põhjavalgust

Põhjavalgust is an Estonian term that translates to "northern lights" or "aurora borealis" in English. It refers to the natural light display in the Earth's sky, predominantly seen in high-latitude regions. This phenomenon is caused by disturbances in the magnetosphere caused by the solar wind.

The solar wind is a stream of charged particles released from the upper atmosphere of the Sun. When these particles encounter Earth's magnetic field, they are guided towards the polar regions. As these particles collide with atoms and molecules in the Earth's atmosphere, they excite these atmospheric constituents, causing them to emit light. The specific colors of the aurora depend on the type of gas particles involved and the altitude at which the collision occurs. Oxygen typically produces green and red light, while nitrogen can create blue and purple hues.

Põhjavalgust is most frequently observed during periods of increased solar activity, such as solar flares or coronal mass ejections, which result in a stronger solar wind. While the aurora borealis is visible in the Northern Hemisphere, its counterpart in the Southern Hemisphere is known as the aurora australis. In Estonia, while not as common as in regions closer to the Arctic Circle, põhjavalgust can occasionally be seen, especially during intense geomagnetic storms. Its appearance is often a subject of wonder and has historical significance in local folklore.