PROCEEDINGS OF THE SYMPOSIUM ON THE STUDY OF THE SUN AND INTERPLANETARY MEDIUM IN THREE DIMENSIONS (NASA-Tn-X-71397) FFCCE?EINGS OF THE 376-24119 SYRFOSIOF CK THE STUCY CF THE SUN ANC THRU INTPRPLBNETAFY EELIO?I IN THREE DIREMSIONS K76-24135 (NlSA) 345 F HC SJC.Cr3 SSCL 03E Unclas G3/92 2746b MARW 1976 -. , -GODDARD SPACE FLIGHT CENTER GREENBELT, MARYLAND PROCEEDINGS of the SYMPOSIUM ON THE STUDY OF THE SL.3 AND INTERPLANETARY FIEDIUY IN THREE DIbENSIONS held at GODDAP! SPACE FLIGHT CENTER under the sponsorship of HASA ESA AMERICAN ASTRONOMICAL SOCIETY AFIERICAN GEOPHYSICAL UNION The proceedinqs were edited by L. A. FISK PI. I. AXFORD Laboratory for Nigh Energy Astrophysics Max-Planck Institute for Aeronorq Goddard Space Flight Center Katlenhurg-Lindau, Germany Greenbelt, Maryland PREFACE On May 15-16, 1975, a symposium was held at the Goddard Space Flight Center on the Study of the Sun and Interplanetary Medium in Three Dimensions. The symposium brought together more than 200 scientists from the U. S. and Europe to discuss the importance of exploring the inter- planetary medium, and viewing the Sun over a wide range of heliographic latitudes. Among the topics discussed were the missions that NASA and ESA are currently considering for possible flight out of the ecliptic plane, and the likely scientific returns of these missions in the areas of solar, interplanetary and cosmic-ray physics. The symposium was sponsored by NASA and ESA, and was a topical meeting of the American Astronomical Society and the American Geophysical Union. In this proceedings an attempt has been made to pro- vide a complete summary of the content of the symposium. J. A. Simpson has kindly summarized the various options for out-of-the-ecliptic missions. The speakers who addressed the likely scientific returns from these mlsslons have In most cases provided detailed summaries of their remarks. In cases where a full summary was not available, an abstract has been provided. In addition, K. C. Hsieh has kindly provided an article on direct measurements of neutral gas out of the ecliptic. Time was not available at the symposium for presentation of these interesting Ideas. The organizing committee of the symposium is very grateful to the authors, all of whom have busy schedules, for providing detailed summaries of their talks. t?e would also like to express our sincere appreciation to Mrs. Sandy Schraeder and Mrs. Martha Harding for their invaluable help in organizing the symposium. A list of all the speakers at the symposium, and their topics is given in Appendix A to this proceedings. A list of all the attendees at the symposium is provided in Appendix B. L. A. Fisk W. I, Axford TABLE OF CONTENTS Page Some Introductory Remarks . 1 CHAPTER I - THE MISSIONS Experiments Out of the Solar System Ecliptic Plane: An Introduction to the Execliptic Mission; J. A. Simpson . 10-31 An Alternative Option to the Dual-Probe Out-of- Ecliptic Mission Via Jupiter Swingby; G. Colombo, D. A. Lautman and G. Pettengill . 379z CHAPTER I1 - SOLAR PHYSICS Out-of-Ecliptic Studies of Coronal Holes and Their Relation to the Solar Wind; R. W. Noyes . 48- Solar Magnetic Fields and the Corona; G. Newkirk, Jr. 5937 3-D Solar Radioastronomy and the Structure of the Corona and the Solar Wind; J. L. Steinberg and C . Caroubalos . 65-35 CHAPTER I11 - SOLAR WIND IPS Observations of the Solar Wind Speed Out of the Ecliptic; W. A. Coles and B. J. Rickett . 84~6 Latitudinal Properties of the Solar Wind from Studies of Ionic Comet Tails; J. C. Brandt . 95 Implications of Saito's Coronal Density Model on the Po!ar Solar Wind Flow and Heavy Ion Abundances; W. C. Feldman . 108 Thermal Properties of the Solar Wind at High Lati- tudes; M. D. Montgomery . 138&)73/r CHAPTER IV - INTERPLANETARY MAGNETIC FIELDS The Large-Scale Magnetic Field in the Solar Wind; L. F. Burlaga and N. F. Ness . 142 Three-Dimensional Aspects of Interplanetary Shock Waves; G. L. Siscoe . 166 (Continued) (Continued) TABLE OF CONTENTS Page CHAPTER V - SOLAR AND GALACTIC COSMIC RAYS Cosmic-Ray Transport Theory and Out-of-the-Ecliptic Exploration; J. R. Jokipii . 188 Cosmic-Ray Modulation in Three Dimensions; J. J. Quenby . 210 Cosmic-Ray Access at Polar Heliographic Latitudes; H. J. Volk . 217 Solar Cosmic-Ray Measurements at High Heliocentric Latitudes; K. A. Anderson . 231 Coronal Propagation: Variations with Solar Longi- tude and Latitude; G. Wibberenz . 261 CHAPTER VI - INTERPLANETARY DUST/INTERSTELLAR NEUTRAL GAS Investigation of Interplanetary Dust from Out-of- Ecliptic Space Probes; H. Fechtig, R. H. Giese, M. S. Hanner and H. A. Zook . 298 A Means of --In Situ Measurements of Neutral H and He on an Out-of-the-Ecliptic Mission; K. C. Hsieh . 321 APPENDIX A - THE PROGRAM . 329 APPENDIX B - ATTENDEES . 333 Some Introductory Remarks Over the years studies of the Sun and interplanetary medium have occupied the attention of a sizeable fraction of the space community, and have constituted a considerable portion of NASA and ESA's efforts in space science. And rightly so. We attempt in this subject to understand our local environment in space. With our continuous and in some cases in situ obser- vations, we also provide in this subject detailed testimony as to what physical processes are possible on a star and in an astrophysical plasma. Our studies of the solar environ- ment thus influence our thinking as to what is possible in other astrophysical settings. In soms cases the influence is quite direct. For example, the solar wind should exhibit many of the properties of stellar winds. Shock waves in interplanetary space may resemble those in interstellar space. The behavior traits of cosmic rays propagating in the interplanetary magnetic field should be similar to those of cosmic rays in the galaxy. And so on. All of the spacecraft that NASA and ESA have flown to study the Sun and interplanetary medium, however, have been limited in one major respect. None of these spacecraft h~ve penetrated off the equatorial plane of the Sun by more than about -+ lo0 in heliographic latitude. We have thus sampled particle emission from the Sun, or interstellar matter impinging on the solar cavity (e.g. galactic cosmic rays), only over a narrow range of latitudes. The look-angle for studying photon emission from the Sun is similarly limited. This latitude limitation would not be serious, of course, if we had any expectation that conditions in the solar environment were invariant with latitude. However, even the most cursory of examinations of a white light photograph of a solar eclipse reveals a strong latitude dependence for conditions in the corona. Sun-spot and flare activity is known to be concentrated in the mid- latitude regions on the Sun. Interplanetary scintillation studies suggest that the flow of the solar wind is faster and more turbulent over the solar poles, than it is in the equatorial plane (See Coles and Rickett, in this proceedings). The expected Archemedes spiral pattern of the interplanetary magnetic field may cause the ratio of thermal to magnetic pressure of the solar wind to vary strongly with latitude, thus resulting in a plasma over the poles which has substan- tially different properties from the local solar wind. This same field pattern may let low energy galactic cosmic rays (-' 100 ~eVjpenetrate unopposed into the region of the solar poles, whereas such particles are excluded from the inner solar system near earth. And the lisk goes on. We are thus forced to conclude that, to date, space- craft exploration of the interplanetary medium, and measure- ments of the Sun which are look-angle dependent, have studied a non-representative sample of our total solar environment. We have studied in only two dimensions, what is a three- dimensional structure. We have not sampled the full variety of astrophysical conditions that are available to direct measurements in our local environment. Thus, we have not adequately broadened the base of knowledge that we can use for deciding what is possible in other astrophysical settings. An Out-of-the-Ecliptic (O/E) Mission, in which the interplanetary medium is explored, and the Sun is viewed over a wide range of heliographic latitudes, will provide the measurements that can help replace our current parochial view, with a more accurate assessment of our local environ- ment in space. The Current Status of the O/E Mission At the time of the publishing of these proceedings, NASA and ESA are engaged in a Phase A study of an O/E mission, which could be launched in the early 1980's. Two possible missions, a primary and a backup, are currently under con- sideration. In the primary mission two spacecraft are to be launched simultaneously by the shuttle, with the Interim Upper Stage (IUS) - 4 stage booster. The spacecraft, which would be similar in design to Pioneers 10 and 11, would then fly to Jupiter. There, one of the spacecraft would be targeted so that after encounter it passes up out of the ecliptic plane and over the north pole of the Sun. The other spacecraft would be targeted so that it passes over the south solar pole. Following their polar passes, each of the space- craft would return to the ecliptic plane, and then would fly up over the opposite solar pole. In the backup mission, one spacecraft is launched from the shuttle /IUS - 2 stage. This spacecraft is targeted at Jupiter to pass over one of the solar poles, return to the ecliptic plane, and then fly up over the opposite solar pole. In both missions the space- craft can obtain high heliographic latitudes ( 80~).