Future China Geomagnetism Satellite Mission (CGS) Aimin Du Institute of Geology and Geophysics, CAS 2012/11/18 Taibei

OUTLINE 1- Promoting of the CGS mission 2- A brief introduction to the Constellation 3- Open discussion about the science object of the CGS mission

Grenoble Workshop about CGS On April 11, 2011

To Promoting the CGS Mission In 2012, China Spacesat Co. Ltd. to design the CGS It is confirmed that the Chinese companies have ability to product the small satellites and suitable rockets for the CGS mission.

Why are Chinese interested in geomagnetic satellite missions? It is related to Chinese history.

Needham has shown that the credit for the discovery of declination must go to the Chinese. Needham has tabulated eighteen recorded Chinese compass observations of declination covering the period about These are of interest not only to historians but also to geophysicists, for they represent the earliest recorded direct observations of the Earth's magnetic field. The question of their validity is therefore of great importance. Magnetic Declination in China

CGS Compass MagNet Magsat Ø rsted CHAMP Swarm Petrus Peregrinus (1269) Epistola de Magnete

CONSTELLATION One satellite is in an orbit close to the equatorial plane One satellite is in an orbit close to the equatorial plane Four satellites are in polar orbits separated by 45° Four satellites are in polar orbits separated by 45° Mass: 115 kg Inclination: 87.4° Altitude: 450 km Pre. rate: °/day

Spacecraft System Architecture Combined GPS, GLONASS, Galileo and Beidou Occultation technique

ComponentObjectives Core Contribute to the long phase of synoptic monitoring of the core field Monitor flows in the core and their time changes Investigate the interplay between velocity and magnetic fields Mantle Perform 3D tomography of mantle conductivity Crust Construct the lithospheric magnetic map Construct the lithospheric magnetic map Environment Investigate the time-space structure of the magnetospheric and ionospheric sources on all time scales CGS Scientific Objectives (Dominique and Jackson, 2010)

1.Core Field Dynamics of the Earth’s core, as estimated from the evolution of the magnetic field, evolves on a variety of timescales. 核幔界面 外核

2. Monitor of Magnetosphere- Ionosphere Current System

Atmosphere Ionosphere GPS CGS 3. Atmosphere and ionosphere occultation technique

4. Crust Field Deep Structure of the Earth and Concentration of Metals in Lithosphere 古亚洲成矿域 环太平洋成矿域 喜马拉雅 - 特提斯成矿域

Considerations of the constellation concept are for: Good coverage in spatial, local time and seasons. Separating of the core field, crust field, induced field. Equatorial satellite is for monitoring the daily variations and equatorial current system.

80% data for single satellite were lost Kp < 2; LT ~ 21: :00

Equatorial satellite monitoring mid-low latitude currents by the assimilation method Ring current: Storm-time geomagnetic disturbance Sq current: ionospheric dynamo Eqatorial ElectroJet (EEJ): cowling current Cross tail current: Substorm current Magnetopause current: Solar wind ram pressure

LONGITUDINAL PROFILE OF  Bj FROM MAGNETOSPHERIC CURRENTS (Le Guan et al., AG, 2004)

EQUATOR CURRENT SYSTEM has a good longitudinal profile Sq C-F current Cross Tail current

DEDUCE THE ELECTRIC POTENTIAL IN POLAR REGION THEN MAPPING TO THE MID-LOW LATITUDE MAGNETOSPHERE

Geomagnetic Indices Global profile in X component on the ground Magnetospheric Current System Ring Current Auroral electrojet and Field-Aligned Current FOR EXAMPLE

SUMMARY The constellation constellation with one near- equatorial orbit satellite and four polar orbit satellites should contribute to: The constellation constellation with one near- equatorial orbit satellite and four polar orbit satellites should contribute to: Separating of outer source field (noise) from the satellite data. Modeling the magnetosphere-ionosphere current system (signal). Discovering the small scale and short term variation of core field. Constructing of mantle conductivity and lithosphere.

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