RPC Meeting, Braunschweig Sept. 2010

Messung planetarer und interplanetarer Magnetfelder Sommersemester 2014

Lehrveranstaltung:  440.413

Dr. Konrad Schwingenschuh/ÖAWKonrad.schwingenschuh@oeaw.ac.at

23. Mai 2014 bis 28. Mai 2014

Folien © Dr. Konrad Schwingenschuh

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)

RPC Meeting, Braunschweig Sept. 2010

Global magnetic and electric properties of a cometary nucleus: Global magnetic and electric properties of a cometary nucleus: ROSETTA combined orbiter and lander magnetic field experiment ROSETTA combined orbiter and lander magnetic field experiment

RPC Meeting, Braunschweig Sept. 2010

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Magnetic properties of asteroids and cometsMagnetic 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

Resume.fol

RPC Meeting, Braunschweig Sept. 2010

Global electrical Global electrical conductivityconductivity - 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

RPC Meeting, Braunschweig Sept. 2010

Combined measurement of ROMAP and RPC

Before descent

During descent

After descent

RPC Meeting, Braunschweig Sept. 2010

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ROMAP – Reminder!ROMAP – Reminder!

Magnetometer2000nT range, 0.05nT resolution, 64Hz

Pressure SensorsPirani: 10-3 –10 mbar

Penning: 10-8 –10-4 mbar

Electrostatic Analyzerions: 40...8000eV; electrons: 0.3...4200eV

Faraday Cupresolution 5x10-12 – 4x10-10

RPC Meeting, Braunschweig Sept. 2010

Descent OperationDescent 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 … 101m)

Determination of magnetic properties of CG

Aubrite (non processed)ALHA 78 113 Magnetization: 2.8mAm²/kg

Diogenite (processed)MIL 07 001Magnetization: 0.05mAm²/kg

RPC Meeting, Braunschweig Sept. 2010

Descent OperationDescent 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: 5kmDensity: 1.0g/cm3NRM: 0.1mAm2/kg

a - c: aligned dipolesd – e: randomly distributedNo. of dipoles: 1 103 106 103 106

B vs. altitude

RPC Meeting, Braunschweig Sept. 2010

FSS / LTSFSS / 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. 2010

LTSLTS

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. 2010

SummarySummary

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