RPC Meeting, Braunschweig Sept Messung planetarer und interplanetarer Magnetfelder Sommersemester 2014 Lehrveranstaltung: Dr. Konrad Schwingenschuh/ÖAW 23. Mai 2014 bis 28. Mai 2014 Folien © Dr. Konrad Schwingenschuh

RPC Meeting, Braunschweig Sept Globale elektrische Leitfähigkeit: Allgemeines Magn. Fluktuationen und Sprünge des interplanetaren Magnetfeldes werden durch die elektr. Leitfähigkeit von Himmelskörpern durch magn. Diffusion gedämpft. Die Bestimmung erfolgt mittels Orbiter- und Lander- Magnetometer. Die Abschätzung der Leitfähigkeit erfolgt durch die Relation Sigma = tau / (mu_0 * L^2) ; tau... char. Diffusionszeit [s]; L... Durchmesser des Himmelskörpers (char. Länge) Beispiel: Rosetta (Kometenkern), Galileo (mögliche Ozeane auf Jupitermonden Europa, Ganymede, Callisto), Mond (Apollo 12 und Explorer 35)

RPC Meeting, Braunschweig Sept Global magnetic and electric properties of a cometary nucleus: ROSETTA combined orbiter and lander magnetic field experiment

RPC Meeting, Braunschweig Sept Magnetic properties of asteroids and comets  - previous magnetic field investigations: § - Gaspra 1993 (magnetic moment?) § - (no significant magnetic moment found) § - ROSETTA Steins 2008 (no evidence for magnetization found) § -ROSETTA-Lutetia 2010 (no evidence for an intrinsic field)  - magnetized dust & accretional remanence: § - Nüboldt 2000 § -Weiss2012  - ROSETTA 2014: remanent magnetization in the solar nebula

RPC Meeting, Braunschweig Sept Global electrical conductivity  - dual point magnetic field and global electrical conductivity [Dyal 1973]  - electromagnetic induction in the cometary nucleus  - study of time varying interplanetary magnetic field (Constantinescu 2012)  References § 1. Dyal, P. and W.P. Curtis, Global Electromagnetic Induction in the Moon and Planets, Physics of the Earth and Planetary Interior, 7 (1973) § 2. Constantinescu-et al.-2012, PSS-On the possibility to determine the electrical conductivity of 67PCG from ROSETTA magnetic field observations

RPC Meeting, Braunschweig Sept Combined measurement of ROMAP and RPC Before descent During descent After descent

RPC Meeting, Braunschweig Sept ROMAP – Reminder!  Magnetometer 2000nT range, 0.05nT resolution, 64Hz  Pressure Sensors Pirani: –10 mbar Penning: –10 -4 mbar  Electrostatic Analyzer ions: eV; electrons: eV  Faraday Cup resolution 5x – 4x10 -10

RPC Meeting, Braunschweig Sept Descent Operation  Why magnetic properties of a comet are interesting  Magnetization of processed and non-processed material is very different  Known examples are Meteorites and Asteroids  Magnetization could explain gap in planetary formation (10 -3 … 10 1 m) Determination of magnetic properties of CG Aubrite (non processed) ALHA Magnetization: 2.8mAm²/kg Diogenite (processed) MIL Magnetization: 0.05mAm²/kg

RPC Meeting, Braunschweig Sept Descent Operation  Why characterization can be done during descent only  Direct measurements of magnetization can be done at different distances  Drop off profile gives information about homogeneity  magnetic field on surface is proportional to NRM Determination of magnetic properties of CG Assumptions: Diameter: 5km Density:1.0g/cm3 NRM:0.1mAm 2 /kg a - c:aligned dipoles d – e:randomly distributed No. of dipoles: B vs. altitude

RPC Meeting, Braunschweig Sept FSS / LTS Onset & evolution of s/w interaction  Measurement Scenario  switching on time: 4 hours centered about noon  Optional (LTS): 8 hours including night  ROMAP in Surface Mode  Constraints  No common operation with “magnetic active” experiments  Favored measurement partners: Concert, Civa, Rolis, Sesame, Mupus  Operation of RPC MAG mandatory  Resources  Operation time: 4 hours (MAG & SPM)  Power consumption: 4 Watt  Data volume: 60 kbyte/hour

RPC Meeting, Braunschweig Sept LTS Combined E- and B-field & P-measurement  Conductivity investigation using variation analysis  Variation of B field (ROMAP/RPC) and E field (SESAME) shall be used to investigate global conductivity  High resolution data (64Hz) necessary, previous measurement helpful for planning effective operation  Lander Day and Night pressure measurement  Promises high scientific return about outgassing behavior  Uncertainty: Penning functionality

RPC Meeting, Braunschweig Sept Summary  Prior Separation (ICEP)  ROMAP supports RPC MAG measurements to separate s/c interferences  During Descent (SDL)  RPC-MAG supports ROMAP measurement to separate temporal variations from CG signature  On Surface (FSS and LTS)  Combined measurement of RPC and ROMAP to separate local and temporal field variation And determine the global electrical conductivity  Magnetized dust and accretional magnetism