St. Patrick’s Day in the Stratosphere

St. Patrick’s Day in the Stratosphere

Last month, on March 17th, a CME hit Earth's magnetic field, sparking the strongest geomagnetic storm of the current solar cycle. Spaceweather.com and the students of Earth to Sky Calculus launched a series of weather balloons--before, during and after the storm--to measure the storm's effect on Earth's upper atmosphere. Here are the results:

During the storm, which lasted for more than two days, cosmic radiation levels in the stratosphere jumped by more than 6%. Radiation levels did not return to normal until a week after the CME strike.
Six percent might not sound like a big increase, but consider the following: Atmospheric radiation levels usually decrease when CMEs sweep past Earth. The effect is called a "Forbush Decrease," named after American physicist Scott Forbush who studied cosmic rays in the early 20th century. Essentially, CMEs sweep aside some of the cosmic rays that surround our planet, causing radiation levels to drop. In Sept. 2014, for instance, our space weather ballooning program detected a sharp Forbush Decrease. A 6% increase--simply because it is an increase--therefore comes as a surprise.
The reason for the jump may lie in the intensity of the St. Patrick's Day geomagnetic storm. While Earth's magnetic field was reverberating on March 17th, high-energy particles normally trapped around Earth's poles spilled down to mid-latitudes where the space weather balloons were launched (from the Sierra Nevada mountains of California). These extra particles could have filled in the deficit and overflowed it, producing an "upside down Forbush Decrease."
These results show that we still have a lot to learn about the response of Earth's atmosphere to solar storms

From SpaceWeather.com