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Lecture

# AST101H1 Lecture Notes - Solar Minimum, Solar Maximum

Department
Astronomy & Astrophysics
Course Code
AST101H1
Professor
Michael Reid

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AST101: The Sun and its Neighbours
November 22, 2012
The Solar Cycle
- sun goes through a cycle from little solar activity to a lot of solar activity
- the two extremes of this cycle are called "solar maximum" and "solar minimum"
- the entire cycle takes 11 years
- sunspot activity peaks at solar maximum, and are rare during solar minimum
- differential rotation tangles the sun's magnetic ﬁeld
!- because the earth is not a solid, it an rotate at a different rate at the equator than
it does at the poles
!- at solar minimum, the magnetic ﬁeld lines are unwound
!- they start to get wound up, and at solar maximum it is almost horizontal
!- this leads to "kinks" in the magnetic ﬁeld
!- the places where the magnetic ﬁeld comes up and goes down through the
surface of the sun is where you get sunspots - this is why they tend to come in pairs,
and why we see loops of charged material (solar ﬂare) come out of the sun
- why are sunspots dark? The magnetic ﬁeld pushes open a hole in the sun, and we can
see below to the cooler area. The contrast makes the sunspot appear darker
- solar plasma follows the pattern of magnetic ﬁeld lines
- coronal mass ejection = large solar ﬂare
- solar maximum usually produces great auroras here on earth
The sun's Power Source
- the heat from the core creates pressure that balances out the sun's gravity
- as long as the sun has a powerful heat source at its core, this balance will continue
- where does the sun get all of this energy?
- mass is converted into energy (e = mc^2)
- proton-proton chain is how nuclear fusion occurs in the sun. Start with 4 protons and
result with one helium, energy, and anti-matter
- the ﬁrst set of stuff has more energy than the second
- the "lost" mass is converted into energy
- fusion = sticking together
- ﬁssion = pulling apart