COSMIC RAY
SOLAR WIND, INCOMING: A stream of solar wind is expected to brush Earth's magnetic field on March 8th. The gaseous material is flowing from a northern hole
in the sun's atmosphere. Although much of the windy stream will sail
north of our planet, its grazing effect may nevertheless spark bright
auroras around the Arctic Circle. Free: Aurora Alerts.
THE WORSENING COSMIC RAY SITUATION: Cosmic rays are bad–and they're getting worse. That's the conclusion of a new paper just published in the research journal Space Weather.
The authors, led by Prof. Nathan Schwadron of the University of New
Hampshire, show that radiation from deep space is dangerous and
intensifying faster than previously predicted.
The story begins four years
ago when Schwadron and colleagues first sounded the alarm about cosmic
rays. Analyzing data from the Cosmic Ray Telescope for the Effects of
Radiation (CRaTER) instrument onboard NASA's Lunar Reconnaissance
Orbiter (LRO), they found that cosmic rays in the Earth-Moon system
were peaking at levels never before seen in the Space Age. The
worsening radiation environment, they pointed out, was a potential
peril to astronauts, curtailing how long they could safely travel
through space.
This figure from their original 2014 paper shows the number of days a 30-year old male astronaut flying in a spaceship with 10 g/cm2 of aluminum shielding could go before hitting NASA-mandated radiation limits:In the 1990s, the astronaut could spend 1000 days in interplanetary space. In 2014 … only 700 days. "That's a huge change," says Schwadron.
Galactic cosmic rays come from outside the solar system. They are a mixture of high-energy photons and sub-atomic particles accelerated toward Earth by supernova explosions and other violent events in the cosmos. Our first line of defense is the sun: The sun's magnetic field and solar wind combine to create a porous 'shield' that fends off cosmic rays attempting to enter the solar system. The shielding action of the sun is strongest during Solar Maximum and weakest during Solar Minimum–hence the 11-year rhythm of the mission duration plot above
spaceweather.com
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