![]() Polar coronal holes are more frequent during solar minima. The low-latitude coronal holes display a similar butterfly pattern, in which they move closer to the equator over the course of the solar cycle. Latitude distribution of 2870 coronal holes (each marked by an x color indicates polarity), overlaid on the magnetic butterfly map of the Sun. The team used these data to produce a database of 3335 coronal hole predictions over nearly 40 years. Recently, a team of scientists led by Ken’ichi Fujiki (ISEE, Nagoya University, Japan) has developed an automated prediction technique for coronal holes that relies instead on magnetic-field data for the Sun, obtained at the National Solar Observatory’s Kitt Peak between 19. Coronal Holes Over Space and TimeĪutomated detection of coronal holes from image-based analysis is notoriously difficult. In these regions, the solar atmosphere escapes via these field lines, rapidly streaming away from the Sun’s surface in what’s known as the “fast solar wind”. These “coronal holes” manifest themselves as dark patches in X-ray and extreme ultraviolet imaging, since the corona is much hotter than the solar surface that peeks through from underneath it.Ĭoronal holes form when magnetic field lines open into space instead of looping back to the solar surface. Source of the Fast Solar WindĪs a part of the Sun’s natural activity cycle, extremely low-density regions sometimes form in the solar corona. ![]() This can trigger major changes in the currents, plasmas, and fields in the magnetosphere, resulting in beautiful auroras but also disruption to satellites and risks to power grids and pipelines on the ground.Coronal holes form where magnetic field lines open into space (B) instead of looping back to the solar surface (A). A geomagnetic storm occurs when a period of high-speed solar wind transfers significant energy into Earth's enclosing magnetic bubble, called the magnetosphere. 9, 2016, according to the Space Weather Prediction Center. The coronal hole seen in the animation above directed a stream of solar wind particles toward Earth, triggering a minor geomagnetic storm here on Friday, Dec. But the wind emanating from coronal holes can blow at twice that velocity. On average, the solar wind blows at a speed of about 1 million miles per hour (400 kilometers per second). That's because material in the corona is so hot, and therefore moving so energetically, that the Sun's gravity cannot hold on to some of it. SEE ALSO: What’s up with that huge dark hole in the Sun?Ĭharged particles spew from the corona all the time, creating the solar wind. The result: When the Sun is viewed in x-ray wavelengths, as it is above, we see a dark region, or "hole," in the corona. This allows charged particles to stream out at high speed, lowering the density and temperature of material in the parts of the corona where this occurs. Such holes occur in areas of the solar atmosphere, called the corona, where the Sun's magnetic field is open to space, rather than closed in on itself. Click on the screenshot above to bring up a video I posted to my Youtube channel showing all the action as seen by SDO between December 2nd and 9th. (Source: NASA SDO/) Over the past week, NASA's Solar Dynamics Observatory spacecraft watched a massive coronal hole rotate into view as the Sun spun on its axis. A coronal hole on the Sun, as seen by a NASA spacecraft between Dec.
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