The Sun sends the Earth:
Solar Radiation
- peak wavelength….visible light
- Travels at the speed of light…..takes 8 minutes to reach Earth
Solar Wind, Solar flares, and Coronal Mass Ejections
of Plasma (ionized gas)
- Solar wind averages 250 miles/sec….takes several days to
reach Earth
- Solar Flares and Coronal Mass Ejections (CMEs) can travel up to
1300 miles/sec….takes 1 to 2 days to reach Earth
Radius
6.96 × 108 m
Mass
1.99 × 1030 kg
Average density
1410 kg/m3
Rotation period
24.9 days (equator); 29.8 days (poles)
Surface temperature
5780 K
Luminosity
3.86 × 1026 W
- Solar energy per sq. meter of surface area every second
Solar Constant
- amount of solar energy reaching the earth every second
- 1400 watts per sq. meter (W/m2)
.5 m2 human body = 700 watts (equal to a typical electric heater)
Sun’s luminosity = 4 x 1026
This energy equates to 100 billion megaton bombs
exploding every second or 4 trillion 100 watt bulbs
- The sun’s interior is determined by
observing pressure waves.
- This is similar to how we
determine the Earth’s interior using
earthquake waves.
- Each wave has a unique
wavelength and frequency which
allows scientists to determine the
sun’s interior
Average Density 1410 kg/m3
- Densest in the core
- Hottest in the core about
15,000,000o K
- 10,000,000o K is needed
for nuclear fusion to ignite
- Photosphere is 5800o K
-
- nuclear fusion in the
core of the sun is the
source of solar radiation
- hydrogen atoms are
fused into heavier
helium atoms
Nuclear Fusion
- the combining of light nuclei into heavier ones.
- nucleus 1 + nucleus 2 = nucleus 3 + energy.
- E = mc2
Law of Conservation of Matter and Energy
- the sum of mass and energy (properly converted to the
same units, using Einstein's equation) must always remain
constant in any physical process
Proton-Proton Chain
- protons repel so must be slammed together at high speeds
(hundred of kilometers /second)
- temperature must be 10,000,000 o K (107) for nuclear fusion
of Hydrogen to Helium to ignite
- Energy reaches the sun’s exterior by convection
- Hot interior gases move outward as cooler gases sink
Convective Zone
(reflection of convection motion)
- bright and dark gases are called granules
- 5 to 10 minute lifetime (continent size)
- millions along the top layer of convection
zone
- uppermost part of the convection zone
- light and dark reflects temperature differences
- bright are hotter gases rising and dark are cooler gases sinking
-layer of the Sun we see
- density decreases
- energy is transferred by
radiation
- solar flares, prominences,
and sunspots occur here
SUNSPOTS - cool areas of photosphere gas
- sun can have 100’s
of sunspots or none
at all.
Sunspots typically grow over a
few days and last anywhere from
a few days to a few months.
- a dark central region known as the umbra
- surrounded by a lighter region called the penumbra
Umbra-4500 o K
Penumbra-5500 o K
Photosphere-5800 o K
- Strong magnetic field tends
to block the convection flow
of hot gases
-A regular pattern of the number and distribution of sunspots
-Average number reaches maximum every 11 years, then goes
down to almost zero
22 year total sunspot cycle…during the 11 year span the northern and
southern hemisphere sunspots have opposite polarity. Every 11 years
the polarity of the sunspots reverse
- violent eruptions of large amounts
of energetic particles from the corona
- tend to follow active sunspot activity
Solar Prominences
- loops of ejected particles
- magnetic field lines
connect pairs of sunspots
- can last for days or weeks
- typically 100,000 km
(10x the earth’s diameter)
- also a result of magnetic instability
- even more violent than prominences
- releases as much energy as prominences, but in minutes or hours
- lower part of the Sun’s atmosphere
- can’t see except during a solar eclipse
- gives off a reddish hue
- red from the hydrogen
emission lines
- small solar storms eject hot matter called
spicules to upper atmosphere every few
minutes
- believed to be caused by magnetic
disturbances in the Sun’s upper atmosphere
- Absorption elements in the spectrum indicates
67 elements in the sun’s lower atmosphere
- If the chromosphere and
photosphere are blocked during an
eclipse the corona is visible
-temperature rises and then
remains constant (scientists are
not sure why)
Solar Corona during sunspot minimum and maximum
- Generated in the corona
- Most violent solar particle eruption
- Up to 10 billion tons of plasma can
be released
- Creates the most adverse effect on
Earth’s magnetosphere…creating
geomagnetic storms
- Solar particles leave the corona in a steady stream (Solar Wind)
- fast moving particles (mainly electrons and protons)
escape the sun’s surface
- high temperature of corona
hot enough to escape the sun’s gravity (emits in X-ray)
- solar wind escapes through coronal holes
- Generated by the acceleration of charged particles
such as electrons
- Represented by imaginary lines from the north magnetic
pole to the south magnetic pole
-region around the Earth in which the
magnetic field is significant
Van Allen Belts
- 2 donut shaped regions
containing magnetically
trapped energized
particles…from solar
wind, flare, CMEs
- Solar wind deforms the magnetosphere creating a bow
shock…compressing on the dayside and expanding
on the night side.
- Layer in the upper atmosphere
- Composed of ionized gas (plasma)
- Radio signals are bounced off the
outer ionosphere and solar activity
can disrupt this communication
- Created when magnetic field lines intersecting
with the atmosphere allow charged particles to
collide with and excite atmosphere molecules.
-we see the northern (aurora borealis) and
southern (aurora australis) lights as photons are
emitted by nitrogen (red colors) and oxygen
(green colors)
Aurora viewed from space by the shuttle
- About 600 satellites are currently orbiting the earth
- The compression and disturbances to the magnetosphere can
affect satellite communications
- Geomagnetic storms can induce currents and cause power outages