What Are Auroral Ovals?


            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)