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Title: A study of density modulation index in the inner heliospheric solar wind during solar cycle 23

The ratio of the rms electron density fluctuations to the background density in the solar wind (density modulation index, ε {sub N} ≡ ΔN/N) is of vital importance for understanding several problems in heliospheric physics related to solar wind turbulence. In this paper, we have investigated the behavior of ε {sub N} in the inner heliosphere from 0.26 to 0.82 AU. The density fluctuations ΔN have been deduced using extensive ground-based observations of interplanetary scintillation at 327 MHz, which probe spatial scales of a few hundred kilometers. The background densities (N) have been derived using near-Earth observations from the Advanced Composition Explorer. Our analysis reveals that 0.001 ≲ ε {sub N} ≲ 0.02 and does not vary appreciably with heliocentric distance. We also find that ε {sub N} declines by 8% from 1998 to 2008. We discuss the impact of these findings on problems ranging from our understanding of Forbush decreases to the behavior of the solar wind dynamic pressure over the recent peculiar solar minimum at the end of cycle 23.
Authors:
;  [1] ; ;  [2] ;  [3] ; ;  [4]
  1. Astronomy and Astrophysics Division, Physical Research Laboratory, Ahmedabad 380009 (India)
  2. Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411021 (India)
  3. Department of Electronic Science, University of Pune, Pune 411007 (India)
  4. Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan)
Publication Date:
OSTI Identifier:
22370297
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 795; 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; DENSITY; DISTANCE; ELECTRON DENSITY; FLUCTUATIONS; FORBUSH DECREASE; HELIOSPHERE; MODULATION; SCINTILLATIONS; SOLAR CYCLE; SOLAR WIND; TURBULENCE