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Last Post 3/28/2017 8:03 AM by  Delores Knipp
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3/27/2017 10:20 AM
    What is the unique role of the ionosphere in the Sun - Earth system? How does it protect us?
    Tags: ionosphere, role

    Claire Raftery

    New Member

    New Member

    3/27/2017 1:56 PM
    That's a great question. The ionosphere is the uppermost layer in the atmosphere, so it's the one that the Sun's radiation hits first. Each layer in the atmosphere does it's part in absorbing some of the Sun's harmful radiation so only the good stuff gets to the Earth's surface.

    The ionosphere only really exists where the Sun's radiation is hitting the Earth. That means that on the side near the Sun, the ionosphere is thick, but on the side of the Earth facing away from the Sun, its almost nonexistent. The ionosphere is important because long-wave communications waves, such as radio waves, use the ionosphere to bounce waves all around the planet. The waves are sooooo long that they can cover huge distances in just one bounce, making them really useful for long-range communications. The tricky thing about that is, when we have lots of solar activity, we have more radiation hitting the atmosphere, making the ionosphere thicker. This changes the way radio waves bounce, making communications less reliable.

    Kris Sigsbee

    Basic Member

    Basic Member

    3/27/2017 5:43 PM
    In addition to affecting how radio waves propagate here on Earth, the ionosphere is also the layer of the atmosphere where the aurora borealis and aurora australis (also called the northern and southern lights) happen. The aurora are produced when electrons and protons trapped in Earth's magnetosphere (the region of outer space where we can measure Earth's magnetic field) precipitate (or rain down on) the Earth's atmosphere and excite oxygen atoms and nitrogen atoms and molecules, causing them to emit the green, red, and sometimes blue and purplish light we see as the aurora. Aurora are also associated with huge electrical currents in Earth's magnetosphere that flow down into the ionosphere during geomagnetic storms and auroral substorms.

    The trapped plasma (or gas of electrons and ions) that fills Earth's magnetosphere comes from two sources - the solar wind and outflows from the ionosphere during geomagnetic storms. One of the scientific topics I am studying is electromagnetic ion cyclotron (EMIC) waves observed by satellites orbiting the Earth. These waves occur in three frequency bands, a hydrogen or proton band, a helium band, and an oxygen band. The oxygen EMIC waves are not observed very often because the oxygen ions needed to produce EMIC waves in space may come from the ionospheric outflows during big geomagnetic storms.

    The ionosphere also has interesting interactions with lightning. You are probably used to seeing lightning that travels between clouds or between the clouds and the ground during thunderstorms. However, there are other forms of lightning that were not discovered until very recently thanks to high-speed cameras. Sprites, jets, and ELVES travel upwards towards the ionosphere from thunderclouds, and they are not completely understood. Lightning can also perturb the ionosphere to generate a type of plasma wave called a whistler. People can hear whistler waves in radio signals, and satellites orbiting the Earth also observe them in space. You can listen to the sounds of whistler waves at Earth and Jupiter and other space sounds here - http://www-pw.physics.uio.../space-audio/sounds/

    Delores Knipp

    New Member

    New Member

    3/28/2017 8:03 AM
    Any planet or solar system body with an atmosphere also has an ionosphere. The very short wavelengths of solar light have enough energy to separate electrons from their parent atoms, thus producing ions in the ionosphere. So, in that regard Earth’s ionosphere could be considered normal rather than unique. Even so, the ionosphere does play an important role on Earth, because Earth has life. The ionosphere blocks (absorbs) the short wavelengths of light that is harmful to life. Thus the ionosphere has a role much like the stratosphere, except that the ionosphere blocks the most energetic solar light, called extreme ultraviolet and X-ray light, while the stratosphere blocks much of the ultraviolet light.

    This blocking has a big impact on our ability to monitor the Sun. It means that we have to put sensors on satellites well above the atmosphere (and the ionosphere) to see what the Sun is doing in very short wavelengths. A lot of research and instrument design efforts are devoted to getting a view of the Sun from space, because the ionosphere does such a good job of blocking the wavelengths at which the Sun reveals most of its interesting variations.
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