The Cluster Mission: Four point observation in space · Magnetic reconnection Fundamental process...
Transcript of The Cluster Mission: Four point observation in space · Magnetic reconnection Fundamental process...
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„„Graz in Graz in SpaceSpace“, September 7“, September 7--8, 2006, Graz8, 2006, Graz
TheThe Cluster Mission:Cluster Mission:FourFour point point observationobservation in in spacespace
Rumi Nakamura(Institut für Weltraumforschung
der österreichischen Akademie der Wissenschaften)
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thisthis talktalk
Earth’s magnetosphere
Cluster: Mission, Instruments, Operation
Data analysis, modeling
Scientific outputs
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SunSun--Earth ConnectionEarth Connection
Copyright: ESA
Solar flare and CME is the key process for driving the active solar wind, which interact with the Earth’s magnetospheric environment
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MagnetosphereMagnetosphere
Key question in magnetospheric physics: How is solar-wind energy processed in the magnetosphere/ ionosphere system?
Earth’s-magnetosphere is a natural “laboratory” for space plasma physics, particularly, for plasma/field interaction at differentboundaries.
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Magnetic reconnectionMagnetic reconnectionFundamental process in space plasma
Anti-parallel field lines move toward one another
Field lines are broken up at X line (‘diffusion’) and reconnected
(slow) plasma flow ⇨ magnetic field stress ⇨ fast plasma jets
Allows mixture of plasma otherwise frozen to the field lines
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SubstormsSubstormsSporadic energy transfer processes involving magnetosphere and
ionosphere as a consequence of solar wind-magnetosphere coupling
Aurora
Current disruptionReconnection
Reconnection and tail current disruption in the near-Earth tail
Energy dissipated in ionosphere
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Cluster missionCluster mission
Solar wind
Magnetospheric mission: with four satellites withidentical set of instrumentsApogee: 19 RE (120,000 km)Perigee: 3 RE (17,000 km)SC separation: 200-10000 kmOrbit period: 56 h Spin period: 4s
Time lines1982 ESA cornerstone proposal (SOHO/Cluster)1996 June Cluster I (launch failure of Ariane5) 1997 April Cluster II accepted by SPC 2000 Jul.16, Aug.9: Launch2000 Aug. 28-Dec.3: Instrument Commission 2000 Dec. 4-: Routine Operation
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44 Cluster instruments44 Cluster instruments
7 DWP (H. Alleyne, UK) Wave processor
8 EFW (M. Andre, S)Electric fields and waves
9 STAFF (N. Cornilleau-Wehrlin, F) Magnetic and electric fluctuations
10 WHISPER (P. Decreau, F)Electron density and
plasma waves11 WBD (D. Gurnett, USA)
Electric field wave-forms
4 FGM (A. Balogh, UK)Magnetic field
5 PEACE (A. Fazakerley, UK)Electrons (E
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IWF mission contributionIWF mission contribution
Data analysis in the field of space plasma physics
Principal Investigator for potential control device(ASPOC)CoI-ship in development and construction of FluxGateMagnetometers(FGM)CoI-ship for Electron Drift Instrument (EDI), Cluster Ion Spectrometry experiment (CIS)Plasma Electron and Current Experiment (PEACE)ACDC(Austrian Cluster Data Center
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Cluster/ASPOCCluster/ASPOC
ASPOC (Active Spacecraft Potential Control) gewährleistet ungestörte Messungen niederenergetischer Teilchen durch Reduktion des Satellitenpotentials.
Flüssigmetall-Ionenemitter kompensiert elektrische Aufladung des SatellitenMasse: 1,9 kgelektrische Leistung: 2,7 W
IWF-Beitrag:FederführungElektronik
Kooperationspartner:RSSD/ESAARC Seibersdorf, AFFI, NUNH, USA
Elektronenzählraten PEACE
mit ASPOC ohne ASPOC
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Cluster/FGMCluster/FGM
FGM (FluxGate-Magnetometer) ermöglicht Magnetfeldmessungen mit einer Auflösung von 10 pT.
IWF-Beitrag:
Analog/Digital-Konvertermit Interface-Elektronik
Studie über magnetischeReinheit der Satelliten
Sensorkalibrierung im höheren Frequenzbereich und Bestimmung des Frequenzgangs
Kooperationspartner:
ICL, UK (Federführung)
NASA/GSFC, USA
TU-Braunschweig, D
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Cluster/EDICluster/EDI
EDI (Electron Drift Instrument) misst das elektrische Feld und den Magnetfeldgradienten über Triangulation und Laufzeitmessung von Elektronenstrahlen.
Messung aller drei Vektorkomponenten unbeeinflusst von lokalen Störungen in SatellitennäheGun-Detektor-Einheit:elektrische Leistung: 3,6 WMasse: 4,4 kgStrahlstrom: 0,1 µA
IWF-Beitrag:Software
Kooperationspartner:MPE, D (Federführung)UNH, USAUCSD, USA
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Science data flowScience data flowReconstruction of current sheet structure from CS crossing Assume: spatial structure remains same during crossing
Bx(t+∆τ) –Bx(t) = (dBx/dz) ∆z/∆τcurrent sheet motion
Effective vertical scale calculation
[Runov et al., 2004]
first determine current sheet normal
integrate ∆z from lobe to equator
Z*(t) = ∫∆t dBl(t)/dt {∂Bl(t)/∂n(t)}-1 dt,
Z*|Bx=0 =0
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Austrian Cluster Data Austrian Cluster Data CenterCenter (ACDC)(ACDC)
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Why four spacecraft ?Why four spacecraft ?Single point measurement cannot differentiate spatial from temporal changes. Four point measurements can determine purely spatial structure
Spatial gradient
Current density (∇xB; ‘curlometer’)
Magnetic field curvature
Plasma flow structure
Boundary crossings
Orientation of boundary
Motion of boundary
Four single-point observations(in four different plasma domains)
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Multipoint analysis of planar structureMultipoint analysis of planar structure
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Spatial scale of fast flowsSpatial scale of fast flowsSpatial gradient of flow obtained from sc-pairs along Y’ (and Z)
Dawn-dusk scale: 2-3 REVertical scale: 1.5-2 RESpatial scale suggests localized source region (reconnection site)
rate of change in velocity along Y
dawnside edge
dusksideedge
dawnion measurements only at 3 SC
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Current Sheet ProfileCurrent Sheet Profile
JYnA/m2
BX
4000 km
ab c
d
Z*
Near ion diffusion region of reconnection region
Bifurcated current sheet in Earthward fast flow region
Thin current sheet in between(flow reversal region)
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Spatial structure of flux ropeSpatial structure of flux rope
Assuming pressure balance and 2D structure, plasma/field configuration around satellite trajectory can be reconstructed
VHT = (237, 27, 23) km/s• Flux rope with half width of ~1 Re. • Strong core field (mostly By).
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The way to go...The way to go...New mission planning
Building SC/instrument
Observation
Data analysis
New theory/modeling
New questionsSolving problems
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WhatWhat nextnext ??
Magnetotail
2009
2005
Cluster:
Different years at different scales
Additional spacecraft
Orbit configuration changes
Together with THEMIS (2007+):toward global scale...
Future (2012+): MMStoward electron scale...
Cross-scale (2015-?)
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Future missionsFuture missionsParticipation in future NASA missions
THEMIS (launch 2006) will probe global (and fluid) scale
MMS (launch 2013) will probe electron (and ion) scale
IWF contributions THEMIS: magnetometer, science def. team MMS/SMART: potential control., electric field, science def. team
Participation in Chinese planned mission
KuaFu magnetometer team
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And then ?And then ?Key plasma processes
Reconnection
Shocks
Turbulence
We need to measure :
In 3D
On 3 scales (electron kinetic, ion kinetic, fluid)
All 3 scales simultaneously
Requirements
About 12 spacecraft (3 nested groups of 4)
Earth orbit, passing through bowshock, magnetopause and magnetotail
Reconnection Shocks Turbulence
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Cross ScaleCross Scale
Many similarities to JAXA SCOPE mission
Opportunity of a joint JAXA/ESA SCOPE/Cross-Scale mission !
A a joint ESA/JAXA A a joint ESA/JAXA CrossCross--Scale/SCOPE Scale/SCOPE mission mission as ESA’s Cosmic Vision 2015-2025 programme ?
Web-site http://www.crosshttp://www.cross--scale.orgscale.org//
„Graz in Space“, September 7-8, 2006, GrazThe Cluster Mission:Four point observation in spacethis talkSun-Earth ConnectionMagnetosphereMagnetic reconnectionSubstormsCluster mission44 Cluster instrumentsIWF mission contributionCluster/ASPOCCluster/FGMCluster/EDIScience data flowAustrian Cluster Data Center (ACDC)Why four spacecraft ?Multipoint analysis of planar structureSpatial scale of fast flowsCurrent Sheet ProfileSpatial structure of flux ropeThe way to go...What next ?Future missionsAnd then ?Cross Scale