Subscribe free to our newsletters via your
. 24/7 Space News .




STELLAR CHEMISTRY
Cosmic Rays Hit Space Age High
Dr. Tony Phillips
Science@NASA
Huntsville AL (SPX) Oct 01, 2009


The heliospheric current sheet is shaped like a ballerina's skirt. Image credit: J. R. Jokipii and B. Thomas, Astrophysical Journal 243, 1115, 1981.

Planning a trip to Mars? Take plenty of shielding. According to sensors on NASA's ACE (Advanced Composition Explorer) spacecraft, galactic cosmic rays have just hit a Space Age high.

"In 2009, cosmic ray intensities have increased 19% beyond anything we've seen in the past 50 years," says Richard Mewaldt of Caltech. "The increase is significant, and it could mean we need to re-think how much radiation shielding astronauts take with them on deep-space missions."

The cause of the surge is solar minimum, a deep lull in solar activity that began around 2007 and continues today. Researchers have long known that cosmic rays go up when solar activity goes down. Right now solar activity is as weak as it has been in modern times, setting the stage for what Mewaldt calls "a perfect storm of cosmic rays."

"We're experiencing the deepest solar minimum in nearly a century," says Dean Pesnell of the Goddard Space Flight Center, "so it is no surprise that cosmic rays are at record levels for the Space Age."

Galactic cosmic rays come from outside the solar system. They are subatomic particles--mainly protons but also some heavy nuclei--accelerated to almost light speed by distant supernova explosions. Cosmic rays cause "air showers" of secondary particles when they hit Earth's atmosphere; they pose a health hazard to astronauts; and a single cosmic ray can disable a satellite if it hits an unlucky integrated circuit.

The sun's magnetic field is our first line of defense against these highly-charged, energetic particles. The entire solar system from Mercury to Pluto and beyond is surrounded by a bubble of magnetism called "the heliosphere."

It springs from the sun's inner magnetic dynamo and is inflated to gargantuan proportions by the solar wind. When a cosmic ray tries to enter the solar system, it must fight through the heliosphere's outer layers; and if it makes it inside, there is a thicket of magnetic fields waiting to scatter and deflect the intruder.

"At times of low solar activity, this natural shielding is weakened, and more cosmic rays are able to reach the inner solar system," explains Pesnell.

Mewaldt lists three aspects of the current solar minimum that are combining to create the perfect storm:

1. The sun's magnetic field is weak. "There has been a sharp decline in the sun's interplanetary magnetic field down to 4 nT (nanoTesla) from typical values of 6 to 8 nT," he says. "This record-low interplanetary magnetic field undoubtedly contributes to the record-high cosmic ray fluxes." [data]

2. The solar wind is flagging. "Measurements by the Ulysses spacecraft show that solar wind pressure is at a 50-year low," he continues, "so the magnetic bubble that protects the solar system is not being inflated as much as usual." A smaller bubble gives cosmic rays a shorter-shot into the solar system. Once a cosmic ray enters the solar system, it must "swim upstream" against the solar wind. Solar wind speeds have dropped to very low levels in 2008 and 2009, making it easier than usual for a cosmic ray to proceed. [data]

3. The current sheet is flattening. Imagine the sun wearing a ballerina's skirt as wide as the entire solar system with an electrical current flowing along its wavy folds. It's real, and it's called the "heliospheric current sheet," a vast transition zone where the polarity of the sun's magnetic field changes from plus to minus. The current sheet is important because cosmic rays are guided by its folds. Lately, the current sheet has been flattening itself out, allowing cosmic rays more direct access to the inner solar system.

"If the flattening continues, we could see cosmic ray fluxes jump all the way to 30% above previous Space Age highs," predicts Mewaldt. [data]

Earth is in no great peril. Our planet's atmosphere and magnetic field provide some defense against the extra cosmic rays. Indeed, we've experienced much worse in the past. Hundreds of years ago, cosmic ray fluxes were at least 200% to 300% higher than anything measured during the Space Age.

Researchers know this because when cosmic rays hit the atmosphere, they produce an isotope of beryllium, 10Be, which is preserved in polar ice. By examining ice cores, it is possible to estimate cosmic ray fluxes more than a thousand years into the past. Even with the recent surge, cosmic rays today are much weaker than they have been at times in the past millennium.

"The space era has so far experienced a time of relatively low cosmic ray activity," says Mewaldt. "We may now be returning to levels typical of past centuries."

NASA spacecraft will continue to monitor the situation as solar minimum unfolds. Stay tuned for updates.

.


Related Links
Science@NASA
Stellar Chemistry, The Universe And All Within It






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





STELLAR CHEMISTRY
Death Rays From Space
Moffett Field CA (SPX) Aug 28, 2009
Cosmic rays pour down on Earth like a constant rain. We don't much notice these high-energy particles, but they may have played a role in the evolution of life on our planet. Some of the mass extinctions identified in the fossil record can be linked to an asteroid impact or increased volcanism, but many of the causes of those ancient die-offs are still open for debate. "There may have been ... read more


STELLAR CHEMISTRY
China says completes 3D moon map

SMART-1 Mapped Crash Scene Of Upcoming LCROSS Impact

Key Process For Space Outpost Proved On 'Vomit Comet' Ride

NASA Goddard Shoots The Moon To Track LRO

STELLAR CHEMISTRY
Opportunity Passes 11 Mile Mark

Spirit Makes Progress On Antenna Actuator

Iceberg Chasing And Laser Lights

Radar Map Of Buried Mars Layers Matches Climate Cycles

STELLAR CHEMISTRY
Clown takes giant leap into space

Russia Sends Circus Man Into Space

Russia's Last Analogue Space Freighter Buried In Pacific

Cirque du Soleil founder reaches for the stars

STELLAR CHEMISTRY
China to build, launch satellite for Laos

China says will push space programme to catch up West

China Begins New Space Center Construction

China breaks ground on new space launch centre: state media

STELLAR CHEMISTRY
Russia To Launch Orbital Lab "Oka-T" In 2015

Light-Duty Day For Crew, Expedition 21 Prepares For Launch

ESA Calls For Ideas For Climate Change Studies From ISS

Progress M-67 Undocks From ISS

STELLAR CHEMISTRY
Arianespace Maintains Record Launch Rate

Space Systems/Loral Delivers SES World Skies Satellite To Launch Base

NSS-12 Satellite Arrives At Kourou

Delta II NASA Launch For MDA Successful

STELLAR CHEMISTRY
Simulation Suggests Rocky Exoplanet Has Bizarre Atmosphere

NASA's Spitzer Spots Clump Of Swirling Planetary Material

Spitzer Spots Clump Of Swirling Planetary Material

Mass And Density Of Smallest Exoplanet Finally Measured

STELLAR CHEMISTRY
ORMatE Returns To NRL After Nearly Two Years In Earth Orbit

Space Debris Gets Some Respect

IKONOS Satellite Marks 10 Years In Operations

NASA works on space age coating




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement