AKR‐like emissions observed at low altitude by the DEMETER satellite

Parrot, M.; Berthelier, Jean‐Jacques

doi:10.1029/2012ja017937

Cited by 14 publications

(20 citation statements)

References 34 publications

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“…The orbit was nearly Sun‐synchronous with an inclination of about 98°. It was launched to an orbital altitude of 710 km, and subsequently lowered to 650 km, with a descending node at ~10:30 LT during the daytime and an ascending node at ~22:30 LT at night [ Parrot and Berthelier , ]. The orbital period was around 100 min, and the satellite observations spanned the regions between −65° and +65° of invariant latitudes nearly continuously.…”

Section: Data Descriptionmentioning

confidence: 99%

“…These results show the reliability and the capability of investigating the relative variation of Ne and Te with DEMETER measurements. Furthermore, to prevent the effect of possible contamination of the ISL data, we set up thresholds for a maximum Te of 7000 K, and a minimum Te of 1000 K, and only considered the relative variation of Ne and Te, as has been done in earlier studies using the same data set [ Wang et al , ; Piddyachiy et al , ; Parrot and Berthelier , ; Kakinami et al , ; Slominska and Rothkaehl , ; Slominska et al , ].…”

Section: Data Descriptionmentioning

confidence: 99%

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The correlation between electron temperature and density in the topside ionosphere during 2006–2009

Wang

Burns

et al. 2015

JGR Space Physics

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Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions satellite data have been used to investigate the global relationship between electron density (Ne) and electron temperature (Te) in the topside ionosphere (~680 km) from 2006 to 2009. Te and Ne were negatively correlated in most of the low and middle latitude regions at ~10:30 solar local time (LT). In these regions, photoelectron heating of the electrons was balanced by cooling through collisions with the ions. The negative correlation became weaker at midlatitudes, due to the increasing influence of heat conduction. The correlation was negative in most seasons during the daytime except at high latitudes in the northern winter, where a positive correlation occurred. There were wave‐like longitudinal structures in Ne and Te around the geomagnetic equator, but they had different patterns in the day and the night. However, no obvious longitudinal variations in the correlation were associated with these structures. A positive correlation occurred near the magnetic equator at ~22:30 LT, which depended on thermal equilibrium between the electrons, ions, and neutrals. A negative correlation occurred at midlatitudes. Around the September equinox, at night around the magnetic equator, the positive correlation had a wider latitudinal range. At midlatitudes, a negative correlation occurred in smaller areas than it did around the March equinox. Around the December solstice the direct nighttime coupling between Ne and Te was weaker than it was around the June solstice. The negative correlation depends on the collisions between the electrons and the ions and the heating source.

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Section: Data Descriptionmentioning

confidence: 99%

Section: Data Descriptionmentioning

confidence: 99%

The correlation between electron temperature and density in the topside ionosphere during 2006–2009

Wang

Burns

et al. 2015

JGR Space Physics

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“…DEMETER was a French microsatellite launched in June 2004 by Centre National d'Etudes Spatiales (CNES) and ended its scientific mission in December 2010. Its measurements were widely used to explore the characteristics of the topside ionosphere [Wang et al, 2010;Kakinami et al, 2011;Piddyachiy et al, 2011;Parrot and Berthelier, 2012;Slominska et al, 2014]. It was launched to a circular orbital altitude of 710 km, and then lowered to 680 km in December 2005, with a descending node at~10:30 LT during the daytime and an ascending node at~22:30 LT in the night sector.…”

Section: Data Descriptionmentioning

confidence: 99%

“…Although DEMETER Ne at 670 km had similar longitudinal patterns to COSMIC Ne around 670 km, they have different absolute values. The relative variations of Ne measurements from DEMETER have been validated in many studies [e.g., Wang et al, 2010;Piddyachiy et al, 2011;Parrot and Berthelier, 2012;Kakinami et al, 2013;Slominska et al, 2014;Su et al, 2015], but the absolute values are not usable for comparison with the presumably more accurate COSMIC products.…”

Section: Data Descriptionmentioning

confidence: 99%

Statistical behavior of the longitudinal variations of daytime electron density in the topside ionosphere at middle latitudes

Wang

Burns

et al. 2016

JGR Space Physics

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Electron density in the topside ionosphere has significant variations with latitude, longitude, altitude, local time, season, and solar cycle. This paper focuses on the global and seasonal features of longitudinal structures of daytime topside electron density (Ne) at middle latitudes and their possible causes. We used in situ Ne measured by DEMETER and F2 layer peak height (hmF2) and peak density (NmF2) from COSMIC. The longitudinal variations of the daytime topside Ne show a wave number 2‐type structure in the Northern Hemisphere, whereas those in the Southern Hemisphere are dominated by a wave number 1 structure and are much larger than those in the Northern Hemisphere. The patterns around December solstice (DS) in the Northern Hemisphere (winter) are different from other seasons, whereas the patterns in the Southern Hemisphere are similar in each season. Around March equinox (ME), June solstice (JS), and September equinox (SE) in the Northern Hemisphere and around ME, SE, and DS in the Southern Hemisphere, the longitudinal variations of topside Ne have similar patterns to hmF2. Around JS in the Southern Hemisphere (winter), the topside Ne has similar patterns to NmF2 and hmF2 does not change much with longitude. Thus, the topside variations may be explained intuitively in terms of hmF2 and NmF2. This approach works reasonably well in most of the situations except in the northern winter in the topside not too far from the F2 peak. In this sense, understanding variations in hmF2 and NmF2 becomes an important and relevant subject for this topside ionospheric study.

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“…Auroral medium frequency burst is a broadband (≥ 1 MHz), impulsive emission that occurs roughly from 1.4 to 4.5 MHz. Auroral kilometric radiation consists of structured emissions in the frequency range 200–600 kHz originating at ∼ 5000 km and has been reported at ground level [ LaBelle and Anderson , ] and low Earth orbit [ Oya et al , ; Parrot and Berthelier , ]. Although X and O mode AKR are primarily restricted to high altitudes, recent evidence suggests that coupling may occur to modes that can be detected at ground level.…”

Section: Introductionmentioning

confidence: 99%

A new natural radio emission observed at South Pole Station

2014

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[1] Continuous waveform data taken at South Pole Station in 2011-2012 within a few hours of magnetic midnight revealed 12 observations of a new natural radio emission. The waves had frequencies ranging from 1320 to 2160 kHz, bandwidths ranging from 94 to 272 kHz, and durations ranging from 16 to 355 s. Spectral analysis of the waveform data revealed that the emission has a complex combination of at least three kinds of fine structures: broad, banded structures; short-lived, narrowband structures; and striated features that occur predominantly near the lower frequency boundary of the emission. For model auroral electron distributions, positive growth rates for the cyclotron maser instability occurred near the electron cyclotron frequency (f ce ), which is inconsistent with the observed wave frequencies. On the other hand, Langmuir wave growth could be excited at frequencies consistent with observations. Spatial Langmuir wave growth is more favorable for electron beam energies of hundreds of eV than for those at higher energies.

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AKR‐like emissions observed at low altitude by the DEMETER satellite

Cited by 14 publications

References 34 publications

The correlation between electron temperature and density in the topside ionosphere during 2006–2009

The correlation between electron temperature and density in the topside ionosphere during 2006–2009

Statistical behavior of the longitudinal variations of daytime electron density in the topside ionosphere at middle latitudes

A new natural radio emission observed at South Pole Station

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