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Cosmic Rays


Phyllis S. Freier

Additional Information

Some Important Contributions:

Annotations by Professor C. J. Waddington.

Primary Cosmic Radiation," Phys. Rev. 74:1818-1827 (1948) with E.J. Lofgren, E.P. Ney, and F. Oppenheimer.

  • The first evidence for the presence of nuclei heavier than helium in the cosmic radiation.  A remarkable discovery to be made by a graduate student which Freier was at that time. Until this discovery, it was not clear that the particles in the cosmic radiation included any of the heavier elements. Since these elements are not produced in the initial stages of the Big Bang universe, their presence in the cosmic radiation shows that these very energetic particles had to have been accelerated later.  Freier continued to study the charge, mass and energy spectra of the heavy nuclei for the next 30 years with a series of collaborators. Many of her papers are related to one or more of these topics.
"Emulsion Measurements of Solar Alpha Particles and Protons," J. Geophys. Res.  68:1605-1629 (1963)
  • Studies of the emission of cosmic radiation that appeared to be associated with activity on the Sun. Solar cosmic rays, now known as Solar Energetic Particles, were observed from detectors flown on balloons during time of large solar flares. The composition and energy spectra of these solar particles was studied in a series of papers from 1959 to the mid 1960's.
"The Helium Nuclei of the Primary Cosmic Radiation as Studied over a Solar Cycle of Activity, Interpreted in Terms of the Electric Field Modulation," Space Science Reviews  4:313-371 (1965) with C.J. Waddington.
  • The modulation of the galactic cosmic radiation during the solar cycle was studied in a series of papers which culminated in the above paper. This paper provided the first modern interpretation of the modulation effect by showing that the experimental data could be explained in terms of an energy loss.
"The Cascading of Cosmic Ray Nuclei in Various Media," Astrophys. and Space Sci.  38:419-436 (1975)with C.J. Waddington.

"Nucleus-Nucleus Collisions and Interpretation of Cosmic Ray Cascades above 100 TeV," Phys. Rev. D  Vol. 25, No. 9, 1 May (1982) with T.K. Gaisser, Todor Stanev, and C.J. Waddington.

"The Interactions of Energetic Gold Nuclei in Nuclear Emulsions," Nucl. Tracks  9:107-111 (1984) with C.J. Waddington.

"Central Collisions 14.6, 60, and 200 GeV/Nucleon 16O Nuclei in Nuclear Emulsion," Phys. Rev. Lett.  60:405 (1988)with L.M. Barbier, R. Holynski, W.V. Jones, A. Jurak, A. Olszewski, O.E. Pruet, C.J. Waddinton, J.P. Wefel, B. Wilczynska, H. Wilczynski, W. Wolter, and B. Wosiek.

  • In these papers the interactions of relativistic heavy nuclei, both in the cosmic rays and later from accelerators, were studied because of their interest to astrophysics and nuclear physics. 


Fellow, American Association for the advancement of Science
Fellow, American Physical Society


1944-45 Physicist, Naval Ordinance Laboratory
1950-70 Research Associate, University of Minnesota, Minneapoli
1970-75 Associate Professor, University of Minnesota, Minneapoli
1975-92 Professor of Physics, University of Minnesota, Minneapoli


B.S. University of Minnesota 1942
M.A. University of Minnesota 1944
Ph.D. University of Minnesota 1950

Sources and References consulted:

Thomas F. Stratton, C. J. Waddinton, and [amw1992] , [pt1993]

Additional Information/Comments:

Married to George Freier.

"She was denied a regular position because her husband was an Associate Professor." -- Thomas F. Stratton

Note that in 1970 she was given a faculty position in the University of Minnesota, and appointed Professor of Physics in 1975.

Field Editor: Professor C. J. Waddington


Original citer's name:

Thomas F. Stratton

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latest revision {4/30/97 mjw} 3/16/01 nb