Jicamarca Radio Observatory

Lima, Peru

Jicamarca Radio Observatory

Lima, Peru
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Hysell D.L.,Cornell University | Milla M.A.,Jicamarca Radio Observatory | Rodrigues F.S.,University of Texas at Dallas | Varney R.H.,SRI International | Huba J.D.,U.S. Navy
Journal of Geophysical Research A: Space Physics | Year: 2015

We present observations of the topside ionosphere made at the Jicamarca Radio Observatory in March and September 2013, made using a full-profile analysis approach. Recent updates to the methodology employed at Jicamarca are also described. Measurements of plasma number density, electron and ion temperatures, and hydrogen and helium ion fractions up to 1500 km altitude are presented for 3 days in March and September. The main features of the observations include a sawtooth-like diurnal variation in ht, the transition height where the O+ ion fraction falls to 50%, the appearance of weak He+ layers just below ht, and a dramatic increase in plasma temperature at dawn followed by a sharp temperature depression around local noon. These features are consistent from day to day and between March and September. Coupled Ion Neutral Dynamics Investigation data from the Communication Navigation Outage Forecast System satellite are used to help validate the March Jicamarca data. The SAMI2-PE model was able to recover many of the features of the topside observations, including the morphology of the plasma density profiles and the light-ion composition. The model, forced using convection speeds and meridional thermospheric winds based on climatological averages, did not reproduce the extreme temperature changes in the topside between sunrise and noon. Some possible causes of the discrepancies are discussed. Key Points New ISR mode at Jicamarca measures topside parameters ISR data compared with C/NOFS CINDI measurements, SAMI2-PE model Extreme, rapid temperature variations in topside poorly understood ©2015. American Geophysical Union. All Rights Reserved.


Rodrigues F.S.,University of Texas at Dallas | Smith J.M.,University of Texas at Dallas | Milla M.,Jicamarca Radio Observatory | Stoneback R.A.,University of Texas at Dallas
Journal of Geophysical Research A: Space Physics | Year: 2015

One of the most interesting observations made by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite mission was the detection of average equatorial ionospheric vertical drifts that largely differed from model predictions. C/NOFS measurements showed, in particular, downward drifts in the afternoon sector, and upward drifts around local midnight hours during the 2008 and 2009 extreme solar minimum. The unexpected behavior of the drifts has important implications for ionospheric modeling and suggests the necessity for a better understanding of the low-latitude electrodynamics. We used ground-based radar measurements to quantify the seasonal and solar flux variability of daytime equatorial drifts at lower altitudes (150 km) than those probed by C/NOFS (above 400 km). We found that average vertical drifts at 150 km altitude are in good agreement with model predictions of F region drifts and did not show the signatures of an enhanced semidiurnal pattern, as seen by C/NOFS. Comparison of the 150 km echo drifts with model predictions also shows that the increase (decrease) with height of the vertical drifts in the morning (afternoon) hours is a regular feature of the equatorial ionosphere. It occurred in all seasons and solar flux conditions between 2001 and 2011. ©2015. American Geophysical Union. All Rights Reserved.


Rodrigues F.S.,University of Texas at Dallas | Shume E.B.,Jet Propulsion Laboratory | De Paula E.R.,National Institute for Space Research | Milla M.,Jicamarca Radio Observatory
Annales Geophysicae | Year: 2013

Previous studies showed that conventional coherent backscatter radar measurements of the Doppler velocity of the so-called 150 km echoes can provide an alternative way of estimating ionospheric vertical plasma drifts during daytime hours (Kudeki and Fawcett, 1993; Chau and Woodman, 2004). Using observations made by a small, low-power 30 MHz coherent backscatter radar located in the equatorial site of São Luís (2.59 S, 44.21 W;-2.35 dip lat), we were able to detect and monitor the occurrence of 150 km echoes in the Brazilian sector. Using these measurements we estimated the local time variation of daytime vertical ionospheric drifts in the eastern American sector. Here, we present a few interesting cases of 150 km-echoes observations made by the São Luís radar and estimates of the diurnal variation of vertical drifts. These cases exemplify the variability of the vertical drifts in the Brazilian sector. Using same-day 150 km-echoes measurements made at the Jicamarca Radio Observatory in Peru, we also demonstrate the variability of the equatorial vertical drifts across the American sector. In addition to first estimates of the absolute vertical plasma drifts in the eastern American (Brazilian) sector, we also present observations of abnormal drifts detected by the São Luís radar associated with the 2009 major sudden stratospheric warming event. © 2013 Author(s).


Akala A.O.,University of Lagos | Seemala G.K.,Kyoto University | Doherty P.H.,Boston College | Valladares C.E.,Boston College | And 2 more authors.
Annales Geophysicae | Year: 2013

GPS-TEC data were observed at the same local time at two equatorial stations on both longitudes: Lagos (6.52° N, 3.4° E, 3.04° S magnetic latitude), Nigeria; and Pucallpa (8.38 S, 74.57 W, 4.25 N magnetic latitude), Peru during the minimum (2009, 2010) and ascending (2011) phases of solar cycle 24. These data were grouped into daily, seasonal and solar activity sets. The day-to-day variations in vertical TEC (VTEC) recorded the maximum during 14:00-16:00 LT and minimum during 04:00-06:00 LT at both longitudes. Seasonally, during solar minimum, maximum VTEC values were observed during March equinox and minimum during solstices. However, during the ascending phase of the solar activity, the maximum values were recorded during the December solstice and minimum during the June solstice. VTEC also increased with solar activity at both longitudes. On longitude by longitude comparison, the African GPS station generally recorded higher VTEC values than the American GPS station. Furthermore, harmonic analysis technique was used to extract the annual and semi-annual components of the amplitudes of the TEC series at both stations. The semi-annual variations dominated the TEC series over the African equatorial station, while the annual variations dominated those over the American equatorial station. The GPS-TEC-derived averages for non-storm days were compared with the corresponding values derived by the IRI-2007 with the NeQuick topside option. The NeQuick option of IRI-2007 showed better performance at the American sector than the African sector, but generally underestimating TEC during the early morning hours at both longitudes. © Author(s) 2013. CC Attribution 3.0 License.


Hysell D.L.,Cornell University | Milla M.A.,Jicamarca Radio Observatory
2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014 | Year: 2014

A full-profile incoherent scatter analysis, in which all ionospheric state variables at all altitudes are estimated simultaneously, has been implemented at Jicamarca for topside research. Such an analysis is particularly expedient at Jicamarca where the correlation time of the 50-MHz echoes is long. Long pulses are interleaved with short double pulses which provide complementary measurements at altitudes below and near the F peak. Absolute number density calibration is performed by exploiting Faraday rotation. We compute range-lag ambiguity functions for lag profile forward modeling in a general way. Autocorrelation function calculations take into account the small magnetic aspect angles of Jicamarca observations. Regularization is used to confine the solution space of the analysis and confer stability. A grid search provides the initial state for the iterative method we use. The overall algorithm can be made to run in real time on a single i7 processor core. Representative data are used to demonstrate the efficacy of the algorithm. © 2014 IEEE.


Hysell D.L.,Cornell University | Milla M.A.,Jicamarca Radio Observatory | Condori L.,Jicamarca Radio Observatory | Vierinen J.,Massachusetts Institute of Technology
Journal of Geophysical Research A: Space Physics | Year: 2015

We present results from a continuing effort to simulate equatorial spread F (ESF) using observations from the Jicamarca Radio Observatory near Lima, Peru. Jicamarca measures vertical and zonal plasma drifts along with plasma number density profiles overhead. The number density profiles are used to initialize a three-dimensional regional model of the ionosphere capable of simulating plasma density irregularities produced during ESF conditions. The vertical drifts measurements are used to drive the numerical simulation continuously. Neutral winds are derived from the new Horizontal Wind Model '14 (HWM-14) model, and the zonal winds are scaled so as to make the zonal plasma flows at the start of the simulation agree with the ISR profile measurements. Coherent scatter radar imagery from Jicamarca is used to validate the simulation results. Campaign data were collected in April and December 2014, and a few events representative of low and high ESF activity were selected for analysis. The numerical simulations are able to reproduce the level of activity observed along with the gross features of the ESF irregularities and radar plumes. Data from a network of HF beacons are being incorporated into the forecast analysis in order to elucidate radar plumes which sometimes appear even when the simulation fails to predict them. ©2015. American Geophysical Union. All Rights Reserved.


Hysell D.L.,Cornell University | Milla M.A.,Jicamarca Radio Observatory
2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014 | Year: 2014

Ionospheric state parameters including plasma number density and vector drift profiles were measured at the Jicamarca Radio Observatory during campaigns throughout 2013. Neutral winds were measured by the redline Fabry Perot interferometer at Jicamarca. Coherent radar backscatter from plasma irregularities associated with equatorial spread F (ESF) was also recorded. Radar imagery of the morphology of the large-scale ESF irregularities is also available from simultaneous measurements. A 3D numerical simulation of ionospheric irregularities, initialized and forced using parametrizations derived from a combination of measurements and empirical models, has been used to reproduce the ESF activity that occurred on a number of different, representative campaign nights. The simulations were able to recover many of the most salient features of the irregularities that formed in each case. The campaign data, numerical simulations, and protocols used to associate them are presented. © 2014 IEEE.


Hysell D.L.,Cornell University | Jafari R.,Cornell University | Milla M.A.,Jicamarca Radio Observatory | Meriwether J.W.,Clemson University
Journal of Geophysical Research: Space Physics | Year: 2014

Ionospheric state parameters including plasma number density and vector drift velocity profiles were measured at the Jicamarca Radio Observatory during a campaign running from 12 to 18 April 2013. Neutral winds were measured by the red-line Fabry Perot interferometer at Jicamarca. Coherent radar backscatter from plasma irregularities associated with equatorial spread F (ESF) was also recorded. A numerical simulation of ionospheric irregularities, initialized and forced using parameterizations derived from a combination of measurements and empirical models, was used to try to reproduce the ESF activity that occurred on three different nights. Simulations were able to recover the salient features of the irregularities that formed in each case and produce bottom-type, bottomside, and topside ESF. Realistic simulations require the accurate representation of the vertical currents that generate irregularities initially at the base of the F region as well as the zonal currents necessary for irregularities to expand in altitude and penetrate to the topside. The campaign data, numerical simulations, and protocols used to associate them are presented and evaluated. Key Points A new mode at Jicamarca acquires data suitable for validating forecast results A numerical simulation cognizant of the physical drivers and mechanisms is used The simulation reproduces the most salient day-to-day features of ESF ©2014. American Geophysical Union. All Rights Reserved.


Hysell D.L.,Cornell University | Chau J.L.,Jicamarca Radio Observatory | Milla M.A.,Jicamarca Radio Observatory
IEEE International Symposium on Phased Array Systems and Technology | Year: 2013

Phased array and spaced antenna radar techniques developed and employed at the Jicamarca Radio Observatory for ionospheric research are reviewed. The ionospheric scatterers studied by Jicamarca are not spatially homogeneous and not beam filling in some cases, and distinguishing the bearing of the radar backscatter is essential for correctly interpreting the radar data as well as for discovery research. Both incoherent and coherent scatter from thermal and nonthermal plasma density irregularities, respectively, are strong functions of magnetic aspect angle. Radar interferometry can be used to discriminate the arrival angle or brightness distribution of the backscatter and, in the case of coherent scatter from field-aligned irregularities, determine its aspect sensitivity. Using multiple spaced receivers, the entire brightness distribution can be estimated from the measured visibility using aperture synthesis imaging techniques. This is the most incisive remote sensing tool available for studying ionospheric plasma irregularities and the instabilities that produce them. Fi-nally, a novel technique for antenna compression introduced at Jicamarca can be used to synthesize very broad radiation patterns that nevertheless make use of the entire Jicamarca phased array for transmission. © 2013 IEEE.


Hall C.M.,University of Tromsø | Hansen G.,Norwegian Institute For Air Research | Sigernes F.,University Center in Svalbard | Kuyeng Ruiz K.M.,Jicamarca Radio Observatory
Atmospheric Chemistry and Physics | Year: 2011

We present a seasonal climatology of tropopause altitude for 78 N 16 E derived from observations 2007-2010 by the SOUSY VHF radar on Svalbard. The spring minimum occurs one month later than that of surface air temperature and instead coincides with the maximum in ozone column density. This confirms similar studies based on radiosonde measurements in the arctic and demonstrates downward control by the stratosphere. If one is to exploit the potential of tropopause height as a metric for climate change at high latitude and elsewhere, it is imperative to observe and understand the processes which establish the tropopause-an understanding to which this study contributes. © 2011 Author(s).

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