Nighttime observations of 0.2‐ to 26‐keV electrons in the South Atlantic Anomaly made by Atmosphere Explorer C

Gledhill, J. A.; Hoffman, R. A.

doi:10.1029/ja086ia08p06739

Cited by 20 publications

(13 citation statements)

References 9 publications

(6 reference statements)

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“…Gledhill and Hoffman (1981) demonstrated a sharp peak of downward electron fluxes (0.2-26.1 keV) with the ranges of 2-3…”

Section: Discussionmentioning

confidence: 99%

“…From a four-year survey by the Atmospheric Explorer Satellite (AE-C) over the SAMA, Gledhill and Hoffman (1981) demonstrated downward electron fluxes with low-energy (0.2-26.1 keV) for 3 < K p < 6 in nighttime over the SAMA. Vampola and Gorney (1983) calculated energy deposition profiles from spectra of locally precipitating 36 keV to 317 keV electrons observed by the S3-2 satellite, and predicted that precipitating electrons into the SAMA could produce ionization more than one order of magnitude greater than that expected from scattered H Lymann α radiation at night.…”

Section: Introductionmentioning

confidence: 99%

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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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“…Gledhill and Hoffman (1981) demonstrated a sharp peak of downward electron fluxes (0.2-26.1 keV) with the ranges of 2-3…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2014

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“…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. It has been recognized for many years, since the report by Zmuda (1966), that there must be a continuous loss of electrons and ions from the magnetosphere into the atmosphere of SAMA region that could cause detectable level of ionization.…”

Section: Introductionmentioning

confidence: 96%

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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“…One of the key factors that could affect our determination of q•,A is the residual ion production rate ql• that we have considered for the totality of the eclipse that is also plotted in In conclusion, we would like to point out that the ion production rate due to precipitating electrons that appears to be a relatively significiant source in the lower ionosphere over the Brazilian region of the south Atlantic anomaly, even under "quiet" conditions, is unlikely to be represented by its height profile calculated by Sears et al [1981] in the height range 92-108 kin. It seems to be at least 2-3 orders of magnitude higher and probably lies between the values obtained from the electron energy spectrum measured by Gledhill and Hoffman [1981] and those deduced from ion density measurements by Abduet al [1979].…”

Section: Ion Pairs S-• Cm-3 In the Region Of 70 Km Decreasing Tomentioning

confidence: 74%

Comment on “Modeling the ion chemistry of the D region: A case study based upon the 1966 total solar eclipse” by Sears et al.

Abdu¹,

Sobral²,

Batista³

1984

J. Geophys. Res.

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In a recent paper, Sears et al. [1981] modeled the data set from the November 12, 1966, total solar eclipse campaign conducted in Casino, Brazil, by using a D region chemical code. One of the main conclusions from their analysis was that for adequate modeling of the D region electron density it was necessary to include in the chemical code an ionization source function arising from the precipitation of inner radiation belt energetic electrons into the lower ionosphere over the south 'Atlantic anomaly. They calculated ion production profile by using electron energy spectra based on the trapped flux in the energy range from 50 kev to 1. [1979] to infer possible ionization rate arising from the precipitation of energetic electrons into anomaly region. They carried out their calculations by comparing the ionospheric parameters measured during the full sun and total eclipse conditions and deducing a residual ion production rate profile, in the height region 92-108 km, that could not be attributed to the residual ionizing radiation coming from the eclipsed sun and to the scattered ultraviolet radiation. This residual ion production rate was attributed to precipitating energetic electrons in the south Atlantic anomaly. Precipitation of energetic neutral particles, resulting from the charge exchange chemistry of the outer radiation belt, is also believed to be an ionizing source over low latitude (see, for example, Mizera and Blake [1973], Tinsley [1976], and Lyons and Richmond [1978]). However, the ion production rate due to this source gets important only during a storm main phase, and the height of the maximum ionization occur usually between 125 and 180 km. Under magnetically moderate periods the maximum ion production rate from this source, as seen from the.calculations of Lyon and Richmond [1978], is less than 10 cm -3 s -•, which is significantly smaller than the ion production rate that we have inferred from our eclipse data analysis (to be presented below), which refers to a lower height region (90-110 km). The purpose of this comment is to point out that the ion pair production rate due to precipitating electrons considered by Sears et al. In Figure 1 we may note that near 95-100 km the ion production rate calculated by Sears et al. [1981] is less, by 3-4 orders of magnitude, than that deduced by Abdu et al. [1979] to represent the same ambient condition. This difference is so large that it raises the question as to which of these values should be representing closer the conditions that prevailed during the eclipse campaign. One of the key factors that could affect our determination of q•,A is the residual ion production rate ql• that we have considered for the totality of the eclipse that is also plotted in Figure 1 with the q!,n derived by us from rocket ion density data. However, the ion production rate obtained from the electron energy spectrum of Gledhill and Hoffman [1981] decreases with increasing altitude, whereas the height profile of q!,n is seen increasing with height, giving rise to large d...

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Nighttime observations of 0.2‐ to 26‐keV electrons in the South Atlantic Anomaly made by Atmosphere Explorer C

Cited by 20 publications

References 9 publications

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

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

Amplitude enhancement of events in the South Atlantic anomaly region

Comment on “Modeling the ion chemistry of the D region: A case study based upon the 1966 total solar eclipse” by Sears et al.

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