A dark coronal hole at the Sun center was captured in extreme ultraviolet light by National Aeronautics and Space Administration’s (NASA) solar dynamics observatory on Jan. 10.
Coronal holes are areas of the Sun's surface that are the source of open magnetic field lines that head way out into space. They are also the source regions of the fast solar wind, which is characterized by a relatively steady speed of about 800 kilometers per second.
As the Sun continues to rotate, the high speed solar wind particles blowing from this hole will likely reach Earth in a few days and may spark some auroral activity, according to NASA.
Here, the solar dynamics observatory detected a giant solar filament that became unstable and erupted from the far side of the Sun. A filament is a large, bright feature extending outward from the Sun's surface, often in a loop shape. Some filaments break apart and give rise to coronal mass ejections.
Forecasters at the Geophysical Institute of University of Alaska, Fairbanks expect auroral activity to be moderate on Friday, Jan. 14 and Saturday, Jan. 15. Weather permitting, moderate displays will be visible overhead from Barrow to as far south as Talkeetna and visible low on the horizon as far south as Bethel, Soldotna and southeast Alaska.
National Oceanic and Atmospheric Administration (NOAA) forecasters said solar activity remained very low with occasional low-level B-class flares and geomagnetic field activity at quiet levels.
NOAA space weather prediction center issued a 3-day solar-activity forecast on Jan. 11 at 10:00 pm UTC, saying solar activity is expected to be very low through Jan. 14.
The center expects the geomagnetic field to be mostly at quiet levels on Jan. 12 and 13, but it may increase to quiet-to-unsettled levels with a chance for brief active levels on Jan. 14 as a recurrent coronal high-speed stream becomes geo-effective.
Aurora: How it works?
Auroras can be spotted throughout the world and on other planets too. They are more visible nearer the poles due to the longer periods of darkness and the magnetic field.
Auroras are more frequent and brighter during the intense phase of the solar cycle when coronal mass ejections increase the intensity of the solar wind. The last solar maximum was in 2000. The next peak is expected by NASA scientists in 2013.
The sun, which is our main source of light, also gives off particles, consisting mostly of electrons and protons. Sunlight takes about 8 minutes to travel from the sun to the Earth (the speed of light is constant and equals 300,000 kilometers per second).
The solar particles make up what we call the solar wind that blows outward from the sun from about 250 kilometers per second to 2,500 kilometers per second. Thus, it takes the solar wind particles from 17 hours to 7 days to travel the 150 million kilometers to reach the Earth.
The solar wind carries with it the sun's magnetic field. Increased solar wind velocity and particle density associated with the solar particle sources act in two ways to connect the solar wind to the Earth's magnetic field.
The sun's magnetic field joins with the Earth's magnetic field and transfers the solar particles to the Earth's magnetosphere. The electrons and protons are separated by the Earth's magnetic field to produce a giant electric field that generates the power for the aurora. Thus, following the solar wind is important to forecasting the aurora.