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