Download presentation
Presentation is loading. Please wait.
Published byAshley Stevens Modified over 9 years ago
1
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
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 Sq P, DP 1,DP 2 Equivalent current systems Sq/S R * 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
Principle of the DYNAMO ACTION MOTION MAGNETIC FIELD OHM’S LAW j = (E + VxB ) AMPERE’S LAW xB = j LORENTZ ‘S FORCE jxB VB E j B VxB Starting point FARADAY’S LAW xE= - B/ t Polarisation Electric field Dynamo Electric field Sunspot cycle Poloidal cycle Flare event Storm etc …..
5
SOLAR DYNAMO Solar differential rotation Dipolar and Toroïdal components Yellow –outward /+ Blue – inward / -
6
B = Bp + Ba Be + Bi main aimantation external induction INTERNAL SOURCES : 1EXTERNAL SOURCES : 2,3 1 2 3 EARTH’S MAGNETIC FIELD Internal Dynamo External Dynamos - Magnetosphere/solar wind - Ionosphere/neutral wind Ec = -VsxBi E= VnxBt Evans, 1977 Friedman, 1987
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 INDICES B = Bp + Ba Be + Bi main aimantation external induction TRANSIENT VARIATIONS B ~ (Be +Bi) [Bi ~ % Be] External sources B ~ S R (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]
9
REGULAR -> QUIET - S R Cross-Tail Current Sheet J // - Region1 J // - Region2 IRREGULAR -> DISTURBANCE DR DCF DT DP 1 DP 2 D dyn Sq S R EEJ J ll
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
4 DYNAMOS IN SUN poloidal /toroidal MAGNETOSPHERE Solar wind IMF IONOSPHERE Earth’s magnetic field Neutral wind EARTH Motions of the core 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 S R, Sq P
12
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
13
Ahluwalia, JGR, Vol; 105, n°A12, 27481-27487, 2000 Ec = - VsxBi
14
Solar wind magnetosphere dynamo : quiet and disturbed time DP 2 Nishida, 1968 -> DP 2 in ionosphere Sq P Nagata and Kokubun, 1962 Slow solar wind -> poloidal component High wind speed streams -> poloidal component CME -> Shock events -> toroidal component
15
IONOSPHERIC DYNAMO Solar Radiation/Regular transient variations of the Earth’s magnetic field J = (E + VnxB ) J : electric current : electric conductivities Vn : neutral wind B: Earth’s magnetic E : Electric field électrique Vertical coupling Dynamics of the Atmosphere Ionospheric Electrodynamics Earth’s magnetic field Diurnal process E Region of the Ionosphere (90km< h< 150km ) Friedman, 1987 Atmospheric Tides Evans 1977 Sq : Chapman and Bartels, 1940 S R : Mayaud 1965
16
Stations Correlation XCorrelation Y Phu Thuy0.740.39 Gnangana-0.430.43 Tamanrasset0.420.16 Hermanus-0.380.38 M’Bour0.340.10 Bangui0.780.41 Trelew-0.130.42 San Juan0.030.51 From Hong PHAM THI THU SqX SqY F 10.7 Rz Earth’s magnetic field – Sq Vietnam Sunspot component
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
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
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.