Leaky Holes Make Lovely Auroras

To show quickly the aurora can change, the top photo was taken at 12:31:32 a.m. today; the bottom at 12:32:06 - only 34 seconds apart. The aurora evolved from a quiet to an active rayed arc. Photos: Bob King

A stronger than anticipated impact from material flung from the sun by a large flare in sunspot group 1429 made for lively auroras last night from the northern U.S. and Canada. They never reached high in the sky, but from a location with a good horizon to the north, the many rays that briefly flared around 12:30-1 a.m. were a pleasant surprise.

A huge coronal hole photographed by the Solar Dynamics Observatory in extreme ultraviolet light on March 13. The loopy magnetic fields that normally retard the solar wind have been added. Credit: NASA/SDO

Guess what? We may be in for more with minor auroral storms predicted for higher latitudes (Minnesota maybe?) this evening as a result of the same coronal mass ejection that sparked last night’s display combined with the effects of a large coronal hole that directly faced Earth earlier this week. These “holes” in the sun atmosphere or corona are very interesting phenomena. Normally the tightly looped magnetic fields around sunspot groups constrain the constant wind of particles that blows from the sun called the solar wind. The loops form the same way iron filings arrange themselves around a magnet here on Earth. On the sun, hot gases trace the magnetism that surrounds sunspot groups.

Coronal holes are places on the sun where the magnetic fields stream directly into space unconstrained. They carry ferry away particles into space at speeds around 1.8 million miles per hour – the reason the wind from holes is called the fast solar wind. Because the particles are moving at high speed, they can sometimes make their way past Earth protective magnetic field and spark displays of northern lights high in our atmosphere. Let’s hope we’re so fortunate tonight.

The Apollo 11 lunar module, LRRR (Lunar Ranging RetroReflector), the PSEP (Passive Seismic Experiment Package) and astronauts' footpaths still in place since the day they were made in July 1969. Credit: NASA

Earlier this month NASA released a new, more detailed image from the Lunar Reconnaissance Orbiter of the Apollo 11 moon landing site taken from only 15 miles high. That’s about twice the cruising altitude of a transcontinental air flight. The details revealed are marvelous and include an experiment to measure moonquakes (PSEP) and the retro reflectors that are still used to this day to precisely measure the distance to the moon via lasers shot at the reflectors and received back on Earth.

My favorite are the footpaths in the lunar soil made by astronauts Neil Armstrong and Buzz Aldrin. The mottled gray ground around the module shows they spent most of their time “close to home”, while a single track made by Armstrong leads to the rim of Little West crater 164 feet (50 meters) away.

Thanks in part to discoveries made by on-the-ground investigation and rock collecting by the Apollo astronauts and closeup photos taken by the LRO, we know a lot more about how the moon evolved. Take a look at the short video below. It provides our best explanation to date – without words – of why the moon looks the way it does today.

11 Responses

  1. caralex

    And despite the excellent LRO pictures, the lunar hoax theorists are still shouting ‘photoshop!’ on other sites where the photos have appeared. Some people just can’t be reasoned with, unfortunately.

    1. astrobob

      Hi Melanie,
      Yes, possible, but all’s quiet on the northern front as of 10 o’clock here in Duluth. Kp is back in the green.

    1. astrobob

      Diana,
      Glad you’re watching the index. Duluth has clear skies and there might be a faint glow very low in the north. Nothing obvious as of midnight. The OVATION aurora site shows the line of visibility further north up near Grand Marais and International Falls.

  2. joanne

    Hi Bob. I`ve been reading about asteroid 2012 EG5 that will pass us on April 1st this year, and asteroid 2012 DA14 that will pass us February 15th next year. There is a little scaremongering going on and i wondered what your thoughts were on them. They`re big pieces of rock. What damage could they do if they hit our planet?

    1. astrobob

      Joanne,
      2012 EG5 will pass about one moon distance (about 239,000 miles) from Earth at closest approach. Nothing to worry about there. 2012 DA14, a very small asteroid, will pass much closer at 17,000 miles, but that’s still a healthy distance from us. Neither is a threat to Earth. Try plugging their diameters into the Impact Simulator to see what would result if one were to hit us (which they aren’t): http://simulator.down2earth.eu/
      * 2012 EG5 diameter = 40-89 meters
      * 2012 DA14 = 44 meters

  3. Lola

    Would the reason that the auroras are so low on the horizon be because of the earth’s tilt on it’s axis? I usually don’t have the opportunity to drive somewhere else as I have a 3 year old at home. I remember in years past when the auroras were up over my head. I’m in Two Harbors but am blocked in the north by trees and a hill.

    1. astrobob

      Hi Lola,
      No, the tilt of Earth’s axis doesn’t change the position of the aurora. The auroras – auroral oval – form a ring centered on Earth’s geomagnetic pole, the place our compasses point. It expands and contracts in response to how solar activity affects our planet. When expanding, it moves southward and appears higher in the sky because it’s closer to your location. When contracted, it’s too far north to see from Minnesota.

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