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| Weaker solar wind from the polar coronal holes and the whole Sun |
| Observations of solar wind from both large polar coronal holes (PCHs) during Ulysses' third orbit showed that the fast solar wind was slightly slower, significantly less dense, cooler, and had less mass and momentum flux than during the previous solar minimum (first) orbit. In addition, while much more variable, measurements in the slower, in-ecliptic wind match quantitatively with Ulysses and show essentially identical trends. Thus, these combined observations indicate significant, long-term variations in solar wind output from the entire Sun. The significant, long-term trend to lower dynamic pressures means that the heliosphere has been shrinking and the heliopause must be moving inward toward the Voyager spacecraft. In addition, our observations suggest a significant and global reduction in the mass and energy fed in below the sonic point in the corona. The lower supply of mass and energy may result naturally from a reduction of open magnetic flux during this period. |
| Publication date: 18 Sep 2008 |
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| The Heliosphere through the Solar Activity Cycle |
Editors: A. Balogh, L.J. Lanzerotti, and S.T. Suess
A principal objective of space research has been to increase understanding of the way the Sun changes through its 11-year sunspot cycle, and how these changes affect the space around the Sun - the heliosphere. "The Heliosphere through the Solar Activity Cycle" is the first book to describe and analyze ground and space-based data on the three-dimensional heliosphere taken as the Ulysses spacecraft made orbital passes of the Sun's north and south poles in 1994-1995 and again in 2000-2001. The chapters explain the many different aspects of changes in the heliosphere in response to solar activity, and describe the rise in solar activity from the last minimum in 1998 to its maximum in 2000, and its subsequent decline.
"The Heliosphere through the Solar Activity Cycle" was written by leading scientists directly involved with the Ulysses mission and edited by André Balogh, Louis J. Lanzerotti, and Steven T. Suess. It provides the definitive discussion of the subject to date and looks forward to discoveries to be made by Ulysses and potential follow-on missions in the future.
Contents
| 1. | The heliosphere: Its origin and exploration
A. Balogh & L.J. Lanzerotti |
| 2. | Solar Cycle 23
D.H. Hathaway & S.T. Suess |
| 3. | The solar wind throughout the solar cycle
R. von Steiger |
| 4. | The global heliospheric magnetic field
E.J. Smith |
| 5. | Heliospheric energetic particle variations
D. Lario & M. Pick |
| 6. | Galactic and anomalous cosmic rays through the solar cycle: New insight from Ulysses
B. Heber & M.S. Potgieter |
| 7. | Overview: The heliosphere then and now
S.T. Suess |
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| Publication date: 01 Nov 2007 |
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| Solar Modal Structure of the Engineering Environment |
| This paper describes some unanticipated effects of the normal modes of the Sun on engineering and scientific systems. We begin with historical, scientific, and statistical background, then present evidence for the effects of solar modes on various systems. Engineering evidence for these modes was first noticed in an investigation of communications satellite failures and second in a study of excessive dropped calls in cellular phone systems. The paper also includes several sections on multitaper estimates of spectra, canonical coherences, robust, and cyclostationary variants of multitapering, and related statistical techniques used to separate the various components of this complex system. In our attempt to understand this unexpected source of problems, we have found that solar modes are detectable in the interplanetary magnetic fields and energetic particles at the Ulysses spacecraft, five astronomical units from the Earth. These modes couple into the magnetosphere, the ionosphere, the geomagnetic field, and atmospheric pressure. Estimates of the power spectrum of data from solar radio telescopes and induced voltages on ocean cables show what appear to be solar modes at both lower and higher frequencies than the optically measured solar p-modes. Most surprisingly, these modes are easily detected in seismic data, where they literally shake the Earth. |
| Publication date: 15 May 2007 |
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| ESA SP-1296: ESA's Report to the 36th COSPAR Meeting |
Scientific editor: R. Marsden
Editor: A. Wilson
The report for the 36th COSPAR Meeting covers, as in previous issues, the missions of the Scientific Programme of ESA in the areas of astronomy, Solar System science and fundamental physics. This year's COSPAR meeting will take place only weeks before the end of the SMART-1 mission to the Moon, a technology project that provided the first European look at our natural satellite from lunar orbit.In October of this year, a new mission will be launched: COROT. ESA, together with a number of countries, is contributing to this unique, French-led project that will provide an insight into the interior of the stars, by means of the asteroseismology technique successfully applied by SOHO. COROT will also perform a systematic search for new extrasolar planets using photometric transits.
The record number of ESA Science Programme missions in operation established at the time of the last report was maintained in 2006 (Huygens having been replaced in the list by Venus Express). Eleven different missions, involving 14 operating spacecraft, are providing excellent science to the worldwide scientific community. The Research and Scientific Support Department (RSSD) is responsible for the science operations of these missions and makes every effort to ensure the best possible science return. The Department also supports the realisation of approved projects in all phases of their development. |
| Publication date: 15 Jun 2006 |
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| Ulysses mission report from the 36th COSPAR meeting |
| This extract of ESA's Report to the 36th COSPAR Meeting held in Beijing, China in July 2006, covers the Ulysses mission. |
| Publication date: 01 Jun 2006 |
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| From the Sun to the outer heliosphere: Modeling and analyses of the interplanetary propagation of the October/November (Halloween) 2003 solar events |
| We use the space weather validated 3-D HAFv2 model to help us study the interplanetary propagation of the October/November 2003 solar eruptions from the Sun to >90 AU and over a wide range of heliolongitudes and heliolatitudes. The HAFv2 model predictions at ACE (1 AU), Ulysses (5.23 AU), Cassini (8.67 AU), Voyager 2 (73 AU), and Voyager 1 (93 AU) are compared with available data. These comparisons indicate the importance of asymmetric interplanetary propagation both in heliolongitude and heliolatitude. We recommend that these effects explicitly be taken into account. The HAFv2 results appear to be useful for interpreting the Voyager 2 and Voyager 1 energetic particle data in the outer heliosphere. They are consistent with the effects of the Halloween solar events observed in the energetic particle data at both spacecraft. The HAFv2 results also may be helpful for predicting the plasma wave 2-3 kHz radio emission previously associated with large shocks and their interaction with the heliopause. Our study indicates that the Halloween events may give rise to 2-3 kHz radio emission in early 2005, assuming that the shocks which propagated beyond Voyager 1 will be strong enough. |
| Publication date: 30 Sep 2005 |
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| ESA SP-1276: ESA's Report to the 35th COSPAR Meeting |
Scientific editor: A. Gimenez
Editor: A. Wilson
The report for the 35th COSPAR Meeting covers, as in previous issues, the missions
of the Scientific Programme of ESA in the areas of astronomy, Solar System
exploration and fundamental physics. This year's COSPAR Meeting occurs only
weeks after the Saturn-orbit insertion of the Cassini spacecraft - carrying Europe's
Huygens probe to explore the atmosphere of Titan - and at the same time as the
launch of the second satellite of the Double Star project. |
| Publication date: 15 Jun 2004 |
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| News from the Sun's Poles Courtesy of Ulysses |
| Launched from Cape Canaveral more than 13 years ago, Ulysses is well on its way to completing two full circuits of the Sun in a unique orbit that takes it over the north and south poles of our star. In doing so, the European-built space probe and its payload of scientific instruments have added a fundamentally new perspective to our knowledge of the bubble in space in which the Sun and the Solar System exist, called 'the heliosphere'. |
| Publication date: 01 Aug 2003 |
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| Ulysses and Beyond |
| Eds. Marsden, R., Scherer, K. and Heber, B. |
| Publication date: 01 Jun 2003 |
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| The three-dimensional solar wind around solar maximum |
| Ulysses is now completing its second solar polar orbit, dropping back down in latitude as the Sun passes through its post-maximum phase of the solar cycle. A mid-sized circumpolar coronal hole that formed around solar maximum in the northern hemisphere has persisted and produced a highly inclined CIR, which was observed from ~70°N down to ~30°N. We find that the speed maxima in the high-speed streams follow the same slow drop in speed with decreasing latitude observed in the large polar coronal holes around solar minimum. These results suggest a solar wind acceleration effect that is related to heliolatitude or solar rotation. We also find that the solar wind dynamic pressure is significantly lower in the post-maximum phase of this solar cycle than during the previous one, indicating that while the heliosphere is larger than near solar minimum, it should be smaller than during or after the previous maximum. |
| Publication date: 22 May 2003 |
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| ESA SP-1259: ESA's Report to the 34th COSPAR Meeting |
Scientific editor: B. Foing
Editor: A. Wilson
The report to the 34th COSPAR Meeting covers the missions of the Scientific Programme of ESA in the areas of astronomy, Solar System exploration and fundamental physics. |
| Publication date: 01 Oct 2002 |
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| The Heliosphere Near Solar Minimum: The Ulysses Perspective |
| The Ulysses mission has explored and charted the heliosphere around the minimum in the 11-year cycle of solar activity from a high-latitude perspective. Here, for the first time, is a comprehensive review of the results of that mission. The book furthers our knowledge of the heliosphere near solar minimum and provides the basis for understanding the more complex state of the heliosphere around solar maximum. Amongst other topics, the book covers: the solar wind, the large- and small-scale structure of the heliosphere in 3 dimensions, cosmic rays and energetic particles, interstellar aspects, including cosmic dust.
In "The Heliosphere Near Solar Minimum: The Ulysses Perspective", Eds. Balogh, A., Marsden, R.G. & Smith, E.J., Springer-Praxis, Chichester (2001) ISBN 1-85233-204-2, XXV + 411 pp. |
| Publication date: 01 Jun 2001 |
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| The 3-D Heliosphere at Solar Maximum |
| Proceedings of the 34th ESLAB Symposium held 3-6 October 2000 at ESTEC, Noordwijk, The Netherlands. Ed. Marsden, R.G.
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| Publication date: 01 Mar 2001 |
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| Ulysses at Solar Maximum and Beyond |
| The year 2000 promises to be highly eventful for the joint ESA-NASA Ulysses mission. Not only does it mark an important anniversary - on 6 October, Ulysses will have been in orbit for 10 years - it also sees the return of Ulysses to the poles of the Sun. Given the spectacular success of the spacecraft's first visit to these previously unexplored regions in 1994/95, there is every reason to expect a rich scientific harvest once again. |
| Publication date: 01 Aug 2000 |
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| Identification of comet Hyakutake's extremely long ion tail from magnetic field signatures |
| Observations of the varying orientations of comet tails led to the suggestion of the existence of the solar wind - a continuous outflow of ionized material from the Sun. It is now well established that gas from comets is ionized by several processes and joins the solar wind, forming an ion (plasma) tail that points away from the Sun. The plasma environments of three comets have been measured in situ, but only in the upstream direction or less than 8,000 km downstream of the nucleus. Here we report a fortuitous crossing by a spacecraft of the plasma tail of comet Hyakutake (C/1996 B2), at a distance of more than 3.8 astronomical units (550 million kilometres) from its nucleus. This surpasses the tail length of 2 au determined for the Great March Comet of 1843 (C/1843 D1). Our measurements reveal that, at this distance, the tail of comet Hyakutake was a structured entity at least 7 million kilometres in diameter. |
| Publication date: 06 Apr 2000 |
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| Interception of comet Hyakutake's ion tail at a distance of 500 million kilometres |
Remote sensing observations and the direct sampling of material from a few comets have established the characteristic composition of cometary gas. This gas is ionized by solar ultraviolet radiation and the solar wind to form 'pick-up' ions, ions in a low ionization state that retain the same compositional signatures as the original gas.
The pick-up ions are carried outward by the solar wind, and they could in principle be detected far from the coma. (Sampling of pick-up ions has also been used to study interplanetary dust, Venus' tail and the interstellar medium.)
Here we report the serendipitous detection of cometary pick-up ions, most probably associated with the tail of comet Hyakutake, at a distance of 3.4 au from the nucleus. Previous observations have provided a wealth of physical and chemical information about a small sample of comets, but this detection suggests that remote sampling of comet compositions, and the discovery of otherwise invisible comets, may be possible. |
| Publication date: 06 Apr 2000 |
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| The Ulysses Mission |
| For much of the past four decades, the scientific probes sent into space stayed relatively close to the equatorial plane of the Sun, which contains the orbits of Earth and other planets. But a few years ago a single craft, Ulysses, ventured out of that thin zone and into the 'polar regions' of interplanetary space. |
| Publication date: 01 Jan 1998 |
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| ESA Bulletin 92 - The Heliosphere in Perspective - Key Results from the Ulysses Mission at Solar Minimum |
| In this article, we summarise the key findings of the mission to date, and discuss the exciting results to be expected from the second phase of Ulysses' out-of-ecliptic journey. |
| Publication date: 01 Nov 1997 |
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| Ulysses at High Heliographic Latitudes |
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| Publication date: 01 Dec 1996 |
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| Ulysses at High Heliographic Latitudes: an Introduction |
| The articles that comprise this special issue are devoted to recent results from the high-latitude passes of Ulysses, including the rapid transit from the southern to the northern hemisphere. This paper serves as an introduction to these articles, and provides a short summary of the major scientific findings from the mission to date. Also included is a description of the various Ulysses data archives and their access. |
| Publication date: 01 Dec 1996 |
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