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| Highlights from SOHO and Future Space Missions |
| Proc. Kanzelhoehe Summer School,
eds. A. Hanslmeier and M. Messerotti, Kluwer, 2001
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| Publication date: 01 Jul 2000 |
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| The Sun from Space |
| The Sun from Space is a comprehensive account of solar astrophysics and how our perception and knowledge of this star have gradually evolved as mankind has elucidated ever more of its mysteries. The emphasis is on the last decade, which has seen three successful solar spacecraft missions: SOHO, Ulysses and Yohkoh. Together these have confirmed many aspects of the SUN and its output, and provided new clues to the numerous open questions that remain.
The author, a leading researcher in the field, writes in a clear and concise style. Known also for his famous books "Astrophysical Formulae", "Sun, Earth and Sky", and the prize-winning "Wanderers in Space", he has succeeded once again in addressing a complex scientific topic in a very approachable way. Hence, this generously illustrated book, whilst primarily addressing students, will also be of interest to a broader readership covering all levels from the amateur to the expert. |
| Publication date: 01 Jun 2000 |
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| Four Years of SOHO Discoveries - Some Highlights |
| Since its launch on 2 December 1995, the Solar and Heliospheric Observatory (SOHO) has provided an unparalleled breadth and depth of information about the Sun, from its interior, through the hot and
dynamic atmosphere, out to the solar wind. Analysis of the helioseismology data from SOHO has shed new light on a number of structural and dynamic phenomena in the solar interior, such as the absence of differential rotation in the radiative zone, subsurface zonal and meridional flows, sub-convection-zone mixing, a possible circumpolar jet, and very slow polar rotation. The ultraviolet imagers and spectrometers have revealed an extremely dynamic solar atmosphere in which plasma flows play an important role. Evidence
for an upward transfer of magnetic energy from the Sun's surface toward the corona has been found. Electrons in coronal holes have been found to be relatively 'cool', whereas heavy ions are extremely hot and have highly anisotropic velocity distributions. The source region for the high-speed solar wind has been identified and the acceleration profiles of both the slow and fast solar wind have been measured. |
| Publication date: 01 May 2000 |
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| Seismic Images of the Far Side of the Sun |
| Images of an active region on the far side of the Sun were derived by applying seismic holography
to recent helioseismic observations from space. Active regions are the centers of energetic
phenomena such as solar flares and coronal mass ejections whose resulting electromagnetic and particle radiation interfere with telecommunications and power transmissions on Earth and can pose significant hazards to astronauts and spacecraft. Synoptic seismic imaging of far-side solar activity will now allow us to anticipate the appearance of large active regions more than a week ahead of their arrival on the east solar limb. |
| Publication date: 10 Mar 2000 |
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| Proc. 9th SOHO Workshop: Helioseismic Diagnostics of Solar Convection and Activity |
| Kosovichev, A.G., Duvall, T.L. (eds.) |
| Publication date: 01 Mar 2000 |
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| ESA SP-446 - Plasma Dynamics and Diagnostics in the Solar Transition Region and Corona |
| Workshop held 22-25 June 1999 in Paris, France.
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| Publication date: 01 Sep 1999 |
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| SOHO's Recovery -An Unprecedented Success Story |
| The SOHO mission is a major element of the joint ESA/NASA International Solar Terrestrial Programme (ISTP). ESA was responsible for the spacecraft's procurement, integration and testing. NASA provided the launcher, launch services and ground-segment system and is responsible for in-flight operations following the launch on 2 December 1995. The SOHO mission operations are therefore conducted under a NASA/Goddard Space Flight Center (GSFC) contract with Allied-Signal Technology Corporation (ATSC). Following the spacecraft's in-orbit checkout and the transit from low Earth orbit to its operational halo orbit around the Lagrangian point (L1) between the Earth and the Sun, the SOHO mission was declared fully operational in April 1996. SOHO then completed its two-year primary mission and entered an extended-mission phase in May 1998. On 25 June 1998, all contact with SOHO was lost. |
| Publication date: 01 Mar 1999 |
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| Solar Wind Outflow and the Chromospheric Magnetic Network |
| Observations of outflow velocities in coronal holes (regions of open coronal magnetic field) have recently been obtained with the Solar and Heliospheric Observatory (SOHO) spacecraft. Velocity maps of Ne7+ from its bright resonance line at 770 angstroms, formed at the base of the corona, show a relationship between outflow velocity and chromospheric magnetic network structure, suggesting that the solar wind is rooted at its base to this structure, emanating from localized regions along boundaries and boundary intersections of magnetic network cells. This apparent relation to the chromospheric magnetic network and the relatively large outflow velocity signatures will improve understanding of the complex structure and dynamics at the base of the corona and the source region of the solar wind. |
| Publication date: 05 Feb 1999 |
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| Proc. 7th SOHO Workshop: Coronal Holes and Solar Wind Acceleration |
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| Publication date: 01 Jan 1999 |
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| Proceedings of the 6h SOHO Workshop |
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| Publication date: 01 Jun 1998 |
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| X-ray flare sparks quake inside Sun |
| Solar flares involve a release of the Suns
magnetic energy as X-radiation, particle
beams and high-speed plasma flows. But we
have discovered, using data from the Solar
and Heliospheric Observatory (SOHO), that
these flares also affect the Suns interior, generating
seismic waves similar to earthquakes.
For example, a three-kilometre-high seismic
wave was caused by a moderate X-ray flare
that occurred on 9 July 1996 and propagated
at about 50 kilometres per second to a distance
120 000 kilometres from the flare site. |
| Publication date: 28 May 1998 |
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| The SOHO spacecraft finds intricate plasma flows coursing through the sun |
| A couple years ago researchers announced
that they had discovered traces of water on the sun. A team at Stanford University has just gone them one better, discovering entire rivers on the sun. These are not rivers in the familiar sense, of course; rather they are huge, snaking flows within the white-hot plasma (electrically charged gas) that makes up the sun. |
| Publication date: 15 Sep 1997 |
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| Proceedings of the 5th SOHO Workshop: The Corona and Solar Wind |
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| Publication date: 17 Jun 1997 |
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| The First Results from SOHO |
| SUMER - the Solar Ultraviolet Measurements of the Emitted Radiation instrument on the Solar and Heliospheric Observatory (SOHO) - observed its first light on January 24, 1996, and subsequently obtained a detailed spectrum with detector B in the wavelength range from 660 to 1490 Å (in first order) inside and above the limb in the north polar coronal hole. Using detector A of the instrument, this range was later extended to 1610 Å. The second-order spectra of detectors A and B cover 330 to 805 Å and are superimposed on the first-order spectra. Many more features and areas of the Sun and their spectra have been observed since, including coronal holes, polar plumes and active regions. The atoms and ions emitting this radiation exist at temperatures below 2 ×106 K and are thus ideally suited to investigate the solar transition region where the temperature increases from chromospheric to coronal values. SUMER can also be operated in a manner such that it makes images or spectroheliograms of different sizes in selected spectral lines. A detailed line profile with spectral resolution elements between 22 and 45 mÅ is produced for each line at each spatial location along the slit. From the line width, intensity and wavelength position we are able to deduce temperature, density, and velocity of the emitting atoms and ions for each emission line and spatial element in the spectroheliogram. Because of the high spectral resolution and low noise of SUMER, we have been able to detect faint lines not previously observed and, in addition, to determine their spectral profiles. SUMER has already recorded over 2000 extreme ultraviolet emission lines and many identifications have been made on the disk and in the corona. |
| Publication date: 01 Jan 1997 |
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| The First Results from SOHO |
| SOHO, launched by an Atlas II-AS from Cape Canaveral on 2 December 1995, was inserted into its halo orbit around the L1 Lagrangian point on 14 February, six weeks ahead of schedule. The launch and the orbital manoeuvres were so accurate and efficient that sufficient fuel remains on board to maintain the halo orbit for more than a decade, i.e. for at least twice as long as originally foreseen.
Already during their commissioning phase, the SOHO experiments have returned a wealth of data, impressive in terms of both its quality and diversity. Some of the images can be viewed via the SOHO pages (http://sohowww.nascom.nasa.gov) on the World Wide Web, and on the individual experiment pages, all with links from the SOHO home page.
Typical examples of the unique results being obtained with SOHO's instruments are presented here. Although they have been obtained with single instruments, it is worth noting that the main scientific advances from SOHO are expected to come from the joint analysis of coordinated observations. |
| Publication date: 01 Aug 1996 |
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| The History of the SOHO Mission |
| The roots of the SOHO mission and the story leading to the comprehensive observatory that the spacecraft is today are summarised here. Now fully operational in its halo orbit around the first Lagrangian point (L1) between the Earth and the Sun, SOHO is providing the international scientific community with the unique opportunity, and also challenge, of understanding the Sun and heliosphere as one complex, global system. It is a superb tool with which to investigate our daylight star and its circumstellar environment, from the Sun's centre, through its visible surface and tenuous corona, and out into the heliosphere to distances corresponding to more than ten times the orbital distance of the Earth. |
| Publication date: 01 May 1996 |
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| The SOHO Mission |
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| Publication date: 01 Jun 1995 |
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