The eerie curtains of light in night sky which illuminate the night is an aurora. If you come across one such, then you are very much destined.

2. Table of content
 Introduction
 Legends behind Aurora
 Causes of Aurora
 Auroral Oval
 Auroral mechanism
 How high aurora occur ?
 When does Aurora occur ?
 Place where Aurora occur ?
 Aurora on other planets
 Discovery of Aurora
 Types of Aurora
 Colours of Aurora
 Summary
 Objective
Aurora

3. Keywords
 Solar Wind
 Ionosphere
 Auroral Oval
 UV image
Aurora

4. Introduction
 The Beautiful and eerie
curtains of light in night
time sky is known as
aurora.
 Aurora is natural
phenomenon of light in the
upper atmosphere of earth.
 The Latin word aurora
means ‘sunrise’ or ‘Roman
goddess of dawn’.
Aurora

5.  In Northern hemisphere they are called as ‘Aurora Borealis’ which
means ‘Dawn to north’.
 In Southern hemisphere they are called as ‘Aurora Australis’ which
means ‘Dawn to south’.
 They can be seen above the magnetic poles of northern & southern
hemisphere.
Aurora

6. Legends behind Aurora
 The early dragon legends of
China and Europe, are said to
be originated from aurora.
 In medieval times, the
occurrence of aurora was seen
as harbingers of war or famine.
 The Maori of New Zealand
believed that the lights were
reflections from torches or
campfires.
Aurora

7.  The Menominee Indians of Wisconsin believed that the lights
indicated the location of giants who were the spirits of great hunters
and fisherman.
 The Inuit of Alaska believed that the lights were the spirits of the
animals they hunted.
Aurora

8. Causes of Aurora
 Sun emits electrically
charged particles called
as ‘solar wind’.
 Most of these charged
particles gets deflected by
earths magnetic field.
 Some of the trapped
particles move towards
polar regions since low
magnetic field.
Solar wind affecting earths magnetic field
Aurora

9.  In polar regions they collide with gases in earths ionosphere and
leads to formation of aurora.
 The variation in colour of aurora depends on gas with which it
undergo collision.
Solar wind entering earths magnetic field
Aurora

10. Auroral Oval
 The electrically charged
particles which stream down
the magnetic field of earth
reach the neutral
atmosphere in the rough
circle called auroral oval.
 This circle is around 3000
km in diameter.
UV image of auroral oval
Aurora

11. Auroral mechanism
 Electrically charged particles
when undergo collision with
gases from earths
atmosphere, leads to transfer
of energy.
 Due to high energy, atoms
undergo excitation to high
energy levels.
 These excited electrons later
gets to normal state by release
of photons (Light).
 The colour of light depends on
gas which gets excited and
amount of energy absorbed by
the gas.
Effect of charged particles on atoms
Aurora

12. How high Aurora occur ?
 Most aurora occur between 90 to 130 km above sea level, but some
extend to several hundred kilometers.
 The usual altitude for jet aircraft is 10 km and the ozone layer lie
between 20 and 30 km so we have to be at the height of satellite to
be at same height as of aurora.
 The consequence of its great height is that aurora is visible at
horizontal distance of several hundred kilometers.
Satellite picture of an aurora
Aurora

13. When does Aurora occur ?
 Mainly observed daily
somewhere in the sky (but in
the day time it is out-shined by
the sunlight).
 Due to low intensity they are
not visible through out the day
and hence seen during
midnight.
 Winter season is considered to
be the best time to view aurora.
Aurora

14.  Aurora is displayed after every 27 days in active regions.
 Full moon and light pollution affect the visibility of aurora.
 Aurora Borealis and Aurora Australis occur at same time and are
mirror image of each other.
Aurora

15. Place where Aurora occur
 Aurora Borealis are seen in
southern tip of Greenland, north
Canada, Alaska, northern coast
of Siberia, coasts of Troms and
Finnmark.
 Aurora Australis are seen only
from Antarctica and surrounding
ocean and may only be
glimpsed from Tasmania and
southern New Zealand
Aurora

16. Places of auroral occurrence in world map
Aurora

17. Aurora on other planets
 Auroras have been observed on
Jupiter, Saturn and Uranus but
not on Mars, Venus or Mercury.
 Any planet with a magnetic field
and an atmosphere should likely
have auroras (Mars and Venus
have no global magnetosphere;
Mercury has almost no
atmosphere).
Conjugate auroras on Saturn
Aurora

18. Discovery of Aurora
 In 4th century B.C. Aristotle made one of the first accounts of aurora
borealis, describing “glowing clouds”.
 In late 16th century, William Gilbert conducted experiments and came
to conclusion that earth itself is a giant magnet with north and south
pole.
 Late around 20th century, Norwegian scientist Kristian Birkeland
placed a spherical magnet inside the vacuum chamber and shot an
electron beam at it.
 It was founded that beam was guided by magnetic field to hit near the
pole.
Aurora

19. Birkeland in his lab testing his theories on what causes aurora
Aurora
 This experiment concluded that magnetic field played an important
role in auroral occurrence.

20. Types of Aurora
 Aurora are classified as
Discrete Aurora and Diffuse
Aurora.
 Discrete aurora can be
seen by naked eyes.
 Diffuse aurora is a
featureless glow in sky
which cannot be seen by
naked eyes.
Diffuse Aurora
Discrete Aurora
Aurora

21. Colours of Aurora
 The colour of aurora
depends on energy of
electron and colliding gas.
 High energy electron
cause oxygen to emit
green light and low energy
electron cause red light.
 Nitrogen emit blue light.
 Blending of these colour
also lead to purple, pink
and white.
Rainbow Aurora
Aurora

22. Summary
 Aurora is bright light appearing in night sky.
 It is a natural phenomena which occurs only in polar regions
 The charged particles thrown out of suns surface, enters into earths
atmosphere and undergo collision with the gases.
Aurora

23.  The variation in colour of aurora depends on energy of charged
particles and gas with which collision takes place.
 The occurrence of aurora on other planet depicts presence of
atmosphere and magnetic field.
 Places where aurora occurs are the tourist attraction.
Aurora

24. Objective
 To create public awareness of natural yet rare phenomena occurring
on our planet.
 To study scientific reason behind occurrence of auroral lights.
Aurora

25. Reference
 www.gi.alaska.edu
 www.wikipedia.org
 www.alaskascience.com
[ Types of aurora ]
 www.phy6.org
[ Causes of aurora ]
 www.sunearth.gsfc.nasa.gov
[ Aurora on other planets,
Formation of auroral oval ]
Aurora