1. U. Rajitha
M.Sc Space Physics
Department of Physics
Visakhapatnam
ANDHRA UNIVERSITY
2. Organization of the talk
Introduction
Space weather
Sun (Sun spots, Coronal Mass Ejection, Aurora)
Magnetosphere
Geomagnetic storms
Effects of geomagnetic storms
3. SPACE WEATHER
Space weather refers to conditions on the Sun and in the space
environment that can influence the performance and reliability
of space-borne and ground-based technological systems, and
can endanger human life or health.
4. This diagram shows the different zones of the Sun, from its
core out to the corona.
5. Solar activity
The output of the sun in all forms , light , solar wind , and energetic particles ,
is not constant.
It varies with both time ( seconds to centuries!) and position on the Sun.
These changes are called Solar activity and are probably reflections
of changes below the Sun’s surface.
The Sun’s energy output takes two main forms:
Electromagnetic radiation
The emission of charged particles
Solar activity produces Space weather that effects the Earth
6. SUN SPOTS
Dark spots some as large as 50000 miles diameter move
across the surface of the sun contracting and expanding as
they go. These strange and powerful phenomena is known as
sunspot.
7. Solar flares
Solar flares are tremendous explosions on the surface of
the Sun. In a matter of just a few minutes they heat
material to many millions of degrees and release as much
energy as a billion megatons of TNT.
8. Coronal Holes
Coronal holes are areas of the Sun's surface that are the source of open magnetic field lines that head
way out into space. They are also the source regions of the fast solar wind, which is characterized by a
relatively steady speed of approximately 800 km/s. As the Sun continues to rotate, the high speed solar wind
particles blowing from this hole will likely reach Earth in a few days and may spark some auroral activity.
9. Coronal Mass Ejection
What are CMEs?
Large-scale magnetized plasma ejected from the Sun (part of the corona is expelled
with its magnetic field)
Propagate into the interplanetary medium and impact planets in the solar system
12. Aurorae are a luminous glow of the upper atmosphere caused by
energetic particles descending from the Earth’s magnetosphere or
coming directly from the Sun. These energetic particles are
mostly electrons, but protons can also be involved, and their
energetic rain into the atmosphere is greatest during magnetic
storms.
13. The aurora becomes active during geomagnetic storms which occur often
about 40 h after an intense solar flare.
14. Is the earth magnet?
The crust of the Earth has some permanent magnetization, and the core of the
Earth, the outer part of which is liquid iron and the inner of which is solid iron,
generates its own magnetic field, sustaining the main part of the field we measure
at the surface. So we could say that the Earth is, therefore, a magnet.
15. VAN ALLEN
BELTS
The earth’s core behaviour is like a very large magnet. The geomagnetic
field associated with core is like a magnetic oriented South-North. Like poles
of two magnets repel.
So a north seeking compass will direct itself towards the south oriented
magnet inside the earth.
The Van Allen radiation belt is a torus of energetic charged particles (
plasma) around Earth, held in place by Earth's magnetic field.
16. MAGNETOSPHERE
The earth resides in a vast magnetic cavity, is called the
magnetosphere.
The magnetospheric cavity is created by the electrodynamic
interaction between the solar wind (a gas of charged particles
continuously flowing from sun) and the earths magnetic field.
The geomagnetic cavity is formed as the solar wind is swept
around.
The boundary terminating the magnetosphere is called the
magnetopause
A shockwave is a discontinuity of the medium ,produced when
information about an approaching perturbation is not reached into
the medium.
17.
18. Geomagnetic storm
A geomagnetic storm is a temporary disturbance of the earth’s
magnetosphere caused by a disturbance in space weather.
They are associated with solar mass ejections(CME) or solar flares
Geomagnetic storm is caused by a solar wind shock wave which
strikes the earths magnetic field 24 to 36 hours after the event. The
shock waves should travel towards earth.
Geomagnetic storm have a duration of several days, during which
the geomagnetic field is severely disturbed from the normal.
There is another phenomenon called as a sub storm in which
geomagnetic field in the polar region is perturbed by strong electric
currents flowing in the upper atmosphere with a time scale of ten of
minutes. Bright auroras show intense variations at the time of sub
storm.
19. Geomagnetic storm effects
Radiation hazards to humans
Biology
Disrupted systems
o Communications
o Navigation systems
o Satellites
