This is an image of a dynamo model suggested for the planet Jupiter. Credit: Robert MacDowall, NASA.

Radiative dynamo is a lecture and an article about a specific aspect of astrophysics applied to plasma, gaseous, liquid, and rocky objects. It is from the astronomy department initially for the course on the principles of radiation astronomy.

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## Quiz

1

True or False, The differential profile of the Sun's surface extends into the solar interior as rotating cylinders of constant angular momentum.

 TRUE FALSE

2

Complete the text:

 Magnetic fields can be created in stratified (non-convective) layers in a rotating star.

3

True or False, A magnetic instability in the toroidal field (wound up by differential rotation) replaces the role of convection in opening the field amplification loop.

 TRUE FALSE

4

Complete the text:

 Match up the characteristics with the type of dynamo: disc dynamo - A geodynamo - B radiative dynamo - C α dynamo - D Ω dynamo - E radiative α-Ω dynamo - F Taylor-Spruit dynamo - G convection . pinch-type instabilites . molten outer core . turbulence, a radiative layer, and differential rotation . radiative layers . differential rotation . a rotating cylinder .

5

True or False, For stars more massive than around 15 M the Kelvin–Helmholtz turbulence dominates over the magnetic turbulence and a stable field cannot be sustained by a dynamo.

 TRUE FALSE

6

What are the requirements for a dynamo to occur and subsequently operate?

 plate tectonics in its past an electrically conductive fluid medium a spheroidal object stripes of crustal magnetism local magnetohydrodynamic instabilities transform faults shear between different parts two natural satellites an energy source

7

True or False, Any conversion of mechanical energy into electrical energy and associated magnetic fields is a dynamo.

 TRUE FALSE

8

Which of the following are associated with the dynamo of the Sun?

 plate tectonics in its past dipole magnetic field it is spheroidal stripes of crustal magnetism a circular electric current flowing deep within the star it appears to be in hydrostatic equilibrium transform faults shear between different parts of the Sun two natural satellites it has a radiative zone

9

True or False, Electrons in the Earth's magnetosphere are energized by neutral particles from the Sun

 TRUE FALSE

10

Which of the following are associated with the geodynamo of Mars?

 plate tectonics in its past Mars is spheroidal stripes of crustal magnetism it appears to be in hydrostatic equilibrium transform faults two natural satelites the direction of the magnetic field changes dramatically from place to place

11

True or False, An antidynamo theorem is one of several results that restrict the type of magnetic fields that may be produced by dynamo action.

 TRUE FALSE

12

Which phenomena are associated with the heliosphere?

 a region of space where the interstellar medium is blown away by the solar wind a bubble in space virtually all the material emanates from the Sun itself Voyager 2 Voyager 1 the termination shock

13

True or False, A dynamo taking place in the radiative layers of a star is a radiative dynamo.

 TRUE FALSE

14

A disc dynamo has which of the following characteristics?

 an alternating current an electrically insulating disc a uniform static magnetic field potential difference between the center of the disc and the magnetic field the disc rotates in a plane parallel to the magnetic field

15

True or False, No axisymmetric magnetic field can be maintained through a self-sustaining dynamo action by an axially symmetric current.

 TRUE FALSE

16

Which of the following is associated the Earth's geodynamo?

 the Sun and the Moon the Earth's magnetic field convection currents heat flow from the inner core ice ages plate tectonics the Coriolis force

17

True or False, The mathematical symbol ${\displaystyle \nabla }$ indicates a differential equation in which only one variable such as 'x' is differentiated.

 TRUE FALSE

18

Which geological phenomena are associated with Earth?

 lava-spewing volcanoes sulfur volcanoes plate tectonics water oceans liquid methane oceans silicate minerals

19

Yes or No, Motion resulting from a magnetodynamic instability may act as a dynamo to sustain a magnetic field.

 Yes No

20

Which phenomena are associated with the dynamo of Uranus?

 axisymmetric magnetic field sulfur volcanoes non-dipolar water oceans bipolar magnetotail detached bow shock obtuse rotation

## Hypotheses

1. The dynamo lectures may be better as a part of a magnetohydrodynamics course.