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Title: Ulysses observations of magnetic waves due to newborn interstellar pickup ions. I. New observations and linear analysis

We have examined Ulysses magnetic field data using dynamic spectrogram techniques that compute wave amplitude, polarization, and direction of propagation over a broad range of frequencies and time. Events were identified that showed a strong polarization signature and an enhancement of power above the local proton gyrofrequency. We perform a statistical study of 502 wave events in an effort to determine when, where, and why they are observed. Most notably, we find that waves arising from newborn interstellar pickup ions are relatively rare and difficult to find. The quantities normally employed in theories of wave growth are neutral atom density and quantities related to their ionization and the subsequent dynamics such as wind speed, solar wind flux, and magnetic field orientation. We find the observations of waves to be largely uncorrelated to these quantities except for mean field direction where quasi-radial magnetic fields are favored and solar wind proton flux where wave observations appear to be favored by low flux conditions which runs contrary to theoretical expectations of wave generation. It would appear that an explanation based on source physics and instability growth rates alone is not adequate to account for the times when these waves are seen.
Authors:
 [1] ; ; ;  [2] ;  [3] ;  [4]
  1. Physics Department, Florida State University, Tallahassee, FL (United States)
  2. Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH (United States)
  3. Jet Propulsion Laboratory, Mail Stop 180-600, 4800 Oak Grove Drive, Pasadena, CA (United States)
  4. School of Earth and Space Exploration, Arizona State University, Tempe, AZ (United States)
Publication Date:
OSTI Identifier:
22357218
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 784; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DENSITY; GYROFREQUENCY; HELIOSPHERE; INSTABILITY GROWTH RATES; MAGNETIC FIELDS; MEAN-FIELD THEORY; POLARIZATION; PROTONS; SOLAR WIND; SUN