Interplanetary Scintillation Observations of Stream Interaction Regions in the Solar Wind

We present a summary of results from ten years of interplanetary scintillation (IPS) observations of stream interaction regions (SIRs) in the solar wind. Previous studies had shown that SIRs were characterized by intermediate-velocity solar wind and – in the case of compressive interactions – higher levels of scintillation. In this study we considered all cases of intermediate velocities in IPS observations from the European Incoherent SCATter (EISCAT) radar facility made at low- and mid-heliographic latitudes between 1994 and 2003. After dismissing intermediate-velocity observations which were associated with solar-wind transients (such as coronal mass ejections) we found that the remaining cases of intermediate velocities lay above coronal structures where stream interaction would be expected. An improved ballistic mapping method (compared to that used in earlier EISCAT studies of interaction regions) was used to identify the regions of raypath in IPS observations which might be expected to include interaction regions and to project these regions out to the distances of in-situ observations. The early stages of developing compression regions, consistent with their development on the leading edges of compressive stream interaction regions, were clearly detected as close to the Sun as 30 R⊙, and further ballistic projection out to the distances of in-situ observations clearly associated these developing structures with density and velocity features characteristic of developed interaction regions in in-situ data in the cases when such data were available. The same approach was applied to study non-compressive interaction regions (shear layers) between solar-wind streams of different velocities where the stream interface lay at near-constant latitude and the results compared with those from compressive interaction regions. The results confirm that intermediate velocities seen in IPS observations above stream boundaries may arise from either detection of intermediate-velocity flow in compression regions, or from non-compressive shear layers. The variation in velocity about the mean determined from IPS measurements (representing the spread in velocity across that part of the raypath associated with the interaction region in the analysis) was comparable in compressive and non-compressive regions – a potentially interesting result which may contain important information on the geometry of developing SIRs. It is clear from these results that compressive and non-compressive interaction regions belong to the same class of stream – stream interaction, with the dominant mode determined by the latitudinal gradient of the stream interface. Finally, we discuss the results from this survey in the light of new data from the Heliospheric Imagers (HI) on the Solar TErrestrial RElations Observatory (STEREO) spacecraft and other instruments, and suggest possible directions for further work.

[1]  David J. McComas,et al.  The Ulysses solar wind plasma experiment , 1992 .

[2]  H. R. Middleton,et al.  The Solar Eruption of 2005 May 13 and Its Effects: Long-Baseline Interplanetary Scintillation Observations of the Earth-Directed Coronal Mass Ejection , 2008 .

[3]  B. Rickett,et al.  Evolution of the solar wind structure over a solar cycle: Interplanetary scintillation velocity measurements compared with coronal observations , 1991 .

[4]  Christopher J. Eyles,et al.  The STEREO heliospheric imager: how to detect CMEs in the heliosphere , 2004 .

[5]  R. Wimmer–Schweingruber,et al.  Solar wind stream interfaces in corotating interaction regions: New SWICS/Ulysses results , 1997 .

[6]  J. Gosling,et al.  Formation and Evolution of Corotating Interaction Regions and their Three Dimensional Structure , 1999 .

[7]  Bernard V. Jackson,et al.  Three-Dimensional Tomography of Interplanetary Disturbances , 2004 .

[8]  P. J. Williams,et al.  EISCAT measurements of the solar wind , 1996 .

[9]  A. Mavretic,et al.  SWE, a comprehensive plasma instrument for the WIND spacecraft , 1995 .

[10]  P. J. Williams,et al.  Interplanetary scintillation observations of interaction regions in the solar wind , 1998 .

[11]  Andrew Robert Breen,et al.  Slow and fast solar wind acceleration near solar maximum , 2002 .

[12]  M. Lockwood,et al.  First imaging of corotating interaction regions using the STEREO spacecraft , 2008 .

[13]  K. Ogilvie,et al.  The wind spacecraft and its early scientific results , 1997 .

[14]  J. Markkanen,et al.  EISCAT measurements of interplanetary scintillation , 1996 .

[15]  M. Kojima,et al.  Solar cycle evolution of solar wind speed structure between 1973 and 1985 observed with the interplanetary scintillation method , 1987 .

[16]  L. Burlaga,et al.  Interplanetary stream interfaces , 1974 .

[17]  M. Neugebauer,et al.  The relation of Mariner-2 plasma data to solar phenomena , 1966 .

[18]  W. Wilkinson,et al.  EISCAT measurements of the solar wind: Observations of interaction regions , 1997 .

[19]  Y. Hu.  Evolution of corotating stream structures in the heliospheric equatorial plane , 1993 .

[20]  M. Kaiser,et al.  Stereo Mission Overview , 2004, 2007 IEEE Aerospace Conference.

[21]  V. Sarabhai.  Some consequences of nonuniformity of solar wind velocity , 1963 .

[22]  P. J. Williams,et al.  Measurements of the direction of the solar wind using interplanetary scintillation , 1998 .

[23]  W. Feldman,et al.  Solar wind stream interfaces , 1978 .

[24]  G. Bourgois,et al.  Measurements of the solar wind velocity with EISCAT , 1985 .

[25]  Bernard V. Jackson,et al.  The Solar Mass Ejection Imager (Smei) , 2003 .

[26]  P. J. Williams,et al.  Rapid acceleration of the polar solar wind , 1996, Nature.

[27]  W. A. Coles,et al.  Analysis of three-station interplanetary scintillation , 1972 .

[28]  J. Linker,et al.  Interplanetary scintillation measurements of the solar wind during Whole Sun Month: Comparisons with coronal and in situ observations , 1999 .

[29]  M. Bisi,et al.  Interplanetary scintillation studies of the large-scale structure of the solar wind , 2006 .

[30]  R. Fallows,et al.  Large-scale structure of the solar wind from interplanetary scintillation measurements during the rising phase of cycle 23 , 2002 .

[31]  P. J. Williams,et al.  Eiscat measurements of interaction regions in the solar wind , 1997 .

[32]  J. Davies,et al.  First Imaging of Coronal Mass Ejections in the Heliosphere Viewed from Outside the Sun – Earth Line , 2008 .

[33]  A. Buffington,et al.  Low-Resolution STELab IPS 3D Reconstructions of the Whole Heliosphere Interval and Comparison with in-Ecliptic Solar Wind Measurements from STEREO and Wind Instrumentation , 2009 .

[34]  Mario M. Bisi,et al.  Large-scale structure of the fast solar wind , 2007 .

[35]  R. A. Jones,et al.  Combined EISCAT/ESR/MERLIN interplanetary scintillation observations of the solar wind , 2005 .

[36]  W. A. Coles,et al.  A bimodal model of the solar wind speed , 1996 .

[37]  R. Fallows,et al.  Developments in the use of EISCAT for interplanetary scintillation , 2008 .

[38]  M. Neugebauer,et al.  Interplanetary solar-wind measurements by Mariner II , 1965 .

[39]  J. Gosling.  COROTATING AND TRANSIENT SOLAR WIND FLOWS IN THREE DIMENSIONS , 1996 .

[40]  J. Linker,et al.  The solar wind at solar maximum: comparisons of EISCAT IPS and in situ observations , 2002 .

[41]  J. Asbridge.  Compressions and Rarefactions in the Solar Wind' Vela 3 J. T. GosLInG, A. J. HUN)HAUSEN, AND V. Pzzo , 1972 .

[42]  A. Buffington,et al.  Three-dimensional reconstructions of the early November 2004 Coordinated Data Analysis Workshop geomagnetic storms: Analyses of STELab IPS speed and SMEI density data , 2008 .

[43]  V. Pizzo.  The evolution of corotating stream fronts near the ecliptic plane in the inner solar system: 2. Three‐dimensional tilted‐dipole fronts , 1991 .

[44]  J. T. Hoeksema,et al.  Ulysses at 50° south: constant immersion in the high‐speed solar wind , 1994 .

[45]  Bernard V. Jackson,et al.  The Solar Mass-Ejection Imager (SMEI) Mission , 2003 .

[46]  P. K. Manoharan,et al.  Solar Wind and CME Studies of the Inner Heliosphere Using IPS Data from Stelab, ORT, and EISCAT , 2010 .

[47]  Christine Jordan,et al.  Extremely long baseline interplanetary scintillation measurements of solar wind velocity , 2006 .

[48]  S. Ananthakrishnan,et al.  Very long baseline IPS observations of the solar wind speed in the fast polar streams , 1995 .

[49]  Edward J. Smith,et al.  The Ulysses mission , 1986 .

[50]  J. Linker,et al.  Measurements of the solar wind over a wide range of heliocentric distances — a comparison of results from the first three Whole Sun Months , 2000 .

[51]  M. M. Bisi,et al.  Interaction between coronal mass ejections and the solar wind , 2007 .

[52]  E. Roelof,et al.  A coronal hole and its identification as the source of a high velocity solar wind stream , 1973 .

[53]  E. Christian,et al.  The STEREO Mission: An Introduction , 2008 .

[54]  J. Davies,et al.  The Heliospheric Imagers Onboard the STEREO Mission , 2009 .

[55]  J. T. Hoeksema,et al.  Synoptic Sun during the first Whole Sun Month Campaign: August 10 to September 8, 1996 , 1999 .

[56]  R. Schwenn.  Large-scale structure of the interplanetary medium , 1990 .

[57]  W. Neupert,et al.  Solar coronal holes as sources of recurrent geomagnetic disturbances , 1974 .