Dynamo Processes in the Sun Earth System

Variations of the Earth’s magnetic Field

Christine Amory-Mazaudier

LPP/CNRS/UMPC, 4 Avenue d Neptune 94107 Saint-Maur-des-Fossés

Christine.mazaudier@lpp.polytechnique.fr

UNBSS & IHY Workshop 21-25 September 2009SEOUL/KOREA

Outlines

*Gravity and electromagnetic forces

*The large scale dynamos

*Transient variations of the Earth’s magnetic field

*The component of the solar magnetic field and • magnetic aa, ap indices

• equivalent current systems SqP, DP1,DP2

• Equivalent current systems Sq/SR

* On the necessity of global approach -> interest of project like IHY

GRAVITY FORCE CELESTIAL MECHANICS/ KEPLER’s LAWS

rotation-> Diurnal ,revolution -> Seasonnal, Semi annual, Annual ………precession, excentricity,obliquity ->Climatic change (Milankovitch’s theory)

Principle of the DYNAMO ACTION

MOTION MAGNETIC FIELD

OHM’S LAWj = (E +

VxB)AMPERE’S LAWxB = j

LORENTZ ‘S FORCEjxB

V

B

E

j B

VxB

Starting point

FARADAY’S LAWxE= -B/t

Polarisation Electric field

Dynamo Electric field

Sunspot cyclePoloidal cycleFlare eventStormetc …..

SOLAR DYNAMO

Solar differential rotation

Dipolar and Toroïdal components

Yellow –outward /+Blue – inward / -

B = Bp + Ba Be + Bi

main aimantation external induction

INTERNAL SOURCES : 1 EXTERNAL SOURCES : 2,3

1

2

3

EARTH’S MAGNETIC FIELD

Internal DynamoExternal Dynamos - Magnetosphere/solar wind - Ionosphere/neutral wind

Ec = -VsxBi

E= VnxBt

Evans, 1977Friedman, 1987

• SUN DYNAMO

• Motions ->rotation and convection (rotation 2km/s at the equator)

• Magnetic field -> Solar dipolar field (~ 10 G)

• 2 components dipolar and toroïdal (3-5 kG)

• SOLAR WIND MAGNETOSPHERE DYNAMO

• Motion ->solar wind speed (~ 400km/s – 800km/s)

• Magnetic field -> Interplanetary magnetic field (~10nT)

• IONOSPHERIC DYNAMO

• Motion ->atmopsheric wind (Vn ~ 100m/s)

• Magnetic field ->terrestrial magnetic field (~30000-60000nT)

• EARTH’S DYNAMO

• Motion of the core ~ qq km/year

• Magnetic field -> Bt ~ qq 10 000 nT

MAGNETIC VARIATIONS / MAGNETIC INDICESB = Bp + Ba Be + Bi

main aimantation external induction

• TRANSIENT VARIATIONS

B ~ (Be +Bi) [Bi ~ % Be]

• External sourcesB ~ SR (Sq) + D (Sd)

• regular/quiet + irregular/disturbed

• D = D (Magnetosphere) + D (Ionosphere) + D induction

• DCF + DT + DR + DI + DG • Courants magnetospphere -> DCF : Chapman Ferraro currents/ T:tail currents /DR: Ring current

• Courants ionosphere -> DP1, DP2, Ddyn

[ Bp ~+ Ba ~ 0]

REGULAR -> QUIET - SR

Cross-Tail Current Sheet

J//-Region1J//-

Region2

IRREGULAR -> DISTURBANCE

DRDCFDT

DP1

DP2

Ddyn

SqSR

EEJ

Jll

B = Bp + Ba + Be + BiBp = main field

(30000-60000nT)Ba = magnetization of the rocks in the Lithosphere (~ 10-20 nT)Be = external field related to Ionosphere and magnetosphere 10nT to 2000nT)Bi = induced field generated by the external field Be , (Kamide and Brekke, 1975) (% of Be)The disturbed D variation is the sum of the effects of the various electric current systems (Cole, 1966) D = DCF + DR + DT + DI + DGDCF : magnetic disturbance due to the Chapman Ferraro current (~ qq nT to 30 nT) DR : magnetic disturbance due to the ring current (~ qqnT to ~ 600nT) DT : magnetic disturbance due to the Tail currents (~ qq nT to 20 nT)DI : magnetic disturbance due to the ionospheric disturbed electric current (~qq nT to 2000 nT)DG : magnetic disturbance due to electric currents flowing in the ground related to external electric current systems (~30 %)

4 DYNAMOS IN

SUNpoloidal /toroidal

MAGNETOSPHERESolar windIMF

IONOSPHEREEarth’s magnetic fieldNeutral wind

EARTHMotions of the core

CURRENT SYSTEMS

MAGNETOSPHEREChapman FerraroRing currentTail current

FIELD ALIGNED

IONOSPHERE Aurorals electrojetsMidlatitude currentsEquatorial electrojet

EARTH’s MAGNETICFIELD -> Transient variations

Indices -> disturbancesDstAa, Kp, ApKm, AmAU, AL

Equivalent currentsDP1, DP2DdynSR <Sq>, SqP

Sunspot maximum

Transient variations of the Earth’s magnetic field aa index (2 antipodale stations)

Poloidal component

SIGNATURE OF THE 2 SOLAR COMPONENTS

Magnetic indices <-> disturbances

Ahluwalia, JGR, Vol; 105, n°A12, 27481-27487, 2000

Ec = - VsxBi

Solar wind magnetosphere dynamo : quiet and disturbed time

DP2 Nishida, 1968 -> DP2 in ionosphere

SqP Nagata and Kokubun, 1962

Slow solar wind -> poloidal component

High wind speed streams -> poloidal component

CME -> Shock events -> toroidal component

IONOSPHERIC DYNAMOSolar Radiation/Regular transient variations of the Earth’s magnetic field

J = (E + VnxB)J : electric current : electric conductivitiesVn : neutral windB: Earth’s magnetic E : Electric field électrique

Vertical couplingDynamics of the AtmosphereIonospheric Electrodynamics

Earth’s magnetic field

Diurnal processE Region of the Ionosphere

(90km< h< 150km)

Friedman, 1987 Atmospheric Tides Evans 1977

Sq : Chapman and Bartels, 1940SR : Mayaud 1965

Stations Correlation X Correlation Y

Phu Thuy 0.74 0.39

Gnangana -0.43 0.43

Tamanrasset 0.42 0.16

Hermanus -0.38 0.38

M’Bour 0.34 0.10

Bangui 0.78 0.41

Trelew -0.13 0.42

San Juan 0.03 0.51

From Hong PHAM THI THU

SqX

SqY

F 10.7 <-> Rz

Earth’s magnetic field – Sq VietnamSunspot component

Sq X component of the Earth’s magnetic field

3 magnetic seasonsObsolete

Asymmetry equinoctialSqX (spring)> SqX (autumn)

Asymmetry of theIonospheric dynamo

From Hong PHAM THI THU

0

5

10

15

-5

0

5

10

J F M A M J J A S O N D

Plu

ie(m

m/jo

ur)

U(m

/s)

M o is

From Hong PHAM THI THU

Absorption in stratosphereMigrating tides

Deep convectionNon migrating tides

Conclusion

• Neccessity of integrated studies to advance in the Sun Earth System

• New discoveries at the interface of disciplines

• Neccessity of large data set to understand the Sun Earth’s System