1. Formation of Aurora Anni Leinonen and Anniina Väyrynen
Ionospheric physics project work

2. Contents Background Formation of Aurora Classification of Aurora
Incidence of Aurora
Forecasting of Aurora
Picture 1. Auroras in Lapland [7]

3. Background
Sunspots
Places where magneticfield go through the surface of the Sun
The plasma can’t go back inside the Sun at those places
 radiation
Place of sunspots moves with magnetic field
Picture 2. Sunspots. [8]

4. In heliosphere and heliopause Transports the magneticfield of the Sun
Solar wind
Hot gas of corona
Consists of ions: protons, electrons, He- nuclei and other charged particles of the Sun
In heliosphere and heliopause
Transports the magneticfield of the Sun
At the orbit of the Earth
v=400 km/h
T= ⁰C
B=2-4 nT

5. Electromagnetic radiation and particles with great amount of energy
Flares and coronal mass ejections
There are gas clouds in the magneticfield of the Sun: protuberances and prominences
Because of flares energy of the magneticfield of the Sun is released explosively
Electromagnetic radiation and particles with great amount of energy
Coronal mass ejections are giant gas clouds
10 billion tons of matter
Strenghten the solar wind and the transported magnetic field it
Picture 3. [9]

6. Protects the Earth against particles of the solar wind
The magnetic field of the Earth
Protects the Earth against particles of the solar wind
Comes from the liquid outer nucleus of the Earth
Dipolic structure
Solar wind prolongs a tail for the magnetic field of the Earth
Picture 4. The Earth’s dipole magnetic field [2]
Picture 5. Magnetosphere [2]

7. Formation of Aurora Dipolic form of the magnetc field of the Earth
Auroral oval
Dipolic form of the magnetc field of the Earth
 Charged particles access the atmosphere of the Earth  circle formed areas = auroral oval
Continuous band on both hemispheres
Size of the auroral oval depends on the magnetic activity of the Sun
Area where Auroras appears most likely
Mainitse alussa, että aurinkotuuli synnyttää revontulet
Alue jolla tod näk ilmenee: ESIINTYVYYS, kilpisjärvellä 75% ja utsjoella 65% (?)!! Oulussa 25%
Picture 6. Auroral oval. [2]

8. In the atmosphere ions collide with molecules of the ionosphere
Excitation of the atoms in the atmosphere and formation of the colors
In the atmosphere ions collide with molecules of the ionosphere
molecules become excited to higher energy level
Excitation level release
 Released energy can be seen as different colors of Aurora
C-type:
100 km
Oxygengreen Aurora
Nitrogenhuman eye can’t see the spectrum of nitrogen
Picture 7. The lowest energy levels of oxygen atom. [2]

9. D-type: A-type: B-type: E-type: 150 km Oxygenred Aurora
Combination of types C and D
Green Auroras shading to red at the top
B-type: km
OxygenGreen Aurora
Nitrogen red lower border
E-type:
Fast moving B-type Aurora

10. In addition, Hα- and Hβ- proton emissions form Auroras
F-type:
Sunlit Auroras
Nitrogen blue and purple Auroras
Resonance scattering
In addition, Hα- and Hβ- proton emissions form Auroras
Protons capture electron and produce excited hydrogen atom
 Excitation level release
 Auroras are seen
Proton aurora is much weaker than electron aurora

11. Picture 8. Type C Aurora [2]
Picture 9. Type A Aurora [2]

12. Picture 11. Type D Aurora [2]
Picture 10. Type F Aurora [6]

13. Classification of Aurora
Diffuse Aurora are wide spread
No internal structure, matt
Discrete Aurora
Internal structure, bright
Aurora band and Auroral arc
Aurora rays
Pulsating Aurora
Auroras can be either quiet or active
Quiet are slow, active are fast
The brightness of Aurora is classified into four groups
Picture 12. Auroral arc [5]
Picture 13. Auroral band [5]
Picture 14. Auroral rays [5]

14. Forecasting of Aurora
Incidence of Aurora debends on activity of the Sun and the amount of the sunspots
Forecasting the amount and of the Auroras and how great they look like
Magnetic field of the Sun changes direction every 11th year
During the maximum activity the magnetic field is messy
During the decrease of the activity there are lots of holes in the corona
 solar wind
 more Auroras

15. Solar wind comes to Earth in 3 days
When consirdered from the Earth, the rotation time of the Sun is 27 days
Holes of corona can remain for couple rotations
 the same hole can cause many Auroras
Coronal mass ejections are single and therefore they can’t be forecasted
Solar wind comes to Earth in 3 days
From the mass ejections in the Sun, the velocity of the solar wind can be forecasted
 Forecast of the time of the Auroral performance
There are satellites in the L1-point, those measure the solar wind
It takes 0,5-2,0 hours for the solar wind to come to the Earth
The changes of the magnetic field of the Earth are reflected to the Auroras
Disturbances occur at the same time
Impacts are seen immediately

16. References
[1] (check ) [2] Aikio Anita. Auroral Physics. Luentomoniste. Fysiikan laitos. Oulun yliopisto [3] Aikio Anita. Ionospheric Physics. Luentomoniste ja luentodiat. Fysiikan laitos. Oulun Yliopisto [4] (check ) [5] (check ) [6] (check ) [7] muut.html (check ) [8] (check ) [9] (check )