Space Forum / Shuttle / January 2005

American Geophysical Union
Washington, D.C.

Contact:
Harvey Leifert, +1 (202) 777-7507, hleifert@agu.org

For Immediate Release: 17 January 2005

AGU Release No. 05-01

Columbia crew catches a mysterious TIGER in the Indian Ocean

WASHINGTON -- An unprecedented flash observed by the space shuttle Columbia crew
in 2003 over the Indian Ocean may be a new type of transient luminous event,
like lightning sprites, but one that is not necessarily caused by a
thunderstorm. The discharge was observed less than two weeks before the shuttle
was lost during its Earth reentry.

The authors describe the discharge as a Transient Ionospheric Glow Emission in
Red, or TIGER, event. It was recorded by a video camera in the near-infrared
spectrum in the nighttime sky just south of Madagascar on 20 January 2003. The
authors analyzed the video several months later and found what visually looks
like a bright flash. They report that the emission did not resemble any known
class of luminous events, which typically appear in conjunction with
thunderstorm activity.

The space shuttle experiment that observed the unusual discharge was conducted
by Israeli astronaut Ilan Ramon as part of the MEIDEX (Mediterranean Israeli
Dust Experiment), and is reported by Yoav Yair of the Open University of Israel
and an international group of colleagues. The article will be published on 18
January in Geophysical Research Letters, a journal of the American Geophysical
Union.

The researchers also analyzed ground and satellite measurements of lightning in
the region and note that the particular flash was not detected by equipment
monitoring the skies for electromagnetic radiation in the very low and extremely
low frequency domains usually associated with strong lightning discharges. In
fact, no cloud-to-ground lightning was seen in the area for nearly two seconds
around the emission's detection time. They note, however, that meteor trails
were observed by the same equipment on another orbit two days later and posit
that an extraterrestrial source of the event cannot be discounted.

They note that the TIGER event was delayed from a distant lightning flash far
longer than previously observed sprite or ELVES discharges and did not retain
the jellyfish like (sprites) or doughnut (ELVES) shape often seen in those
emissions. Most sprites, for example, appear within 10 milliseconds or less
after strong positive cloud-to-ground flashes, while the observed event was
delayed for nearly a quarter of a second and was approximately 1,000 kilometers
[600 miles] removed from the closest visible lightning flash. For those reasons
and the fact that 17 other luminous emissions detected at other times by the
Columbia equipment were easily classified, the authors believe that the unusual
event was likely a new type of emission, rather than a delayed sprite.

"The major point of this research, in my mind, is to show that there are some
upper atmosphere processes that we do not know enough about," Yair said about
the study. "The best way we can monitor or research this properly is from space."

The research team found no errors in its equipment and note that the sky was
clear in the direct vicinity of their observations, leading them to discount
suppositions that the emission may have been a reflection from another type of
flash. They also suggest that meteors -- still another possibility -- would
likely have produced a continuous trail of emissions that would have been seen
during the short period when the astronauts observed and recorded the flash.

A third proposed explanation is that electron beams emitted from lightning in
thunderstorms believed to be present near Cyprus at around the same time may
have been carried by the Earth's geomagnetic field into the upper atmosphere and
created a purple glow near Madagascar, similar to a sprite that would have had
nearly equal red and blue intensities. The authors discount that possibility,
however, noting that the thunderstorm did not produce strong enough lightning to
spark the TIGER event. The researchers indicate that further space-based
observations may be able to detect similar instances of such emissions and help
to solve the mystery of its cause.

The research was supported by the Israeli National Academy for Sciences and the
Humanities.

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Notes for Journalists

Journalists (only) may obtain a pdf copy of this paper upon request to Harvey
Leifert: hleifert@agu.org. Please provide your name, name of publication, phone,
and email address. The paper and this press release are not under embargo.

Title: Space shuttle observation of an unusual transient atmospheric emission

Authors:
Yoav Yair, Baruch Ziv, Adam D. Devir, Open University, Ra'anana, Israel;
Colin Price, Peter L. Israelevich, Meir Moalem, Eran Greenberg, Ofer Yaron, Tel
Aviv University, Tel Aviv, Israel;
Davis D. Sentman, University of Alaska-Fairbanks, Alaska, USA;
Fernanda T. Sao-Sabbas, National Institute of Space Research (INPE), Sao-Jose
Dos Campos, Brazil;
Mitsuteru Sato, RIKEN Institute of Physical and Chemical Research, Wako, Japan;
Craig J. Rodger, University of Otago, Dunedin, New Zealand.

Citation:
Yair, Y., et al. (2005), Space shuttle observation of an unusual transient
atmospheric emission, Geophys. Res. Lett., 32, L02801, doi:10.1029/2004GL021551,
2005

Contact information for author:
Yoav Yair, E-mail: yoavya@openu.ac.il or +972-9-7781341.