CLUSTER II

     The project Cluster-II is continuation of the activities in the  PRODEX programme. It is aimed at the study of interaction of the solar wind with the Earth magnetosphere at different levels (global, meso- and micro-), using kinetic codes (Vlasov/PIC/hybrid) and in situ data analysis (PRASSADCO, IDFS/ISDAT data interface). The studies will be done in cooperation with UCLA (University of California), LESIA in Meudon (France) and University of Iowa. Besides the scientific research the project is also a preparation for the BepiColombo space project. It includes utilization of the present knowledge in development of coil sensors and dwarf pre-amplifiers for mid and low frequences.
 

Principal Investigator  :   Pavel Trávníček

WORKING PLAN

WP1: Global structure of magnetosphere and its interaction with the solar wind
(with LESIA, CESR, UCLA):
The interaction between a collisionless solar wind flow and an obstacle includes many different transition regions (shock, magnetosheath, magnetopause, etc.) dominated by various kinetic processes (micro-instabilities, particle reflection, accelerations, etc.). We plan to study the global structure of this inter-action using a 3-D hybrid code, first in the case of Mercury in view of BepiColombo mission, continuing the work of [Travnicek et al, 2003] who found a good agreement between the simulation and Mariner 10 data. Later on, we plan to extend the hybrid model to the Earth's magnetosphere.

WP2: Multi-dimensional structure of collisionless shocks
Contrary to collision dominated shocks, the dissipation in collisionless shocks takes place in a large region around the shock ramp through many different kinetic processes. Multipoint Cluster II[Hellinger, 2003]. In situ observation indicate that for wide range of upstream parameters the quasi-perpendicular shocks are nearly stationary. On the other hand, numerical simulation indicate that the strong quasi-perpendicular shocks has multi-dimensional structure, shock front ripples. These ripples play important role in the shock structure, however, there are no observational evidences of them. We plan to determine experimentally of the geometrical and spatio-temporal properties of the shock front based on Cluster II  mesurements and compare them with the simulation data.

WP3: Electron Foreshock (with A. Mangeney, LESIA, and D. Schriver, UCLA)
Electron beams reflected off the shock are a natural source of electrostatic turbulence at the plasma frequency fpe in the electron foreshock. In addition, electromagnetic waves at 2fpe are usually observed and their origin and generating mechanism are not yet well understood. The generating mechanism is probably nonlinear, for example these waves could be the result of a mode conversion from the nonlinear 2fpe electrostatic waves [Yoon, 2000; Travnicek et al, 2003] on density gradients. To address this question we plan to perform two-dimensional electromagnetic Vlasov simulations with parameters as close as possible to the Cluster II observation. measurememts brings a new insight into properties and a structure of collisionless Earth's bow shock. The collisionless shocks are in general neither stationary nor one-dimensional.

WP4: Current driven instabilities (with S. D. Bale, UCB, , A. Mangeney, LESIA, J. D. Menietti, U. Iowa)
A electron-proton coupling via curent driven instabilities, inducing diffusion and anomalous resitivity, play an important role in the dissipation and field-line merging in collisionless shocks, magnetopauses end current sheaths. Properties of the current driven instabilities are relatively well known, however, there are still some discrepancy between theoretical estimates results of numerical simulations [Watt et al. 2002]. We plan to study the current driven instabilities using electrostatic  and electromagnetic Vlasov codes. First results for the ion acoustic instability [Hellinger et al. 2004] show a good agreement between the simulation and quasi-linear theory. We plan to continue this work for other current drivent instabilities in the shock and magnetopause contexts.

WP5:  Solar wind instabilities (with A. Mangeney, LESIA)
We plan to study ion and electon instabilities and their consequences for the thermodynamics of the solar wind. For ion instabilities (driven by temperature anisotropy, ion beams, etc.) we will use hybrid and hybrid expanding box codes [Hellinger et al. 2003]. For electron instabilities we will use electromagnetic Vlasov code. The simulation results will be compared with observations (Cluster II, BepiColombo).

WP6: Generation of Alfven waves in the magnetotail (with D.Schriver, UCLA)
Alfven waves generated in the magnetotail propagate towards the Earth at high latitudes, enter the auroral zone and significanly energize the auroral plasma, especially during active times. An outstanding scientific question, however, is how and where these Alfven waves are generated. They are probably generated in the plasma sheet boundary layer (PSBL) region where fast ion beam flows are often observed and may be a source of Alfven waves. To address this problem, we plan to model (using a hybrid code) a long segment of the PSBL region.  The system will be driven by ion beams being injected at one boundary. The instabilities excited for different ion beam conditions will be examined, as well as resulting wave-particle interactions that affect both the beam and the background PSBL plasma. Results for the simulations will be compared directly with Cluster II wave and particle data.

WP7: Solar wind instabilities (with A. Mangeney, LESIA)
We plan to study ion and electon instabilities and their consequences for the thermodynamics of the solar wind. For ion instabilities (driven by temperature anisotropy, ion beams, etc.) we will use hybrid and hybrid expanding box codes[Hellinger et al. 2003] . For electron instabilities we will use electromagnetic Vlasov code. The simulation results will be compared with observations (Cluster II, BepiColombo).

WP8: Extension of Hybrid code, Vlasov-hybrid code (with LESIA)
Standard hybrid code where electron intertial effects are neglected are not generally suitable to a description of collisionless shock[Hellinger et al, 2002] . We plan to develop a hybrid and Vlasov-hybrid codes including the electron intertial terms in to the generalized Ohm's law (cf. electron-MHD approximation) and use these codes instead of the standard hybrid code when necessary.

WP9 Vlasov and full particle-in-cell codes (with LESIA, UCLA: D. Schriver, J.-N. Leboeuf)
For high frequency, electron phenomena we plan to use, develop and improove (electrostatic and electromagnetic) Vlasov code [Mangeney et al. 2002] and (electromagnetic, relativistic) full particle-in-cell (PIC) codes.

WP10: Data analysis and visualisation tools (with MSSL UCL: A. Fazakerley, LESIA: M.Maksimovic)
Maintenance and updates of software tools, namely the IDFS/ISDAT data interface and PRASSADCO.

WP11: Technology of Low cost high performance computing (with SPRINX Systems)
We will continue to improove our parallel facility in view of up to date technological advances. Our knowledge in the area of the design of these systems will be published in the form of technical reports.

WP12 (optional): Development of search coil sensors and low/middle frequency pre-amplifiers (with CSRC)
Our laboratory has an outstanding record in the preparation of space experiments (c.f. five Czech built Magion spacecrafts). This tradition has continued within the PRODEX programe (ISL experiment on DEMETER), DSLP/TPMU experiments on Proba 2 of ESA). To use this heritage we propose to develop search-coil sensors and appropriate low/middle frequency electronics in collaboration with CNRS-LESIA (M. Moncuquet, M. Maksimovic) and University of California, Berkeley (S. D. Bale). Sensors and electronics will be developed, manufactured (IAP, ASCR; CSRC ), and primarily tested (VZLU) in Czech Republic, then by our partners from ESA member states (LESIA), furthermore on balloon flights (ESA member state and/or NASA). The electronic part will be minitaturized (CSRC) and if applicable used as a part of payload on forthcomming ESA missions (for example, Proba 3, etc.).