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We report the results of a multi-instrument, multi-technique, coordinated study of the solar eruptive event of 13 May 2005. We discuss the resultant Earth-directed (halo) coronal mass ejection (CME), and the effects on the terrestrial space environment and upper Earth atmosphere. The interplanetary CME (ICME) impacted the Earth's magnetosphere and caused the most-intense geomagnetic storm of 2005 with a Disturbed Storm Time (Dst) index reaching −263 nT at its peak. The terrestrial environment responded to the storm on a global scale. We have combined observations and measurements from coronal and interplanetary remote-sensing instruments, interplanetary and near-Earth in-situ measurements, remote-sensing observations and in-situ measurements of the terrestrial magnetosphere and ionosphere, along with coronal and heliospheric modelling. These analyses are used to trace the origin, development, propagation, terrestrial impact, and subsequent consequences of this event to obtain the most comprehensive view of a geo-effective solar eruption to date. This particular event is also part of a NASA-sponsored Living With a Star (LWS) study and an on-going US NSF-sponsored Solar, Heliospheric, and INterplanetary Environment (SHINE) community investigation.

[1] We present the results of a comprehensive study of the fast solar wind near solar minimum conditions using interplanetary scintillation (IPS) data taken with the EISCAT system in northern Scandinavia, and a recent extremely long baseline observation using both EISCAT and MERLIN systems. The results from IPS observations suggest that the fast wind inside 100 solar radii (R ) can be represented by a two-mode model in some cases but this distinction is much less clear by in situ distances beyond 1 astronomical unit (215 R ). Two distinct fast streams are seen in the extremely long baseline IPS observation; comparison of the IPS line of sight with a synoptic map of white light indicates the faster mode overlies the polar crown and the slower fast mode overlies an equatorial extension of the polar coronal hole.

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Abstract. The antennas of EISCAT have been used for interplanetary scintillation (IPS) studies of the solar wind for many years. The main science found from these studies is obtained through the cross-correlation of signals from antennas having the longest baseline, providing more accurate information on the different solar wind streams which may be present in the line of sight. The development of dualfrequency IPS observations between the 1.4 GHz receivers at the remote sites and Tromsø, has allowed the use of the EISCAT Svalbard Radar for IPS, increasing the available baselines to the extent that three solar wind streams can sometimes be identified in the cross-correlation functions. A weak-scattering model incorporating three possible solar wind streams and dual observing frequencies is discussed and some results presented. A recent study found that the current sampling bandwidth limits the sensitivity of IPS observations at EISCAT. Methods of increasing the sensitivity, and the results of trials, are discussed.

[1] We present results of observations of interplanetary scintillation (IPS) made using the telescopes of the MERLIN and EISCAT networks in which the beam separation approached 2000 km, much larger than in any previous IPS experiments. Significant correlation between the scintillation patterns was observed at time lags of up to 8 s and fast and slow streams of solar wind were very clearly resolved. One observation showed clear evidence of two discrete modes of fast solar wind, which we interpret as originating in the crown of the northern polar coronal hole and in an equatorward extension of the polar hole. We suggest that experiments of this type will provide a new and important source of information on the temporal and spatial variation of small-scale turbulence in the solar wind. The improved velocity resolution available from extremely long baseline measurements also provides new information on the development of the large-scale velocity structure of the solar wind in interplanetary space.

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Jones, R. A.; Breen, A. R.; Fallows, R. A.; Canals, A.; Bisi, M. M.; Lawrence, G. (2007). Interaction between coronal mass ejections and the solar wind, Journal of Geophysical Research, 112, Issue A8 RAE2008Observations suggest that the interplanetary extensions of coronal mass ejections (iCMEs) may be accelerated or decelerated in their passage through the solar wind. Interplanetary scintillation measurements (IPS) can detect the passage of iCMEs beyond the field of view of the Large-Angle and Spectrometric Coronagraph coronagraphs and can provide information on their velocities. The European Incoherent Scatter Radar and the Multi Element Radio Linked Interferometer Network systems, with a field of view covering 10-120 solar radii, can provide information on iCMEs in the inner regions of the solar wind. IPS observations can also provide solar wind velocity measurements ahead of the iCME, and using this information, we consider the velocity profile of a number of clearly defined iCMEs and the relationship between iCME velocities and that of the background solar wind. The results provide additional confirmation that iCMEs converge toward the velocity of the solar wind ahead of the event and that most of the resulting acceleration or deceleration occurs in the innermost regions of the solar wind.Peer reviewe