Solar Physics

, 259:323

In Situ Observations of Solar Wind Stream Interface Evolution

  • K. D. C. Simunac
  • L. M. Kistler
  • A. B. Galvin
  • M. A. Lee
  • M. A. Popecki
  • C. Farrugia
  • E. Moebius
  • L. M. Blush
  • P. Bochsler
  • P. Wurz
  • B. Klecker
  • R. F. Wimmer-Schweingruber
  • B. Thompson
  • J. G. Luhmann
  • C. T. Russell
  • R. A. Howard
Open Access
STEREO Science Results at Solar Minimum

DOI: 10.1007/s11207-009-9393-y

Cite this article as:
Simunac, K.D.C., Kistler, L.M., Galvin, A.B. et al. Sol Phys (2009) 259: 323. doi:10.1007/s11207-009-9393-y

Abstract

The heliocentric orbits of the two STEREO satellites are similar in radius and ecliptic latitude, with separation in longitude increasing by about 45° per year. This arrangement provides a unique opportunity to study the evolution of stream interfaces near 1 AU over time scales of hours to a few days, much less than the period of a Carrington rotation. Assuming nonevolving solar wind sources that corotate with the Sun, we calculated the expected time and longitude of arrival of stream interfaces at the Ahead observatory based on the in situ solar wind speeds measured at the Behind observatory. We find agreement to within 5° between the expected and actual arrival longitude until the spacecraft are separated by more than 20° in heliocentric inertial longitude. This corresponds to about one day between the measurement times. Much larger deviations, up to 25° in longitude, are observed after 20° separation. Some of the deviations can be explained by a latitude difference between the spacecraft, but other deviations most likely result from evolution of the source region. Both remote and in situ measurements show that changes at the source boundary can occur on a time scale much shorter than one solar rotation. In 32 of 41 cases, the interface was observed earlier than expected at STEREO/Ahead.

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Copyright information

© The Author(s) 2009

Authors and Affiliations

  • K. D. C. Simunac
    • 1
  • L. M. Kistler
    • 1
  • A. B. Galvin
    • 1
  • M. A. Lee
    • 1
  • M. A. Popecki
    • 1
  • C. Farrugia
    • 1
  • E. Moebius
    • 1
  • L. M. Blush
    • 2
  • P. Bochsler
    • 1
    • 2
  • P. Wurz
    • 2
  • B. Klecker
    • 3
  • R. F. Wimmer-Schweingruber
    • 4
  • B. Thompson
    • 5
  • J. G. Luhmann
    • 6
  • C. T. Russell
    • 7
  • R. A. Howard
    • 8
  1. 1.University of New Hampshire Space Science CenterDurhamUSA
  2. 2.Physikalisches InstitutUniversity of BernBernSwitzerland
  3. 3.Max-Planck Institut für Extraterrestrische PhysikGarchingGermany
  4. 4.Institute for Experimental and Applied PhysicsUniversity of KielKielGermany
  5. 5.NASA Goddard Space Flight CenterGreenbeltUSA
  6. 6.Space Sciences LaboratoryUniversity of CaliforniaBerkeleyUSA
  7. 7.Institute of Geophysics and Planetary PhysicsUniversity of CaliforniaLos AngelesUSA
  8. 8.E.O. Hulburt Center for Space ResearchNaval Research LaboratoryWashingtonUSA

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