Friday, April 20, 2018

Morning Twilight Aurora 4/20/2018

  Earlier this week a coronal hole opened up on the Sun and allowed charged particles to stream toward Earth.  So even though the Sun was relatively inactive and devoid of sunspots a slight uptick in geomagnetic activity (to a Kp index of 4) was forecast for April 20.  When my ailing dog woke me at 5 AM a quick check of spaceweather.com   showed the index surged to 6, which put it within camera range at my latitude of nearly 44 North.
   I went to the end of the driveway and braced my camera against my mailbox and pointed it north for a two second exposure.  The photo below shows a purple glow through the trees.  At this point I knew I needed to get to a location with a clearer northern horizon fast because of the encroaching morning twilight.
     I quickly packed my camera gear and in seven minutes I was parked at a pull-off on M-116 where I took a quick photo with the camera held steady against the roof of my car.
   That method had my car's shark-fin antenna blocking the most intense part of the aurora.  I quickly searched through the car and found my tripod which allowed an unobstructed steadier view.
   The growing glow of dawn had me aiming more toward the northwest over Lake Michigan away from the eastern sky.  It appears that an atmospheric inversion was exposing the skyglow of cities across the lake in Wisconsin.
    In the photo above the two bright lights are from the freighter Roger Blough.
   The ship's ID was found on marinetraffic.com

  On a side note- last Friday our area experienced a seiche on the Lake Michigan shore.  News site Mlive reported this story........ ....http://www.mlive.com/weather/index.ssf/2018/04/thunderstorm_induced_seiche_ca.html
   It kind of sells the event short because what they described was a 1 foot increase of lake level in an hour was not what was observed elsewhere.  At my worksite the lake level is constantly monitored and recorded.  Our data and surveillance video show that at 1243 EDT the lake had dropped to 573' above sea level from the normal level of 580.5'.  Four minutes later at 1247 EDT the lake surged to 588' above sea level, a change of 15'. At my former worksite on Lake Erie we had seiches of 10-15 feet almost yearly when strong southwest winds would set up across the whole fetch of the lake and push the water toward Buffalo, NY.  But the time elapsed between the high and low was typically 6-10 hours not 4 minutes.

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