Doppler velocities are obtained, while using the east-west beam position both the vertical and zonal ion velocities are measured. In the latter case, two beams are used at the same time using diffent antenna sections.

An important finding from the study of these 150-km echoes is that the daytime vertical Doppler velocities of the 150-km irregularities averaged over the altitudinal region of the irregularities were in excellent agreement with the mean F region (200-500 km) ISR vertical drifts [Chau and Woodman, 2004]. Vertical is perpendicular north at the magnetic equator where the B field is horizontally directed from the south to the north. The zonal ion Doppler velocities from the east-west JULIA beam are in reasonable agreement with the ISR zonal ion velocities. Although 150-km echoes have been observed and studied for many years, the physical mechanism which causes them is still unknown. This JULIA database of representative zonal and vertical (perpendicular north) ion drifts could contribute in providing very precise proxy measurements of F region drifts using less powerful and more economical radar.


Balsley, B. B. (1964), Evidence of a stratified echoing region at 150 kilometers in the vicinity of the magnetic equator during daylight hours, J. Geophys. Res. Lett., 24, 2941-2944.
Chau, J. L. and R. F. Woodman, (2004), Daytime vertical and zonal velocities from 150-km echoes: Their relevance to F-region dynamics, Geophys. Res. Lett., 31, doi:10.1029/2004GL020800.
Kudeki, E. and C. D. Fawcett, (1993), High resolution observations of 150 Km echoes at Jicamarca, Geophys. Res. Lett., 20, 1987-1990.

150-km echoe observations of Doppler drifts that correspond to F-region drifts

These drifts are averages between 140 and 170 km.

Daily Listing for IS/HF Radars

-Revised 11 Jun 2007 by Barbara Emery