Arbitrary-order Hilbert spectral analysis and intermittency in solar wind density fluctuations

The properties of inertial and kinetic range solar wind turbulence have been investigated with the arbitrary-order Hilbert spectral analysis method, applied to high-resolution density measurements. Due to the small sample size, and to the presence of strong non-stationary behavior and large-scale structures, the classical structure function analysis fails to detect power law behavior in the inertial range, and may underestimate the scaling exponents. However, the Hilbert spectral method provides an optimal estimation of the scaling exponents, which have been found to be close to those for velocity fluctuations in fully developed hydrodynamic turbulence. At smaller scales, below the proton gyroscale, the system loses its intermittent multiscaling properties, and converges to a monofractal process. The resulting scaling exponents, obtained at small scales, are in good agreement with those of classical fractional Brownian motion, indicating a long-term memory in the process, and the absence of correlations around the spectral break scale. These results provide important constraints on models of kinetic range turbulence in the solar wind

Decay of Solar Wind Turbulence behind Interplanetary Shocks

n/

Overview of APEX Project Results

The APEX mother-daughter project (Active Plasma EXperiments) was launched into an elliptical polar orbit (440–3,080 km) in December 1991. It consisted of the main Russian Interkosmos–25 (IK–25) satellite and the Czech MAGION–3 subsatellite, both with international scientific payloads. The mission used intensive modulated electron beam emissions and xenon plasma or neutral releases from the main satellite for studies of dynamic processes in the magnetosphere and upper ionosphere. Its main scientific objectives were to simulate an artificial aurora and to study optical and radio emissions from the aurora region, and to investigate the dynamics and relaxation of modulated electron and plasma jets, artificially injected into the ionospheric plasma. The experiments studied the Critical Ionization Velocity phenomenon and a diamagnetic cavity formation during the xenon releases, local and distant effects of the electron beam injection, spacecraft charging and potential balance, and plasma-wave interactions during the artificial emissions. Attempts were performed to utilize the modulated electron beam as an active transmitting antenna in the space. The theory of ballistic wave propagation across plasma barrier was tested in a joint active experiment with the Dushanbe ionospheric heater facility. In the paper, we give a short overview of the IK–25/MAGION–3 scientific instrumentation and methodology of experiments with artificial beam injections and we provide a review of the main APEX active experiments results, many of which have been published only in the Russian language so far. From a historical 25-years-long perspective, we try to put the results of the APEX experiments into the context of other active experiments in the space plasma

One-Year Analysis of Dust Impact-Like Events Onto the MMS Spacecraft

We present an analysis of 1‐year data of dust impacts observed on two of the Earth‐orbiting Magnetospheric Multiscale mission (MMS) spacecraft. The dust impact signals were identified in observations of the electric field probes and were registered simultaneously by monopole and dipole configurations of the instrument. This unique setup allows us to reliably identify changes in the spacecraft potential as candidates for dust impacts. We present a detailed study of the properties of the pulses generated by the dust impacts and show the influence of the local plasma environment (spacecraft location in the Earth magnetosphere) on signals generated by dust impacts and their detection. We discuss the credibility of impact identification and possible sources of signal misinterpretation. We find a total of 784 observed events that we can interpret as dust impacts and that we use to derive a dust flux. We show that MMS1 registered 0.7 and MMS3 0.8 dust impact‐like events per hour. This corresponds to dust flux of 2.5–6 × 10−5 m−2 s−1

HENON: the HEliospheric pioNeer for sOlar and interplanetary threats defeNce

International audienc

HENON: the HEliospheric pioNeer for sOlar and interplanetary threats defeNce

International audienc

Dusty plasma effects in near earth space and interplanetary medium

We review dust and meteoroid fluxes and their dusty plasma effects in the interplanetary medium near Earth orbit and in the Earth’s ionosphere. Aside from in-situ measurements from sounding rockets and spacecraft, experimental data cover radar and optical observations of meteors. Dust plasma interactions in the interplanetary medium are observed by the detection of charged dust particles, by the detection of dust that is accelerated in the solar wind and by the detection of ions and neutrals that are released from the dust. These interactions are not well understood and lack quantitative description. There is still a huge discrepancy in the estimates of meteoroid mass deposition into the atmosphere. The radar meteor observations are of particular interest for determining this number. Dust measurements from spacecraft require a better understanding of the dust impact ionization process,as well as of the dust charging processes. The latter are also important for further studying nanodust trajectories in the solar wind. Moreover understanding of the complex dependencies that cause the variation of nanodust fluxes is still a challenge.540010117 Gästprofessur Mann540010110 Driftsmedel Pellinen-Wannber