Some features of the equatorial anomaly revealed by ionospheric tomography

Andreeva, Elena; Franke, Steven; Yeh, K. C.; Куницын, В. Е.

doi:10.1029/1999gl003725

Cited by 60 publications

(55 citation statements)

References 7 publications

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“…In a previous paper, by way of typical examples, we reported the fully developed anomaly crest around noon for three typical days [Andreeva et al, 2000]. When fully developed, the anomaly core was found to tilt and align approximately along the geomagnetic field lines.…”

Section: Observationsmentioning

confidence: 99%

An investigation of motions of the equatorial anomaly crest

Yeh

Franke

Andreeva

et al. 2001

Geophysical Research Letters

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Abstract.Using more than 350 ionospheric images reconstructed tomographically, studies on the motion of the anomaly crest and its geophysical implications are carried out. On an average day, the crest forms at 09:00 LT and,,in the next two hours, moves poleward with a speed of about 1 ø per hour as it intensifies. This poleward motion is slowed as the crest reaches its highest latitude where it stays for several hours until early afternoon. Thereafter, the crest starts to weaken as it recedes with a speed of about 0.5 ø per hour equatorward. During 12:00-14:00 LT, the crest latitude is found to correlate with the fountain strength and the total number of electrons in a cross sectional plane at the observational longitude of the whole equatorial ionosphere.

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Section: Observationsmentioning

confidence: 99%

An investigation of motions of the equatorial anomaly crest

Yeh

Franke

Andreeva

et al. 2001

Geophysical Research Letters

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“…At equatorial and low latitudes ionospheric imaging technique has provided relevant information on the vertical structure of the electron density, its temporal variation and how it is lifted up and transported to other regions. Moreover, tomographic imaging has been applied at different longitude sectors and contributed signi cantly in the understanding of the ionospheric dynamics in the equatorial anomaly region, its seasonal and day-to-day variability and response under different geomagnetic conditions (Huang et al, 1997;Andreeva et al, 2000;Kunitsyn et al, 2003;Thampi et al, 2004). In the South-American sector the rst attempt to reconstruct the ionosphere by using tomographic inversion technique is due to Pakula et al (1994).…”

Section: Introductionmentioning

confidence: 99%

Tomographic imaging of the equatorial and low-latitude ionosphere over central-eastern Brazil

et al. 2011

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A four-dimensional time-dependent tomographic algorithm, named Multi Instrument Data Analysis System (MIDAS), is used to image the equatorial and low-latitude ionosphere over the central-eastern sides of the Brazilian territory. From differential phase data obtained by a chain of ground-based GPS receiver the total electron content (TEC) is estimated and then, together with a modeled ionosphere from International Reference Ionosphere (IRI) model, the electron density distribution is reconstructed and the parameters of the F 2 -peak layer are accessed from the images. This paper presents the rst study of ionospheric tomography using real dual-frequency data from the Brazilian Network for Continuous GPS Monitoring (RBMC). Ionospheric F 2 -peak electron density (N m F 2 ) accessed from the images are compared to concurrent measurements from three ionosondes installed across Brazil. One year of data during the solar maximum period from March/2001 to February/2002 is used to analyze the seasonal and hourly variation of the F 2 -layer peak density. The accuracy with which MIDAS images the electron density during geomagnetic quiet periods is investigated through its correlation and deviation with the ionosonde and IRI model data, respectively. The main aspects of the reconstruction results at the equatorial ionization anomaly (EIA) region over Brazil are highlighted and discussed.

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“…The maximum electron density in the southern region is observed in the image obtained at these times, which agrees with the daytime EIA behavior in the low-latitude region (Sastri, 1990). The EIA feature has been successfully imaged using tomographic methods (e.g., Andreeva et al, 2000;Franke et al, 2003;Materassi et al, 2003;Yizengaw et al, 2007). It must be mentioned here that what we are seeing is not the crest of the EIA (which would be further south of the imaged region), but the edge of the EIA-associated enhancement, because of which the southern region has more electron density than the northern region.…”

Section: Resultsmentioning

confidence: 81%

“…This technique has subsequently been widely used to study the large-scale structures of the ionosphere over high-, mid-, and low-latitude regions (e.g., see Raymund et al, 1993;Foster et al, 1994;Kunitsyn et al, 1995;Andreeva et al, 2000;Materassi et al, 2003;Thampi et al, 2007). The primary data used for the tomographic inversion is the line of sight TECs estimated along a number of ray paths from a chain of ground receivers aligned along the same longitude.…”

Section: Introductionmentioning

confidence: 99%

First results from the ionospheric tomography experiment using beacon TEC data obtained by means of a network along a longitude of 136°E over Japan

Thampi

Yamamoto

2010

Earth Planet Sp

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A chain of newly designed GNU (GNU is not UNIX) Radio Beacon Receivers (GRBR) has recently been established over Japan, primarily for tomographic imaging of the ionosphere over this region. Receivers installed at Shionomisaki (33.45 • N, 135.8• E), Shigaraki (34.8 • N, 136.1 • E), and Fukui (36 • N, 136• E) continuously track low earth orbiting satellites (LEOS), mainly OSCAR, Cosmos, and FORMOSAT-3/COSMIC, to obtain simultaneous total electron content (TEC) data from these three locations, which are then used for the tomographic reconstruction of ionospheric electron densities. This is the first GRBR network established for TEC observations, and the first beacon-based tomographic imaging in Japanese longitudes. The first tomographic images revealed the temporal evolution with all of the major features in the ionospheric electron density distribution over Japan. A comparison of the tomographically reconstructed electron densities with the f o F 2 data from Kokubunji (35 • N, 139• E) revealed that there was good agreement between the datasets. These first results show the potential of GRBR and its network for making continuous, unattended ionospheric TEC measurements and for tomographic imaging of the ionosphere.

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Some features of the equatorial anomaly revealed by ionospheric tomography

Cited by 60 publications

References 7 publications

An investigation of motions of the equatorial anomaly crest

An investigation of motions of the equatorial anomaly crest

Tomographic imaging of the equatorial and low-latitude ionosphere over central-eastern Brazil

First results from the ionospheric tomography experiment using beacon TEC data obtained by means of a network along a longitude of 136°E over Japan

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