On the Torque Exerted by a Magnetically Threaded Accretion Disk Reference:1979ApJ...232..259G apj449L153 Reporter: Xu Kun 2015.3.17 1.

1

On the Torque Exerted by a Magnetically Threaded Accretion Disk

Reference:1979ApJ...232..259G apj449L153

Reporter: Xu Kun

2015.3.17

2

Outline

*The GL79a model

*Evaluation of the torque

3

The Ghosh & Lamb (1979a,b) Model for Disk-Field Interaction

4

The GL79a Model

5

Structure of the Transition Zone

6

Equations of the Boundary LayerRadial-Structure Vertical-Structure

7

Dimensionless

8

Rewrite the Equations in Nondimensional Form

9

Examples of Boundary-Layer Structure (1)0.3s

0 0.5

2.5

2b

p

C

C

0 1

1.5

1.5b

p

C

C

0 2

2

1.5b

p

C

C

0 4

4

1b

p

C

C

10

Examples of Boundary-Layer Structure (2)0 1 2.5 2b pC C ， ，

11

Existence of Maximum Fastness

max 1

12

Evaluation of the torque

13

The Torque

14

15

16

17

Discussion

• ranging from 0.875-0.950• The most plausible of the three is the third

18