The Aurora occurs most often in regions known as the "Auroral
Ovals". These are rings of a
radius roughly 1500 miles
(2400 km) around the Earth's
magnetic Poles. In 1868 Elias Loomis of Yale University identified this auroral
zone. On very rare occasions, aurora can occur at lower latitudes, and even at
the equator. People, who live near this auroral oval, are able to see the aurora
on most clear, dark nights (when Sunspot activity is enough). But for people
living far away from the oval, are able to see the aurora when there is maximum
solar activity. The shape of auroral
oval changes with the sunspot
activity.
1910, a Norwegian physicist
performed a series of experiments to reproduce many of the characteristics of
the aurora. Birkeland
placed a magnetized sphere inside a vacuum chamber and projected a beam of
electrons at the sphere. Birkeland called this little sphere as “Terrella”
(this is a Latin
word which means little earth)
and hence his experiments are known as Terrella experiments. This little sphere
was coated with fluorescent paint to enable Birkeland to view the trajectories
of streaming electrons. Birkeland was able to accurately reproduce how Solar
wind would make its way into the Earth's magnetic poles, and was able to
simulate the auroral ovals near the Earth's magnetic poles.
We
have developed a similar device which can demonstrate the auroral ovals. We have
also checked that there is variation in magnetic field when the discharge takes
place. Photograph 1 show the “Terrella”, which is coated with green fluorescent paint. The
“Terrella” is magnetized sphere (magnetic field intensity of 1.2 KG).The
second photograph shows the apparatus in action!
One can clearly see the auroral oval (that is the fluorescent
oval region in the photograph).One can also identify the trajectories of the
electrons near the magnetized sphere.
Name: Miss
Ekata Hemant Ghate (M. Sc .Physics)
E-mail Address: ekatahghate@hotmail.com
Working place: Sir Parashurambhau College, Physics Department., India
Designation: Lecturer in Physics
Students who
worked under my guidance in this project
1 Miss Padmashree R. Dekhane (First year of graduation)
2. Mr. Niwrutti Kumbhar. (Last year
of graduation)