Red Sprites

Jason Ahrns, University of Alaska Fairbanks

I like to cover ongoing mysteries in science, and the topic of Sprites is a good one!  Although they were reported in scientific literature as far back as 1886, it wasn't until 1925 that the theoretical underpinnings were discussed.  Experimental proof didn't come for almost 7 decades!

This recent photo was taken by Jason Ahrns of the University of Alaska Fairbanks who was working with an airborne team of researchers from NCAR, using a 'normal' dSLR camera with an image intensifier and settings of f/1.8, ISO 6400, 3/4 second exposure.  They use more sophisticated equipment for the actual research, but bring their personal cameras along to get shots like this which are nicer to look at!

So, what are they?

Sprites are a form of electrical discharge in the upper atmosphere, called the "mesosphere" in the range of 50 to 90 km above Earth.  They are not lightning, but are related to lightning strikes.  As I said in the intro, they are a mystery and we have just begun to get a rough idea about them.  Here's a bullet list of what we do know so far:

•    they are a cold plasma phenomenon
•    they were named after "air spirits", for their rare sightings
•    they are red-orange at the tops, and bluish at their bottoms
•    they tend to appear in clusters of at least 2
•    they can be preceded by an orange halo above
•    they last for just milliseconds
•    they can be produced by both positive and negative (cloud to ground) lightning strikes, but are most often produced by the more rare positive strikes
•    positive lightning produces 7 to 10 times more halos than negative
•    every lightning strike 'tries' to create them
•    initial estimates of their energy were low by a factor of 50
•    they produce VLF & ELF radio waves
•    they consist of balls of ionization that move downward at ~10% of the speed of light, followed by upward moving balls
•    they were theoretically anticipated by C.T.E. Wilson, Cavendish Laboratory, in 1925
•    they were first captured in images by J.R. Winckler,  University of Minnesota in 1989

If you're interested in using Sprites for classroom material, I recommend this publication: THE DISCOVERY OF RED SPRITES AS AN OPPORTUNITY FOR INFORMAL SCIENCE EDUCATION


References (including above):
http://www.spaceweather.com/
http://musubk.blogspot.com/
http://www.scienceblog.com/community/older/2002/B/20026035.html
http://onlinelibrary.wiley.com/doi/10.1029/2004GL021943/abstract
http://www.nobelprize.org/nobel_prizes/physics/laureates/1927/wilson-bio.html
http://en.wikipedia.org/wiki/Sprite_%28lightning%29


UPDATE: August 18, 2013

Some of the comments from a G+ version of this story

UPDATE: Sept 17, 2013

A new video from NASA talks about their Firestation experiment aboard the ISS, which has started operations recently.

In recent decades researchers have discovered some strange things happening in the cloud tops.  High above ordinary lightning, exotic forms known as red sprites and blue elves shoot toward the heavens, cold cousins to the fiery bolts below. In some places jets of antimatter fly upwards, triggering the detectors on NASA's orbiting high-energy observatories.  And as often as 500 times a day, Earth briefly mimics a supernova, producing a powerful blast of gamma-rays known as a Terrestrial Gamma-ray Flash or TGF.

No know knows exactly how these phenomena are related either to each other or to the lightning down below. 

A new experiment called "Firestation" onboard the ISS aims to find out.  Firestation is a package of sensors designed to explore the links between TGFs, ordinary lightning, and sprites.

  

Something up there is accelerating low-energy particles of air to nearly the speed of light, producing gamma-radiation and, sometimes, a cascade of antimatter.  Rowland wants to find out what that strange, unknown "something" is.  Firestation is poised to crack the mystery. 

The full story can be read here: ISS "Firestation" to Explore the Tops of Thunderstorms

Stay tuned for the latest findings!
 

Are Noctilucent Clouds connected with Climate Change?

NLCs in Finland.  (c) Pekka Parviainen

NASA reported yesterday that their AIM Mission continues to add to our understanding of Noctilucent Clouds (NLC).

"The 2013 season is remarkable because it started in the northern hemisphere a week earlier than any other season that AIM has observed," reports Cora Randall of the Laboratory for Atmospheric and Space Physics at the University of Colorado. "This is quite possibly earlier than ever before."

The ScienceCast video below was posted in the STEM on Google+ Community, where the focus was aimed toward work that connects NLCs to climate change.

NLCs are cloud-like phenomena that are located near the edge of polar mesospheric clouds in the upper
atmosphere. They are made of ice crystals and are typically observed in the summer months at latitudes between 50° and 70° north and south of the equator when the Sun is below the horizon.

Their occurrence can be used as a sensitive guide to changes in the upper atmosphere.

Wikipedia pulls some of the connections together:

There is evidence that the relatively recent appearance of noctilucent clouds, and their gradual increase, may be linked to climate change.[1] The author of this study, atmospheric scientist Gary Thomas of the Laboratory for Atmospheric and Space Physics at the University of Colorado has pointed out[2] that the first sightings coincide with both Krakatoa and the nascent Industrial Revolution, and they have become more widespread and frequent throughout the twentieth century, including an uptick between 1964 and 1986. The connecting of global warming and noctilucent clouds however, remains controversial.[2]

Climate models predict that increased greenhouse gas emissions cause a cooling of the mesosphere, which would lead to more frequent and widespread occurrences of noctilucent clouds.[3] A competing theory is that larger methane emissions from intensive farming activities produce more water vapour in the upper atmosphere.[4] Methane concentrations have more than doubled in the past 100 years.[5]

One possible weakness is the timing coincidence of the first sightings.  Given the limited time of day, typical geographic location, and overall appearance of NLCs being so similar to aurora, they may have been lumped together with that phenomenon.  See photos [A, B] of recent low latitude aurora, which is also a fairly rare event.  Oddly, NLCs are anti-correlated with the peak of the solar cycle which is going on right now, and is the direct cause of the conditions that spark the aurora.

It's also curious to me that the word "competing" is used between cooling of the mesosphere and more water vapor in the upper atmosphere, as both are necessary characteristics of NLCs.
 
Relating to the last post here is the question: Is it better to push the envelope when it comes to possible connections to climate change in order to increase awareness, or is it too risky given that many people won't have adequate knowledge of varied and lessor known phenomena, and how they would relate?  The risk being that either people will dismiss these connections out of hand, or if ultimately disproved, would become fodder for denialism.


[1] Thomas, GE; Olivero, J (2001). "Noctilucent clouds as possible indicators of global change in the mesosphere". Advances in Space Research 28 (7): 939–946. 
[2] Phillips, Tony (August 25, 2008). "Strange Clouds at the Edge of Space". NASA.
[3] A. Klekociuk, R. Morris, J. French (2008). "First Antarctic ground-satellite view of ice aerosol clouds at the edge of space". Australian Antarctic Division. Retrieved 2008-10-19.
[4] "Noctilucent clouds". Australian Antarctic Division.
[5] Hsu, Jeremy (2008-09-03). "Strange clouds spotted at the edge of Earth's atmosphere". USAtoday.