GREEN SKIES ON ST. PATRICK'S DAY? Today is St. Patrick's Day. Arctic sky watchers may be able to celebrate with a splash of green in the sky. A weak CIR is expected to hit Earth's magnetic field on March 17th. CIRs (co-rotating interaction regions) are transition zones between slow- and fast-moving streams of solar wind. Compressed magnetic fields in CIRs often do a good job of sparking auroras. Free: Aurora Alerts
BIG CORONAL HOLE TURNS TOWARD EARTH: A hole has opened in the sun's atmosphere, and it is turning toward Earth. NASA's Solar Dynamics Observatory is tracking the opening, which researchers call a "coronal hole" (CH):
Coronal holes are places--big places--where the sun's magnetic field opens up and allows solar wind to escape. A wide stream of solar wind flowing from this coronal hole is expected to reach our planet on March 23rd. The impact of the solar wind should produce magnetic activity around Earth's poles and could spark the first auroras of northern spring. Stay tuned. Free: Aurora Alerts
NEUTRONS ON A PLANE: It is well known that air travelers are exposed to cosmic rays. High-energy particles and photons from deep space penetrate Earth's atmosphere and go right through the hulls of commercial aircraft. This has prompted the International Commission on Radiological Protection (ICRP) to classify pilots and flight attendants as occupational radiation workers.
Most studies of this problem focus on ionizing radiation such as x-rays and gamma-rays. Yesterday, Spaceweather.com turned the tables and measured neutrons instead. With help from the students of Earth to Sky Calculus, we used a pair of bubble chambers to monitor neutron activity inside a Scandinavian Airlines jetliner. In this photo taken 35,000 feet above Greenland, each bubble shows where a neutron passed through the chamber and vaporized a superheated droplet:
During the 11-hour flight we measured almost 20 uSv (microsieverts) of radiation from neutrons. That's more than the dose from X-rays and gamma-rays combined. (We measured X-rays and gamma-rays using other sensors.) This confirms that neutrons are an important form of aviation radiation, providing much of the biologically effective radiation dose at altitudes of interest to air travelers and space tourists.
Earlier in the week, we flew these same bubble chambers to the Arctic stratosphere using a space weather balloon. Interestingly, the 11-hour plane flight yielded 6 times more neutrons than the shorter (2 hour) but far higher (97,000 ft) balloon flight. Stay tuned for more data from our week-long trip to the Arctic Circle.
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