IMPRS Lindau, 6.2.2003 Space weather and plasma simulation Jörg Büchner, MPAe Lindau...
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Transcript of IMPRS Lindau, 6.2.2003 Space weather and plasma simulation Jörg Büchner, MPAe Lindau...
IMPRS Lindau, 6.2.2003
Space weather and plasma Space weather and plasma simulationsimulation
Jörg Büchner, MPAe LindauJörg Büchner, MPAe Lindau
Collaborators: Collaborators:
B. Nikutowski and I.Silin, LindauB. Nikutowski and I.Silin, Lindau
A. Otto, FairbanksA. Otto, Fairbanks
IMPRS Lindau, 6.2.2003
OutlineOutline What is „Space Weather“: Manifestation, What is „Space Weather“: Manifestation,
consequences, action at Earth and in spaceconsequences, action at Earth and in space How does it work ? - Main scenarios of plasma How does it work ? - Main scenarios of plasma
heating and particle acceleration by artists‘s moviesheating and particle acceleration by artists‘s movies MODELING AND SIMULATION APPROACHESMODELING AND SIMULATION APPROACHES:: Force free magnetic fields -> lowest order solar Force free magnetic fields -> lowest order solar
fieldsfields Ideal MHD -> large scale motion in the coronaIdeal MHD -> large scale motion in the corona Resistive MHD -> reconnection in the transition Resistive MHD -> reconnection in the transition
regionregion Kinetic simulation -> dissipation, structure Kinetic simulation -> dissipation, structure
formationformation State of the art global simulation and outlookState of the art global simulation and outlook
IMPRS Lindau, 6.2.2003
Manifestation: Aurora Manifestation: Aurora
IMPRS Lindau, 6.2.2003
Action in SpaceAction in Space
IMPRS Lindau, 6.2.2003
Space Weather: consequencesSpace Weather: consequences
IMPRS Lindau, 6.2.2003
How does it work? How does it work? Solar Wind and Magnetic Solar Wind and Magnetic
Substorms Substorms
IMPRS Lindau, 6.2.2003
Source: motion of solar Source: motion of solar plasmasplasmas
Solar plasma Solar plasma convection:convection:
Dynamo effect -> magnetic fields Dynamo effect -> magnetic fields Flows -> upward Poynting flux Flows -> upward Poynting flux
Estimated energy fluxes:Estimated energy fluxes:Active regions (0.5 -1) 104 W m-2Active regions (0.5 -1) 104 W m-2 Quiet regions 300 W mQuiet regions 300 W m-2-2
Coronal holes 800 W mCoronal holes 800 W m-2-2
IMPRS Lindau, 6.2.2003
Typical dimensionless Typical dimensionless parametersparameters
If: L – Geometrical scale, n – Number density; If: L – Geometrical scale, n – Number density; Tj – Temperature and B – Magnetic field,
then:Tj – Temperature and B – Magnetic field, then:Ion-gyro radius:Ion-gyro radius:
Mean-free path:Mean-free path:
Dreicer-fieldDreicer-field
If EA > ED collisions don‘t prevent runaway: collisionless!If EA > ED collisions don‘t prevent runaway: collisionless!
<<
Magnetic Reynolds numberMagnetic Reynolds number
E = v B ~E = v B ~
IMPRS Lindau, 6.2.2003
Typical valuesTypical values
Rm > 1 >> 1 >>>1Rm > 1 >> 1 >>>1
IMPRS Lindau, 6.2.2003
Force-free approximationForce-free approximation
04:20 04:20 18.10.96 18.10.96 04:4004:40
i.e. Currents flow only parallel to the magnetic field ->
IMPRS Lindau, 6.2.2003
Ideal MHD Ideal MHD (magnetohydrodynamics) (magnetohydrodynamics)
E + v x B=0 -> „ideal“ magnetohydrodynamics, i.e.E + v x B=0 -> „ideal“ magnetohydrodynamics, i.e.magnetic flux and plasma move togethermagnetic flux and plasma move together
SOHO-MDI photospheric B fields on 17./18.10.1996 60“, 23MmSOHO-MDI photospheric B fields on 17./18.10.1996 60“, 23Mm
IMPRS Lindau, 6.2.2003
MHD Simulation mit MHD Simulation mit Dissipation und Dissipation und
Neutralgas-StößenNeutralgas-Stößen
Non-ideal MHD Non-ideal MHD simulationssimulations
IMPRS Lindau, 6.2.2003
MHD Simulation mit MHD Simulation mit Dissipation und Dissipation und
Neutralgas-StößenNeutralgas-Stößen
Non-ideal MHD Non-ideal MHD simulationssimulations
IMPRS Lindau, 6.2.2003
MHD - simulations: MHD - simulations: exampleexample
Eruptive Eruptive magneticmagneticReconnection Reconnection directly in the directly in the transition regiontransition region
The question remains The question remains open: what is the nature open: what is the nature of dissipation?of dissipation?-> plasmakinetic -> plasmakinetic investigation necessaryinvestigation necessary
IMPRS Lindau, 6.2.2003
Next order - smaller - scalesNext order - smaller - scalesElectron equation of motion (Electron equation of motion (“Ohm’s law”“Ohm’s law”):):
• Below c/pi electrons and ions decouple, i.e. electrons are magnetized, ions not -> Plasma- Hall- Effect• Below c/pe : Electrons demagnetized as well
c/pic/pee <- Scales
Jpne1
BJnec1
Bvc1
EdtJd4
ei2pe
Electroninertia
Whistlerwaves
kinetic Alfvenwaves
<- Effects<- Effects
IMPRS Lindau, 6.2.2003
Crucial point: current sheets
Lznn /cosh 20
yx j
cz
B 4
IMPRS Lindau, 6.2.2003
Hall currents in current Hall currents in current sheets sheets
(Thin current sheet with io ~> L)
(Thin current sheet with io ~> L)
IMPRS Lindau, 6.2.2003
Vlasov-code kinetic Simulation
0)(1 ,
,
,,,
v
fBv
cE
m
e
r
fv
t
f ei
ei
eieiei
vdfvej
vdfe
ei
Veijei
V
eieij
ei
3,
,,
3,
,,
IMPRS Lindau, 6.2.2003
From microscopic fluctuations and From microscopic fluctuations and turbulence to a global instability: turbulence to a global instability:
TIMETIME
IMPRS Lindau, 6.2.2003
From microscopic fluctuations and From microscopic fluctuations and turbulence to global instability: turbulence to global instability: SPACE
IMPRS Lindau, 6.2.2003
Current sheet Current sheet decaydecay: from : from microscopic fluctuations to global microscopic fluctuations to global
instabilityinstability
IMPRS Lindau, 6.2.2003
Microscopic dissipationIonen distribution in the
current directionElectron distribution in the
current direction
Ions drive waves → plateau - formation → electron-heating
IMPRS Lindau, 6.2.2003
Current reduction -> disspation
Ion distribution function
Electron distribution function
IMPRS Lindau, 6.2.2003
3D current instability3D current instability
Plasma density wave Plasma density wave
IMPRS Lindau, 6.2.2003
Transition to reconnectionTransition to reconnection
IMPRS Lindau, 6.2.2003
3D magnetic reconnection3D magnetic reconnection
IMPRS Lindau, 6.2.2003
State of the art: global MHD State of the art: global MHD modelsmodels
IMPRS Lindau, 6.2.2003
Multiscale processes in complex Multiscale processes in complex system system -> plasma simulations necessary-> plasma simulations necessary
IMPRS Lindau, 6.2.2003
Comparison with Comparison with observationsobservations
IInternational program „nternational program „LLiving iving WWith a ith a SStar“ tar“ (ILWS)(ILWS) Missions 2006-08: SUNRISE, STEREO, MMS, SDO ...Missions 2006-08: SUNRISE, STEREO, MMS, SDO ...
South Pole Sitter
L2