2. Solar and Stellar Winds
Interplanetary Magnetic and Electric Fields
Solar and Stellar Activities
Shock Waves
Magnetosphere
Heliosphere and Heliopause
outline
3. The sun
Is an ordinary star of average sized.
Its temperature is with an absolute magnitude of 4.8.
It is about 4.6 billion years old.
its life expectancy is estimated at another 5 billion years.
Its atmosphere is divided into three parts; the
photosphere, the chromosphere and the corona.
Solar and Stellar Winds
5. Solar and Stellar Winds
Solar Winds Stellar Winds
is created by the outward
expansion of plasma (a
collection of charged
particles) from the Sun's
corona (outermost
atmosphere).
is fairly gentle.
fast-flowing streams of
particles that are emitted
from a star.
as gentle as the solar
wind
are difficult to detect
from the earth
6. The space permeated between the sun and planets
Is a part of the Sun's magnetic field
is carried into interplanetary space by the solar wind.
are said to be "frozen in" to the solar wind plasma.
originates in regions on the Sun
Interplanetary magnetic field
7. is closely tied to how the expanding solar wind
produces currents in space.
The sun is magnetic star.
magnetic field is present in sunspots
Sunspots have lateral dimensions of about 104 km
Cont.
8. In the solar wind frame of reference, the charge
density is vanishingly small
space is not without electric fields.
The solar wind motion across IMF induces EMF and
an electric field will be observed in the stationary
frame.
Electric and magnetic field depend on the coordinate
frame
An E will also be induced by the motion of rotating
plasma across a B.
Interplanetary electric field
9. In ideal plasmas, the E in the rotating frame vanishes and
the plasma corotates perfectly with the rotating body.
a rotating frame is not an inertial frame of reference
magnetospheres whose plasmas
may be partially corotating (Earth)
almost entirely corotating (Jupiter)
not corotating at all (Mercury).
Cont.
10. The activity of the sun varies with a period of about 22
years.
Solar flares and CMEs are an example of solar activity.
Solar flares
occurs during solar active years.
consist of as much as 1031 ergs of energy.
produce high energy particles.
Solar and stellar activities
11. Coronal Mass Ejections (CMEs)
are large expulsions of plasma and magnetic field from
the Sun's corona.
They can eject billions of tons of coronal material.
carry an embedded magnetic field (frozen in flux).
stronger than the background solar wind IMF strength.
Cont.
12. As the solar corona expands into space, the expansion
velocity increases and it becomes supersonic.
shock wave that develops when a supersonic jet breaks
the sound barrier in Earth’s atmosphere.
It forms in front of planets (the planet is supersonic in the
solar wind frame).
It also arise from solar flares, coronal mass ejections and
stellar explosions such as supernovas.
Collisionless shock waves
13. is the region around a planet dominated by the planet's
magnetic field.
Many planets, stars and cosmic bodies are magnetized.
Neutron stars are remnants of supernova expansions and
they have intense B.
Pulsars are thought to be fast rotating neutron stars.
A pulsar magnetosphere is formed by the protons and
electrons.
Magnetosphere
14. Magnetosphere of planets
The planets, their moons and the comets that are
magnetized all have magnetospheres.
magnetized bodies such as mercury, Jupiter, Earth,
Saturn, Uranus and Neptune, immersed in the
expanding coronal atmosphere.
unmagnetized bodies such as Mars, Venus, and
Comets.
Unmagnetized planets and moons without an ionized
atmosphere act much like a dielectric obstacle.
16. Heliosphere
a bubble that extends far past the orbits of the planets.
shaped like a long wind sock
it moves with the Sun through interstellar space.
17. Heliopause
Is the boundary between solar wind and interstellar
wind.
the pressure of the two winds is in balance.
This balance in pressure causes the solar wind to turn
back and flow down the tail of the heliosphere.
