Solar Storm Threat Analysis - Impact

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