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Radio Science

Cover image for Radio Science

August 2012

Volume 47, Issue 4

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      Analysis of strong ionospheric scintillation events measured by means of GPS signals at low latitudes during disturbed conditions

      B. Forte

      Article first published online: 25 AUG 2012 | DOI: 10.1029/2011RS004789

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      Key Points

      • Strong scintillation event from GPS signals
      • Spectral broadening observed, different scattering mechanisms appear possible
      • Refractive scattering as a possible explanation
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      Estimation of higher-order ionospheric errors in GNSS positioning using a realistic 3-D electron density model

      A. Kashcheyev, B. Nava and S. M. Radicella

      Article first published online: 21 AUG 2012 | DOI: 10.1029/2011RS004976

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      Key Points

      • To estimate the higher-order ionospheric errors in GNSS positioning
      • Using a realistic 3-D electron density model
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      Impacts of ionospheric scintillations on GPS receivers intended for equatorial aviation applications

      A. O. Akala, P. H. Doherty, C. S. Carrano, C. E. Valladares and K. M. Groves

      Article first published online: 25 JUL 2012 | DOI: 10.1029/2012RS004995

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      Key Points

      • Impacts of ionospheric scintillations on GPS aviation
      • Severe scintillations degrade GPS signals
      • Scintillations cause fades in excess of 20 dB-Hz on GNSS channels
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      Long-term ionospheric anomaly monitoring for ground based augmentation systems

      Sungwook Jung and Jiyun Lee

      Article first published online: 25 JUL 2012 | DOI: 10.1029/2012RS005016

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      Key Points

      • A methodology for automated long-term ionospheric anomaly monitoring
      • The results demonstrate the effectiveness of simplified truth processing
      • The automated procedure successfully identified extreme ionospheric anomalies
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      Fast and accurate calculation of multipath spread from VOACAP predictions

      A. J. Stocker

      Article first published online: 24 JUL 2012 | DOI: 10.1029/2011RS004965

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      Key Points

      • Novel method of calculating delay spread from VOACAP predictions
      • The method is faster than that previously reported
      • The predictions are comparable with observations
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      Comparison between Huynen and Cameron monostatic parameters

      C. Titin-Schnaider

      Article first published online: 21 JUL 2012 | DOI: 10.1029/2011RS004876

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      Key Points

      • Comparison between Huynen and Cameron characteristic parameters
      • Test of the connection of Huynen parameters to physical properties
      • Comparison using the monostatic full polarimetric scattering model
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      The effect of phase scintillations on the accuracy of phase screen simulation using deterministic screens derived from GPS and ALTAIR measurements

      Charles S. Carrano, Keith M. Groves and Ronald G. Caton

      Article first published online: 20 JUL 2012 | DOI: 10.1029/2011RS004958

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      Key Points

      • Phase scintillation limits the accuracy of phase screen simulations
      • We quantify this accuracy by cross-correlating predicted and measured signals
      • Back-propagation techniques can improve this correlation
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      Ionospheric signatures of Tohoku-Oki tsunami of March 11, 2011: Model comparisons near the epicenter

      David A. Galvan, Attila Komjathy, Michael P. Hickey, Philip Stephens, Jonathan Snively, Y. Tony Song, Mark D. Butala and Anthony J. Mannucci

      Article first published online: 12 JUL 2012 | DOI: 10.1029/2012RS005023

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      Key Points

      • The Tohoku tsunami caused perturbations to ionospheric GPS TEC measurements
      • GPS TEC observations of ionospheric response compare well with tsunami models
      • Observations compare well with an atmosphere-ionosphere coupling model
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      Current subsidiary peak in triggered lightning strokes

      Caixia Wang, Rubin Jiang, Jing Yang and Mingyuan Liu

      Article first published online: 11 JUL 2012 | DOI: 10.1029/2011RS004933

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      Key Points

      • The statistical characteristics of strokes current subsidiary peak are summarized
      • Four kinds of possible physical interpretations of subsidiary peak were proposed
      • A methodology of analytical simulating multiple peaks current was proposed
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      Time domain waveform and azimuth variation of ionospherically reflected VLF/LF radio emissions from lightning

      Abram R. Jacobson, Xuan-Min Shao and Erin Lay

      Article first published online: 6 JUL 2012 | DOI: 10.1029/2012RS004980

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      Key Points

      • D-region radio reflection depends on azimuth
      • Westward propagation is weakest for f < 30 kHz
      • Delayed ringing reflections at f > 50 kHz
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      Importance of data assimilation technique in defining the model drivers for the space weather specification of the high-latitude ionosphere

      L. Zhu, R. Schunk, L. Scherliess and V. Eccles

      Article first published online: 4 JUL 2012 | DOI: 10.1029/2011RS004936

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      Key Points

      • Data assimilation technique is important for space weather
      • Empirical model cannot provide accurate weather features
      • Space weather ability of the global MHD is restricted by solar wind data
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      Problems associated with uncertain parameters and missing physics for long-term ionosphere-thermosphere forecasting

      R. W. Schunk, L. Gardner, L. Scherliess and L. Zhu

      Article first published online: 19 JUN 2012 | DOI: 10.1029/2011RS004911

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      Key Points

      • Missing physics in global models
      • Ionosphere-thermosphere model uncertainties
      • Problems for space weather forecasting
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      Characteristics of traveling ionospheric disturbances observed by the TIDDBIT sounder

      G. Crowley and F. S. Rodrigues

      Article first published online: 9 JUN 2012 | DOI: 10.1029/2011RS004959

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      Key Points

      • HF Doppler sounders obtain comprehensive TID characteristics on bottomside
      • TID azimuths and speeds suggest TIDs are filtered by thermospheric winds
      • TID azimuths in Virginia rotate opposite direction from those in Antarctic
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      Sharpening our thinking about polar cap ionospheric patch morphology, research, and mitigation techniques

      Herbert C. Carlson

      Article first published online: 31 MAY 2012 | DOI: 10.1029/2011RS004946

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      Key Points

      • Magnetic reconnection produces most patches
      • Scintillation is driven by shear, not gradient drift instability
      • Magnetic reconnection impacts satellite drag
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      Simulating the impacts of ionospheric scintillation on L band SAR image formation

      Charles S. Carrano, Keith M. Groves and Ronald G. Caton

      Article first published online: 26 MAY 2012 | DOI: 10.1029/2011RS004956

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      Key Points

      • Ionospheric scintillation degrades SAR imagery
      • We present a phase screen technique to predict this effect
      • We compare simulated and observed images from PALSAR
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      Global observations of L band scintillation at solar minimum made by COSMIC

      Kenneth F. Dymond

      Article first published online: 19 MAY 2012 | DOI: 10.1029/2011RS004931

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      Key Points

      • Global observations of L band scintillation made using radio occultation (RO)
      • Viewing geometry causes RO measurements to be very sensitive to scintillation
      • RO can measure the 3-D distribution of ionospheric irregularities
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      Use of the Auroral Boundary Index for potential forecasting of ionospheric scintillation

      James M. Griffin, Thomas C. Connor and Hilary E. Snell

      Article first published online: 19 MAY 2012 | DOI: 10.1029/2011RS004954

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      Key Points

      • Proxy Ap index based on ABI will have higher temporal resolution
      • Forecast of geomagnetic activity can be made using ABI-based Ap
      • Ionospheric models using ABI-based Ap can then be used in nowcast/forecast mode
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      The Low-Latitude Ionosphere Sensor Network: Initial results

      C. E. Valladares and J. L. Chau

      Article first published online: 18 MAY 2012 | DOI: 10.1029/2011RS004978

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      Key Points

      • Presents capabilities of a new distributed observatory
      • Gives longitudinal extension of midnight TEC enhancements
      • Uses TEC values from GPS stations in South America to measure GWs
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      New Vary-Chap profile of the topside ionosphere electron density distribution for use with the IRI model and the GIRO real time data

      Patrick Nsumei, Bodo W. Reinisch, Xueqin Huang and Dieter Bilitza

      Article first published online: 17 MAY 2012 | DOI: 10.1029/2012RS004989

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      Key Points

      • Topside electron density model for IRI and GIRO
      • Empirical electron density model using ISIS-2 data
      • New Vary-Chap profile representation
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      Sounding of HF heating-induced artificial ionospheric disturbances by navigational satellite radio transmissions

      V. E. Kunitsyn, E. S. Andreeva, V. L. Frolov, G. P. Komrakov, M. O. Nazarenko and A. M. Padokhin

      Article first published online: 16 MAY 2012 | DOI: 10.1029/2011RS004957

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      Key Points

      • Influence of HF heating-induced irregularities on navigational signals
      • Spectrum of TEC variations during heating experiments
      • Tomographic image of wave disturbances in ionosphere generated by HF heating
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      Introducing a disturbance ionosphere index

      N. Jakowski, C. Borries and V. Wilken

      Article first published online: 8 MAY 2012 | DOI: 10.1029/2011RS004939

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      Key Points

      • Definition of a disturbance ionosphere index based on GNSS measurements
      • Application demonstration of DIX on ionospheric response to solar flares
      • Application demonstration of DIX on medium- and large-scale perturbations
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      HF propagation modeling within the polar ionosphere

      E. M. Warrington, N. Y. Zaalov, J. S. Naylor and A. J. Stocker

      Article first published online: 1 MAY 2012 | DOI: 10.1029/2011RS004909

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      Key Points

      • Current propagation prediction methods inadequate in polar cap
      • Improved area coverage by taking into account presence of polar patches
      • Further improvements possible with inclusion of near-real-time data
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      Inversion of backscatter ionograms and TEC data for over-the-horizon radar

      Sergey V. Fridman, L. J. Nickisch and Mark Hausman

      Article first published online: 26 APR 2012 | DOI: 10.1029/2011RS004932

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      Key Points

      • OTHR coordinate registration requires real-time ionosphere model
      • Ionospheric model supported by backscatter and vertical ionograms is useful
      • Ionospheric model is further improved by incorporating GPS TEC data
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      HiCIRF: A high-fidelity HF channel simulation

      L. J. Nickisch, Gavin St. John, Sergey V. Fridman, Mark A. Hausman and C. J. Coleman

      Article first published online: 26 APR 2012 | DOI: 10.1029/2011RS004928

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      Key Points

      • A high-fidelity HF ionospheric channel simulation has been developed
      • The simulation includes HF multimode and small-scale scatter
      • The simulation generates pulse-by-pulse channel impulse response realizations
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      Modeling the daytime, equatorial ionospheric ion densities associated with the observed, four-cell longitude patterns in E × B drift velocities

      Eduardo A. Araujo-Pradere, Tzu-Wei Fang, David N. Anderson, Mariangel Fedrizzi and Russell Stoneback

      Article first published online: 26 APR 2012 | DOI: 10.1029/2011RS004930

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      Key Points

      • C/NOFS data to quantify the four-cell pattern
      • Modeling ion density at boundary conditions
      • Comparing calculated densities against observed ExB drift patterns
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      Comparison of propagation predictions and measurements for midlatitude HF near-vertical incidence sky wave links at 5 MHz

      Marcus C. Walden

      Article first published online: 19 APR 2012 | DOI: 10.1029/2011RS004914

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      Key Points

      • HF NVIS measurements and VOACAP/ASAPS predictions compared over 23 months
      • RMS differences between measurements and predictions show cyclical pattern
      • VOACAP and ASAPS generally overpredict median signal level for these NVIS links
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      Excited spherical waves in unbounded cold magnetoplasma and applications in radio sounding

      Xueqin Huang and Bodo W. Reinisch

      Article first published online: 18 APR 2012 | DOI: 10.1029/2011RS004940

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      Key Points

      • Spherical wave excitation in plasma
      • Rigorous solution for far field
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      Assimilation of GIRO data into a real-time IRI

      I. A. Galkin, B. W. Reinisch, X. Huang and D. Bilitza

      Article first published online: 17 APR 2012 | DOI: 10.1029/2011RS004952

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      Key Points

      • Assimilating GIRO data in IRI allows accurate global ionospheric specification
      • Assimilative IRI adjusts coefficients of its empirical maps to match the data
      • Assimilation of low-latency GIRO data allows real-time IRI for space weather
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      Further determinations of strong scintillation effects on GNSS signals using the Hybrid Scintillation Propagation Model

      Nikolay N. Zernov, Vadim E. Gherm and Hal J. Strangeways

      Article first published online: 17 APR 2012 | DOI: 10.1029/2011RS004935

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      Key Points

      • Finding the variation of spectral indices with ionospheric scintillation level
      • Calculating cycle slip frequency as a function of amplitude scintillation index
      • Comparison of Hybrid Scintillation Propagation Model and equivalent phase screen
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      Typhoon Melor and ionospheric weather in the Asian sector: A case study

      D. D. Rice, J. J. Sojka, J. V. Eccles and R. W. Schunk

      Article first published online: 13 APR 2012 | DOI: 10.1029/2011RS004917

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      Key Points

      • Significant F-region anomaly was observed following Typhoon Melor landfall
      • No geophysical cause was obvious; solar min conditions existed
      • Anomaly was seen in ionosonde and GAIM model results
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      Imaging equatorial spread F irregularities with the São Luís coherent backscatter radar interferometer

      F. S. Rodrigues, A. O. Moraes and E. R. de Paula

      Article first published online: 30 MAR 2012 | DOI: 10.1029/2011RS004929

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      Key Points

      • New in-beam images of ESF structures in the Brazilian sector are presented
      • Scattering structures causing distinct types of ESF echoes are presented
      • Images are discussed in terms of ESF theories and independent observations
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      Improving the automatic inversion of digital Alouette/ISIS ionogram reflection traces into topside electron density profiles

      Robert F. Benson, Vladimir Truhlik, Xueqin Huang, Yongli Wang and Dieter Bilitza

      Article first published online: 30 MAR 2012 | DOI: 10.1029/2011RS004963

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      Key Points

      • Topside ionospheric solar cycle variations
      • Improved automatic inversion of ISIS topside ionogram traces is needed
      • Improve the quality of topside ISIS digital ionograms and their inversion
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      A new technique for spectral analysis of ionospheric TEC fluctuations observed with the Very Large Array VHF system: From QP echoes to MSTIDs

      J. F. Helmboldt, T. J. W. Lazio, H. T. Intema and K. F. Dymond

      Article first published online: 18 FEB 2012 | DOI: 10.1029/2011RS004787

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      Key Points

      • We have shown that the VLA can detect TEC fluctuations </=0.001 TECU
      • The VLA can observe medium (~100 km) and small (~few km) waves simultaneously
      • We have detected the direction dependent E-F coupling instability with the VLA

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