Sporadic E-layer phenomena in the Brazilian geomagnetic anomaly: evidence for a regular particle ionization source

Abdu, M. A.; Batista, I. S.

doi:10.1016/0021-9169(77)90059-9

Cited by 48 publications

(32 citation statements)

References 30 publications

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“…This tells us that maximum electron precipitation is concentrated around the position of F minimum and falls off away from it. This is in agreement with the finding from ionosonde results by Abdu and Batista (1977) that particle precipitation is a regular source of ionization in the E-region over SAMA even under quiet conditions. Abel and Thorne (1999) also have shown from numerical simulation study that precipitating electrons should be a prominent ionization source near the SAMA but relatively insignificant elsewhere.…”

Section: Article In Presssupporting

confidence: 94%

“…Abdu et al (1981) have observed significant lowering of VLF reflection height in the SAMA region during magnetic storms which was consistent with enhanced ionization of the D-region due to particle precipitation. Abdu and Batista (1977), and Batista and Abdu (1977) have reported sporadic E-layer enhancements that indicated energetic particle precipitation as a regular night time ionization source in the SAMA region. Also Gledhill and Hoffman (1981) have reported 0.2 to 26 keV electron flux precipitating in the SAMA region capable of producing detectable effects in the D-and E-regions of the ionosphere during night time.…”

Section: Introductionmentioning

confidence: 95%

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Amplitude enhancement of events in the South Atlantic anomaly region

Trivedi¹,

Abdu

Pathan

et al. 2005

Journal of Atmospheric and Solar-Terrestrial Physics

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Section: Article In Presssupporting

confidence: 94%

Section: Introductionmentioning

confidence: 95%

Amplitude enhancement of events in the South Atlantic anomaly region

Trivedi¹,

Abdu

Pathan

et al. 2005

Journal of Atmospheric and Solar-Terrestrial Physics

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“…Phase advances of the 13.6 kHz Argentina VLF signals were linearly proportional to a logarithmic function of the intensity of the geomagnetic storm, given by the peak D st (Pinto et al, 1990). Abdu and Batista (1977) revealed from the ionosonde measurements that sporadic E-layer enhancements over Cachoeira Paulista…”

Section: Introductionmentioning

confidence: 98%

Unusual ionospheric absorption characterizing energetic electron precipitation into the South Atlantic Magnetic Anomaly

et al. 2014

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An imaging riometer (IRIS) was installed newly in the southern area of Brazil in order to investigate precipitation of energetic electrons into the South Atlantic Magnetic Anomaly (SAMA). An unusual ionospheric absorption event was observed in the nighttime (∼20 h LT) near the maximum depression (D st ∼ −164 nT) and the following positive excursion during the strong geomagnetic storm on September 22-23, 1999. The unusual absorption that has short time-duration of 30-40 min shows two characteristic features: One feature is a sheet structure of the absorption appearing at the high-latitude part of the IRIS field-of-view, showing an eastward drift from the western to the eastern parts and subsequent retreat to the western part. Another feature is a meridionally elongated structure with a narrow longitudinal width (100-150 km) appearing from the zenith to the low-latitude part of the IRIS fieldof-view, enhanced simultaneously with the sheet absorption, and is subsequently changed to a localized structure. These features likely characterize precipitation of energetic electrons into the SAMA ionosphere, associated with substorm occurrences during the strong geomagnetic storm. From the eastward drift (∼250 m/s) of the sheet absorption, precipitating electrons are estimated to be ∼20 keV energies, assuming plasmaspheric electric fields of 1.8 mV/m. However, no ionospheric effect due to the precipitating electrons was definitely detected by the ionosonde measurements at Cachoeira Paulista, separated eastward by about 1000 km from the IRIS station.

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“…It is well known that the SSA region has the lowest geomagnetic field intensity around the globe and several investigators (e.g., Pinto and Gonzalez, 1989;Pinto et al, 1992) have observed charged particle precipitation in this region. Also, Abdu and Batista (1977) pointed out that during day-time, the solar EUV flux does not seem to be sufficient to produce the observed fbEs values at Cachoeira Paulista and an additional source must therefore be considered. Precipitating electron flux in the SAA region is the most probable candidate for the additional ionization source.…”

Section: Resultsmentioning

confidence: 97%