Presentation is loading. Please wait.

Presentation is loading. Please wait.

The Earth’s Magnetic Field. Source: NASA

Similar presentations


Presentation on theme: "The Earth’s Magnetic Field. Source: NASA"— Presentation transcript:

1 The Earth’s Magnetic Field

2

3 Source: NASA

4 Source: NASA

5 spher. harmonic analyses

6

7

8

9 magnetic reversals, secular variation

10

11 Earth’s Magnetic Field Mostly a dipole field (modern and paleomagnetic evidence) Can change direction (polarity) Secular variation (small-scale changes in direction and magnitude)

12 Magnetic Units: Magnetic field – Tesla field mostly described in micro-Tesla or gamma (γ) 1γ = T

13

14

15

16 Mathematical description: Spherical harmonic analyses

17

18 Short-term changes: Careful measurements since 1600 Navigational purposes

19

20

21

22 Paleomagnetism – history of the earth’s magnetic field Earth is dipole field –Relationship between Inclination and latitude tan I = 2 tan λ

23

24

25 Identification of magnetic minerals in rocks Rocks are assemblages of diamagnetic, paramagnetic, and ferrimagnetic minerals. Concentration of ferrimagnetic minerals is usually very small (< 1 %) Microphotograph of a thin section of norite dolomite limestone sandstone shale Sedimentary rocks Volcanic rocks granite gabbro basalt Magnetic susceptibility, κ (SI units) Median values and ranges of the magnetic susceptibility in common rock types Modified from Lowrie, 1997

26

27

28

29

30

31 Magnetic Polarity

32 Duration of a Polarity Chron

33

34

35

36 Generation of the Magnetic Field No big fat bar magnet Dynamic processes inside the outer core

37 Early (Simplistic) Model

38

39

40

41

42

43

44

45

46 Ultimate driver of magnetic field ?

47 Magnetic Field of Other Planets Mercury – yes, but weak Venus – no, or very weak Mars – no clear evidence for field, but might have had field in the past Jupiter – yes, very strong (20,000 times earth) Saturn – yes 500 times earth Uranus – yes, strong tilt with respect to rotational axis

48 Source: NASA

49


Download ppt "The Earth’s Magnetic Field. Source: NASA"

Similar presentations


Ads by Google