Atmosphere and Waves A Mc GourtyRideout Tutorial Layers

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Atmosphere and Waves A Mc. Gourty-Rideout Tutorial

Atmosphere and Waves A Mc. Gourty-Rideout Tutorial

Layers of the Atmosphere

Layers of the Atmosphere

The Troposphere • Most dense • All weather takes place here

The Troposphere • Most dense • All weather takes place here

The Stratosphere • • Dry Absorbs ultraviolet radiation (UV) Ozone layer is here Ozone

The Stratosphere • • Dry Absorbs ultraviolet radiation (UV) Ozone layer is here Ozone (O 3) absorbs much UV C and UV B waves.

The Mesosphere • Coldest • Many meteors burn up here

The Mesosphere • Coldest • Many meteors burn up here

The Ionosphere • Region of charged ions (positive) and electrons • Electrons are torn

The Ionosphere • Region of charged ions (positive) and electrons • Electrons are torn off atoms by sunlight of short wavelengths • Electrons don’t recombine easily because the distance between molecules is large at high altitudes and collisions are not frequent

How Far Does the Atmosphere Extend? images are courtesy of Windows to the Universe,

How Far Does the Atmosphere Extend? images are courtesy of Windows to the Universe, http: //www. windows. ucar. edu

Which waves on the EM spectrum get through to us on Earth?

Which waves on the EM spectrum get through to us on Earth?

Visible Light and some Infrared get through But that’s NOT all!!! images are courtesy

Visible Light and some Infrared get through But that’s NOT all!!! images are courtesy of Windows to the Universe, http: //www. windows. ucar. edu

So Do Radio Waves!!!!!

So Do Radio Waves!!!!!

Troposphere – Most radio waves are refracted – Short wavelength-absorbed

Troposphere – Most radio waves are refracted – Short wavelength-absorbed

Attenuation by the troposphere • All wavelengths >25 cm pass through • O 2,

Attenuation by the troposphere • All wavelengths >25 cm pass through • O 2, H 2 O, and weather ( rain, fog, etc) cause attenuation

Refraction in the troposphere • nair= 1. 00029 when T=0°C and P=760 mm of

Refraction in the troposphere • nair= 1. 00029 when T=0°C and P=760 mm of Hg • “n” differs for light and radio waves only due to presence of water vapor which increases dielectric constant

As a ray moves from one layer of the atmosphere to another it bends

As a ray moves from one layer of the atmosphere to another it bends

The Ionosphere Can Cause Reflection • The ionosphere is known to reflect most radio

The Ionosphere Can Cause Reflection • The ionosphere is known to reflect most radio waves because of its ions and free electrons

Penetration and Refraction • Penetration and refraction- dependent on electron density and wave frequency

Penetration and Refraction • Penetration and refraction- dependent on electron density and wave frequency

Radio Ga-Ga • The ionosphere refracts radio waves of certain frequencies ( 3 -30

Radio Ga-Ga • The ionosphere refracts radio waves of certain frequencies ( 3 -30 MHz or short waves) • This refraction makes worldwide radio communication possible without using satellites

Refraction in the ionosphere • Larger than tropospheric • Refraction at lower frequencies <40

Refraction in the ionosphere • Larger than tropospheric • Refraction at lower frequencies <40 MHz • Wedge refraction- east-west electron density gradients due to local solar time- cause ionosphere to act like tiny prism

Attenuation by the Ionosphere • Ionization varies with latitude, season, solar time, and phase

Attenuation by the Ionosphere • Ionization varies with latitude, season, solar time, and phase of sunspot cycle • 2 regions- E and F where penetration take place • Region D- absorption • Divergence occurs at angles of incidence<30° and intensity on ground is reduced • Absorption loss increases with air densitygreatest in lower ionosphere

Check out the ionosphere and the role its layers play in radio wave communication

Check out the ionosphere and the role its layers play in radio wave communication in this really cool video.

Still don’t get it, then move onto the next slide. If not click here:

Still don’t get it, then move onto the next slide. If not click here:

Layers of the Ionosphere • Lowest part: D layer has enough collisions to cause

Layers of the Ionosphere • Lowest part: D layer has enough collisions to cause it to disappear after sunset • Remaining ions and electrons recombine, without sunlight new ones are no longer produced • Layer return at sunrise

D Layer and Radio Transmission • Low frequencies ( below 10 MHz) absorbed -

D Layer and Radio Transmission • Low frequencies ( below 10 MHz) absorbed - high frequencies pass through • More ionized = more radio wave absorption • Maximum usable frequency ( highest frequency that can be refracted) : 16 MHz • Optimal usable frequency: 13. 6 MHz • Most abundant molecule present: O 3

E Layer of Ionosphere • Ionized gas • Reflects medium frequency waves, causes radio

E Layer of Ionosphere • Ionized gas • Reflects medium frequency waves, causes radio waves to be propagated beyond horizon • Day- solar wind presses this layer closer to the Earth limiting distance radio waves can be reflected • Night - solar wind drags the ionosphere further away, increasing the range of radio waves • Season and sunspot activity also influence reflection

E Layer and Radio Transmission • Refracts radio signals and causes them to skip

E Layer and Radio Transmission • Refracts radio signals and causes them to skip back to earth • Weakest at night - radio signals pass right through • Maximum usable frequency : 28 MHz • Optimal usable frequency : 23. 8 MHz • Most abundant molecule: O 2 • Few seasonal or daily differences for transmission

F Layer of Ionosphere • Most important in terms of high frequency communications •

F Layer of Ionosphere • Most important in terms of high frequency communications • During the day- 2 layers; combines into one layer at night • Thickest • Most reflective of radio on the side of the Earth facing the sun

F Layer and Radio Transmission • Ionized all night • Refracts higher frequencies by

F Layer and Radio Transmission • Ionized all night • Refracts higher frequencies by day, but passes them through at night • Low frequencies ( 10 -15 MHz) are refracted back to earth at night • Maximum usable frequency : 16 MHz • Optimal usable frequency : 13. 6 MHz • Most abundant molecules present: Nitrogen in F 1 sub layer and Oxygen in F 2 sub layer.

Radio Waves Through the Atmosphere • D layer disappears at night- low frequencies can

Radio Waves Through the Atmosphere • D layer disappears at night- low frequencies can now be used ( AM vs. FM) • E Layer weak at night • F sublayers combine into one layer at night • Sunspots can increase the ionosphere’s ability to refract high frequency radio waves • Solar flares can increase the amount of radio wave absorption, thus hurting radio communications

Space Weather • What happens in the Sun and in space effects what happens

Space Weather • What happens in the Sun and in space effects what happens here on Earth. To find out more click

What Else Can the Sun Do? • The Earth has a magnetic field that

What Else Can the Sun Do? • The Earth has a magnetic field that reaches into space • The magnetic field of the Earth is surrounded in a region called the magnetosphere. The magnetosphere prevents most of the particles from the sun ( solar wind) from hitting the Earth • Some particles from the solar wind can enter the magnetosphere and cause auroras

Earth’s Magnetic Field

Earth’s Magnetic Field

Solar Wind Coming Towards Earth’s Magnetosphere- watch the video

Solar Wind Coming Towards Earth’s Magnetosphere- watch the video

Radio Waves Paths the images are courtesy of Windows to the Universe, http: //www.

Radio Waves Paths the images are courtesy of Windows to the Universe, http: //www. windows. ucar. edu

Ionosphere , Plasma, and Communication

Ionosphere , Plasma, and Communication

Radio window to the universe • Extends from. 5 mm to 10 m •

Radio window to the universe • Extends from. 5 mm to 10 m • <3 cm water vapor absorbs incoming radio emissions • Between 3 cm-50 cm atmospheric conditions don’t effect observations • >50 cm ionosphere and solar activity play crucial role in observations- night observations are best • Any electrical devices between the 3 cm-50 cm band can effect observations- microwaves, garage door openers, cell phones, and remote controls due to harmonics