Plasma Turbulence in the Interstellar Medium: Characteristics and Consequences

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Dr. Steven Spangler (University of Iowa) will explore turbulence in the interstellar medium and the role such turbulence plays in interstellar processes. Methods of inquiry in the research program include (1) new radio-astronomical observations using the Very Large Array (VLA) of extragalactic radio sources viewed through HII regions, (2) new observations at low radio frequencies of nearby pulsars with the VLA and the Murchison Widefield Array, and (3) examination and re-analysis of extensive spectroscopic measurements of turbulence in nearby interstellar clouds. Specific research projects to be undertaken in the grant period are the following: (1) Faraday rotation observations will be made with the VLA of a sample of about 150 extragalactic radio sources viewed through 6 HII regions and their associated bubbles; (2) low frequency (less than 100 MHz) scintillation measurements will be made of four pulsars which are weakly scattered and viewed through the "Local Bubble": the scintillation data will be examined for the presence of "pulsar arcs", which contain information on the distance and distribution of turbulence along the line of sight; (3) an existing, high quality set of measurements of absorption lines due to nearby interstellar clouds will be analysed for the information it contains on the properties of turbulence in these clouds; (4) the properties of turbulence in the lightly ionized molecular clouds, and its interaction with molecular ions, will both be investigated.This research will benefit society as a whole through the individualized training of young scientists in the methods of physical science research, the capabilities of radioastronomical and radiophysical measurements, and in fundamentals of plasma physics. Dr. Spangler's mentorship of University of Iowa undergraduate and graduate students will continue under this award. This research program also has an outreach component, consisting of an association with amateur astronomy groups in Iowa, particularly the Cedar Amateur Astronomers in Cedar Rapids, Iowa.