Heliosphere and Solar Wind Quiz

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Questions and Answers

What is the role of the hydrogen wall in the heliosphere?

It helps stabilize the solar wind speeds.

It acts as a source of energetic neutral atoms.

It is formed from the charge-exchange with solar protons. (correct)

It provides a protective barrier against cosmic rays.

What new shape was suggested for the heliosphere based on the preliminary Cassini data?

A long-tailed comet shape

A deflated croissant shape (correct)

A flat disk shape

A rectangular prism shape

What does the IBEX mission's all-sky map reveal?

The exact location of the hydrogen wall

The temperature variations in the heliosphere

The trajectory of solar winds

A bright filament of unknown origin (correct)

How does the galactic magnetic field affect the heliosphere?

It drapes over the heliosphere, shaping its boundary. Signup and view all the answers

What major advancement regarding the heliosphere boundary was reported recently?

It has been distinctly mapped for the first time. Signup and view all the answers

What primarily accelerates the fast solar wind according to recent studies?

Magnetic (Alfven) waves Signup and view all the answers

What velocity range characterizes the slow solar wind?

300-400 km/s Signup and view all the answers

Which region of the corona is mainly responsible for the origin of the fast solar wind?

Polar dark corona Signup and view all the answers

What is a significant characteristic of the solar wind in relation to density?

Fast wind is low density and quite uniform Signup and view all the answers

What phenomenon can interrupt both types of solar wind?

Coronal mass ejections (CMEs) Signup and view all the answers

What effect does the solar wind have on the atmosphere of planets such as Venus?

It gradually strips the atmosphere from the planet. Signup and view all the answers

What happens when solar wind particles impact the surface of rocky objects like the Moon?

They release oxygen that combines with solar wind hydrogen to produce water. Signup and view all the answers

What determines the point at which solar wind can no longer expand?

When the pressure of solar wind equals the pressure of interstellar gas. Signup and view all the answers

What is the termination shock in the context of solar wind?

The sudden stop of solar wind expansion when interstellar pressure balances. Signup and view all the answers

What significant information was announced on September 24, 2009, regarding lunar soil?

The presence of water in lunar soil. Signup and view all the answers

What is the primary origin of the slow solar wind?

Around the equator primarily Signup and view all the answers

How does the solar wind interact with planets that have strong magnetic fields?

They create magnetic cavities known as magnetospheres Signup and view all the answers

What occurs to the magnetopause on a planet with a weak magnetic field and high solar wind pressure?

It is forced downward Signup and view all the answers

What is the role of the solar wind’s expansion in the solar system?

It carries the Sun's magnetic field outward Signup and view all the answers

Which description is correct for planets with no magnetic fields but with atmospheres?

The atmosphere screens the surface from solar wind Signup and view all the answers

During solar maximum, where else besides the equator can slow solar wind be emitted from?

From the solar poles as well Signup and view all the answers

What happens to a planet like Mercury due to its weak magnetic field when solar wind pressure is high?

Solar wind can penetrate to the surface at times Signup and view all the answers

What is the primary factor causing the interaction between solar wind and a planet's atmosphere?

The strength of the planet's magnetic field Signup and view all the answers

At what speed is the solar system moving relative to nearby stars?

16.5 km/s Signup and view all the answers

What shape does the heliosphere resemble?

A comet Signup and view all the answers

What phenomenon did Voyager 2 experience on 31 August – 1 September 2007?

Termination shock Signup and view all the answers

What causes the termination shock to move in and out?

Variations in solar wind pressure Signup and view all the answers

How does the shock wave of the heliosphere compare to basic models?

Less dramatic than predicted Signup and view all the answers

Study Notes

### Hydrogen Wall

Interstellar neutrals stream freely into the heliosphere, where they undergo charge-exchange with solar protons, resulting in a “wall” of hydrogen.
The heliosphere may not be the comet-like shape previously predicted but may be a large, round bubble.

IBEX Mission (2009/10/15)

IBEX's all-sky map reveals a bright filament of unknown origin.

Heliosphere Shape

Recent results suggest the heliosphere is a deflated croissant shape rather than a long-tailed comet, as previously believed.
The galactic magnetic field drapes over the heliosphere, shaping it.

The Extended Corona

The visible "white light" corona is photospheric light scattered by electrons in the corona; brighter features represent higher density.

The Solar Wind

E. Parker predicted the solar wind in 1958, later confirmed by Soviet satellites.
The solar wind is a supersonically expanding extension of the corona.
The corona’s heat is too great to be held back by gravity.
The solar wind is measured at supersonic speeds at 4 solar radii.
SOHO measurements show supersonic velocities are reached much faster than expected, indicating thermodynamic expansion alone cannot explain the acceleration.
The fast solar wind has low density, 700-800 km/s, and is uniform. It originates mainly in the polar dark corona ("coronal holes").
The slow solar wind has approximately three times the density of the fast wind, 300-400 km/s, and is highly variable. It originates mainly around the equator ("streamer belt").

Fast Solar Wind Acceleration

The fast solar wind can be accelerated by magnetic (Alfven) waves.

Slow Solar Wind

Streamers are produced by magnetic flux draping over closed field lines.
At solar maximum, the poles also emit a slow solar wind.

Solar Wind and Planets

The solar wind continues to expand outward, carrying the Sun’s magnetic field.
Planets within the solar wind have different interactions with the solar wind based on their magnetic fields and atmospheres.
Planets with magnetic fields carve out their own magnetic cavities, called magnetospheres.
Planets without magnetic fields but with atmospheres have their surfaces screened from the solar wind by the atmosphere.
Other bodies have direct interaction between the solar wind and their surface.

Solar Wind and Planetary Atmospheres

Planets with atmospheres but no magnetic fields can experience charge-exchange between solar wind particles and their atmospheric gases.
Newly formed atmospheric ions follow the solar magnetic field, flowing away from the planet with the solar wind.
This gradual process can strip atmospheres from planets, as seen at Mars and Venus.

Solar Wind and Surfaces

Objects with no atmospheres and no magnetic fields (e.g., the Moon), experience impacts from solar particles.
These impacts disrupt molecule bonds in rocky objects, releasing oxygen which combines with hydrogen in the solar wind to produce water.

The Termination Shock

The termination shock occurs when the pressure of the solar wind equals the pressure of the interstellar gas.
The shock front heats gas and accelerates energetic particles, forming the "hot hydrogen" wall.
Simple calculations suggest the termination shock is located at about 170 AU from the sun.
The heliosphere's shape resembles that of a comet due to the solar system's velocity.
The termination shock is less dramatic than predicted. It is not symmetric.

The Heliosphere/Interstellar Medium Coupling

The solar wind pressure changes, causing the termination shock to move in and out, which can result in multiple crossings.

Voyager 2

Voyager 2 passed through the termination shock several times between August 31st and September 1st, 2007, at ~84 AU from the Sun.

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Description

Test your knowledge on the heliosphere, solar wind, and the IBEX mission. This quiz covers recent findings regarding the shape of the heliosphere and the hydrogen wall effect. Explore how these phenomena relate to the solar corona and galactic magnetic field.