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Uri Feldman (1935-2023)

Feldman was a leader in the study of astrophysical and laboratory plasmas using innovative high-resolution spectroscopic techniques.

Published onJan 22, 2024
Uri Feldman (1935-2023)
Figure 1

Photo credit: Dr. John Seely

Uri Feldman, an internationally recognized expert in the field of astrophysical and laboratory plasma physics, died on Sunday, February 26, 2023. He was 87.

On February 26, 2023, we lost Uri Feldman, a pioneer in the spectroscopy of highly ionized atoms. Uri’s work focused on developing instruments, making observations, and formulating theoretical models to understand astrophysical and laboratory plasmas using high-resolution spectroscopic techniques, primarily in the extreme ultraviolet and X-ray ranges. His astrophysical studies concerned the Sun’s upper atmosphere, while the laboratory studies involved laser produced plasmas, tokamaks, and Electron Beam Ion Traps (EBITs).

Uri Feldman was born on April 17, 1935, in Kfar Ganim, a small village in Petach Tikvah, Israel, and grew up there. He entered the Israeli army in 1952, and in 1956, after his military service, he began studying physics at the Hebrew University in Jerusalem, obtaining a Ph.D. in physics in 1965 under Professor B.S. Fraenkel.

Uri obtained a postdoctoral position at NASA’s Goddard Space Flight Center (GSFC) in Maryland in 1966 and began identifying spectral lines of highly ionized atoms. He developed a low inductance vacuum spark that produced highly ionized atoms, resulting in an ion spark spectral line list in the 10-18 Å region. Uri and William Behring at GSFC also developed a superb solar physics grazing incidence 3-m rocket spectrometer. Following his postdoctoral research, Uri returned to Israel and took a position at Tel Aviv University.

In 1969, Yuval Ne’eman, head of the Physics & Astronomy Department at Tel Aviv University, asked Uri to oversee the building of the first major astronomical observatory in Israel, the Wise Astronomical Observatory in the Negev desert. Uri consulted extensively with Ira Bowen at Mt. Palomar on optical design of large telescopes. Completed in 1971, Wise Observatory has been in continuous operation for over 50 years.

In 1976 Uri joined the Space Science Division (SSD) of the Naval Research Laboratory (NRL) in Washington, D.C. and worked there until his retirement. With NRL co-workers, Uri began analyzing NRL solar spectroscopic data as well as laboratory extreme-ultraviolet (EUV) and X-ray spectra produced by lasers in the NRL Plasma Physics Division.

Uri collaborated with many scientists at NRL and other laboratories. His enthusiasm was infectious, and it was a pleasure to work with him on projects. Uri had strong views on the physics of the Sun’s upper atmosphere. This frequently resulted in lively discussions and arguments. In the SSD Uri’s main collaborators in his activities were Charles Brown, George Doschek, Martin Laming, John Mariska, John Seely, Harry Warren, Kenneth Widing, and engineer Glenn Holland.

Uri and co-workers obtained spectra with the Pharos 100 GW glass laser at NRL and from an NRL CO2 laser. Later, Uri and co-workers obtained spectra and/or developed spectrometers for work at the Rochester Laboratory of Laser Energetics (LLE), the Lawrence Livermore National Laboratory (LLNL), and the National Institute of Standards and Technology.

From spectra obtained by NRL instruments on Skylab, Uri and collaborators developed many diagnostics for measuring plasma temperature distributions, densities, and chemical abundances in the Sun’s chromosphere, transition region, and corona, greatly extending what was known about the Sun’s highly dynamic atmosphere. These measurements led him to be among the first to recognize that the structure of the Sun’s upper atmosphere was much more complex than originally thought. Uri also had a special interest in determining element abundances in the solar corona.

From the NRL laser-produced plasma EUV and X-ray spectra, with Robert Cowan at Los Alamos National Laboratory, Uri and colleagues identified many new EUV and X-ray spectral lines of highly ionized atoms. They compiled a database of n=2-2 transitions in the B I through F I isoelectronic sequences enabling the determination of highly accurate energy levels for a wide range of elements.

Uri participated in designing solar physics X-ray spectrometers that were flown on the Department of Defense’s P78-1 spacecraft and later the Japanese Yohkoh spacecraft. He collaborated with scientists at the Aerospace Corporation in analyzing solar flare and active region X-ray spectra from the NRL instrument and from an Aerospace X-ray spectrometer flown on P78-1. Later, Uri participated in analyzing extreme ultraviolet spectra from the Japanese Hinode spacecraft.

In the 1980s, more powerful lasers became available at NRL, LLNL and LLE. Uri helped develop spectroscopic instrumentation for use at these laboratories that greatly extended line identifications of highly ionized iron and heavier elements up to uranium.

Uri Feldman was an author or co‑author of over 400 papers published in refereed journals. He was a member of the International Astronomical Union, and a Fellow of the Optical Society of America and the American Physical Society. In 1989 he was awarded the NRL E.O. Hulburt Annual Science and Engineering Award for outstanding research.

Uri Feldman was a superb scientist and a great colleague. He was always enthusiastic and eager to attack new problems in atomic and solar physics. Uri never missed an opportunity to engage colleagues in spirited discussions of ongoing solar and atomic physics problems. He will be greatly missed.

Adapted and reproduced with permission from the AAS Solar Physics Division Obituary

Additional material provided by: Charles Brown, John Mariska, John Seely, and Harry Warren

Feldman’s AstroGen entry

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