Crepuscular Rays • Dust, water droplets, and haze all scatter light from the sun after passing through breaks in the clouds • Rays are parallel • Perspective makes rays appear
Jan 28, 2016
Crepuscular Rays
• Dust, water droplets, and haze all scatter light from the sun after passing through breaks in the clouds
• Rays are parallel
• Perspective makes rays appear to diverge
Crepuscular Rays
ScatteringScattering
Anticrepuscular Rays
• Convergent at the anti-solar point (the point opposite the sun)
• Extension of crepuscular rays
WestWestEastEastAnti-solar point
Anticrepuscular Rays
© C. Godfrey ScatteringScattering
Green Flash
Green Flash
22º Halo
© S. Hudson
Halos and sundog
46 º Halo
22 º Halo
Sundog
Parhelic Circle
© S. Hudson
22º Halo and sundog
22 º Halo
Sundog
Parhelic Circle
Sundog
Sun
© S. Hudson
Sundog (parhelion)
© C. Godfrey
22 º Halo
Sundog (parhelion)
Parhelic Circle
Parhelic Circle
Sun
© E. Godfrey
Complex Display at South Pole
© Marko Riikonen
Sun Pillar
Reflection
Upper Tangent Arc
© C. Godfrey
Positioned at top of 22 halo
Refraction
Circumzenithal Arc
You are looking almost straight up with the sun at the bottom of the image
22º Halo
Circumzenithal Arc
46º Halo
© C. Godfrey
Formed by refraction through hexagonal plate
crystals
Sun is below 32° elevation
Upper Tangent Arc with Circumzenithal Arc
© S. Hudson
© C. Godfrey
Alexander’s Dark Band
Secondary Bow
Primary Bow
Supernumerary Rainbows
Supernumerary Rainbows
Coronas (diffraction)• Light waves pass around tiny cloud droplets
• Light waves cancel or reinforce each other
• Colors appear when particles have uniform size
• Blue is on the inside, red is on the outside
This is similar to what happens when light bounces off a CD onto the ceiling!
Corona Around the Moon
Iridescence (diffraction)• Different size droplets distort a corona
• Pastel colors appear in high, thin clouds
© Shannon Story
Glory
Reflection, then refraction
Glory
Brocken bow (glory)
Heiligenschein
Reflection
Heiligenschein
Noctiluscent Clouds
• Form in upper mesosphere above 75 km (46 miles) altitude
• Composed of tiny ice crystals, possibly from disintegrated meteoroids or from chemical breakdown of methane gas
Nacreous (Mother-of-Pearl) Clouds
• Form in stratosphere above 30 km altitude in polar regions
• Made of supercooled water or ice crystals at temperatures < 80°C
Aurora Borealis (Northern Lights)
Aurora From Space
Aurora Borealis (Northern Lights)• Solar particles disturb Earth’s magnetic field
• Magnetic field rearranges itself and converts some of its energy into kinetic energy – fast moving particles
• Some particles are from Earth and others are from the Sun
• Particles flow inward along magnetic field lines and collide with air molecules to produce light
• Oxygen green and red (high altitudes)
•Nitrogen red, blue, violet
Aurora Borealis (Northern Lights)
Aurora• Northern Hemisphere: Aurora Borealis/Northern Lights
• Southern Hemisphere: Aurora Australis/Southern Lights
21 October 1999
Newfield, NY
© S. Hudson
Aurora• When particles from the Sun are energetic enough, the auroral oval can reach Oklahoma!
November 2004
Mulhall, OK
© C. Godfrey
Aurora on Saturn
Aurora on Jupiter