NEWTON: Purple Lightning
 
Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page Visit Our Archives Ask A Question How To Ask A Question Question of the Week NEWTON Teachers Our Expert Scientists Volunteer at NEWTON! Referencing NEWTON Frequently Asked Questions About Ask A Scientist About NEWTON Education At Argonne Purple Lightning

Name: Fredrik
Status: student
Grade: 9-12
Country: Norway
Date: Spring 2013


Question:
I saw in a documentary once about some Purple Lightning 30'000 meters above storms that people on the ground could not see. Why don't those bolts of lightning hit the ground. I am just 14 and the teacher know nearly less than me on these subjects, please help.


Replies:
Very fine observation! The "purple lightning" is due to the strongest line in the Balmer series of atomic hydrogen. This is produced by the emission of atomic hydrogen that in turn is the consequence of the result of the dissociation of water vapor by the lightning discharge. The details of the specific transitions you can find on a Google search on the term: purple lightning.

Vince Calder


Static charges in the clouds build up with the high winds and lightning results to equalize the positive and negative charges that are created due to the friction within the cloud. Much like the effect of rubbing a balloon in your hair so it sticks to the ceiling for example. If the charge differences are between the cloud and the ground, the lightning discharges between the ground and the cloud; however, often the charges are within the cloud and the lightning results between these opposite charges. This lightning will not involve the ground. If you are ever taking a plane ride with a storm in the distance, you will see lightning discharges throughout the upper areas of the storm cloud. Pretty site indeed.

The purple colors is a bit more complex to explain. Lightning is an example of the plasma state of matter. The colors in lightning comes from the atoms in the air around the lightning bolt. You may have seen an demonstration of burning chemicals whereby each gives off a different color when burned. The atom concentration at high altitudes are different than those nearer the ground. The violet color results when the plasma heat strips electrons off atoms that give off purple (and other colors) when the electrons return to their proper place in the atom's electron field. The colors result when the electrons give off the energy they received from the plasma lightning bolt.

Steve Sample


Hi Fredrik,

Thanks for the question. Lightning does occur in the upper atmosphere and may or may not reach the ground. Generally, lightning will hit the ground if the ground is at a lower potential energy that the other clouds in the atmosphere. The electrons want to go from high potential energy to lower potential energy. In doing this, they excite gas molecules in the atmosphere and that is how lightning is caused--it is similar to a neon bulb.

I hope this helps. Please let me know if you have more questions. Thanks Jeff Grell


Fredrik,

What you are probably referring to is a transient luminous event (TLE) called a Blue Jet. It is one of a class of discharge events that occur above a thunderstorm, extending into the Stratosphere. Thunderstorms produce a large amount of energy, and this is channeled either to the ground by cloud to ground lightning, to other clouds by cloud to cloud lightning, to the air in the troposphere by cloud to air discharges, or to the stratosphere by Elves, Sprites, and Blue Jets.

You will find much interesting information on and explanations of red Sprites, Elves, and Blue Jets at http://en.wikipedia.org/wiki/Upper-atmospheric_lightning.

David R. Cook Meteorologist Atmospheric and Climate Research Program Environmental Science Division Argonne National Laboratory


Click here to return to the Weather Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 223
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: November 2011
Weclome To Newton

Argonne National Laboratory