ACTIVITY ON THE SUN:

1
ACTIVITY ON THE SUN

• Prominences
• Sunspots
• Solar Flares
• CMEs Coronal Mass Ejections
• Solar Wind
• Space Weather

2
Prominences

• Prominences are clouds of gas forming above
  sunspots that follow the magnetic field line
  loops. So-called quietones form in the corona.
  (about 40,000 kilometers above the surface) Quiet
  prominences last several days to several weeks.
  Surge prominences lasting up to a few hours
  shoot gas up to 300,000 kilometers above the
  photosphere.

3
Prominence Image
4
Sunspots

• Sunspots are areas on the sun with strong
  magnetic fields. The solar magnetic field is
  responsible for the sunspot cycle. Alternating
  every 11 years between solar maximum (11 years)
  and solar minimum (11years) making one entire
  cycle 22 years long.
• Most sunspots form in groups around the solar
  equator.

5
Sunspots

6
Sunspots

• Galileo discovered that the Sun's surface is
  sprinkled with small dark regions called
  sunspots.
• Sunspots are cooler regions on the photosphere.
  Since they are 1000--1500 K cooler than the rest
  of the photosphere, they do not emit as much
  light and appear darker.
• They can last a few days to a few months.

7
Sunspots

• Galileo used the longer-lasting sunspots to map
  the rotation patterns of the Sun. Because the Sun
  is gaseous, not all parts of it rotate at the the
  same rate.
• The solar equator rotates once every 25 days,
  while regions at 30 above and below the equator
  take 26.5 days to rotate and regions at 60 from
  the equator take up to 30 days to rotate.

8
Solar Flares

• Solar Flare eruptions are larger than
  prominences. Solar Flares will last only a few
  minutes to a few hours.
• A lot of ionized material is ejected in a flare.
  Unlike the material in prominences, the solar
  flare material moves with enough energy to escape
  the Sun's gravity.
• When this burst of ions reaches the Earth, it
  interferes with radio communication.

9
Solar Flares

• Sometimes a solar flare will cause voltage
  pulses or surges in power and telephone lines.
  Brownouts or blackouts may result.
• Humans traveling outside the protection of the
  Earth's magnetic field will need to have
  shielding from the powerful ions in a flare.

10
CMEs Coronal Mass Ejections

• CMEs are much like Solar Flares
• CMEs and Solar Flares are the biggest
  explosions in our solar system

11
CMEs Continued

• CMEs and Solar Flares have the power of about
  100 billion Hydrogen Bombs!
• Some CME speeds can be 2 million miles a second
  faster than the solar wind.
• And releases 220 billion pounds of material from
  the sun.

12
CME video

13
Solar Wind

• Solar Wind

14
Solar Wind Continued

• Solar Wind is the cause of space weather.
• Solar Wind is charged particles, such as
  electrons and protons, called plasma, coming out
  of the Sun in all directions at very high speeds
  -- an average of about 400 km/sec, almost a
  million mph!.

15
Solar Wind Continued

• Solar Wind is responsible for the anti-sunward
  tails of comets and the shape of the magnetic
  fields around the planets.
• Particles from the solar wind can get trapped
  near the north or south poles of planetary
  magnetic fields causing auroras.

16
Aurora Borealis Northern Lights
17
Aurora Australis South Pole
18
Space Weather

• Major solar activity is a very serious concern
  in space flight.
• Communications may be disrupted. Large solar
  disturbances heat the upper atmosphere, causing
  it to expand and create increased drag on
  spacecraft in low orbits, shortening their
  orbital lifetime.
• Spacecraft could potentially tumble and burn up
  in the atmosphere.
• Also, radiation exposure to astronauts is also
  seriously increased and of high risk!

19
Space Weather Continued

• Radiation sickness can result when humans are
  outside the protective magnetosphere of the
  Earth, as in missions to the moon and to Mars.
• NASA Monitors astronaut's exposure to radiation
  
• High-energy solar protons can produce increased
  radiation in the atmosphere at altitudes where
  supersonic aircraft fly. This is especially true
  for flights over the north and south magnetic
  poles, areas unprotected by the Earth's magnetic
  field, where the radiation has direct access to
  the atmosphere.

20
Space Weather

• To reduce the risk to aircraft, crews and
  passengers, routine forecasts and alerts are sent
  through the Federal Aviation Administration so
  that a flight in potential danger can consider
  what course of action to take to minimize
  radiation exposure.
• The National Oceanic and Atmospheric
  Administration (NOAA) Space Environment Center
  (SEC) forecasts high-speed solar wind
  advisories.

21
REVIEW - Solar Activity