Ionosphere

The ionosphere is the part of the atmosphere that is ionized by solar radiation. It forms the inner edge of the magnetosphere and has practical importance because it influences high-frequency (HF) (3–30 MHz) radio propagation to distant places on the Earth.

Ionospheric Perturbations

X-rays : Sudden Ionospheric Disturbances, SID

When the sun is active, strong solar flares can occur that will hit the Earth with hard X-rays on the sunlit side of the Earth. They will penetrate to the D-region, release electrons which will rapidly increase absorption causing a High Frequency (3-30 MHz) radio blackout. During this time Very Low Frequency (3 - 30 KHz) signals will become reflected by the D layer instead of the E layer, avoiding the signal loss through the D layer. As soon as the X-rays end, the sudden ionospheric disturbance (SID) or radio black-out ends as the electrons in the D-region recombine rapidly and signal strengths return to normal.

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Protons : Polar Cap Absorption (PCA)

Associated with solar flares is a release of high-energy protons. These particles can hit the earth within 15 minutes to 2 hours of the solar flare. The protons spiral around and down the magnetic field lines of the Earth and penetrate into the atmosphere near the magnetic poles increasing the ionization of the D and E layers. PCA's typically last anywhere from about an hour to several days, with an average of around 24 to 36 hours.

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Geomagnetic Storms

A geomagnetic storm is a temporary intense disturbance of the Earth's magnetosphere.

Related Topics:
Geomagnetic storm - Magnetosphere

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• During a geomagnetic storm the F₂ layer will become unstable, fragment, and may even disappear completely.
• In the Northern and Southern pole regions of the Earth aurora will be observable in the sky.