Researchers believe they have finally cracked the mystery of the origins of the mysterious "theta" aurora, a stunning natural light show that takes place in the night sky.
The phenomenon, also known as the Northern or Southern lights, are caused by solar winds hitting the Earth's atmosphere, the University of Southampton reported. These electrically charged atomic particles interact with the Earth's magnetic field, causing the shimmering displays.
Researchers have conducted plenty of research on what causes auroras within the "auroral oval" encircling the polar ice caps, but are still unsure of how "theta auroras" (which occur at much higher latitudes) are born.
To gain insight into these types of auroras researchers looked at particles in two "lobe" regions of the magnetosphere. Past research has suggested theta auroras are linked to unusually hot activity in these lobes.
"Previously it was unclear whether this hot plasma was a result of direct solar wind entry through the lobes of the magnetosphere, or if the plasma is somehow related to the plasma sheet on the night side of Earth," said lead author Robert Fear from the University of Southampton. "One idea is that the process of magnetic reconnection on the night side of Earth causes a build-up of 'trapped' hot plasma in the higher latitude lobes."
The team looked at data collected from the European Space Agency's (ESA) Cluster and NASA's IMAGE back in 2005.
"We found that the energetic plasma signatures occur on high-latitude magnetic field lines that have been 'closed' by the process of magnetic reconnection, which then causes the plasma to become relatively hot," Fear said.
Once these lines are closed solar wind can no longer enter, and the evidence suggests this plasma-trapping phenomenon contributes to the creation of theta auroras.
"This is the first time that the origin of the theta aurora phenomenon has been revealed, and it is thanks to localised measurements from Cluster combined with the wide-field view of IMAGE that we can better understand another aspect of the Sun-Earth connection," said Philippe Escoubet, ESA's Cluster project scientist.
The findings were published in a recent edition of the journal Science.
