heliosphere

(hee -lee-ŏ-sfeer) The vast region around the Sun that is permeated by the solar wind and the weak interplanetary magnetic field, and in which the solar-wind plasma plays a dominant role. It is bounded by the heliopause, which is estimated to be 100 AU or more from the Sun's center but has not yet been encountered by any spacecraft. The heliosphere may be very elongated owing to the presence of an interstellar wind of neutral hydrogen flowing from the direction of the galactic center.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

heliosphere

[′hē·lē·ə‚sfir]

(astronomy)

The region surrounding the sun where the solar wind dominates the interstellar medium. Also known as solar cavity.

(geophysics)

The region in the ionosphere where helium ions are predominant (sometimes there may be no region in which helium ions dominate).

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References in periodicals archive

The position of NASA's Voyager 1 and Voyager 2 probes, outside of the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto, is shown in this NASA/JPL-Caltech illustration.

Voyager 2 has entered the space between solar systems

While the probes have left the heliosphere, Voyager 1 and Voyager 2 are yet to leavethe solar system and won't be leaving anytime soon either.

NASA's Voyager 2 enters interstellar space

In the ram direction the outer boundary of the heliosphere is compressed, whereas in the opposite direction the heliosphere is stretched out into an elongated tail.

UNDERSTANDING SPACE WEATHER: Part III: The Sun's Domain: The solar wind is a continuous, varying outflow of high-temperature plasma, traveling at hundreds of kilometers per second and stretching to over 100 au from the Sun

"Instead of a prolonged, comet-like tail, this rough bubble-shape of the heliosphere is due to the strong interstellar magnetic field-much stronger than what was anticipated in the past-combined with the fact that the ratio between particle pressure and magnetic pressure inside the heliosheath is high," said Kostas Dialynas, a space scientist at the Academy of Athens in Greece and lead author on the study.

Cassini, Voyager Missions Suggest New Picture of Sun's Interaction with Galaxy

Since then, scientists have eagerly anticipated the probes' departure from the heliosphere, the bubble of particles that encircles the sun and planets, and their entry into the unexplored space between stars.

Voyager 1 may still be in solar bubble: scientists argue that probe has not reached interstellar space

Some scientists have said that the spacecraft was still within the heliosphere, the region of space dominated by the Sun and its wind of energetic particles and has not yet reached the space between the stars.

Did NASA's Voyager 1 reach interstellar space?

After much debate, data at last persuaded scientists that the car-size spacecraft had slipped outside the heliosphere, a huge bubble of particles blown out by the sun.

Beyond the beyond; Voyager I the eyes, ears of Earth

space agency scientists now agree that Voyager is officially outside the protective bubble known as the heliosphere that extends at least 13 billion kilometers beyond all the planets in our solar system, and has entered a cold, dark region known as interstellar space.

Voyager first spacecraft to exit solar system

Scientists have been waiting for years for a signal from Voyager 1announcing that it had left the solar system and reached interstellar space as it explored the boundary region known as the heliosphere.

Voyager 1 becomes first probe to leave solar system, study says

His topics include radiative transfer in the sun's atmosphere, the dynamics of solar plasmas, observations of photospheric activity and magnetism, the solar wind and heliosphere, and influences of solar variability on Earth.

Solar astrophysics, 3d ed