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The 19th ESLAB Symposium on 'The Sun and the Heliosphere in Three Dimensions' was held in Les Diablerets (Switzerland) on 4-6 June 1985. Organised almost exactly ten years after the Goddard Space Fl i ght Center Sympos i um dea 1 i ng with the Sun and the i nterp 1 anetary medium in three dimensions, the aim of this Symposium was not only to review the progress made in understanding the three-dimensional structure and dynamics of the heliosphere, but also to look ahead to the scientific return to be expected from the Ulysses mission. Scheduled for launch in May 1986, the scientific instrumentation on board Ulysses will shed light on the conditions and processes occurring away from the ecliptic plane, thereby adding literally a new dimension to our understanding of the only stellar plasmasphere to which we have direct access. The scientific programme of the Symposium was built around a series of invited review papers dealing with aspects of the corona and its influence on the interplanetary medium via transient ejecta, the solar wind, energetic solar particles and galactic cosmic rays, interplanetary dust and neutral gas. These invited talks were supplemented by a number of contributed and poster papers. With the exception of three contributed talks and Wibberenz' review of coronal and acceleration of energetic particles, all papers propagation presented at the Symposium are included in this volume.
Our knowledge of the heliosphere in three dimensions near solar minimum has advanced significantly in the last 10 years, largely as a result of the on-going ESAINASA Ulysses mission. Similar advances in our understanding of the global heliosphere near solar maximum are to be expected with the return of Ulysses to high solar latitudes in 2000/200 I. With this in mind, the 34th ESLAB Symposium, held at ESTEC in Noordwijk, The Netherlands, on 3-6 October, 2000, was devoted to 'The 3-D Heliosphere at Solar Maximum'. This was the third ESLAB Sympo sium focusing on the three-dimensional heliosphere (previous symposia being in 1985 and 1994), and the timing was particularly appropriate, marking as it did the 10th anniversary of the launch of the Ulysses spacecraft. Furthermore, Ulysses had just started its third high-latitude pass, the second over the Sun's south polar regions. The symposium addressed a wide range of topics related to the solar-maximum heliosphere, with presentations on many of the latest findings from Ulysses and other space-based missions. Ground-based studies and theoretical modeling were also well represented. Specific questions to which answers were sought included the following.
Coronal mass ejections (CMEs) are massive outflows of material from the Sun's corona, traveling into the surrounding heliosphere at speeds up to 1000-2000 kilometers per second. When directed toward the Earth, CMEs can result in damage to satellites, enhanced auroral displays, blackouts of power grids on Earth, and interference with surface radio communications. The first CME detected from space was observed by an NRL coronagraph onboard the Seventh Orbiting Solar Observatory (OSO-7) in December 1971. Much of our recent knowledge of CMEs has been obtained from an NRL visible-light coronagraph (LASCO, the Large Angle Spectroscopic Coronagraph(2)) on the Solar and Heliospheric Observatory (SOHO) spacecraft, launched in 1995. But SOHO observes from only one viewpoint, leaving three-dimensional structure ambiguous for individual CMEs. The next step beyond SOHO is the Solar Terrestrial Relations Observatory (STEREO) mission, consisting of two spacecraft observing the Sun from two different viewpoints, allowing a three-dimensional view of the initiation of CMEs and their propagation outwards. In addition, STEREO will carry a new type of heliospheric coronagraph that is off-pointed from the solar disk, and can observe from the side the Sun-Earth line all the way out to Earth. The STEREO mission is meant to increase our understanding of such topics as solar structures and their properties involved in CME initiation; threedimensional structure and kinematics of CMEs; three-dimensional structure of active regions, coronal loops, and streamers; propagation of CMEs into the corona and interplanetary medium; and the effects of CMEs through the heliosphere to the Earth.
The solar cycle has a profound influence on the solar wind (SW) interaction with the local interstellar medium (LISM) on more than one timescales. Also, there are substantial differences in individual solar cycle lengths and SW behavior within them. The presence of a slow SW belt, with a variable latitudinal extent changing within each solar cycle from rather small angles to 90°, separated from the fast wind that originates at coronal holes substantially affects plasma in the inner heliosheath (IHS)--the SW region between the termination shock (TS) and the heliopause (HP). The solar cycle may be the reason why the complicated flow structure is observed in the IHS by Voyager 1. Here, we show that a substantial decrease in the SW ram pressure observed by Ulysses between the TS crossings by Voyager 1 and 2 contributes significantly to the difference in the heliocentric distances at which these crossings occurred. The Ulysses spacecraft is the source of valuable information about the three-dimensional and time-dependent properties of the SW. Its unique fast latitudinal scans of the SW regions make it possible to create a solar cycle model based on the spacecraft in situ measurements. On the basis of our analysis of the Ulysses data over the entire life of the mission, we generated time-dependent boundary conditions at 10 AU from the Sun and applied our MHD-neutral model to perform a numerical simulation of the SW-LISM interaction. We analyzed the global variations in the interaction pattern, the excursions of the TS and the HP, and the details of the plasma and magnetic field distributions in the IHS. The resulting numbers are compared with Voyager data as functions of time in the spacecraft frame. We also discuss solar cycle effects which may be reasons for the recent decrease in the TS particles (ions accelerated to anomalous cosmic-ray energies) flux observed by Voyager 1.
9 MHDTurbulence in the Heliosphere: Evolution and Intermittency 253 Bruno Bavassano, Roberto Bruno and Vincenzo Carbone 1 Introduction 254 2 MHD Turbulence Evolution 255 2. 1 Ecliptic Turbulence 256 2. 2 Polar Turbulence 258 2. 3 Conclusions on Turbulence Evolution 263 3 Intermittency 264 3. 1 Probability Distribution Functions of Fluctuations and Self-similarity 269 3. 2 Radial Evolution of Intermittency 271 3. 3 Identifying Intermittent Events 273 3. 4 Conclusions on Intermittency 277 10 283 Waves and Turbulence in the Solar Corona Eckart Marsch 1 Introduction 284 2 Coronal Magnetic Field Structures 284 3 Magnetic Network Activity and Coronal Heating 287 4 Waves and Flows in Loops and Funnels 290 5 Magnetohydrodynamic Waves and Flux Tube Oscillations 293 5. 1 Observation and Theory 293 5. 2 Oscillations of Thin Flux Tubes 295 5. 3 Wave Amplitudes Versus Height from Numerical Mod- ~ 2~ 5. 4 A Standing Slow Magnetoacoustic Wave 299 6 Plasma Waves and Heating of Particles 301 7 Generation, Transfer and Dissipation of Coronal Turbulence 303 7. 1 Generation of Magnetohydrodynamic Waves 303 7. 2 Wave Energy Transfer and Turbulent Cascade 304 7. 3 Wave Dissipation in the Kinetic Domain 307 7. 4 Origin and Generation of Coronal High-Frequency Waves 308 7.
This volume helps the reader to understand the ways and means of how dynamical phenomena are generated at the Sun, how they travel through the Heliosphere, and how they affect Earth. It provides an integrated account of the three principal chains of events all the way from the Sun to Earth: the normal solar wind, coronal mass ejections, and solar energetic particles.
Knowledge about the outer heliosphere and the interstellar medium, which were long treated as two separate fields, has improved dramatically over the past 25 years as a consequence of recent developments: The discovery of interstellar pickup ions and neutral helium inside the heliosphere, the determination of the interstellar hydrogen distribution in the heliosphere obtained using backscattered solar Lyman-alpha radiation, the prediction and subsequent detection of the hydrogen wall just outside of the heliopause, the development of detailed global models for the interaction of solar wind plasma with the interstellar medium, and most recently, direct in-situ plasma and field measurements inside of the heliosheath. At the same time, our understanding of the nearby galactic environment, including the composition and dynamics of the warm gas clouds and hot gas in the local bubble, has benefited greatly from absorption-line spectroscopy using nearby stars as background sources and dynamic modeling. The present volume provides a synopsis of these developments organised into seven sections: Dominant physical processes in the termination shock and heliosheath, three-dimensional shape and structure of the dynamic heliosphere, relation of the plasmas and dust inside and outside of the heliosphere, origin and properties of the very local interstellar medium, energy and pressure equilibria in the local bubble, physical processes in the multiphase interstellar medium inside of the local bubble, and the roles that magnetic fields play in the outer heliosphere and the local bubble. The last theme is probably the most basic of all as magnetic fields play important roles in most of the phenomena discussed here. The volume concludes with four papers providing the "big picture" by looking at the time evolution of both the heliosphere and the local bubble, looking beyond the local bubble, and finally addressing the challenges in modeling the interface between the two media.