Coronal holes appear as dark areas in the solar corona in extreme ultraviolet EUV and soft x-ray solar images. They appear dark because they are cooler, less dense regions than the surrounding plasma and are regions of open, unipolar magnetic fields.
This open, magnetic field line structure allows the solar wind to escape more readily into space, resulting in streams of relatively fast solar wind and is often referred to as a high speed stream in the context of analysis of structures in interplanetary space. Coronal holes can develop at any time and location on the Sun, but are more common and persistent during the years around solar minimum. The more persistent coronal holes can sometimes last through several solar rotations day periods.
Coronal holes are most prevalent and stable at the solar north and south poles; but these polar holes can grow and expand to lower solar latitudes.
It is also possible for coronal holes to develop in isolation from the polar holes; or for an extension of a polar hole to split off and become an isolated structure. Coronal holes in the Sun's atmosphere from an ultraviolet image taken in January Coronal holes are areas in the Sun's atmosphere that appear dark in X-ray and ultraviolet images of the Sun. The plasma electrified gas in these regions of the Sun's corona it's upper atmosphere is cooler and more dense than in other parts of the corona.
In most places on the Sun , magnetic field lines loop back onto the Sun's surface. Plasma in those regions flows along the field lines, giving rise to features like coronal loops and solar prominences.
When solar wind collides with Earth's magnetic field. Image courtesy: National Geophysical Data Cantre. Heard of the aurora borealis? This natural and spectacular phenomenon that takes place on the north and south poles are also caused by the solar winds interacting with the Earth's magnetic field and the oxygen and nitrogen ions trapped in it. The moon does not have a magnetic field and is exposed and absorbs any and all radiation that comes its way.
The only protection it has is from small magnetic rocks on its surface that provide the lunar surface with small, localised pockets of protection from these winds. Similar to human beings getting a sunburn from staying outside for too long, the moon also gets a kind of sunburn. Instead of looking splotchy and red like we do, the moon gets swirls on its surface. Scientists also believe that solar winds could be one reason why the moon has water-ice on its surface.
Studying the effects of solar winds can also help space agencies find the best way to protect its astronauts , from radiation, when they travel to the moon and beyond. They can suffer serious health issues if they are caught in the path of a solar storm without sufficient protection. Different space agencies also send their satellites, spacecrafts, and other research missions to space and it is also important that they can are protected and that they are made from materials that can stand the rigours of space.
By studying solar winds, researchers can develop protective gear or materials that can withstand the high levels of radiation. The SDO just completed its 10th year in space even though its original mission life was for five years.
Throughout its time in space, the SDO has been constantly looking at the Sun to understand space weather and its effects it has on Earth.
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