Sprites



A completely new discovery was made in recent years related to thunderstorms. It has been observed that far above thunderstorm tops at altitudes between 50-100km there often occur optical flashes now known as red sprites and blue jets . These optical flashes are very faint and last for only a fraction of a second, so even if you saw one yourself you would probably think you were dreaming. Other strange lights above thunderstorms have been termed elves, halos and trolls.  However, we now know that these upper atmopsheric discharges occur simultaneously with a very specific type of powerful lightning in the thunderstorm underneath these transient luminous events (TLEs). These powerful lightning flashes that produce the sprites also produce strong extremely low frequency (ELF) radiation that can be picked up tens of thousands of miles away, at our Negev desert ELF station.

We have been involved in a number of field projects to detect the electromagnetic signals that are related to sprite formation, that can be detected in Israel, more than 11,000 km away from the parent thunderstorms.  Below (left) is shown the first color image of a red sprite taken by a team from the University of Alaska, from a research aircraft flying at 15 km altitude around a thunderstorm in the United States. The black disk at the bottom of the image (below 20km) is the thunderhead anvil, which blocks out the light from the regular lightning (white light) in the cloud.   On the right is one of our black & white sprite images taken with our cameras in France looking horizontally toward the horizon.  The thunderstorm is a few hundred kilometers away from the camera, allowing us to see the sprite in the upper atmosphere 50-100km above the ground.

Hundreds of thousands of sprites have now been documented and studied.  They are red in colour due to the excitation of Nitrogen gas in our atmosphere.  The lightning below the sprites results in large electric fields in the mesosphere (50-100 km altitude) which result in the breakdown of air (mainly N2) a fraction of a second after the lightning discharge.  This intense lightning discharge also sends radio waves propagating outward into the earth-ionosphere waveguide in all directions.  Hence, when a sprite occurs somewhere on the earth, we receive simultaneously a strong radio wave pulse here in Israel  that can be clearly differentiated from all other signals.  An example of one of these signals is shown below.  This signal occurred exactly at the time (within half a second accuracy) a sprite was observed optically in the United States.  Could this be a coincidence?  Well, besides the time correlation we can also calculate the direction of arrival of this signal using the 2 horizontal components of the magnetic field (not shown).  This tells us that the signal arrived from approximately 30 degrees west of north.  This is the great circle angle between Israel and the United States.  Finally, using the magnetic and electric fields we can estimate the distance (range) between the lightning/sprite and the observation station.  This gives us a distance of approximately 11,500 km.  So with these three bits of information the signal was found to orignate from the same thunderstorm being observed by our colleagues in the United States.  One additional bit of information we can obtain from the ELF measurements is related to the type of lightning that produced this pulse.  The vertical electric field plot below shows that the initial deviation of the field was POSITIVE, implying a lightning discharge bringing positive charge to earth (or negative charge to the cloud).  These are very rare lightnings (less that 5% globally) but are now known to be the lightnings that produce sprites.


During January 2003 the first Israeli astronaut, Ilan Ramon, participated in the STS-107 flight of the Columbia Space Shuttle as part of the MEIDEX mission.  Part of this mission was to study sprites from space.  While the astronauts photographed the sprites from above, we were sitting in the Negev desert, Israel, looking for the radio signals related to these events.   Although the Columbia mission ended tragically, the scientific mission was a great success, with the astronauts observing numerous sprites and elves from space with calibrated cameras.  Our research in the field of sprites is now dedicated to the memory of the 7 brave Columbia astronauts. Below we can see an image of an ELVE and sprite observed from space by the Columbia astronauts.  Our project is called ILAN after the Israeli astronaut Ilan Ramon.

columbia

 In the recent few years we have also started doing laboratory experiments with our colleagues in Holland to investigate the possiblility of sprites occurring on other planets.  We know that lightning exists on Jupiter and Saturn, and maybe Venus.  If so, we should expect to find also sprites there.  But this depends on the gaseous makeup of planetary atmospheres, the existence of an ionosphere high enough above the clouds to allow sprites to form, and low enough gas densitites to allow for discharges to occur.  Such conditions can be produced in a laboratory, and our findings show that sprites on other planers should exist. Below are three images of "sprites" in the laboratory on different "planets".


References:

    Price, C., M. Asfur, W. Lyons and T. Nelson, 2002: An improved ELF/VLF method for globally geolocating sprite-producing lightning, Geophys. Res. Lett., 29(3), 1.1-1.4.     Price, C., W. Burrows and P. King, 2002: The likelihood of winter sprites over the Gulf Stream, Geophys. Res. Lett., 29(22),  27.1-27.4.
    Yair, Y., C. Price, Z. Levin, J.Joseph, P. Israelevich, A. Dvir, M. Moalem, B. Ziv and M. Asfur, Sprite observations from the space shuttle during the Mediterranean Israeli Dust Experiment (MEIDEX), J. of Atmos. and Solar-Terr. Phys., 65(5), 635-642, 2003.

    Hsu, R.R., H.T. Su, A.B. Chen, L.C. Lee, M. Asfur, C. Price and Y.Yair, 2003: Transient luminous events in the vicinity of Taiwan, J. of Atmos. Solar-Terr. Phys., 65(5), 561-566.
    Israelevich, P., Y. Yair, A. Dvir, J.H. Joseph, Z. Levin, I. Mayo, M. Moalem, C. Price and A. Sternlieb, 2004: Transient airglow enhancements observed from the space shuttle Columbia during the MEIDEX sprite campaign, Geophys. Res. Lett., 31, L06124:1-5.
    Yair, Y., P. Israelevich, A. Dvir, M. Moalem, C. Price, J. Joseph, Z. Levin, B. Ziv, A. Teller, 2004: New observations of sprites from the Space Shuttle, J. Geophys. Res., 109, D15201, doi:10.1029/2003JD004497.
    Greenberg, E., and C. Price, 2004, A global lightning location algorithm based on the electromagnetic signature in the Schumann resonance band, J. Geophys. Res., 109, D21111, doi:10.1029/2004JD004845.
    Price, C., E. Greenberg, Y. Yair, G. Sátori, J. Bór, H. Fukunishi, M. Sato, P. Israelevich, M. Moalem, A. Devir,  Z. Levin, J.H. Joseph, I. Mayo, B. Ziv and A. Sternlieb, 2004: Ground-based detection of TLE-producing intense lightning during the MEIDEX mission on board the Space Shuttle Columbia, Geophys. Res. Lett., 31, L20107, doi:1029/2004GL020711.
    Yair, Y., C. Price, B. Ziv, P.L. Israelevich, D.D. Sentman, F. T. Sao-Sabbas, A.D. Devir, M. Sato, C.J. Rodger, M. Moalem, E. Greenberg and O. Yaron, 2005:  Space shuttle observation of an unusual transient atmospheric emission, Geophys. Res. Lett., 32, L02801, doi:10.1029/2004GL021551.
    Williams, E.R., R. Boldi, J. Bor, G. Satori, C. Price, E. Greenburg, Y. Takahashi, K. Yamamoto, T. Chronis, E. Anagnostou, D. Smith, L. Lopez, 2006: Lightning flashes conducive to the production and escape of gamma radiation to space, J. Geophys. Res., 111, D16209, doi:10.1029/2005JD006447.
    Ganot, M., Y. Yair, C. Price, B. Ziv, Y. Sherez, E. Greenberg, A. Dvir and R. Yaniv, 2007:  First detection of Transient Luminous Events associated with winter thunderstorms in the eastern Mediterranean, Geophys. Res. Lett.., 34, L12801, doi:10.1029/2007GL029258.
    Greenberg, E., C. Price, Y. Yair, M. Ganot, J. Bór and G. Sátori, 2007: ELF transients associated with sprites and elves in eastern Mediterranean winter thunderstorms, J. Atmos. Solar-Terr. Physics, 69, 1569-1586.
    Yair, Y., C. Price, M. Ganot, E. Greenberg, R. Yaniv, B. Ziv, Y. Sherez, A. Devir, J. Bór, G. Sátori, 2008: Optical observations of transient luminous events associated with winter thunderstorms near the coast of Israel, Atmos. Res., 91, 529-537.
    Greenberg, E., C. Price, Y. Yair, C. Haldoupis, O. Chanrion and T. Neubert, 2009:  On the ELF charge moment change, VLF bursts and subionospheric perturbations associated with sprites, J. Atmos. Terr.-Solar Phys., doi:1016/j.jastp.2009.05.005.
    Williams, E., W. Lyons, Y. Hobara, V. Mushtak, N. Asencio, R. Boldi, J. Bór, S. Cummer, E. Greenberg, M. Hayakawa, R. Holzworth, V. Kotroni, J. Li, C. Morales, T. Nelson, C. Price, B. Russell, G. Sátori, K. Shirahata, Y. Takahashi, K. Yamashita, 2009:  Ground-Based Detection of Sprites and their Parent Lightning Flashes over Africa during the 2006 AMMA Campaign, Q. J.  Roy. Met. Soc., 136, 257-271.
    Yaniv, R., A.D. Devir, Y. Yair, C. Price, B. Ziv and N. Reicher, 2009:  Calibration of CCD cameras for sprites and elves measurements, Amer. Inst. of Phys. Conf. Proc., submitted.
    Vadislavsky, E., Y. Yair, C. Erlick, C. Price, E. Greenberg, R. Yaniv, B. Ziv, N. Reicher and A. Devir, 2009: Indication for Circular Organization of Column Sprite Elements Associated with Eastern Mediterranean Winter Thunderstorms, J. Atmos. Solar Terr. Phys.,  doi:10.1016/j.jastp.2009.07.001.
    Dubrovin, D., S. Nijdam, E. van Veldhuizen, U.  Ebert, Y. Yair and  C. Price, 2010: Sprite discharges on Venus and Jupiter-like planets: laboratory investigation, J. Geophys. Res, doi:10.1020/2009JA014851.

 Tel Aviv Universtiy coverage of sprite research

Related websites:

Lightning and thunderstorm information
Sprites research at Yucca Ridge
Sprites research in Alaska
Sprites research in New Mexico
Theoretical explanations from Stanford University