ELF and VLF signatures of sprites registered onboard the low altitude satellite DEMETER

We report the observation of ELF and VLF signature of sprites recorded on the low altitude satellite DEMETER during thunderstorm activity. At an altitude of ~700 km, waves observed on the E-field spectrograms at mid-to-low latitudes during night time are mainly dominated by up-going 0+ whistlers. During the night of 20 July 2007 two sprites have been observed around 20:10:08 UT from the observatory located on the top of the mountain Śnieżka in Poland (50°44'09" N, 15°44'21" E, 1603 m) and, ELF and VLF data have been recorded by the satellite at about 1200 km from the region of thunderstorm activity. During this event, the DEMETER instruments were switched in the burst mode and it was possible to register the wave forms. It is shown that the two sprites have been triggered by two intense +CG lightning strokes (100 kA) occurring during the same millisecond but not at the same location. Despite the distance DEMETER has recorded at the same time intense and unusual ELF and VLF emissions. It is shown that the whistler wave propagates from the thunderstorm regions in the Earth-ionosphere guide and enters in the ionosphere below the satellite. They last several tens of milliseconds and the intensity of the ELF waveform is close to 1 mV/m. A particularly intense proton whistler is also associated with these emissions

Can the Relativistic Maser Mechanism Cause the Strong Emissions Registered by Cluster and Demeter Satellites in the Polar Cusp? (abstract). Planetary Radio Emissions| PLANETARY RADIO EMISSIONS VII 7|

The emissions with extremely high intensity around electron cyclotron frequency have been sometimes registered by satellite Magion 4 - companion of Interball 1. These waves correlate with strong fluxes of high energetic electrons often observed within the polar cusp by Interball 1 and Magion 4 as well as by Polar satellites. Multipoint measurements done by Cluster satellites give new insight of these emissions. Taking into account the plasma and magnetic field parameters in the polar cusp as well as geometry of the waves propagation, one has found that one type of these emissions can be generated by so called ”fan instability” (FI) , but as a source of the emissions around electron cyclotron frequency the ’horse shoe’ instability has been also discussed. Beam instability and interaction of Langmuir waves with energetic electrons give the broad band emissions around plasma frequency, which can be discussed as Langmuir turbulence (LT). Kilometric radiation (KR) typical for auroral zone is observed in the vicinity of the cusp’s boundary and is associated with fluxes of electrons with energy up to 100keV. The wave measurements done by DEMETER satellite in the polar cusp at the ionospheric level shown similar effects to registered by Interball and Cluster in the outer cusp. The presence of the energetic electrons during the bursts of the plasma waves can suggest another mechanism - relativistic maser instability. The discussion of the possibility of this mechanism in relation to the presented observation will be given in our paper

Applications of wavelet and bispectral analysis for studies of wave processes in the polar cusp.

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SAS wave experiment on board Magion 4

A short description of the SAS (subsatellite analyser of spectra) wave experiment on board the Magion-4 subsatellite is given. We present first measurements of the magnetic-field fluctuations in the frequency range 32–2000 Hz obtained in the magnetotail during the disturbed period at the magnetopause and in the polar cusp

High energetic electrons and electron cyclotron waves and their harmonics in the polar cusp.

The most characteristic features of the wave spectra measured in the polar cusp found by Interball 1 and Polar satellites and confirmed by Cluster are the broad band emissions with maxima at the lower hybrid, around electron cyclotron and its harmonics frequencies. Interball 1 and its companion Magion 4 sometimes registered emissions with extremely high intensity in these frequencies ranges. These waves correlate with strong fluxes of high energetic electrons often observed within the polar cusp by Interball 1 and Magion 4 as well as by Polar satellites. Cluster measurements give new insight of these emissions. The observations of electron cyclotron and their harmonics gathered on Magion 4 and Cluster satellites associated with strong fluxes of energetic electrons will be presented. Short discussion of the possible generation mechanism, such as 'fan' instability, will be added

Geodynamic research at the Department of Planetary Geodesy, SRC PAS

The Department of Planetary Geodesy of the Space Research Centre PAS has been conducting research on a broad spectrum of problems within a field of global dynamics of the Earth. In this report we describe the investigations on selected subjects concerning polar motion (modeling and geophysical interpretation of the Chandler wobble, hydrological excitation of seasonal signals, search for optimal prediction methods), tectonic activity in the region of the Książ Geodynamic Laboratory of the SRC, and finally the new joint Polish-Italian project GalAc analyzing feasibility and usefulness of equipping second-generation Galileo satellites with accelerometers