Enhanced E-layer ionization in the auroral zones observed by radio occultation measurements onboard CHAMP and Formosat-3/COSMIC

Mayer, C.; Jakowski, N.

doi:10.5194/angeo-27-1207-2009

Cited by 28 publications

(45 citation statements)

References 16 publications

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“…The first two criteria are basically similar to those adopted by Mayer and Jakowski (2009) and Wu et al (2013), whilst the last one has been applied to exclude possible "fake" events induced by random errors in observations. Compared to radio occultation measurements, the advantage of ground-based instrument observations is their capability to determine the duration of an ELDI event.…”

Section: Discussionmentioning

confidence: 99%

“…Based on their radio occultation measurements, Mayer and Jakowski (2009) claimed that ELDI is a regular phenomenon in the nighttime auroral zone, since ELDI signatures were found in up to 80 % of all measured profiles between 07:00 and 08:00 local time during geomagnetic quiet conditions. Wu et al (2013) came to a similar conclusion, showing that the occurrence rates of ELDI were up to 70 and 90 % for the Arctic and Antarctic, respectively.…”

Section: Is Eldi a Regular Phenomenon In A Dark Polar Region?mentioning

confidence: 99%

“…Farley et al, 1970). Recently, Mayer and Jakowski (2009) found that ionospheric profiles in the polar region sometimes have their maximum density at E layer altitude, which was identified as another class of anomaly: E layer dominant ionosphere (ELDI). E s formation or other types of ionization were not distinguished in the concept of ELDI.…”

Section: Introductionmentioning

confidence: 99%

“…The authors claimed that these observed ELDIs were mainly caused by energetic particle precipitation in the auroral zone. Based on RO measurements, Wu et al (2013) found that ELDI occurrence was up to 90 % in the nighttime auroral zone, whilst Mayer and Jakowski (2009) claimed that ELDI was a regular phenomenon in darkness.…”

Section: Introductionmentioning

confidence: 99%

“…Their global distribution in the Northern Hemisphere as well as their spatial distribution and solar-cycle variability were investigated by Mayer and Jakowski (2009) using electron density profiles retrieved from GPS radio occultation (RO) measurements from the COSMIC and CHAMP satellites. It was found that ELDI occurrence was distributed symmetrically around the magnetic pole and that the shape of the spatial distribution could be approximated by an ellipse.…”

Section: Introductionmentioning

confidence: 99%

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E layer dominated ionosphere observed by EISCAT/ESR radars during solar minimum

Cai

Shen

et al. 2014

Ann. Geophys.

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Abstract. According to the study by Mayer and Jakowski (2009), periods of E layer dominated ionosphere (ELDI) are defined as being characterized by vertical electron density profiles having a maximum density at E layer altitudes. In this paper, characteristics of ELDI intervals have been investigated, focusing on their temporal variations, using field-aligned measurements from the EIS-CAT and ESR radars during the interval 2009-2011. ELDI events were identified using simple but reasonable criteria, in which a minimal duration was required to exclude possible "fake" events induced by random errors in measurements. It was found that ELDIs were observed more often in winter and earlier spring than other seasons, especially in the auroral zone. The occurrence of ELDI intervals peaks around geomagnetic midnight at auroral latitudes, while it reaches a maximum around geomagnetic local noon at the latitude of the ESR. Our results imply that ELDI intervals appear to be a sporadic rather than a regular phenomenon, in disagreement with previous results inferred from radio occultation measurements. The discrepancy between the typical durations of ELDI events observed by the two radars is remarkable, being 30 min on average at Tromsø but about a half of this at Svalbard. During intervals of ELDI, the mean thicknesses of the E layer are quite close at the two sites, as are the values of H m E and the ratio of N m E / N m F 2 . Case studies confirm that either extra E layer ionization or F layer density depletion alone could lead to the presence of ELDIs. Based on a careful check on ELDI intervals of various types, however, we suggest that both of them play a critical role in ELDI formation.

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Section: Discussionmentioning

confidence: 99%

Section: Is Eldi a Regular Phenomenon In A Dark Polar Region?mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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E layer dominated ionosphere observed by EISCAT/ESR radars during solar minimum

Cai

Shen

et al. 2014

Ann. Geophys.

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Empirical orthogonal function analysis and modeling of the ionospheric peak height during the years 2002–2011

et al. 2014

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The ionospheric peak electron density height (h m ) is one of the most important ionospheric parameters characterizing high-frequency radio wave propagation conditions. In this paper, a global h m model based on the empirical orthogonal function (EOF) analysis method is constructed by using Global Navigation Satellite Systems ionospheric radio occultation measurements from COSMIC and CHAMP as well as global ionosonde data during the years 2002-2011. The variability of h m can be well represented by the several EOF base functions E k and the corresponding coefficients P k . The rapid convergence of EOF decomposition makes it possible to use only the first four EOFs components, which express 99.133% of total variance in this study, to construct the empirical model. The variations of h m with respect to the magnetic latitude, local time, season, and solar cycle have been studied, and the EOF-based h m model has been validated through comparisons with the International Reference Ionosphere (IRI) model and other observation. The evaluations indicate that the EOF and IRI model give better h m F 2 at middle and high latitudes than those at low latitudes. Since the limited data were used in the EOF model during high solar activity years, its accuracy degrades to some extent. During nighttime of spring, summer, and winter in the auroral zone, the h m derived from the EOF model may range from 90 to 150 km because of the reduction of h m , which is due to particle precipitation, whereas the IRI model does not include this reduction. During the periods of low solar activity, the F 2 peak heights (h m F 2 ) from the EOF model are in good agreement with the observed data, while the IRI model tends to overestimate the h m F 2 in the middle and high latitudes.

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Localized thermosphere ionization events during the high‐speed stream interval of 29 April to 5 May 2011

et al. 2015

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We analyze localized ionospheric-thermospheric (IT) events in response to external driving by a high-speed stream (HSS) during the ascending phase of the Solar Cycle 24. The HSS event occurred from~29 April to 5 May, 2011. The HSS itself (and not the associated corotating interaction region) caused a moderate geomagnetic storm with peak SYM-H = À55 nT and prolonged auroral activity. We analyze TIMED (Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics)/SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) measurements of nitric oxide (NO) cooling emission during the interval as a measure of thermospheric response to auroral heating. We identify several local cooling emission (LCE) events in high to subauroral latitudes. Individual cooling emission profiles during these LCE events are enhanced at ionospheric E layer altitudes. For the first time, we present electron density profiles in the vicinity of the LCE events using collocated COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) radio occultation (RO) measurements. Measurements at local nighttime show the formation of an enhanced E layer (about 2.5 times increase over the undisturbed value) at ≥100 km altitude. Daytime electron density profiles show relatively smaller enhancements in the E layer. We suggest that the IT response is due to additional ionization caused by medium energy electron (>10 keV) precipitation into the subauroral to high-latitude atmosphere associated with geomagnetic activity during the HSS event.

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Enhanced E-layer ionization in the auroral zones observed by radio occultation measurements onboard CHAMP and Formosat-3/COSMIC

Cited by 28 publications

References 16 publications

E layer dominated ionosphere observed by EISCAT/ESR radars during solar minimum

E layer dominated ionosphere observed by EISCAT/ESR radars during solar minimum

Empirical orthogonal function analysis and modeling of the ionospheric peak height during the years 2002–2011

Localized thermosphere ionization events during the high‐speed stream interval of 29 April to 5 May 2011

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