Hole-y auroras possible tonight Aug. 30-31 / Jupiter returns

The dark opening at the center of the sun’s disk, seen here in ultraviolet light, is a coronal hole photographed on August 28 by the Solar Dynamics Observatory. Holes are ports through which high speed particles from the sun can pour freely into space unconstrained by solar magnetic fields. Credit: NASA

Sometimes it doesn’t take a big solar storm to incite an aurora. Often enough, a hole will do. Midweek, a blizzard of electrons and protons called a coronal mass ejection arrived in Earth’s vicinity, snuck past our magnetic defenses and painted northern skies for several nights in a row with glowing curtains and rays.

Yesterday night, a coronal hole did the same. Coronal holes are openings in the sun’s otherwise ‘locked down’ magnetic canopy. In the photo above, swirls of magnetism form closed loops over most of the sun’s lower atmosphere, keeping the bubbling sea of solar plasma (charged particles) at bay.

Enhancements in the solar wind either from solar storms (CMEs) and coronal holes send a thin soup of electrons and protons into space. If a batch happens to have a southward-pointing magnetic field, it can open a crack in Earth’s northward-pointing field and stimulate oxgen atoms and nitrogen molecules to glow in the upper atmosphere. The aurora is concentrated in two ovals, one hovering over each magnetic pole. Credit: Todd Salat

The sun’s so hot that it energizes and accelerates bits and pieces of itself – electrons and protons – to speeds high enough to escape its gravitational pull. Astronomers call the gust of departing particles the solar wind. Typical speeds hover around 250 miles per second (400 km/sec), but winds leave coronal holes unchecked and can blast into space at up to 500 miles per second (800 km/sec).

When the tempest arrives at Earth and harbors south-pointing magnetism, it links into Earth’s north-pointing magnetic field, sending electrons and protons at high speed down the planet’s magnetic field lines into the upper atmosphere to spark auroras.

Coronal holes are holes where the sun’s magnetic field where the solar wind can escape at high speed. Credit: NASA

NOAA space weather forecasters expect the effects of coronal holes to continue tonight and linger through Monday. Peak possibility for northern lights tonight happens between 10 p.m. and 1 a.m. CDT. Sometimes a particular hole can persist for several solar rotations causing repeat auroras every 27 days.

Stay tuned to Ovation aurora to see if any auroras are dropping south toward your region tonight.  I’ll be in touch.

Jupiter (top) and Venus in bright twilight on August 27, 2014. Credit: Bob King

The other morning while watching aurora I was happy to see that Jupiter had jumped back into the sky. It cleared the trees during twilight and was followed a half hour later by Venus. Low elevation and wiggly air currents meant I couldn’t magnify it much, but at 64x but north and south equatorial belts were unmistakeable.

I always look forward to that first view of Jupiter after conjunction with the sun. We last saw the planet in June, quite a while back. Jupiter’s weather and cloud patterns constantly change. One never knows what to expect when it’s out of sight for a couple months – sometimes an entire equatorial belt can disappear! I’m hear to report that both are still intact.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

3 thoughts on “Hole-y auroras possible tonight Aug. 30-31 / Jupiter returns

  1. I managed to get up early enough to see Jupiter on Sunday September 7. After hearing that the GRS was shrinking, I wanted to see. Seeing conditions were extremely poor and of course dawn is always breathing down your neck. Even so I did get semi-satisfactory results making a stacked image.
    http://i1305.photobucket.com/albums/s556/Pyrolon/Jupiter-Returns1-50percent_zpscb6ed63f.png
    The GRS wasn’t evident through the eyepiece, so I find it very cool that with a stack of images it becomes visible.

    • Troy,
      That’s a very clear picture, the best I’ve seen so far this new apparition. I was out too over the weekend and saw Jupiter for a second time this season, but low-altitude turbulence only made it possible to see the main belts.

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