Dynamo Processes in the Sun Earth System Variations of the Earth’s magnetic Field Christine...
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Transcript of Dynamo Processes in the Sun Earth System Variations of the Earth’s magnetic Field Christine...
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
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