dynamo processes in the sun earth system variations of the earth’s magnetic field christine...
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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