Nyrkkisäde

Nyrkkisäde, also known as the "fist ray," is a phenomenon observed in the Northern Lights, where the aurora appears to form a distinct, vertical column or ray that resembles a clenched fist. This unique auroral form is typically seen during periods of high geomagnetic activity, when the Earth's magnetic field is disturbed by solar wind. The nyrkkisäde is characterized by its bright, greenish hue and its vertical orientation, which can sometimes appear to stretch across the entire sky.

The exact cause of the nyrkkisäde is still a topic of scientific research, but it is believed to be related to the interaction between charged particles from the sun and the Earth's magnetic field. These particles, primarily electrons and protons, are funneled along the magnetic field lines towards the polar regions, where they collide with atmospheric gases. These collisions excite the gas molecules, causing them to emit light and create the aurora.

The nyrkkisäde is often associated with other auroral forms, such as the corona and the drapery. It can appear as a single ray or as part of a larger auroral display, and its appearance can vary in intensity and duration. Observers of the Northern Lights often report seeing the nyrkkisäde as a particularly striking and memorable feature of the aurora.