Solar Physics

, Volume 266, Issue 2, pp 369–377 | Cite as

Temporal Evolution of the Solar-Wind Electron Core Density at Solar Minimum by Correlating SWEA Measurements from STEREO A and B

  • A. Opitz
  • J.-A. Sauvaud
  • A. Fedorov
  • P. Wurz
  • J. G. Luhmann
  • B. Lavraud
  • C. T. Russell
  • P. Kellogg
  • C. Briand
  • P. Henri
  • D. M. Malaspina
  • P. Louarn
  • D. W. Curtis
  • E. Penou
  • R. Karrer
  • A. B. Galvin
  • D. E. Larson
  • I. Dandouras
  • P. Schroeder
Open Access
Article

Abstract

The twin STEREO spacecraft provide a unique tool to study the temporal evolution of the solar-wind properties in the ecliptic since their longitudinal separation increases with time. We derive the characteristic temporal variations at ∼ 1 AU between two different plasma parcels ejected from the same solar source by excluding the spatial variations from our datasets. As part of the onboard IMPACT instrument suite, the SWEA electron experiment provides the solar-wind electron core density at two different heliospheric vantage points. We analyze these density datasets between March and August 2007 and find typical solar minimum conditions. After adjusting for the theoretical time lag between the two spacecraft, we compare the two density datasets. We find that their correlation decreases as the time difference increases between two ejections. The correlation coefficient is about 0.80 for a time lag of a half day and 0.65 for two days. These correlation coefficients from the electron core density are somewhat lower than the ones from the proton bulk velocity obtained in an earlier study, though they are still high enough to consider the solar wind as persistent after two days. These quantitative results reflect the variability of the solar-wind properties in space and time, and they might serve as input for solar-wind models.

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Copyright information

© The Author(s) 2010

Authors and Affiliations

  • A. Opitz
    • 1
  • J.-A. Sauvaud
    • 1
  • A. Fedorov
    • 1
  • P. Wurz
    • 2
  • J. G. Luhmann
    • 3
  • B. Lavraud
    • 1
  • C. T. Russell
    • 4
  • P. Kellogg
    • 5
  • C. Briand
    • 6
  • P. Henri
    • 6
  • D. M. Malaspina
    • 7
  • P. Louarn
    • 1
  • D. W. Curtis
    • 3
  • E. Penou
    • 1
  • R. Karrer
    • 2
  • A. B. Galvin
    • 8
  • D. E. Larson
    • 3
  • I. Dandouras
    • 1
  • P. Schroeder
    • 3
  1. 1.Centre d’Etude Spatiale des Rayonnements (CNRS-UPS)University of ToulouseToulouseFrance
  2. 2.Department of Space Science and Planetology, Physics InstituteUniversity of BernBernSwitzerland
  3. 3.Space Sciences LaboratoryUniversity of CaliforniaBerkeleyUSA
  4. 4.Institute of Geophysics and Planetary PhysicsUniversity of CaliforniaLos AngelesUSA
  5. 5.Department of Physics and AstronomyUniversity of MinnesotaMinneapolisUSA
  6. 6.LESIA, Observatoire de Paris, CNRS, Université Pierre et Marie CurieUniversité Paris-DiderotMeudonFrance
  7. 7.Laboratory for Atmospheric and Space PhysicsUniversity of ColoradoBoulderUSA
  8. 8.Space Science CenterUniversity of New HampshireDurhamUSA

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