London: Scientists have captured the sharpest ever images of the Sun's outer atmosphere, using an innovative new camera on-board a sounding rocket. An international team of scientists discovered fast-track 'highways' and intriguing 'sparkles' that may help answer a long-standing solar mystery.
Researchers used a sounding rocket to launch the NASA High Resolution Coronal Imager (Hi-C) which obtained images of the solar atmosphere (the solar corona) five times sharper than anything seen before and acquired data at a rate of about one image every five seconds.
The new camera observed the Sun in extreme ultraviolet light and focused on a large, magnetically-active sunspot region. Images from Hi-C reveal a number of new features in the corona, including 'blobs' of gas ricocheting along 'highways' and bright dots that switch on and off rapidly which the group call 'sparkles'.
In the new images, small clumps of electrified gas (plasma) at a temperature of about one million degrees Celsius are seen racing along highways shaped by the Sun's magnetic field, researchers said.
These blobs travel at around 80 km per second - the equivalent of 235 times the speed of sound on Earth. The highways are 450 km across. The flows of material are inside a so-called solar filament, a region of dense plasma that can erupt outwards from the Sun. These eruptions, known as coronal mass ejections (CMEs),
carry billions of tonnes of plasma into space. If a CME travels in the right direction it can interact with Earth, disturbing the terrestrial magnetic field in a 'space weather' event that can have a range of destructive consequences from damaging satellite electronics to overloading power grids.
The discovery and nature of the solar highways allows scientists to better understand the driving force for these eruptions and help predict with greater accuracy when CMEs might take place.
Another new set of images could help explain why, with a temperature of two million degrees, the corona is around 400 times hotter than the solar surface. Hi-C images reveal dynamic bright dots which switch on and off at high speed.
These 'sparkles' typically last around 25 seconds, are about 680 km across and release at least 1024 Joules of energy in each event. The sparkles are thus a clear signal that enormous amounts of energy are being added into the corona and may then be released violently to heat the plasma.
"The camera is effectively a microscope that lets us view small scale events on the Sun in unprecedented detail. For the first time we can unpick the detailed nature of the solar corona, helping us to predict when outbursts from this region might head towards the Earth," said Robert Walsh Director of Research at University of Central Lancashire (UCLan). The findings will be presented at the Royal Astronomical Society (RAS) Meeting in St Andrews, Scotland.
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