Theta Auroras are strange and dynamic, but scientists weren’t really aware of how they formed. That has now changed. These “light shows” form in the atmosphere at much higher latitudes than standard auroras. Their name comes from the Greek letter theta due to their resemblance to said letter when looked at from below. Theta is shaped like an oval bisected by a straight line.
Normally, auroras are the result of charge particles from solar winds being diverted into our atmosphere by the planet’s magnetic field. These “shows” are generally known as the northern and southern lights and can be seen along most latitudes, regardless of temperature.
Astronomers took a closer look at particles present in the two of the magnetosphere’s lobes. The plasma found in these lobes is usually cool, but when it comes to theta auroras, the ionized gas seems to be hot.
The University of Southampton’s Robert Fear explained that before it wasn’t clear if the hot plasma was caused by solar winds entering directly through the magnetosphere’s lobes or if the plasma had any form of connection to the sheet of plasma found on Earth’s night side. One theory is that magnetic reconnection process on the Earth’s night side leads to hot plasma that is trapped building up in the lobes found at higher latitudes.
The areas where auroras usually form are referred to as the aurora ovals and they are found at latitudes of approximately 65 degrees north or 65 degrees south. Unlike standard auroras, thetas form closer to the poles, at higher latitudes.
Scientists were able to study theta auroras thanks to the information collected by the NASA-managed Image satellite and by the ESA (European Space Agency) Cluster observatory. When one of the cluster satellites saw high-energy plasma amassing in a southern lobe, the formation of a theta aurora was recorded by the Image observatory. Dynamic plasma forms above the magnetic field lines close to the poles, where they combine into magnetic loops that are closed. Research found that this can conduct energy, which then heats up the formation.
Magnetic reconnection occurs when the solar wind is lined up on the opposite side of the Earth’s magnetic field where they intersect. When a solar wind that’s got a southern alignment interests with part of the Earth’s magnetic field that is facing north, the remaining particles in the wind quickly line up with the south. This creates a funnel that allows solar wind to enter the magnetosphere, which fuels the theta aurora.
Philippe Escoubet, a scientist on the ESA Cluster project, explained to the press that this is the first time the origins of theta auroras have been seen clearly, which is thanks to localized measurements taken by the Cluster along with IMAGE’s wide-field view. This has allowed scientists to gain a better understanding of the connection between the Earth and the Sun.
The report on the probe into theta auroras appeared in the Science journal. Solar winds are comprised of charged particles that are constantly streaming out of the sun. They occasionally cause stunning aurora shows in the sky.