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 Mass 6.96 10 8 m 1.99 10 30 kg Average density 1410 kg/m 3 Rotation period Surface temperature Luminosity 24.9 days (equator); 29.8 days (poles) 5780 K 3.86 10 26 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/m 2 ).5 m 2 human body = 700 watts (equal to a typical electric heater) Sun s luminosity = 4 x 10 26 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 15,000,000 o K - 10,000,000 o K is needed for nuclear fusion to ignite - Photosphere is 5800 o 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 = mc 2 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 (10 7 ) 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
-temperature rises and then remains constant (scientists are not sure why) - If the chromosphere and photosphere are blocked during an eclipse the corona is visible
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