Bibliography

Properties of AKR-Like Emissions Recorded by the Low Altitude Satellite DEMETER During 6.5 Years

Normally, auroral kilometric radiation (AKR) which is emitted in the auroral zones escapes from the Earth. But since a few decades very similar radiations are observed by ground-based receivers and by satellites at altitudes below the AKR generation area. They are called leaked AKR or AKR-like emissions because it is expected that there are linked to AKR. This paper deals with observations of such AKR-like emissions observed in the auroral zones (in the North and in the South) by the low-altitude satellite DEMETER. In total, 2,526 events have been recorded during 6.5 years. These events are not very rare as they occur at least 2\% of the time. Although this data set has a severe flaw due to a latitudinal constraint, it was possible to draw interesting properties of these emissions. In fact they are very similar to usual AKR observed at much higher altitudes during auroral activities (the same frequency range, magnetic local time (MLT) sector, and invariant latitude). The main difference concerns a strong asymmetry between the Northern and the Southern hemispheres: (a) the number of AKR-like emissions in the Northern hemisphere is 32\% larger than in the Southern hemisphere but this percentage decreases when the auroral activity increases, and (b) there is an important seasonal effect because the number of events decreases during the winter season both in the North and in the South.

Parrot, M.; Němec, F.; Santolík, O.;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2022     DOI: 10.1029/2022JA030495

AKR; Ionosphere; magnetic activity

Seasonal trends of nighttime plasma density enhancements in the topside ionosphere

In situ registrations of electron density from the Langmuir probe on board Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions satellite are used to study spatial and temporal evolution of nighttime plasma density enhancements (NPDEs). The study introduces the normalized density difference index I_NDD in order to provide global estimates of the phenomenon. In the validation test, in situ data are compared with synthetic data set generated with the International Reference Ionosphere model. We find signatures of two most common examples of NPDEs, the Weddell Sea Anomaly (WSA) and midlatitude nighttime summer anomaly (MSNA) with proposed index, in the topside ionosphere. The study provides evidence that the occurrence of the WSA and MSNA is not limited to the local summer conditions. Analyzed annual trend of I_NDD and in particular spatial pattern obtained during equinoxes suggest that mechanisms governing the behavior of the equatorial ionosphere cannot be neglected in the explanation of the development of NPDEs.

Slominska, Ewa; Blecki, Jan; Lebreton, Jean-Pierre; Parrot, Michel; Slominski, Jan;

Published by: Journal of Geophysical Research: Space Physics      Published on: 08/2014

YEAR: 2014     DOI: 10.1002/2014JA020181

Electron density; Ionosphere; Langmuir probe; Weddell Sea Anomaly

Statistical analysis of an ionospheric parameter as a base for earthquake prediction

This paper is related to the use of ionospheric density variations to tentatively predict earthquakes. The results of this statistical analysis are presented as a function of various parameters. The ion density was recorded by the low-altitude satellite DEMETER during more than 6 years, and a search for anomalies was automatically conducted with the complete data set. In a second time, a software checked if each anomaly could correspond to an earthquake. The search was conducted at less than 1500 km from the anomaly positions, and until 15 days after the anomaly time. The earthquakes have been classified depending on their magnitude, depth, and position (below the sea or inland). This attempt to predict earthquakes of course generates a lot of false alarms and wrong detections. Nevertheless, it is shown that the number of good detections increases with the magnitude of the earthquakes. In average the number of perturbations is higher the day of the earthquake, and then smoothly decreases for the days before. Earthquakes below the sea are better detected. There are seismic areas close to the South Atlantic Magnetic Anomaly and at high latitudes where the number of natural perturbations is too important to expect a high number of good detections. Finally, when there are several perturbations corresponding to a single earthquake, it is possible to combine their positions to have a better estimation of the location of the future epicenter. However, uncertainties about the time and the magnitude are large.

Li, Mei; Parrot, Michel;

Published by: Journal of Geophysical Research: Space Physics      Published on: 06/2013

YEAR: 2013     DOI: 10.1002/jgra.50313

earthquake; Ionosphere

WN4 effect on longitudinal distribution of different ion species in the topside ionosphere at low latitudes by means of DEMETER, DMSP-F13 and DMSP-F15 data

Plasma probe data from DMSP-F13, DMSP-F15 and DEMETER satellites were used to examine longitudinal structures in the topside equatorial ionosphere during fall equinox conditions of 2004 year. Since the launch of DEMETER satellite on 29 June 2004, all these satellites operate close together in the topside ionosphere. Here, data taken from\ Special Sensor-Ion, Electron and Scintillations\ (SSIES) instruments on board DMSP-F13, F15 and\ Instrument Analyser de Plasma\ (IAP) on DEMETER, are used. Longitudinal variations in the major ions at two altitudes (~730 km for DEMETER and ~840 km for DMSP) are studied to further describe the recently observed "wavenumber-four" (WN4) structures in the equatorial topside ionosphere. Different ion species H⁺, He⁺\ and O⁺\ have a rather complex longitudinal behavior. It is shown that WN4 is almost a regular feature in O⁺\ the density distribution over all local times covered by these satellites. In the evening local time sector, H⁺\ ions follow the O⁺\ behavior within WN4 structures up to the pre-midnight hours. Near sunrise H⁺\ and later in the daytime, He⁺longitudinal variations are out of phase with respect to O⁺\ ions and effectively reduce the effect of WN4 on total ion density distribution at altitudes 730\textendash840 km. It is shown that both a WN4\ E\texttimesB\ drift driver and local F-region winds must be considered to explain the observed ion composition variations.

Bankov, L.; Heelis, R.; Parrot, M.; Berthelier, J.-J.; Marinov, P.; Vassileva, A.;

Published by: Annales Geophysicae      Published on: Jan-01-2009

YEAR: 2009     DOI: 10.5194/angeo-27-2893-2009

Decrease of intensity of ELF/VLF waves observed in the upper ionosphere close to earthquakes: A statistical study

N\vemec, F; ik, Santol\; Parrot, Michel;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2009     DOI: