Stig Östlund

måndag, december 19, 2016

AURORAS FOR CHRISTMAS?


The source of the solar wind is a gigantic hole in the sun's atmosphere, now directly facing Earth. Earlier today NASA's Solar Dynamics Observatory photographed the structure, which covers nearly 1/3rd of the solar disk:




This is a "coronal hole"--a region in the sun's atmosphere where the magnetic field opens up and allows solar wind to escape. We've actually seen this coronal hole before--at least twice.  It is rotating around with the sun, strobing Earth like a lighthouse every ~27 days. The last two times we experienced its solar wind (Oct. 25-28 and Nov. 23-26) G1- and G2-class magnetic storms sparked bright polar auroras. A repeat performance is likely in the week ahead.


The solar wind is a stream of charged particles released from the upper atmosphere of the Sun. This plasma consists of mostly electrons, protons and alpha particles with energies usually between 1.5 and 10 keV (--> https://en.wikipedia.org/wiki/Electronvolt); embedded in the solar-wind plasma is the interplanetary magnetic field.
More --> https://en.wikipedia.org/wiki/Solar_wind



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