1. RPC Meeting, Braunschweig Sept. 2010 Messung planetarer und interplanetarer Magnetfelder Sommersemester 2014 Lehrveranstaltung: 440.413 Dr. Konrad Schwingenschuh/ÖAW Konrad.schwingenschuh@oeaw.ac.at 23. Mai 2014 bis 28. Mai 2014 Folien © Dr. Konrad Schwingenschuh

2. RPC Meeting, Braunschweig Sept. 2010 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)

3. RPC Meeting, Braunschweig Sept. 2010 Global magnetic and electric properties of a cometary nucleus: ROSETTA combined orbiter and lander magnetic field experiment

4. RPC Meeting, Braunschweig Sept. 2010 4 Magnetic properties of asteroids and comets  - previous magnetic field investigations: § - Gaspra 1993 (magnetic moment?) § - NEAR@433EROS_2000 (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

5. RPC Meeting, Braunschweig Sept. 2010 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) 251-265 § 2. Constantinescu-et al.-2012, PSS-On the possibility to determine the electrical conductivity of 67PCG from ROSETTA magnetic field observations

6. RPC Meeting, Braunschweig Sept. 2010 Combined measurement of ROMAP and RPC Before descent During descent After descent

7. RPC Meeting, Braunschweig Sept. 2010 7 ROMAP – Reminder!  Magnetometer 2000nT range, 0.05nT resolution, 64Hz  Pressure Sensors Pirani: 10 -3 –10 mbar Penning: 10 -8 –10 -4 mbar  Electrostatic Analyzer ions: 40...8000eV; electrons: 0.3...4200eV  Faraday Cup resolution 5x10 -12 – 4x10 -10

8. RPC Meeting, Braunschweig Sept. 2010 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 78 113 Magnetization: 2.8mAm²/kg Diogenite (processed) MIL 07 001 Magnetization: 0.05mAm²/kg

9. RPC Meeting, Braunschweig Sept. 2010 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: 1 10 3 10 6 10 3 10 6 B vs. altitude

10. RPC Meeting, Braunschweig Sept. 2010 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

11. RPC Meeting, Braunschweig Sept. 2010 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

12. RPC Meeting, Braunschweig Sept. 2010 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