On the deviations of measured electron density profiles from IRI predictions for low latitudes

Muralikrishna, P.; Vieira, L.P.; Abdu, M. A.; Paula, E. R. de

doi:10.1016/s0273-1177(03)00035-8

Cited by 4 publications

(2 citation statements)

References 12 publications

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“…These results consistently show that L o ≫ L b and that p < q . Rocket in situ electron density data [ Singh and Szuszczewicz , 1984; LaBelle et al , 1986; Hysell et al , 1994a, 1994b; Hysell , 2000; Muralikrishna et al , 2003] from altitudes above 280 km have shown double‐slope one‐dimensional power spectral densities with spectral indices ( p ‐1) between 1.9 and 2.5 for medium‐scale sizes and ( q ‐1) between 4.5 and 5.0 for small‐scale sizes. The typical value for the outer scale size is L o ≈ 12.5 km and the scale size of the spectral break point has been found in the vicinity of 60 m to 100 m. However, it should be remembered that in situ satellite measurements [ Basu et al , 1983; Singh and Szuszczewicz , 1984] yielded smaller values for the spectral indices ( p ‐1) and ( q ‐1), indicating shallower power spectral densities than those indicated above.…”

Section: Power Spectral Density Model Of the Irregularities: Estimatimentioning

confidence: 99%

Equatorial scintillation calculations based on coherent scatter radar and C/NOFS data

et al. 2011

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During its transit through a region of equatorial ionospheric irregularities, sensors on board the Communication/Navigation Outage Forecasting System (C/NOFS) satellite provide a one‐dimensional description of the medium, which can be extended to two dimensions if the structures are assumed to be elongated in the direction of the magnetic field lines. The C/NOFS scintillation calculation approach assumes that the medium is equivalent to a diffracting screen with random phase fluctuations that are proportional to the irregularities in the total electron content, specified through the product of the directly measured electron density by an estimated extent of the irregularity layer along the raypaths. Within the international collaborative effort anticipated by the C/NOFS Science Definition Team, the present work takes the vertical structure of the irregularities into more detailed consideration, which could lead to improved predictions of scintillation. Initially, it describes a flexible model for the power spectral density of the equatorial ionospheric irregularities, estimates its shape parameters from C/NOFS in situ data and uses the signal‐to‐noise ratio S/N measurements by the São Luís coherent scatter radar to estimate the mean square electron density fluctuation 〈ΔN2〉 within the corresponding sampled volume. Next, it presents an algorithm for the wave propagation through a three‐dimensional irregularity layer which considers the variations of 〈ΔN2〉 along the propagation paths according to observations by the radar. Data corresponding to several range‐time‐intensity maps from the radar is used to predict time variations of the scintillation index S4 at the L1 Global Positioning System (GPS) frequency (1575.42 MHz). The results from the scintillation calculations are compared with corresponding measurements by the colocated São Luís GPS scintillation monitor for an assessment of the prediction capability of the present formulation.

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Section: Power Spectral Density Model Of the Irregularities: Estimatimentioning

confidence: 99%

Equatorial scintillation calculations based on coherent scatter radar and C/NOFS data

et al. 2011

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“…As can be clearly seen, the morphology of the model results shows good agreement with the data. Examples of IRI‐2000 giving values of ion concentration much larger than experimental results at low latitudes are not unknown [ Souza et al , 2003; Muralikrishna et al , 2003]. Thus, while there are quantitative differences between the model results and the data, the differences are not entirely unexpected.…”

Section: Observationsmentioning

confidence: 99%

Effects of the 16 February 1980 solar eclipse on the composition of the low‐latitude ionosphere as seen by Atmosphere Explorer E

et al. 2008

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[1] Solar eclipses are known to locally disrupt the transport, production, and loss mechanisms in the ionosphere. Ion composition, ion temperature, and neutral temperature data from the Atmosphere Explorer E spacecraft are examined for the total solar eclipse of 16 February 1980. The spacecraft transited twice across the dayside face of the Earth during the course of the eclipse, allowing for examination of eclipse effects to be made over a wide longitude and local time range and for examination of posteclipse recovery of the ionosphere. One orbit from 14 February, occurring over a longitude and local time range similar to that of the first eclipse orbit, is used as control data. The eclipse had a significant effect on the concentrations of both O + and N + , which both dropped. The concentration of H + seems to show an eclipse effect, but the concentrations are too low to draw definite conclusions. Signatures of charge exchange between H + and neutral oxygen are seen in the data from the second eclipse orbit. The ion temperature drops by as much as 60 K. The neutral atmosphere shows no change in temperature during the course of the eclipse. The second eclipse orbit occurred closer to the path of the eclipse than did the first orbit, and the perturbations caused by the eclipse are greater in the second orbit. The control and second eclipse orbit data are compared to results from the International Reference Ionosphere 2000 model. The model results show good qualitative agreement with the ion concentration data.

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Rocket measurements of ionospheric electron density from Brazil in the last two decades

Muralikrishna

Abdu

2006

Advances in Space Research

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On the deviations of measured electron density profiles from IRI predictions for low latitudes

Cited by 4 publications

References 12 publications

Equatorial scintillation calculations based on coherent scatter radar and C/NOFS data

Equatorial scintillation calculations based on coherent scatter radar and C/NOFS data

Effects of the 16 February 1980 solar eclipse on the composition of the low‐latitude ionosphere as seen by Atmosphere Explorer E

Rocket measurements of ionospheric electron density from Brazil in the last two decades

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