ROMAP: Rosetta Magnetometer and Plasma Monitor

The scientific objectives, design and capabilities of the Rosetta Lander’s ROMAP instrument are presented. ROMAP’s main scientific goals are longterm magnetic field and plasma measurements of the surface of Comet 67P/Churyumov-Gerasimenko in order to study cometary activity as a function of heliocentric distance, and measurements during the Lander’s descent to investigate the structure of the comet’s remanent magnetisation. The ROMAP fluxgate magnetometer, electrostatic analyser and Faraday cup measure the magnetic field from 0 to 32 Hz, ions of up to 8000 keV and electrons of up to 4200 keV. Additional two types of pressure sensors – Penning and Minipirani – cover a pressure range from 10⁻⁸ to 10¹ mbar. ROMAP’s sensors and electronics are highly integrated, as required by a combined field/plasma instrument with less than 1 W power consumption and 1 kg mass.     

HYDRODYNAMIC AND MHD EQUATIONS ACROSS THE BOW SHOCK AND ALONG THE SURFACES OF PLANETARY OBSTACLES

Examinations of the magnetohydrodynamic (MHD) equations across a bow shock are presented. These equations are written in the familiar Rankine–Hugoniot set, and an exact solution to this set is given which involves the upstream magnetosonic Mach number, plasma , polytropic index, and _B-v , as a function of position along the shock surface. The asymptotic Mach cone angle of the shock surface is also given as a function of the upstream parameters, as a set of transcendental equations. The standoff position of a detached bow shock from an obstacle is also reviewed. In addition, a detailed examination of the hydrodynamic equations along the boundary of the obstacle is performed. Lastly, the MHD relations along the obstacle surface are examined, for specific orientations of the upstream interplanetary magnetic field (IMF) in relation to the upstream flow velocity vector.