Dec 29, 2016

A Hole in the Sun Could Unleash New Year's Fireworks

Like watching an ominous storm brew on the horizon, solar astronomers have spied a large coronal hole emerge deep inside the sun's magnetized atmosphere (known as the corona), signalling that turbulent space weather is possibly headed our way. But don't prepare your tornado shelters or board up your windows, this kind of storm will have minimal impacts on the ground and could actually generate some timely auroral fireworks to kick of 2017 in style.

As reported by, NASA's Solar Dynamics Observatory (SDO) has been tracking a dark region in the sun's lower corona rotate into view. Coronal holes are associated with streams of fast-moving superheated plasma that emerges from the sun's interior and then accelerated into space, following magnetic fields that reach from the lower corona and flow out into interplanetary space.

As the sun rotates, it sweeps magnetic streams out into the solar system, like a spinning garden sprinkler, sending these high-energy particles along with it as the fast solar wind. The sun also sweeps out slow-moving streams of plasma (the slow solar wind), which can create a barrier to these fast streams. The regions where these two streams interact are known as co-rotating interaction regions (CIRs) and they are known to cause plasma to "bunch up", creating dense flows of shocked plasma. And as we are basically staring into a fast stream's sprinkler's head, a CIR is likely on its way.

The SDO observes the sun's hot atmosphere through many different filters that are sensitive to different wavelengths of light. Each wavelength represents a different plasma temperature and in the observation above, the SDO is looking at plasma that is glowing at a temperature of 2.25 million Fahrenheit (1.25 million Kelvin). At this wavelength, coronal holes become obvious — they appear dark as the density of plasma is very low (as the particles are being lost to space very quickly); bright regions are dense with plasma at this temperature as they are trapped in closed magnetic field lines, features known as coronal loops.

Typically, solar wind particles in fast streams coming from coronal holes take a couple of days to travel from the sun to the Earth, so by using these SDO observations, solar physicists can make predictions as to what might happen when a CIR washes over Earth. Although we can expect more dramatic impacts if the sun unleashed an explosive event, like a coronal mass ejection or solar flare, CIRs are known to intensify space weather conditions, likely sparking auroras.

When solar particles hit our planet's powerful magnetic field, these electrically charged particles (known as ions) are deflected by the global magnetosphere and channeled to polar regions where Earth's magnetic field passes into the planet's crust. When a solar storm hits, these particles rain through the Earth's atmosphere at high latitudes, hitting atmospheric gases. This is when the magic happens. As solar plasma hits the atmosphere, light is produced. This light is known as the aurora. And as we are seeing this coronal hole emerge now, it could mean auroral activity on New Year's Eve.

Read more at Discovery News

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