Despite being far removed from everyday experience, events on the sun have a surprising range of effects on many aspects of modern life. Some important effects of the sun include:

• HF Radio Communications:

The variation of the solar ultra-violet flux during the solar cycle results in changes in the range of frequencies available to HF communications. Also, X-rays during solar flares produce short wave fadeouts, often preventing HF communications. Ionospheric storms also affect HF communications by reducing the available band of frequencies and degrading their quality.
• VHF and UHF Communications:

Solar radio bursts can interfere with VHF and UHF signals in the sunlit hemisphere of the earth. Communications satellites using this frequency band are also affected by solar interference, especially around equinox (March and September) when the satellites are close to the direction of the sun, at times during the day.
• LF and VLF Communications:

LF and VLF communications are ducted by the ionosphere. Sudden changes to the ionosphere can produce phase anomalies in these communications.
• Geomagnetic Surveys for Minerals:

Magnetic storms affect surveys for minerals which use either ground-based or airborne magnetometers to measure the small changes in the earth's magnetic field associated with deposits of minerals. These surveys are more difficult, perhaps impossible, during major magnetic storms.
• Pipelines:

Electric currents induced in the earth during magnetic storms can result in corrosion in buried conductors such as pipelines, despite protection by special coatings and by electrical voltages applied along the pipeline.
• Powerlines:

Electric currents induced in powerlines during magnetic storms can damage power relays and even cause the power grid to fail. These effects are most likely at high latitudes.
• Satellite Orbits and Orientation:

During bursts of solar activity the outer atmosphere of the earth expands slightly. Satellites can experience increased drag reducing the lifetime of their orbits. The increased drag can also affect the orientation of the craft, disrupting its operation.
• Satellite Control:

The flow of charged particles from the sun can result in the build up of charge on the craft, interfering with sensitive electronics. This can result in phantom commands disrupting the control of the satellite, even leading to it's loss.
• Manned Spacecraft:

High energy charged particles during major bursts of solar activity are potentially lethal to the crews of space vehicles. This danger is most significant for crews on interplanetary missions such as to Mars.
• Auroral Sightings:

Charged particles spiral down the magnetic field of the earth and collide with atoms in the atmosphere producing the beautiful displays of lights known as aurorae ("the northern or the southern lights"). During intense solar events aurorae are sighted at more equatorial latitudes than is normal.

Material Prepared by Richard Thompson. © Copyright IPS - Radio and Space Services.
Comments or suggestions can be directed to education@ips.gov.au