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

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 2009 SEOUL/KOREA. Outlines.

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

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  1. Dynamo Processes in the Sun Earth SystemVariations 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 2009 SEOUL/KOREA

  2. 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

  3. GRAVITY FORCE CELESTIAL MECHANICS/ KEPLER’s LAWS rotation-> Diurnal , revolution -> Seasonnal, Semi annual, Annual ……… precession, excentricity,obliquity ->Climatic change (Milankovitch’s theory)

  4. Starting point MAGNETIC FIELD MOTION V B Sunspot cycle Poloidal cycle Flare event Storm etc ….. VxB Dynamo Electric field LORENTZ ‘S FORCE jxB E Polarisation Electric field FARADAY’S LAW xE= -dB/dt OHM’S LAW j = s (E + VxB) B j AMPERE’S LAW xB = mj Principle of the DYNAMO ACTION

  5. SOLAR DYNAMO Solar differential rotation Dipolar and Toroïdal components Yellow –outward /+ Blue – inward / -

  6. EARTH’S MAGNETIC FIELD Ec = -VsxBi 2 Internal Dynamo External Dynamos - Magnetosphere/solar wind - Ionosphere/neutral wind 3 E= VnxBt 1 Evans, 1977 Friedman, 1987 B = Bp + Ba Be + Bi main aimantation external induction INTERNAL SOURCES : 1 EXTERNAL SOURCES : 2,3

  7. 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

  8. MAGNETIC VARIATIONS / MAGNETIC INDICESB = Bp + Ba Be + Bi main aimantation external induction • TRANSIENT VARIATIONS • DB ~ D(Be +Bi) [Bi ~ % Be] • External sources • DB ~ 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 [ DBp ~+ DBa ~ 0]

  9. J//-Region1 J//-Region2 Cross-Tail Current Sheet IRREGULAR -> DISTURBANCE REGULAR -> QUIET - SR DR DCF DT Jll DP1 DP2Ddyn Sq SR EEJ

  10. B = Bp + Ba + Be + Bi Bp = 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 + DG DCF : 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 %)

  11. CURRENT SYSTEMS MAGNETOSPHERE Chapman Ferraro Ring current Tail current FIELD ALIGNED IONOSPHERE Aurorals electrojets Midlatitude currents Equatorial electrojet EARTH’s MAGNETIC FIELD -> Transient variations Indices -> disturbances Dst Aa, Kp, Ap Km, Am AU, AL Equivalent currents DP1, DP2 Ddyn SR <Sq>, SqP 4 DYNAMOS IN SUN poloidal /toroidal MAGNETOSPHERE Solar wind IMF IONOSPHERE Earth’s magnetic field Neutral wind EARTH Motions of the core

  12. SIGNATURE OF THE 2 SOLAR COMPONENTS Sunspot maximum Poloidal component Transient variations of the Earth’s magnetic field aa index (2 antipodale stations) Magnetic indices <-> disturbances

  13. Ec = - VsxBi Ahluwalia, JGR, Vol; 105, n°A12, 27481-27487, 2000

  14. Solar wind magnetosphere dynamo : quiet and disturbed time Slow solar wind -> poloidal component SqP Nagata and Kokubun, 1962 High wind speed streams -> poloidal component CME -> Shock events -> toroidal component DP2Nishida, 1968 -> DP2 in ionosphere

  15. IONOSPHERIC DYNAMOSolar Radiation/Regular transient variations of the Earth’s magnetic field Friedman, 1987 Atmospheric Tides Evans 1977 Vertical coupling Dynamics of the Atmosphere Ionospheric Electrodynamics Earth’s magnetic field J = s (E + VnxB) J : electric current s : electric conductivities Vn : neutral wind B: Earth’s magnetic E : Electric field électrique Diurnal process E Region of the Ionosphere (90km< h< 150km) Sq : Chapman and Bartels, 1940 SR : Mayaud 1965

  16. Earth’s magnetic field – Sq Vietnam Sunspot component F 10.7 <-> Rz SqX SqY From Hong PHAM THI THU

  17. Sq X component of the Earth’s magnetic field 3 magnetic seasons Obsolete Asymmetry equinoctial SqX (spring)> SqX (autumn) Asymmetry of the Ionospheric dynamo From Hong PHAM THI THU

  18. From Hong PHAM THI THU Absorption in stratosphere Migrating tides Deep convection Non migrating tides

  19. 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

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