Unit 1 Sun Flashcards
Sun’s diameter
1,400,000km
Corona
Top of the solar atmosphere. 2 million degrees K. Ionised gas that is hot enough to emit X-rays.
Chromosphere
Lower part of the Sun’s atmosphere. Temperature ranges between 6000 degrees K to 2 million degrees K.
Solar wind
Flow of charged particles from the Sun.
Photosphere
Surface of the Sun. 5800 degrees K.
Rotational period at equator
25 days
Rotational period at poles
36 days
Thermonuclear fusion
Binding of atomic nuclei to form new elements. In the Sun it is generally hydrogen colliding with hydrogen to make helium.
Partial eclipse
Part of the Sun is blocked out due to the Moon.
Full eclipse
The whole sun is blocked by the Moon giving complete darkness.
Lunar eclipse
The Earth is between the Sun and the Moon making it red.
Solar
The Moon gets in the way of the Sun and blocks the view of the Sun from the Earth.
Distance to Sun: 1AU
150,000,000km
What is the Sun made of?
75% hydrogen, 25% helium and small amounts of other elements.
Sunspots
Sunspots are cooler areas of the photosphere that correspond to strong localised magnetic fields.
Umbra (sunspot)
Central, darker, cooler region. About 2000 degrees K cooler than the photosphere.
Penumbra (sunspot)
Lighter surrounding area with a temperature about 200 degrees K cooler than the photosphere.
Solar cycle
The 11 year pattern which the total number of sunspots reaches it’s maximum before falling again.
The Butterfly Diagram
The traditional way to plot sunspots with time(Y) on the x-axis and latitude(^o) on the y-axis.
Solar Wind
Solar wind is a steady stream of particles (mainly protons and electrons) flowing outwards in all directions from the Sun’s corona at speeds of typically 400 km/s.
Fast Solar Wind
This is thought to be from coronal holes (cooler areas of the corona nearer the Sun’s magnetic poles) where open magnetic field lines (as opposed to closed “loops”) permit charged particles from the photosphere to escape at speeds as fast a 850 km/s.
Solar Eclipse
Moon between the Earth and Sun.
Umbra (eclipse)
Area that experiences full solar eclipse during a solar eclipse. Appears as a darker shadow on the Earth from space.
Penumbra (eclipse)
Area that experiences partial solar eclipse during a solar eclipse. Appears as a lighter shadow on the Earth from space.
Diamond ring (eclipse)
At the beginning and end of totality in a solar eclipse when one bead of sunlight shines through a valley on the moon.
Lunar eclipse
When the Moon is in full moon it is possible to have a lunar eclipse. This is when the Moon is behind the Earth and refraction of the Sun’s light makes the Moon appear an orange/red colour.
Equation of Time
Eot= Apparent Solar Time - Mean Solar Time
How many days of the year is the EoT 0?
4 days.
What are the names of the two aurorae?
Aurorae Borealis and Aurorae Australis.
What causes aurorae?
Electrons from the solar wind accelerate at high speeds into the atmosphere directed by the Earth’s magnetic field. As the atoms that the electrons have excited de-excite they emit certain colours of light.
