Size, shape, orientation, speed, and duration of GPS equatorial anomaly scintillations

[1] GPS L1 C/A signal scintillation data were collected at the equatorial anomaly over a period of three months using five receivers spaced on magnetic east-west and north-south axes to examine the speed, orientation, shape, width, and duration of GPS scintillation fade patterns. The nighttime speeds were primarily eastward in the range of 100–200 m/s with a significant spread to both larger values and negative (westward) values as expected, given the known behavior of ionospheric drifts and GPS signal path movement. The characteristic velocity was found to be small so that the true velocity was equal to the apparent velocity to a very good approximation. The orientation of the scintillation fade patterns was organized by a simple projection model of the magnetic field along the GPS signal path onto the horizontal plane when the signal paths were aligned no closer than 60° from the magnetic field. The shape of the scintillation fade pattern was greatly elongated in the magnetic north-south direction, and no change could be detected over a distance of 1 km. The east-west widths of the scintillation fade patterns were variable, but after normalizing to the elevation angle, accounting for the fade orientation, and eliminating signal paths within 60° of the magnetic field, an organized scale length of about 450 m was determined. The duration of the scintillation fade patterns was examined using the optimal cross-correlation amplitude as a measure of change. For a 5 s duration, 49% of the optimal cross-correlation amplitudes exceed a value of 0.8.

[1]  John A. Klobuchar,et al.  Ionospheric Scintillation Effects in the Equatorial and Auroral Regions , 2000 .

[2]  B. Rickett.  Radio Sources and Scintillation , 2001 .

[3]  S. Basu,et al.  Gigahertz scintillations and spaced receiver drift measurements during Project Condor Equatorial F Region Rocket Campaign in Peru , 1986 .

[4]  J. Hoffman,et al.  Plasma bubbles and irregularities in the equatorial ionosphere , 1977 .

[5]  L. Kramer,et al.  Global Scale Observations of Ionospheric Instabilities from GPS in Low Earth Orbit , 2001 .

[6]  G. J. Phillips,et al.  The Analysis of Observations on Spaced Receivers of the Fading of Radio Signals , 1950 .

[7]  Paul M. Kintner,et al.  Latitudinal variations of scintillation activity and zonal plasma drifts in South America , 2002 .

[8]  K. Yeh,et al.  A theoretical study of the ionospheric scintillation behavior caused by multiple scattering , 1975 .

[9]  S. Musman,et al.  Imaging spread‐F structures using GPS observations at Alcântara, Brazil , 1997 .

[10]  K. Iyer,et al.  Interplanetary and terrestrial observations of an Earth‐directed coronal mass ejection , 2001 .

[11]  Jeffrey Baumgardner,et al.  Airglow characteristics of equatorial plasma depletions , 1982 .

[12]  M. Abdu,et al.  Solar activity effects on equatorial plasma bubble zonal velocity and its latitude gradient as measured by airglow scanning photometers , 1991 .

[13]  M. Mendillo,et al.  Imaging science contributions to equatorial aeronomy: Initial results from the MISETA program , 1997 .

[14]  J. Klobuchar,et al.  VHF amplitude scintillations and associated electron content depletions as observed at Arequipa, Peru , 1983 .

[15]  S. Basu,et al.  Preliminary comparisons of VHF radar maps of F-region irregularities with scintillations in the equatorial region , 1977 .

[16]  Paul M. Kintner,et al.  Global Positioning System measurements of the ionospheric zonal apparent velocity at Cachoeira Paulista in Brazil , 2000 .

[17]  Cesar E. Valladares,et al.  Scintillations, plasma drifts, and neutral winds in the equatorial ionosphere after sunset , 1996 .

[18]  M. Tokumaru,et al.  Three‐dimensional propagation of interplanetary disturbances detected with radio scintillation measurements at 327 MHz , 2000 .

[19]  William R. Coley,et al.  Low‐latitude zonal and vertical ion drifts seen by DE 2 , 1989 .

[20]  Ronald F. Woodman,et al.  Equatorial spread F: Implications of VHF radar observations , 1970 .

[21]  James A. Secan,et al.  Impacts of Ionospheric Fading on GPS Navigation Integrity , 1994 .

[22]  Paul M. Kintner,et al.  Development and use of a GPS ionospheric scintillation monitor , 2001, IEEE Trans. Geosci. Remote. Sens..

[23]  K. Yeh,et al.  Radio wave scintillations in the ionosphere , 1982 .

[24]  S. Musman,et al.  Simultaneous Global Positioning System and radar observations of equatorial spread F at Kwajalein , 1996 .

[25]  Keith M. Groves,et al.  Dynamics of equatorial F region irregularities from spaced receiver scintillation observations , 2001 .

[26]  J. Austen,et al.  Gigahertz scintillations associated with equatorial patches , 1983 .

[27]  Leonard Kramer,et al.  Scintillation Effects On Space Shuttle GPS Data , 2001 .

[28]  S. Franke,et al.  A new analysis technique for estimating zonal irregularity drifts and variability in the equatorial F region using spaced receiver scintillation data , 1987 .

[29]  Jules Aarons,et al.  The dynamics of equatorial irregularity patch formation, motion, and decay , 1980 .

[30]  E. R. Paula,et al.  Effects of the vertical plasma drift velocity on the generation and evolution of equatorial spread F , 1999 .

[31]  Jules Aarons,et al.  The longitudinal morphology of equatorial F-layer irregularities relevant to their occurrence , 1993 .

[32]  R. Woodman.  East-west ionospheric drifts at the magnetic equator. , 1972 .

[33]  R. Yantosca,et al.  GPS phase fluctuations in the equatorial region during the MISETA 1994 campaign , 1996 .

[34]  J. Owen,et al.  The time structure of transionospheric radio wave scintillation , 1980 .

[35]  S. Franke,et al.  Analysis and interpretation of spaced receiver scintillation data recorded at an equatorial station , 1988 .

[36]  Jules Aarons,et al.  Coordinated study of equatorial scintillation and in situ and radar observations of nighttime F region irregularities , 1980 .

[37]  C. J. Zamlutti,et al.  Responses of the low-latitude ionosphere to very intense geomagnetic storms , 2001 .

[38]  Paul M. Kintner,et al.  Fading timescales associated with GPS signals and potential consequences , 2001 .

[39]  Paul M. Kintner,et al.  Simultaneous Global Positioning System observations of equatorial scintillations and total electron content fluctuations , 1999 .

[40]  S. Basu,et al.  The multi‐instrumented studies of equatorial thermosphere aeronomy scintillation system: Climatology of zonal drifts , 1996 .

[41]  J. Aarons,et al.  50 years of radio-scintillation observations , 1997 .

[42]  E. R. Paula,et al.  East‐west plasma bubble irregularity motion determined from spaced VHF polarimeters: Implications on velocity shear in the zonal F region bulk plasma motion , 1985 .

[43]  Warner L. Ecklund,et al.  Evidence for a Rayleigh-Taylor type instability and upwelling of depleted density regions during equatorial spread F , 1976 .

[44]  S. Basu.  Equatorial scintillations—a review , 1981 .

[45]  Xiaoqing Pi,et al.  Monitoring of global ionospheric irregularities using the Worldwide GPS Network , 1997 .

[46]  I. Batista,et al.  Equatorial spread-F occurrence statistics in the American longitudes: Diurnal, seasonal and solar cycle variations , 1998 .

[47]  J. Meriwether,et al.  Zonal irregularity drifts and neutral winds measured near the magnetic equator in Peru , 1991 .

[48]  C. J. Zamlutti,et al.  Equatorial plasma bubble zonal velocity height gradient from spaced VHF polarimeter and scanning 630 nm measurements , 1987 .

[49]  Jules Aarons,et al.  GPS phase fluctuations in the equatorial region during sunspot minimum , 1997 .

[50]  Ronald F. Woodman,et al.  F region east‐west drifts at Jicamarca , 1981 .

[51]  E. Salpeter.  Interplanetary Scintillations. I. Theory , 1966 .

[52]  J. Aarons,et al.  Global positioning system phase fluctuations at auroral latitudes , 1997 .

[53]  J. Aarons,et al.  Global morphology of ionospheric scintillations , 1971, Proceedings of the IEEE.

[54]  D. Hysell.  Imaging coherent backscatter radar studies of equatorial spread F , 1999 .

[55]  B. Tinsley.  Images of transequatorial F region bubbles in 630- and 777-nm emissions compared with satellite , 1997 .

[56]  I. J. Kantor,et al.  Plasma bubble irregularity occurrence and zonal velocities under quiet and disturbed conditions, from polarimeter observations , 1984 .

[57]  Ronald F. Woodman,et al.  Radar observations of F region equatorial irregularities , 1976 .

[58]  L. H. Brace,et al.  Geomagnetic equatorial anomaly in zonal plasma flow , 1987 .