Every night when the skies are clear, I look outside to see if the Northern
Lights are shining. I check SpaceWeather.com
and SpaceWeatherNow websites to
see where the current auroral loop is on Earth. On the evening of June 1, 2013, I checked the website and saw that the auroral loop was over Minnesota, so I took a short drive over to the back of Wayzata High School and shot a few pictures. This is my favorite ... the Northern Lights with the International Space Station flying through the picture. I often wish I lived farther
north so I could see the Northern Lights more often. I just find them fascinating,
and I hope that this page will help you appreciate these phenomenon and understand
their cause a little better.
It has taken a bit of digging, but I think that this page in the course is
really fascinating. Several years ago, I had a student in my Hopkins class named
Keith Wygant. Both of his parents are physicists at the University of Minnesota
working actively in the field of Solar Activity, and part of a satellite project
that monitors Coronal Mass Ejections. Their concern is to predict the timing
of such an ejection with the Earth's atmosphere, thus predicting the potential
negative effects of these powerful solar storms. Even more important is knowing
the timing of the impact so astronauts can shield themselves from the harmful
radiation. I learned a great deal from the Wygant parents, John
Wygant, PhD and Cynthial
Cattell, PhD, during a visit at one of our parent-teacher conferences. While
I am not an expert in the field of the Sun's magnetic field, what I learned
from them has helped me appreciate the awe-inspiring activity that occurs at
the Sun's photosphere. Often the results of these turbulent outbursts is the
Aurora Borealis for those living in the Northern Hemisphere, and the Aurora
Australis for those living in the Southern Hemisphere. I first direct you to
a website from the University of Tromso in Denmark where there is a wonderful
explanation of the Cause
of the Northern Lights.
My Attempt to Explain the North Lights
First, you have to understand the properties of electrons and what happens
to them when they absorb energy. I refer you to a very important explanatory
page that teaches a simplified version of photon absorption and re-emission.
This page is the key to understand where the colors come from in the Aurora.
Once you have read this page, you will be better able to follow what comes next.
The picture above shows the Earth's magnetic field in relation to the Solar
Winds. As the solar wind strikes the magnetic field, it pushes it close to the
Earth on the sunward side, and stretches it on the back side. The magnetic field
is stretched a great distance, and forms a magnetotail.
As the solar wind strikes the Earth's magnetic field, the ions in Earth's
upper atmosphere are pushed all the way to the tip of the magnetotail. As these
ions are snapped back to the Earth by the magnetic field, the positive ions
will flow to the negatively-charged South Pole, and the negative ions will flow
to the positively-charged North Pole. As these ions return, they will release
their absorbed photons. The colorful curtains of the Aurora are the result of
these flowing ions releasing their absorbed photons during their fall to the
magnetic poles. As you learned in the Photon
Emission page, each atom will release colors depending on that atom's structure
and ionic state.
Since ions are falling simultaneously at the North and South Poles, one will
find the Aurora present at the North and South Poles in nearly identical fashion.
The particular colors of the Aurora and the extent of the Auroral display
depend on the strength of the solar wind. There is always an auroral loop at
the highest latitudes, but this loop will extend farther and farther south depending
on the strength of the solar wind. During an intense solar storm, the Auroral
Loop will extend down to the northern states of the US. In extreme instances,
this loop can be seen as far south as Arizona and Florida. The image below shows
the extent of the Auroral Loop during the March 14, 1989 Solar Storm.
The more intense the solar storm, the farther south the aurora will be seen,
and the more colorful the display. Click on the center pictures for more information
The image above came from the Spaceweather.com site and for me, this is one of the most beaufitul photographs of the aurora that I have ever seen. It is NOT my photograph. The credit belongs to: Taken by Jonathan on February 19, 2014 @ Grand Forks, North Dakota
Diurect link: spaceweather realtime aurora
Once you have browsed through that site and gained a better understanding
of the causes of the Aurora, it is now time to look at some pretty fantastic
pictures. You can visit the Borealis 2000
site to see photographs from the recent two peaks of the Solar Sunspot Cycle.
Click on the Flickr Site
for a look at some of the best photographs of the Aurora. Then you can go to
two more websites for:
1) Current images of the Sun and links to spaceweather.
2) Immediate location of the auroral
activity on a global scale.
Below are a few photographs from the above-listed websites to give you a taste
of what you will find upon your visits :) These four images were taken following
a coronal mass ejection August 1, 2002. The first two images were from the evening
of August 2, the next from August 3, and the last from August 4. They can all
be found at the SpaceWeather website Aurora Gallery, and are presented here
in my hopes that you will visit the website, look for Solar Alerts, and go outside
more often at night to look for them. It was clear in Minneapolis the evenings
of August 2 and 3, 2002 and I was able to see these displays with my wife from
our backyard in the Twin Cities area. One particular ribbon of light stretched
from west to east and first looked like a long contrail from a high altitude
jet. When the "contrail" began snaking and undulating in the sky I
knew it was an auroral display.
The photographs above show different auroral displays. I copied these from
the Aurora Gallery within the Spaceweather.com website. None of these pictures
can be reproduced without the permission of the actual photographers or Spaceweather.com
itself. They are included in here to give you a glimpse of what you might see
on a given night during the Minnesota autumn. I included some of my own pictures
form the Northen Lights display on November 7, 2004.
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