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Alaska scientist leaves colorful legacy

Davis

Davis "Dave" Sentman

PHOTO: Courtesy of Tom Sentman

Alaska scientist Davis "Dave" Sentman died in December 2011. The man who
named "sprites," colorful discharges that burst upward from thunderclouds,
was 66 years old.

Sentman, a professor emeritus at the University of Alaska Fairbanks'
Geophysical Institute, retired from the university in spring 2011. This gave
him more time to follow a remarkable sense of curiosity that was evident as
his brothers sorted through Sentman's belongings at his Fairbanks home.
There, they noticed a birch tree strung with wires hooked to a computer;
Sentman was using the tree as an antenna, trying to pick up "Schumann
Resonances," a natural, lighting-generated hum felt around the globe. Some
people have suggested our brains resonate with the frequency; Sentman wanted
to see if a living organism reacted to it. At the time of his death, the
birch tree had not.

Sentman had a background unique among his peers ‹ born in Iowa farm country,
he entered the Air Force when he was 20 and served in Japan during the
Vietnam War. Following that, he was a Peace Corps volunteer teaching physics
and math in Kenya. He started an academic career at the University of Iowa
in the 1970s and studied with James Van Allen, a giant in the field of space
physics. After earning his doctorate in physics, Sentman moved to California
to work at the University of California Los Angeles. He came to Alaska in
1991 to begin work at the Geophysical Institute.

Due to his expertise and likeability, Sentman was a sought-after authority
on electricity in the atmosphere and beyond. He once told a colleague his
field of study was due to opportunity and following his interests rather
than the fact that a lightning strike killed his father when Sentman was
six-months-old.

He gained worldwide notoriety in the mid-1990s when Sentman was part of a
Geophysical Institute team that captured sprites in all their fiery glory on
video from two NASA aircraft circling thunderstorms over the Midwest. Other
researchers had documented the flashes that fire upward from thunderclouds
before, but the UAF team captured them in exquisite detail, sparking
interest from researchers and non-scientists. After a dinner with his friend
Kathy Berry Bertram in which they pored through books, Sentman named the
flashes "sprites." He thought the definition of a woodland nymph that can be
seen only from the corner of one¹s eye was apt. He was careful not to assign
a scientific name because sprites were at the time so mysterious (He later
pointed out that sprites occur about once every minute above thunderstorms
somewhere on Earth). He and his colleagues also developed initial theories
and models for the mechanisms that generate sprites, blue jets and similar
spectacular but short-lived phenomena.

At the largest gathering of Earth scientists in the world, the American
Geophysical Union¹s annual fall meeting in San Francisco, Sentman often
convened sessions on atmospheric electricity. In 2010, AGU officials chose
him to give the prestigious hour-long Franklin Lecture named after Ben
Franklin. For his unique and lasting contributions to the field of
atmospheric electricity, members of the AGU Council in 2011 elected Sentman
as an AGU Fellow, an honor bestowed each year on less than 0.1 percent of
the members of the organization. His colleagues nominated Sentman for the
award before his sudden death.
 

Dave Sentman (Photo courtesy of Tom Sentman)

Following are comments from some of Dave Sentman's coworkers, students and
friends.

Daisy Huang, a UAF graduate student in one of Sentman's physics classes:

"He was a very warm, funny man with a gentle, kindly face and demeanor that
put me in mind of a beloved pediatrician . . . He went off on so many
tangents in the middle of his lectures that I was always amazed that at the
end of the semester, he was always right on schedule with the syllabus."

Earle Williams, Sentman¹s friend and fellow examiner of atmospheric
electricity at the Massachusetts Institute of Technology:

"Dave really brought the whole field (of studying Schumann Resonances) back
to life again in the early 1990s by using a personal computer with
digitizing boards. Virtually everyone followed his approach . . . He was
always interested in exploring new terrain."

Roger Smith, Sentman's former boss and former director of the Geophysical
Institute:

(On Sentman's humble delivery of the Franklin lecture): "He notably promoted
people other than himself. I think people respected him a great deal for
that. He was understating what his contribution was."

(On Sentman's sprite research, performed with Gene Wescott and Dan Osborne):
"NASA adopted a whole new area of research because of those three . . . That
was the power of Dave Sentman. He had the background to interpret what they
did and make the best science out of it."

Glenn Shaw, fellow Geophysical Institute physicist and friend:

"He felt the whole field of atmospheric electricity was very important, and
he felt strongly about doing something different. He would never chase the
money (by writing proposals on popular subjects). He would do his own
thing."

Syun-Ichi Akasofu, the Geophysical Institute Director at the time of the
sprites work:

"He was always one or two steps ahead of everybody, that's a difficulty he
faced. Some reviewers didn't understand what he was doing."

Dan Osborne, retired camera, video and logistics expert from the Geophysical
Institute who suggested to Sentman that sprites work could be done from
smaller aircraft than the Space Shuttle:

"He was a very curious guy about everything. As a kid, he and his brothers
would stare at the night sky and memorize all the stars' names. And he still
remembered them."

(On Sentman's night-owl lifestyle): "Dave would show up at noon and he'd be
there in the morning ready to go home when I showed up at 7 a.m."

Matt Heavner, a doctoral student advised by Sentman who now works at Los
Alamos National Laboratory in New Mexico:

"He had an unbiased curiosity. He was so open-minded it led to a lot of
serendipitous discoveries."

"It always seemed to be the night before a big physics assignment was due
that one of us graduate students would get 'Sentmanned.' Dave would come in
all excited to share the latest cool new analysis tool, scientific result,
or computer technology. These sessions might last two hours, late into the
night."

"A regular staple of the travels (to South America to study sprites or to
rural Alaska for other space-physics work) was a late night wrap-up dinner
and then coffee, discussing the day and the science issues we were working
on. Whether traveling or at Sam's Sourdough Cafe in Fairbanks, Dave had a
tremendous influence on me."

Dolores Baker, a friend at the Geophysical Institute:

"Shortly before Dave left us, I said, 'It's a good thing you're retiring
while you're young and healthy, so you can enjoy it.' He said to me, 'I'm
one of the lucky few. I enjoyed what I did for a living and had fun with
it.'"

This column is provided as a public service by the Geophysical Institute,
University of Alaska Fairbanks, in cooperation with the UAF research
community. Ned Rozell is a science writer at the institute.

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