Information on NASA space radiation research

The Sun is the reason for life on Earth.   It provides almost all of the energy to drive the planet’s ecosystems.   Our technological society is based on fossilised energy from the Sun trapped in oil, gas and coal reserves.   The future energy needs of humans are likely to be solar based and the energy for communication satellites and space stations are now provided by solar panels rather than nuclear reactors.  But not everything about the Sun is good.

On the surface of the Earth few people have to worry about the Sun beyond slapping on factor 15 and wearing a hat. Exposure to the Sun on Earth is dictated by cloud cover, latitude and the seasons.  People go about their lives oblivious of Space Weather.   This situation is thanks to a protective magnetic layer extending 100 thousand kilometres into space and a 50 kilometre thick blanket of atmosphere.   But outside this cocoon the weather can be deadly.

Graphic from IMAGE

The Sun contains a nuclear reactor which releases energy by fusing atoms together.   Although it can self regulate its reactor, the Sun goes through bouts of indigestion when it belches out huge flares of gases into space at 5 million kilometres an hour.   When these head towards the Earth, we can be in for trouble.

 Outside the Earth’s magnetic shield (the magnetosphere), an interplanetary astronaut caught by such a flare would need some sort of special protection.   The Apollo Astronauts reported seeing occasional flashes in their eyes during the Moon missions.   Close examination of their helmets revealed microscopic holes where high velocity particles (hydrogen and helium nuclei) had tunnelled through the spacecraft, through their helmet and through their heads! Some of these particles were cosmic, coming from outside our solar system, but others are thought to have been solar in origin; constituents of the ‘solar wind’ continuously streaming out from the Sun.   But this was the equivalent of a light breeze in space weather terms, a few odd particles  travelling at a pedestrian couple of million kilometres an hour or so.   Luckily no solar flares headed Earthwards during the Apollo missions.

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Microscopic holes made by high energy particles in an Apollo 12 helmet.   The Helmet material has been etched to reveal the holes as spikes.

Inside the International Space Station, astronauts need protection from space weather

90mm thick aluminium would do it!

In 1997 an early warning system for bad space weather was launched in the shape of the ACE (Advanced Composition Explorer) sun observatory; a spacecraft that is locked in a neutral gravity pocket 1.5 million kilometres away between the Earth and the Sun (that’s 1% of the distance to the Sun).   As a flare approaches ACE at 5 million kilometres per hour, the observatory can send a warning to us via radio waves 200 times faster at the speed of light – 1 billion kilometres per hour!   Despite the big numbers, the most energetic flares can cover the distance from ACE to Earth in less than half an hour.    A network of other satellites and ground based observatories provide continuous data streams for the international warning system.

On Earth, 98% of this radiation is deflected by the magnetosphere and absorbed by the atmosphere, but we are not free of its effects.   The flares are able the squash the magnetosphere.   This can create electrical currents in wires such as power cables causing massive current surges, playing havoc with computer equipment and electricity supplies.  It has been reported that in the most severe magnetic storms, sufficient current has been generated in flexes to make switched off lights flicker!

As sunspot activity rose to a peak in a regular 11 year cycle during the Summer of 2002,  a flare hit the Earth.  The background radiation from the Sun rose 10,000 times.      Spacecraft launches were postponed, satellite operators prepared their orbiting hardware, and electricity companies readied themselves for current surges.   A transatlantic plane trip at this time would have given passengers the equivalent radiation exposure of a chest x-ray.   Regular exposure to this radiation could be the cause of significantly elevated incidents of cancer in airline crew and astronauts.

Click the panel above for near-real-time data about the solar wind from NOAA

In a technological society that is reliant on the continuous operation of sensitive electrical equipment, an understanding of space weather is vital.  With so much communication placed in orbit above the protective atmosphere, engineers and scientists are in an ongoing race to predict space weather and protect equipment.   For interplanetary travel, beyond the protection of both the atmosphere and the magnetosphere, the options are simple; we cannot go unless we can fully protect our astronauts or cure cancer, and preferably both!