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Title: Radial distribution of compressive waves in the solar corona revealed by Akatsuki radio occultation observations

Radial variations of the amplitude and the energy flux of compressive waves in the solar corona were explored for the first time using a spacecraft radio occultation technique. By applying wavelet analysis to the frequency time series taken at heliocentric distances of 1.5-20.5 R{sub S} (solar radii), quasi-periodic density disturbances were detected at almost all distances. The period ranges from 100 to 2000 s. The amplitude of the fractional density fluctuation increases with distance and reaches ∼30% around 5 R{sub S} , implying that nonlinearity of the wave field is potentially important. We further estimate the wave energy flux on the assumption that the observed periodical fluctuations are manifestations of acoustic waves. The energy flux increases with distance below ∼6 R{sub S} and seems to saturate above this height, suggesting that the acoustic waves do not propagate from the low corona but are generated in the extended corona, probably through nonlinear dissipation of Alfvén waves. The compressive waves should eventually dissipate through shock generation to heat the corona.
Authors:
 [1] ; ; ; ;  [2] ; ;  [3] ; ;  [4] ;  [5] ;  [6] ;  [7]
  1. Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
  2. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
  3. Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 484-8601 (Japan)
  4. Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto 607-8471 (Japan)
  5. Institut für Raumfahrttechnik, Universität der Bundeswehr München, D-85577 Neubiberg (Germany)
  6. Rheinisches Institut für Umweltforschung, Department Planetenforschung, Universität zu Köln, Aachener Str. 209, D-50931 Köln (Germany)
  7. The Institute of Radio Astronomy, National Academy of Science of Ukraine, Chervonoprapornaya, Str. 4, Kharkov 61002 (Ukraine)
Publication Date:
OSTI Identifier:
22370055
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 797; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALFVEN WAVES; DENSITY; DISTANCE; DISTURBANCES; ECLIPSE; FLUCTUATIONS; PERIODICITY; SOLAR CORONA; SOLAR WIND; SOUND WAVES; SPATIAL DISTRIBUTION; SUN