GPL Lightning Group Florida Institute of Technology Dept. of Physics and Space Sciences

GPL Lightning GroupFlorida Institute of Technology

Dept. of Physics and Space Sciences

GPL Lightning Group - Physics Dept.

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Other Collaborators

J. Dwyer, D. Barnes, E. Cramer, M. Schaal, S. Lazarus, M. Splitt, S. Arabshahi, B. Kosar, S. Sadighi, N. Liu, and H. Rassoul,

Florida Institute of Technology

J. Fishman and M. BriggsMSFC and U. of Alabama

D. SmithUniversity of California at Santa Cruz

M. Uman, D. Jordan, D. Hill, C. Biagi University of Florida


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Lightning is a giant discharge of electricity

accompanied by a brilliant flash of light and a loud

crack of thunder. The spark can reach over five miles (eight

kilometers) in length, raise the temperature of the air

by as much as 50,000 degrees Fahrenheit

(27,700 degrees Celsius), and contain a hundred

million electrical volts. Reference: National Geographic

What is lightning?


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The rapid expansion of heated air causes the

thunder. Since light travels faster than sound, the

thunder is heard after the lightning. If you see lightning

and hear thunder at the same time, that lightning is in

your neighborhood. If you see successive strokes of lightning in the same place on the horizon then you are in line with the storm, and it may be moving toward you.

Reference: National Geographic

What is thunder?


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The odds of becoming a lightning victim in the U.S. in any one year is 1 in 700,000. The odds of being struck in your

lifetime is 1 in 3,000.



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Rubber shoes will not give you any meaningful protection from lightning.


=


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About 10 percent of lightning-stroke victims are killed, and 70 percent suffer serious long-term

effects. About 400 people survive lightning strokes in the

U.S. each year.


Lightning can kill people (3,696 deaths were recorded in the U.S. between 1959 and 2003) or cause cardiac arrest. Injuries range from severe burns and permanent brain

damage to memory loss and personality change.


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What happens if your car gets hit by lightning and you are inside?

Answer:

Nothing (as long as you are not touching the frame of the car, which includes the sides and the steering wheel)

The car acts as a Faraday cage and protects you while you are inside the vehicle!


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What happens if an airplane gets hit by lightning during a thunderstorm?

Answer:

Usually nothing!!

The electrical energy travels through the metal skin of the aircraft leaving you unharmed!

(new.dixie.edu)


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Answers Not Known to this Day

• How does lightning get started with the relatively low electric field strengths inside thunderstorms?

• How does lightning travel through tens of kilometers of air?

• Why does lightning hit one object and not another?(e.g. Why did the lightning hit the tree?)


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Lightning Initiation???

• In 1999, Russian physicist Alex Gurevich and collaborators suggested that cosmic-ray air showers could trigger lightning.

• Cosmic-rays are energetic particles from space. When they strike the earth’s atmosphere, they create large showers of high energy particles.

(www.scifun.ed.ac.uk)


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Air Showers Plus Runaway Breakdown

• Studies have shown that, by itself, even a large air shower will not produce enough particles to significantly affect the conductivity inside the thunderstorm, making it unlikely that it will trigger lightning.

• One way to increase the number of energetic particles so that lightning may be triggered is to include runaway breakdown.

• Runaway breakdown is a kind of discharge involving very fast electrons.


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Model of a 25 MeV electron moving through air

at 1 atm(No electric field)

No Relativistic Runaway Electron Avalanche

Model of a 25 MeV electron moving through

air at 1 atmin a 3 kV/cm electric field

Relativistic Runaway Electron Avalanche


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The International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, FL is the location where most of the ground-based observations take place.

This facility is operated jointly by the University of Florida and Florida Tech. It is capable of measuring magnetic fields, electric fields, and other energetic emissions.

We use the Thunderstorm Energetic Radiation Array (TERA) to measure the x-ray and gamma-ray emissions along with a flat plate antenna to measure the electric field.

TERA is composed of 24 separate aluminum boxes designed specifically to keep light and noise out. Each box houses up to two NaI(T1)/PMT detectors with the necessary fiber optic wiring and electronic equipment to control each detector.


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Instruments and Setup


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Video of Rocket-triggered Lightning


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Video of Rocket-triggered Lightning (slow)


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Video of Rocket-triggered Lightning


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Video of Rocket-triggered Lightning (slow)


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X-Rays From Rocket-Triggered Lightning Dart

Leaders (Dwyer et al. 2004a)


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X-Rays From Natural Cloud-To-Ground Lightning (Dwyer et al. 2005)

www.moonraker.com.au/techni/lightning-marine.htm

GPL Lightning Group - Physics Dept.22

Ground Level Gamma-Ray Burst (Dwyer et al. 2004b)

•In 2003, a ground level gamma-ray burst was seen by rocket-triggered lightning

•The event fit the energy profile that was seen with other terrestrial gamma-ray flashes (TGFs)


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Terrestrial Gamma-Ray Flash• First discovered by

Fishman et al. 1994• CGO/BATSE• High energy gamma-ray

flash

(www.usra.edu) (Fishman et al. 1994)


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Where Do TGFs Come From?

1994 – 2005: People thought Here

After 2005: Here

(www.holoscience.com)

July 21-23, 2009 Lightning 25

ADELE

HIAPER is a joint NSF/NCAR Gulfstream V jet outfitted for atmospheric research.HIAPER is a joint NSF/NCAR Gulfstream V jet outfitted for atmospheric research.

•ADELE was mounted in the NSF/NCAR Gulfstream V operated under the HIAPER program.

•Missions were flown directly above low thunderstorms and to the sides of taller thunderstorms.

Purpose : to detect x-ray and gamma-ray emissions from thunderstorms.

Goal : to capture thousands of gammas per TGF as opposed to the dozens captured by detectors in orbit.


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ADELE - Antenna

•Flat plate antenna measured dE/dt simultaneously with x-ray measurements

GPL Lightning Group - Physics Dept.27

ADELE – Initial Results

•Glows : gamma excesses seen in the ADELE instruments . This could possibly be caused by the electric field being kept at a limiting value by a gradual runaway feedback.

•Surges : second to minute in length enhancements

•TGFs : millisecond in length; MeV energies

•GV flew 14 flights and was within 20 miles of lightning flashes

ADELE – Initial Results


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•2 periods of strong 511 keV positron annihilation lines.•Implies a buildup of positrons and considerable pair-production occurrence.

•Figure resembles other TGFs measured from RHESSI and BATSE. •TGF is believed to have been far away thereby explaining the low count rate.

•On Aug. 21, the GV aircraft mistakenly entered an anvil thundercloud. •Possible positron bursts and a bright surge also occurred from this day as did a TGF.

•Only one TGF was measured on this campaign•Leads us to believe that TGFs are rare and that they probably are not the sole trigger mechanism of lightning.

Mobile Lightning Detector System - MLDS


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•ADELE into the SUV•Around Central Florida•XLB and ADELE x-ray measurements•Radiosonde measurements•FastCam High Speed Camera

Mobile Lightning Detector System - MLDS


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1. ADELE monitor and camera

2. Yoko and Lecroy scopes for XLB

3. Graduate students discussing problems

4. XLB5. Flat plate antenna

1.

5.4.

3.2.

•X-ray burst from natural lightning strike on the

ground campaign


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•Analyze sodium iodide and plastic data with our search algorithm to find TGF-like events that contain unique characteristics for both ground and flight data.

•Start preparing for future ADELE missions.

ADELE – Work to be done

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GPL Lightning Group Florida Institute of Technology Dept. of Physics and Space Sciences

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