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Topic: Heliosphere

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In the News (Tue 23 Apr 19)

  The Heliosphere
The interstellar flow turns at the stagnation point to go around the heliosphere and the subsonic solar wind flow is turned in the "heliosheath" between the termination shock and the heliopause to flow down the "heliotail." The solar wind inside the termination shock is flowing supersonically and radially.
With regard to the cosmic ray pressure in Table 1, the heliosphere is near a bubble of hot gas, evidently recent and not necessarily in equilibrium as far as locally produced cosmic rays are concerned, so it is possible that a low energy component exists locally and contributes to the total pressure.
To summarize, the heliosphere is probably well represented as stagnation point flow occuring between the solar wind and an interstellar wind.
web.mit.edu /space/www/helio.review/axford.suess.html   (2942 words)

 Galactic Frontier. Interstellar Exploration. Mapping the heliopause. Imaging the three-dimensional solar wind.
Several experimental techniques indirectly probed the heliospheric interface region: measurements of interplanetary glow at 121.6 and 58.4 nm, pickup ions in the solar wind, cosmic rays, and anomalous cosmic rays; direct detection of interstellar helium atoms; and spectroscopic observations of nearby stars and interstellar medium.
EUV imaging of the global heliosphere requires advancing the instrumentation state-of-the-art by a factor of 100, with the new instrumental concept formulated and presently being pursued [18,19,25,26].
HELIOSPHERE IN Three main sources contribute to radiation fluxes at 30.4-nm, the spectral band of interest: the glow of interstellar plasma and pickup ions; emissions of the solar wind; and galactic emissions (stars and hot plasmas in the Local Bubble).
astronauticsnow.com /GalacticFrontier/spie_2005.html   (7884 words)

 ESA Science & Technology: Background Science
The closest boundary of the heliosphere is thought to extend about 100 AU out from the Sun, that is 100 times the distance of the Earth from the Sun and at least twice as far out as the Kuiper belt, which contains the most distant objects in the solar system.
The heliosphere acts as a shield, protecting us from the bulk of cosmic rays, very energetic particles generated far away in the universe that would otherwise bombard the Earth continuously, causing damage to living cells.
Schematic of the heliosphere, showing the boundary regions between the heliosphere and the interstellar medium.
sci.esa.int /science-e/www/object/index.cfm?fobjectid=33637   (294 words)

 i-Newswire.com - Press Release And News Distribution - The Distortion of the Heliosphere: our Interstellar Magnetic ...   (Site not responding. Last check: 2007-11-05)
No human object has left the heliosphere, but the Voyager 1 spacecraft, which, after 10 000 days of cruise is at about 94 AU (14 billion km), is heading towards the northern ecliptic hemisphere and the edge of the heliosphere.
A possible explanation recently devised by theoreticians from the University of Tucson (Arizona), is the existence of an offset of the heliosphere from the direction of the incoming interstellar wind.
It would be an unlikely coincidence if the direction of the local galactic field, which depends on the shapes and motions of the interstellar clouds in the solar neighbourhood and of their history, were exactly parallel or perpendicular to the wind axis.
i-newswire.com /pr10389.html   (1460 words)

 SwRI Fall 2003 Technology Today Article
Nathan A. Schwadron (far left), a principal scientist, is actively involved in the theory and modeling of solar wind and its composition, the heliospheric magnetic field, the sources and acceleration of energetic particles in the heliosphere, and cosmic rays generated both within the heliosphere and beyond.
This solar-wind-dominated region of space is known as the heliosphere, which is an example of the fascinating astrophysical structures created by the interaction of a cosmic wind with the ambient interstellar gas.
The heliosphere's structure, dynamics and properties, and its interaction with the interstellar medium, are subjects of vigorous research by the international space science community.
www.swri.edu /3pubs/ttoday/fall03/SolarWind.htm   (2722 words)

 SPACE.com -- Space Weather Glossary, terms and definitions of solar and sunspot activity
Heliosphere: Charged particles streaming away from the Sun envelop Earth and the other planets in a magnetic bubble.
The closest boundary of the heliosphere is thought to extend about 100 AU out from the Sun, which is 100 times the distance of the Earth from the Sun.
The heliosphere is shaped and recharged by the solar wind.
www.space.com /spacewatch/space_weather_glossary.html   (890 words)

 Heliosphere - Research
The heliosphere is a large region of space where the solar wind interacts with the surrounding interstellar gas.
The physics of the heliosphere is made considerably more complex, however, by the presence of neutral hydrogen in the interstellar medium.
The global heliosphere is modeled numerically by solving a set of differential equations (MHD) for the plasma.
www.dartmouth.edu /~hrm/R/heliosphere.html   (697 words)

 Magnetospheric Models for Electron Acceleration and Transport in the Heliosphere
Dependent on flow speed and density the interstellar gas interaction with the upstream heliosphere may be subsonic or supersonic with a detached external shock similar to the earth's bow shock in the latter case.
Diffusion and drifts in the heliospheric case, and wave-particle scattering in the magnetospheric one, drive electrons poleward from the neutral sheet during inward propagation.
It is possible, for example, that heliospheric electron and ion acceleration in the outer heliosphere might contribute significantly to VLISM gas ionization and to radiation processing of cometary surfaces.
ssdoo.gsfc.nasa.gov /education/lectures/cooper.html   (1957 words)

 Circumstellar Debris Shells   (Site not responding. Last check: 2007-11-05)
While the majority of the electrically charged interstellar particles are deflected from entering the heliosphere, high-energy cosmic rays and interstellar neutral gas penetrate the heliosphere.
We define the heliosphere as the region around the Sun that is influenced by the presence of the solar wind.
The variation in the dust flux along the Earth's orbit as measured from satellites was explained by the focussing effect of interstellar dust due to the gravity field of the Sun.
www.gps.caltech.edu /users/mann/webisdx.html   (1243 words)

 The Heliosphere is Tilted - implications for the 'Galactic weather forecast'?
The Heliosphere is Tilted - implications for the 'Galactic weather forecast'?
News Release - heic9911: The Heliosphere is Tilted - implications for the 'Galactic weather forecast'?
Scientists are currently investigating the different particles of interstellar origin that have reached the inner heliosphere using the ESA/NASA solar explorers Ulysses and SOHO.
www.spacetelescope.org /news/html/heic9911.html   (943 words)

 The Outer Heliosphere
It is not yet known whether the plasma heating in the outer heliosphere is caused by turbulent cascades, by instabilities resulting from the pickup of interstellar ions, or by other mechanisms.
The interplanetary magnetic field is, of course, weaker in the outer heliosphere than closer in, but like the plasma speed and temperature, its strength does not decrease monotonically, but shows local maxima and minima related to solar activity as well as to the interaction of fast and slow streams.
The relations between the heliospheric current sheet, magnetic sectors, and stream interaction regions familiar to observers at 1 AU disappear at large distances to be replaced by several types of ``merged interaction regions'' [ Burlaga et al.
www.agu.org /revgeophys/neugeb01/node2.html   (1109 words)

 Science -- Stone 293 (5527): 55   (Site not responding. Last check: 2007-11-05)
Two spacecraft, Voyager 1 and 2 [HN3], are approaching the edge of the heliosphere [HN4]--the heliopause--where the radially decreasing pressure of the expanding solar wind balances the inward pressure of the local interstellar medium [HN5].
In this model, the interstellar wind is supersonic (7) and a bow shock forms upstream of the nose of the heliosphere, where the interstellar wind slows and is warmed to a still relatively cool 20,000 K. The heliopause separates the cool interstellar ions deflected around the heliosphere from the hot solar ions inside the heliosphere.
Although based on a highly uncertain estimate of the interstellar magnetic field, this interstellar pressure is very similar to a more recent assessment that included uncertainties in the various contributions to the interstellar pressure and led to a distance of 88 ± 22 AU (3, 4).
ajdubre.tripod.com /Physics-2/EdgeInterstellarSpace/55.html   (3541 words)

The Heliosphere is Tilted -- implications for the 'Galactic weather forecast'?
The solar particles at the edge of the heliosphere form a barrier to deflect other incoming charged particles and so partially protect the inner Solar System from the surrounding interstellar medium.
At the leading edge of the heliosphere, atoms and ions from the interstellar medium slow down as they approach the head, forming a shock wave, known as the interstellar bow shock.
www.xs4all.nl /~carlkop/tilted.html   (872 words)

 The Heliosphere in Perspective - Key Results from the Ulysses Mission at Solar Minimum
The breadth of scientific topics addressed by the mission is truly impressive, ranging from detailed measurements of the solar wind and its magnetic field, to the properties of interstellar gas and the isotopic composition of cosmic-ray nuclei.
One of the main goals of the Ulysses mission was to determine the global structure of the heliosphere, in particular with regard to the distribution of solar-wind plasma, and its 'frozen-in' magnetic field.
Since the heliosphere is a dynamic structure which undergoes large variations in both large- and fine-scale structure over the period of a solar magnetic cycle (22 years), it is critical that observations also be obtained near solar maximum.
esapub.esrin.esa.it /bulletin/bullet92/b92marsd.htm   (3810 words)

 Voyager - Multimedia - The Great Adventure Continues
The red arrows representing solar wind are seen being deflected at the front of the heliosphere, turning back and moving down the tail of the heliosphere.
The heliopause is the resulting outer boundary of the heliosphere that separates the flows of the internal solar wind and the external interstellar wind.
As the heliosphere plows through the ionized interstellar gas, a bow shock forms, much as forms in front of a boulder in a stream.
voyager.jpl.nasa.gov /multimedia/flash_html.html   (616 words)

 Modulation of galactic cosmic rays (GCR's) in the heliosphere.   (Site not responding. Last check: 2007-11-05)
It is not improper to speak of ``heliosphere tomography'' with cosmic rays.
Between 60 and 100 AU the heliosphere solar wind turns to subsonic velocity due to the resistance of the interstellar gas for what is called the heliospheric termination shock.
A schematic representation of the heliosphere is illustrated in Fig.
www.ba.infn.it /~pamela/proposal/node18.html   (502 words)

 Terms for Scientific Research
The heliosphere is the huge region around the Sun that encloses the Sun's solar wind and its magnetic field, which is "frozen into" and carried out by the wind.
The heliosphere is not at all spherical in shape.
In fact, the heliosphere is expected to have a tail like shape, similar to the magnetotail of Earth's magnetosphere.
lep694.gsfc.nasa.gov /lepedu/terms.htm   (2127 words)

 Pickup Ions Sources, Propagation, and Acceleration in the Heliosphere, 15-9352
This immense cavity (the termination shock in Figure 1), extending to 80–100 astronomical units (AU, with 1 AU the distance from the sun to Earth), and its surrounding boundaries (the heliopause and bow shock) is called the heliosphere.
Pickup ions are formed when interstellar neutral atoms become ionized, and are easily distinguished from the solar wind because of their high initial energies, their subsequent acceleration to form high energy particles, and their single charge (solar wind ions are highly charged, and for many elements are almost fully stripped of their electrons).
So-called heliospheric "FALTS" (Favored Acceleration Locations at the Termination Shock; see Figure 3) are locations in the outer heliosphere where the magnetic field undergoes large-scale systematic departures from the standard spiral configuration thought for many years to be the only magnetic field configuration in the outer heliosphere.
www.swri.edu /3pubs/IRD2003/Synopses/159352.htm   (960 words)

 SPACE.com -- Voyager to Reach Distant Milestones Sooner Than You Think
Their likely arrival at the true balance boundary between the Sun's heliosphere -- the region under its influence -- and the forces of interstellar space will provide scientists with the first direct data on the size of that enormous balloon of power, as well as help answer fundamental questions of interstellar space.
Voyagers 1 and 2 cruise along at a brisk 3.6 and 3.3 AU per year, respectively (1 AU is equivalent to the distance between the Earth and Sun, 93 million miles, or 148 million kilometers), but that trip to what is called the heliopause could take until 2017.
The heliosphere is a comet-shaped (the entire disk is distended by the cosmic wind) bubble of charged particles carved out of interstellar space by the solar wind.
www.space.com /missionlaunches/missions/heliosphere_shock_010706.html   (988 words)

 Cosmic Ray Modulation
The heliosphere is the region of space where the solar wind momentum is sufficiently high that it excludes the interstellar medium.
It is likely that the heliosphere is not spherical but that it interacts with the interstellar medium as shown schematically in Figure 1.
Thus Equation 4 is an equation explicitly representing the transport of cosmic rays in the heliosphere by convection, diffusion and drift.
www.atnf.csiro.au /pasa/18_1/duldig/paper/node5.html   (4430 words)

 Shields Up!
Cosmic rays from the blasts were mostly deflected by the heliosphere, sparing early humanoids a radiation bath.
The bubble is inflated from the inside by the solar wind and compressed on the outside by the cloud.
Coordinated observations of local interstellar Helium in the Heliosphere -- a special series of seven articles written by members of the ISSI team and published in the journal Astronomy and Astrophysics.
science.nasa.gov /headlines/y2004/27sep_shieldsup.htm   (1194 words)

 The Outer Heliosphere   (Site not responding. Last check: 2007-11-05)
The outer heliosphere, where the solar wind meets and interacts with the local interstellar medium, represents the current boundary between space physics and astrophysics.
Study of the outer heliosphere requires the consideration of both kinetic and MHD physics.
The fluid or MHD physics involves the macroscopic plasma structures and boundaries in the outer heliosphere (e.g., the termination shock and heliopause), evolved CIRs and CMEs called ``global merged interaction regions'', and the effects of pickup ions in slowing and heating the flow.
www.physics.usyd.edu.au /~cairns/teaching/lecture20/node1.html   (154 words)

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