ESA\u2019s four Cluster spacecraft have made a remarkable set of observations that has led to a breakthrough in understanding the origin of a peculiar and puzzling type of aurora.<\/p>\n
These aurorae – seen as bright spots in Earth\u2019s atmosphere and called \u2018dayside proton auroral spots\u2019 – occur when fractures appear in the Earth\u2019s magnetic field, allowing particles given out from the Sun to squirt through and collide with the molecules in our atmosphere. This is the first time that a precise and direct connection between the two events has been made.
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\nThe Earth\u2019s magnetic field acts like a shield, protecting Earth from the constant stream of tiny particles ejected by the Sun and known as the \u2018solar wind\u2019. The solar wind itself is made of hydrogen atoms, broken into their constituent pieces: protons and electrons. When electrons find routes into our atmosphere, they collide with and excite the atoms in the air. When these excited atoms release their energy, it is given out as light, creating the glowing \u2018curtains\u2019 we see as the aurora borealis (or the aurora australis in the southern hemisphere). Dayside proton auroral spots are caused by protons \u2018stealing\u2019 electrons from the atoms in our atmosphere.<\/p>\n
On 18 March last year, a jet of energetic solar protons collided with the Earth\u2019s atmosphere and created a bright \u2018spot\u2019 seen by NASA\u2019s IMAGE spacecraft, just as Cluster passed overhead and straight through the region where the proton jet was emanating. An extensive analysis of the Cluster results has now shown that the region was experiencing a turbulent event known as \u2018magnetic reconnection\u2019. Such a phenomenon takes place when the Earth\u2019s usually impenetrable magnetic field fractures and has to find a new stable configuration. Until the field mends itself, solar protons leak through the gap and jet into Earth\u2019s atmosphere creating the dayside proton aurora.<\/p>\n
Philippe Escoubet, ESA\u2019s Cluster Project Scientist, comments, \u201cThanks to Cluster\u2019s observations scientists can directly and firmly link for the first time a dayside proton auroral spot and a magnetic reconnection event.\u201d<\/p>\n
Tai Phan, leading the investigation at the University of California, Berkeley, United States, now looks forward to a new way of studying the Earth\u2019s protective shield. He says, \u201cThis result has opened up a new area of research. We can now watch dayside proton aurorae and use those observations to know where and how the cracks in the magnetic field are formed and how long the cracks remain open. That makes it a powerful tool to study the entry of the solar wind into the Earth\u2019s magnetosphere.\u201d<\/p>\n
The Earth\u2019s interaction with the Sun is a current focus of scientific attention because of its importance in knowing how the Sun affects the Earth, most notably our climate. Also, while not immediately dangerous to us on Earth, it is also important for quantifying the danger to satellites, which can be damaged or destroyed by powerful solar flares.<\/p>\n","protected":false},"excerpt":{"rendered":"
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