Dr. Natalie Mandzhavidze, a respected solar physicist at NASA's Goddard Space Flight Center, died from complications related to multiple sclerosis on 9 April 2001 at her home in Lanham, MD.

photo of Natalie Natalie was born 20 September 1955 in Tblisi, Georgia, in the former Soviet Union. She showed great promise in mathematics and physics from an early age, although her first love was dancing. The daughter of two well-known physicists, Natalie graduated as valedictorian of her high school class and was selected for a full scholarship to attend the Georgian State University. There she received her BSc, with top honors, in particle physics. Natalie was a member of the Geophysics Institute within the Georgian Academy of Sciences where she worked on the influence of solar magnetic fields on the intensity and anisotropy of cosmic rays in interplanetary space.

Natalie went on to receive a PhD in Solar Physics from the Ioffe Physico-Technical Institute in Leningrad. She worked with her adviser, Dr. G. Kocharov, and others at the Institute on the theory of acceleration and transport of high-energy particles in solar flares and the production of neutrons and gamma rays. Natalie's last paper with that group appeared in Izvestiya of the Academy of Science in 1991 and treated her study of the dynamics of accelerated particles in flare loops.

From this work and her articulate and insightful contributions at solar physics conferences in the Soviet Union, Natalie attracted the attention of western researchers.

In 1991, the late Dr. Reuven Ramaty invited her to work with him at NASA's Goddard Space Flight Center, first through a position at the University of Maryland, then under a National Academy of Sciences Resident Research Associates appointment, and finally through the Universities Space Research Association.

Thus began a decade-long productive scientific collaboration. In their early work together, Natalie and Ramaty focused on high-energy gamma-ray emission from pion decay in solar flare magnetic loops. Their detailed calculation took into account magnetic mirroring, MHD pitch-angle scattering and the relevant energy-loss processes and photon production mechanisms. They compared their calculations with high-energy gamma-ray observations and established the criteria for determining whether gamma rays emitted late in a flare came from the interaction of protons trapped in magnetic fields or were freshly accelerated.

Natalie's work then expanded to include other manifestations of particle acceleration, including direct measurements of energetic particles in space and radio observations. Based on this work she was invited to write the rapporteur paper on this subject at the 23rd International Cosmic Ray Conference held in Calgary in 1993. This carefully prepared review was representative of her ability to identify the significant advances in a field that had conflicting observations and theories.
As data on gamma-ray line spectra from solar flares became more available in the mid- nineties, Natalie began working on the physics relating to the production of nuclear gamma rays in solar flares. Her work with Ramaty and Benz Kozlovsky led to fundamental discoveries about the energetics and composition of the accelerated particles and the composition of the medium where they interact and produce gamma rays. They found that flare-accelerated ions produce the gamma rays in a medium with composition similar to that found in the Sun's corona even though they are believed to interact at lower altitudes in the solar atmosphere. By studying various line ratios, they measured the energy spectra of the accelerated ions and surprisingly found that the energy contained in ions >1 MeV is often comparable to that found in electrons >20 keV. This contradicted the long-held view that the energy in electrons was orders of magnitude higher than the energy in ions.

Natalie's most recent work centered on the use of gamma ray spectroscopy to determine the abundance of 4He in the accelerated particles and in the ambient region where the particles interact. She and her co-workers identified gamma-ray lines that could be used to determine these abundances. Their work led to the surprising discovery that the flux in accelerated 4He often was ~50% of that found in accelerated protons. Another facet of this work led to the discovery that accelerated 3He is often enhanced by a factor of 1000 over its photospheric concentration. This increase is similar to that found in impulsive particle events in space.

During Natalie's tenure at NASA Goddard she received numerous invitations to present papers at international scientific meetings. She was both a leading member of the organizing committee and proceedings editor for two important workshops on high-energy solar physics held in 1995 and 1999 and published by the American Institute of Physics.

Natalie had a passion for skiing, swimming, and many forms of dance; she almost embarked on a career as a ballerina. She was also a student of the arts, even serving in her youth as a tour guide at the Hermitage Fine Arts Museum in Leningrad. She had a lively and engaging personality. Very few of Natalie's co-workers were aware of her battle with multiple sclerosis, which began shortly after she arrived in the United States.

It pained Natalie deeply to watch her beloved city of Tblisi suffer during the dissolution of the Soviet Union and the separatist fighting that ensued. Her mother, Nina Roinishvili, in Tblisi, and her brother, Irakli Mandzhavidze, his wife and three children, who live outside of Paris, France, survive her.

Gerald Share
Naval Research Laboratory

Reprinted with permission from the Bulletin of the American Astronomical Society
Bulletin A.A.S., v.33, no.4, p.1575-1576 (2001)