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