Transient Structures and Stream Interaction Regions in the Solar Wind: Results from EISCAT Interplanetary Scintillation, STEREO HI and Venus Express ASPERA-4 Measurements
- First Online:
We discuss the detection and evolution of a complex series of transient and quasi-static solar-wind structures in the days following the well-known comet 2P/Encke tail disconnection event in April 2007. The evolution of transient solar-wind structures ranging in size from <105 km to >106 km was characterised using one-minute time resolution observation of Interplanetary Scintillation (IPS) made using the European Incoherent SCATter (EISCAT) radar system. Simultaneously, the global structure and evolution of these features was characterised by the Heliospheric Imagers (HI) on the Solar TERrestrial RElations Observatory (STEREO) spacecraft, placing the IPS observations in context. Of particular interest was the observation of one transient in the slow wind, apparently being swept up and entrained by a Stream Interaction Region (SIR). The SIR itself was later detected in-situ at Venus by the Analyser of Space Plasma and Energetic Atoms (ASPERA-4) instrument on the Venus Express (VEX) spacecraft. The availability of such diverse data sources over a range of different time resolutions enables us to develop a global picture of these complex events that would not have been possible if these instruments were used in isolation. We suggest that the range of solar-wind transients discussed here may be the interplanetary counterparts of transient structures previously reported from coronagraph observations and are likely to correspond to transient magnetic structures reported in in-situ measurements in interplanetary space. The results reported here also provide the first indication of heliocentric distances at which transients become entrained.
KeywordsMagnetic fields, interplanetary Radio scintillation Solar wind, disturbances, stream interaction region
Unable to display preview. Download preview PDF.
- Asai, K., Kojima, M., Tokumaru, M., Yokobe, A., Jackson, B.V., Hick, P.L., Manoharan, P.K.: 1998, Heliospheric tomography using interplanetary scintillation observations. III – Correlation between speed and electron density fluctuations in the solar wind. J. Geophys. Res. 103, 1991. CrossRefADSGoogle Scholar
- Barabash, S., Sauvaud, J.J., Gunell, H., Anderson, H., Grigoriev, A., Brinkfeldt, K., Holmström, M., Lundin, R., Yamauchi, M., Asamura, K., et al.: 2007, The analyser of space plasmas and energetic atoms (ASPERA-4) for the Venus Express mission. Planet. Space Sci. 55, 1772–1792. CrossRefGoogle Scholar
- Breen, A.R., Mikic, Z., Linker, J.A., Lazarus, A.J., Thompson, B.J., Moran, P.J., Varley, C.A., Williams, P.J.S., Biesecker, D.A., Lecinski, A.: 1999, Interplanetary scintillation measurements of the solar wind during whole sun month: Linking coronal and in-situ observations. J. Geophys. Res. 104, 9847 – 9870. CrossRefADSGoogle Scholar
- Canals, A.: 2002, Interplanetary scintillation studies of the solar wind during the rising phase of the solar cycle. Ph.D. thesis, University of Wales, Aberystwyth. Google Scholar
- Davies, J.A., Harrison, R.A., Rouillard, A.P., Sheeley, N.R., Perry, C.H., Bewsher, D., Davis, C.J., Eyles, C.J., Crothers, S.R., Brown, D.S.: 2009, A synoptic view of solar transient evolution in the inner heliosphere using the Heliospheric Imagers on STEREO. Geophys. Res. Lett. 36, L02102. CrossRefGoogle Scholar
- Klinglesmith, M.T.: 1997, The polar solar wind from 2.5 to 40 solar radii; Results of intensity scintillation measurements. Ph.D. thesis, University of California, San Diego. Google Scholar
- Klinglesmith, M.T., Grall, R.R., Coles, W.A.: 1996, 933 MHz IPS velocity measurements at EISCAT. In: AIP Solar Wind 8 Conference Proceedings 382, 180 – 183. Google Scholar
- Rishbeth, H., Williams, P.J.S.: 1985, The EISCAT ionospheric radar: The system and its early results. Mon. Not. Roy. Astron. Soc. 26, 478 – 512. Google Scholar
- Vourlidas, A., Davis, C.J., Eyles, C.J., Crothers, S.R., Harrison, R.A., Howard, R.A., Moses, D.J., Socker, D.G.: 2007, First direct observation of the interaction between a comet and a coronal mass ejection leading to a complete plasma tail disconnection. Astrophys. J. Lett. 668, L79 – L82. CrossRefADSGoogle Scholar
- Wannberg, G., Vanhein, L.-G., Westman, A., Breen, A., Williams, P.J.S.: 2002, The new 1420 MHz dual-polarisation interplanetary scintillation (IPS) facility at EISCAT. In: Proceedings of the Union of Radio Scientists (URSI). Google Scholar