scholarly journals EMMA - the Electric and Magnetic Monitor of the Aurora on Astrid-2

2004 ◽  
Vol 22 (1) ◽  
pp. 115-123 ◽  
Author(s):  
L. G. Blomberg ◽  
G. T. Marklund ◽  
P.-A. Lindqvist ◽  
F. Primdahl ◽  
P. Brauer ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Plasma Physics ◽  
Electrical Contact ◽  
Digital Signal ◽  
Space Plasma ◽  
Separation Distance ◽  
Fluxgate Magnetometer ◽  
Space Plasma Physics ◽  
Fluxgate Sensor ◽  
Signal Processors

Abstract. The Astrid-2 mission has dual primary objectives. First, it is an orbiting instrument platform for studying auroral electrodynamics. Second, it is a technology demonstration of the feasibility of using micro-satellites for innovative space plasma physics research. The EMMA instrument, which we discuss in the present paper, is designed to provide simultaneous sampling of two electric and three magnetic field components up to about 1kHz. The spin plane components of the electric field are measured by two pairs of opposing probes extended by wire booms with a separation distance of 6.7m. The probes have titanium nitride (TiN) surfaces, which has proved to be a material with excellent properties for providing good electrical contact between probe and plasma. The wire booms are of a new design in which the booms in the stowed position are wound around the exterior of the spacecraft body. The boom system was flown for the first time on this mission and worked flawlessly. The magnetic field is measured by a tri-axial fluxgate sensor located at the tip of a rigid, hinged boom extended along the spacecraft spin axis and facing away from the Sun. The new advanced-design fluxgate magnetometer uses digital signal processors for detection and feedback, thereby reducing the analogue circuitry to a minimum. The instrument characteristics as well as a brief review of the science accomplished and planned are presented. Key words. Ionosphere (auroral ionosphere). Magnetospheric physics (magnetosphere-ionosphere interactions). Space plasma physics (instruments and techniques)

scholarly journals Magnetospheric plasma boundaries: a test of the frozen-in magnetic field theorem

2005 ◽  
Vol 23 (7) ◽  
pp. 2565-2578 ◽  
Author(s):  
R. Lundin ◽  
M. Yamauchi ◽  
J.-A. Sauvaud ◽  
A. Balogh
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Flux ◽  
Plasma Physics ◽  
Electric Fields ◽  
Measurement Data ◽  
Space Plasma ◽  
Space Plasma Physics ◽  
Macroscopic System ◽  
Ideal Mhd

Abstract. The notion of frozen-in magnetic field originates from H. Alfvén, the result of a work on electromagnetic-hydrodynamic waves published in 1942. After that, the notion of frozen-in magnetic field, or ideal MHD, has become widely used in space plasma physics. The controversy on the applicability of ideal MHD started in the late 1950s and has continued ever since. The applicability of ideal MHD is particularly interesting in regions where solar wind plasma may cross the magnetopause and access the magnetosphere. It is generally assumed that a macroscopic system can be described by ideal MHD provided that the violations of ideal MHD are sufficiently small-sized near magnetic x-points (magnetic reconnection). On the other hand, localized departure from ideal MHD also enables other processes to take place, such that plasma may cross the separatrix and access neighbouring magnetic flux tubes. It is therefore important to be able to quantify from direct measurements ideal MHD, a task that has turned out to be a major challenge. An obvious test is to compare the perpendicular electric field with the plasma drift, i.e. to test if E=–v×B. Yet another aspect is to rule out the existence of parallel (to B) electric fields. These two tests have been subject to extensive research for decades. However, the ultimate test of the "frozen-in" condition, based on measurement data, is yet to be identified. We combine Cluster CIS-data and FGM-data, estimating the change in magnetic flux (δB/δt) and the curl of plasma –v×B(∇×(v×B)), the terms in the "frozen-in equation". Our test suggests that ideal MHD applies in a macroscopic sense in major parts of the outer magnetosphere, for instance, in the external cusp and in the high-latitude magnetosheath. However, we also find significant departures from ideal MHD, as expected on smaller scales, but also on larger scales, near the cusp and in the magnetosphere-boundary layer. We discuss the importance of these findings. Keywords. Magnetospheric physics (Magnetopause, cusp and boundary layers; Solar wind-magnetosphere interactions) – Space plasma physics

scholarly journals Modelling the solar wind interaction with Mercury by a quasi-neutral hybrid model

2003 ◽  
Vol 21 (11) ◽  
pp. 2133-2145 ◽  
Author(s):  
E. Kallio ◽  
P. Janhunen
Keyword(s):  
Solar Wind ◽  
Plasma Physics ◽  
Hybrid Model ◽  
Space Plasma ◽  
Physical Processes ◽  
Space Plasma Physics ◽  
Solar Wind Interaction ◽  
Plasma Parameters ◽  
Advantages And Disadvantages ◽  
Self Consistent

Abstract. Quasi-neutral hybrid model is a self-consistent modelling approach that includes positively charged particles and an electron fluid. The approach has received an increasing interest in space plasma physics research because it makes it possible to study several plasma physical processes that are difficult or impossible to model by self-consistent fluid models, such as the effects associated with the ions’ finite gyroradius, the velocity difference between different ion species, or the non-Maxwellian velocity distribution function. By now quasi-neutral hybrid models have been used to study the solar wind interaction with the non-magnetised Solar System bodies of Mars, Venus, Titan and comets. Localized, two-dimensional hybrid model runs have also been made to study terrestrial dayside magnetosheath. However, the Hermean plasma environment has not yet been analysed by a global quasi-neutral hybrid model. In this paper we present a new quasi-neutral hybrid model developed to study various processes associated with the Mercury-solar wind interaction. Emphasis is placed on addressing advantages and disadvantages of the approach to study different plasma physical processes near the planet. The basic assumptions of the approach and the algorithms used in the new model are thoroughly presented. Finally, some of the first three-dimensional hybrid model runs made for Mercury are presented. The resulting macroscopic plasma parameters and the morphology of the magnetic field demonstrate the applicability of the new approach to study the Mercury-solar wind interaction globally. In addition, the real advantage of the kinetic hybrid model approach is to study the property of individual ions, and the study clearly demonstrates the large potential of the approach to address these more detailed issues by a quasi-neutral hybrid model in the future.Key words. Magnetospheric physics (planetary magnetospheres; solar wind-magnetosphere interactions) – Space plasma physics (numerical simulation studies)

Advanced Space Plasma Physics

10.1142/p020 ◽  
1997 ◽  
Author(s):  
R A Treumann ◽  
W Baumjohann
Keyword(s):  
Plasma Physics ◽  
Space Plasma ◽  
Space Plasma Physics
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