A case study of electron precipitation fluxes due to plasmaspheric hiss

We find that during a large geomagnetic storm in October 2011 the trapped fluxes of >30, >100, and >300 keV outer radiation belt electrons were enhanced at L=3-4 during the storm main phase. A gradual decay of the trapped fluxes was observed over the following 5–7 days, even though no significant precipitation fluxes could be observed in the Polar Orbiting Environmental Satellite (POES) electron precipitation detectors. We use the Antarctic-Arctic Radiation-belt (Dynamic) Deposition - VLF Atmospheric Research Konsortium (AARDDVARK) receiver network to investigate the characteristics of the electron precipitation throughout the storm period. Weak electron precipitation was observed on the dayside for 5–7 days, consistent with being driven by plasmaspheric hiss. Using a previously published plasmaspheric hiss-induced electron energy e-folding spectrum of E0=365 keV, the observed radiowave perturbation levels at L=3-4 were found to be caused by >30 keV electron precipitation with flux ~100 el. cm−2 s−1 sr−1. The low levels of precipitation explain the lack of response of the POES telescopes to the flux, because of the effect of the POES lower sensitivity limit and ability to measure weak diffusion-driven precipitation. The detection of dayside, inner plasmasphere electron precipitation during the recovery phase of the storm is consistent with plasmaspheric hiss wave-particle interactions, and shows that the waves can be a significant influence on the evolution of the outer radiation belt trapped flux that resides inside the plasmapause

Experimental Runaway Electron Current Estimation in COMPASS Tokamak

Runaway electrons present a potential threat to the safe operation of future nuclear fusion large facilities based on the tokamak principle (e.g., ITER). The article presents an implementation of runaway electron current estimations at COMPASS tokamak. The method uses a theoretical method developed by Fujita et al., with the difference in using experimental measurements from EFIT and Thomson scattering. The procedure was explained on the COMPASS discharge number 7298, which has a significant runaway electron population. Here, it was found that at least 4 kA of the plasma current is driven by the runaway electrons. Next, the method aws used on the set of plasma discharges with the variable electron plasma density. The difference in the plasma current was explained by runaway electrons, and their current was estimated using the aforementioned method. The experimental results are compared with the theory and simulation. The comparison presented some disagreements, showing the possible direction for the code development. Additional application on runaway electron energy limit is also addressed

Average properties of wave emissions below 4 kHz in the inner magnetosphere based on the data of the STAFF-SA instruments on board the Cluster spacecraft.

International audienc

Average properties of wave emissions below 4 kHz in the inner magnetosphere based on the data of the STAFF-SA instruments on board the Cluster spacecraft.

International audienc

Equatorial noise: Statistical study of its localization and the derived number density

International audienceResults of a statistical study of equatorial noise emissions are presented. These electromagnetic emissions are observed in the inner magnetosphere in the vicinity of the geomagnetic equator at frequencies below the lower hybrid frequency. We use the data recorded by four Cluster spacecraft during years 2001-2003. The data set was processed in three steps. In the first one, we have selected the data with a nearly linear polarization (ellipticity less than 0.2), corresponding to the known properties of the equatorial noise. Secondly, we have found parameters of a Gaussian model of the frequency-averaged power-spectral density of those selected waves as a function of the geomagnetic latitude. Finally, we have analyzed the data in the latitudinal interval defined by the width of the Gaussian model. Our results show that most intensity peaks of equatorial noise occur exactly at the magnetic equator. Incidental deviations are most probably caused by problems in determination of the true magnetic equator, which is shown by using different magnetic field models. We have estimated the plasma number density at the observation points using the cold plasma theory. These estimates are, within experimental errors, close to the values obtained from the spacecraft potential data measured by the EFW instrument

Average properties and variability of whistler-mode chorus emissions measured by the Cluster and Double Star spacecraft.

International audienc

Average properties and variability of whistler-mode chorus emissions measured by the Cluster and Double Star spacecraft.

International audienc

Average properties and variability of whistler-mode chorus emissions measured by the Cluster and Double Star spacecraft.

International audienc

Runaway electron diagnostics for the COMPASS tokamak using EC emission

An electron cyclotron emission (ECE) diagnostic of suprathermal electrons was utilised for runaway electron (RE) experiments purposes in the COMPASS tokamak. Our vertical ECE (V-ECE) system consists of a 16-channel heterodyne radiometer and an E-band horn antenna with a 76.5-88 GHz frequency range front-end. Simulations used for the design of the diagnostic showed a possibility of detecting the emission of low-energy (50-140 keV) runaway electrons. We realized measurements with both extraordinary (X-) and ordinary (O-) mode linear polarizations. The amplitudes of the X-mode and O-mode signals are similar, which can be explained by depolarised reflected radiation. V-ECE measurements in low-density flattop discharges and in discharges with massive gas injections of high-Z elements show correlations with other RE diagnostics. Our results are in the agreement with the principles of the primary runaway generation mechanisms

Runaway electron diagnostics for the COMPASS tokamak using EC emission

An electron cyclotron emission (ECE) diagnostic of suprathermal electrons was utilised for runaway electron (RE) experiments purposes in the COMPASS tokamak. Our vertical ECE (V-ECE) system consists of a 16-channel heterodyne radiometer and an E-band horn antenna with a 76.5-88 GHz frequency range front-end. Simulations used for the design of the diagnostic showed a possibility of detecting the emission of low-energy (50-140 keV) runaway electrons. We realized measurements with both extraordinary (X-) and ordinary (O-) mode linear polarizations. The amplitudes of the X-mode and O-mode signals are similar, which can be explained by depolarised reflected radiation. V-ECE measurements in low-density flattop discharges and in discharges with massive gas injections of high-Z elements show correlations with other RE diagnostics. Our results are in the agreement with the principles of the primary runaway generation mechanisms