GEOMAGNETIC UNREST: Earth is entering a stream of solar wind flowing from a hole
in the sun's atmosphere. This is causing geomagnetic unrest around
the poles. High-latitude sky watchers should be alert for auroras on
July 21st, especially in the southern hemisphere where winter darkness
favors visibility. Free: Aurora Alerts
CME SWEEPS ASIDE COSMIC RAYS: On July 16th, a CME hit Earth's magnetic field, sparking two days of geomagnetic storms and beautiful southern auroras. The
solar storm cloud also swept aside some of the cosmic rays currently
surrounding Earth. Spaceweather.com and the students of Earth to Sky
Calculus launched a space weather balloon to the stratosphere hours
after the CME arrived. We detected a 7% decrease
in X-rays and gamma-rays (two tracers of secondary cosmic rays).
Neutron monitors in the Arctic and Antarctic recorded similar
decrements. For instance, these data from the Bartol Research
Institute show a nearly 8% drop in cosmic ray neutrons reaching the
South Pole:
This is called a "Forbush Decrease," named after physicist Scott E. Forbush
who first described it in the 20th century. Wherever CMEs go, cosmic
rays are deflected by magnetic fields inside the solar storm clouds. As a
result, when solar activity is high, cosmic radiation around Earth is
relatively low--a yin-yang relationship that holds throughout all
phases of the solar cycle.
Lately, cosmic rays around Earth have
been intensifying as the solar cycle plunges toward minimum. The CME
of July 16th reversed that trend--but only for a few days. Solar
activity has returned to low levels and cosmic rays are on the rise
again. Why do we care about cosmic rays? For one thing, they penetrate commercial airlines, dosing passengers and flight crews so much that pilots are classified as occupational radiation workers. Some research shows that cosmic rays can seed clouds and trigger lightning, potentially altering weather and climate. Furthermore, there are studies ( #1, #2, #3, #4) linking cosmic rays with cardiac arrhythmias in the general population.
spaceweather.com
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