Solar Storm Threat Analysis - Impact
Solar Storm Threat Analysis - Impact
Solar Storm Threat Analysis - Impact
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<strong>Impact</strong>, 2007 James A. Marusek<br />
and as a result are used for ground-to-space communications. 30 <strong>Solar</strong> extreme ultraviolet and soft x-ray emissions<br />
from solar flares change the electron density and gradients in the ionosphere which profoundly affects the<br />
ionosphere reflections.<br />
A sudden increase of x-ray radiation from a solar flare causes substantial ionization in the lower region of the<br />
ionosphere on the sunlit side of Earth. This ionization can produce sudden ionospheric disturbances of radio signals,<br />
sudden phase anomalies, sudden enhancement of signals and short wave fade. The radio disturbance can last from<br />
minutes to hours. <strong>Solar</strong> flares also produce a wide spectrum of radio noise. 30<br />
High-energy protons within SPEs are magnetically pulled towards the Earth’s poles. The collision of these particles<br />
in the upper atmosphere creates polar cap absorption. This can impact communications from days to weeks. 30<br />
CMEs producing geomagnetic storms cause HF radio interference. The storms produce rapid and deep signal fading<br />
due to the ionospheric irregularities that scatter radio signals. Auroral absorption, multipathing, and non-great circle<br />
propagation effects combine to disrupt radio communications. The more intense the CME, the greater this zone of<br />
auroral irregularity moves towards the equator. These effects will last a day or two after the CME has ended. 30<br />
A. Communications<br />
<strong>Solar</strong> storms can affect radio communications through ionospheric reflectivity and scintillation including: 1,12,30<br />
• HF radio communications (3-30 MHz)<br />
o effect short-wave propagation through sunlit side of Earth<br />
o increased absorption<br />
o depressed Maximum Usable Frequencies (MUF)<br />
o increased Lowest Usable Frequencies (LUF)<br />
o increased fading and flutter.<br />
o effect ground-to-air, ship-to-shore and amateur radio communications<br />
• VHF propagation (30-300 MHz)<br />
o effect pagers and cellular phones<br />
o effect US Navy’s MARS radio signals worldwide<br />
o television and FM radio stations are little affected by solar activity.<br />
o the high and low band in mobile voice communications for dispatching utility company line crews<br />
very susceptible to fadeout<br />
• Satellite communications (200 MHz to several GHz)<br />
o increased scattering of satellite-to-ground ultra high frequency (UHF) transmissions or<br />
scintillation can seriously interfere with direct satellite communications links.<br />
o drastic loss in spacecraft electrical power due to inability to reposition craft.<br />
o erroneous positioning information from single frequency GPS<br />
o severe distortion of data transmissions from Geosynchronous Satellites.<br />
o some satellites, which employ linear polarization up to 1 GHz are affected by Faraday rotation of<br />
the plane of polarization.<br />
o loss of phase lock<br />
o Radio Frequency Interference (RFI)<br />
B. Radar<br />
<strong>Solar</strong> storms can also affect radar surveillance systems. <strong>Solar</strong> storms can cause range errors, elevation angle errors,<br />
azimuth angle errors and radar energy scatter due to auroral interference.<br />
Satellites are vulnerable to collision damage from space debris. As a precaution, this debris is constantly tracked<br />
and satellite orbits are finely adjusted to avoid potential collisions. During a solar storm, Earth’s atmospheric<br />
envelope expands introducing greater drag which affects the orbits of this space debris. But at the same time, radar<br />
signals become distorted and tracks are often lost.<br />
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