July 24, 2014
Although it is at the solar maximum, the Sun is unusually inactive, keeping its number of sunspots at minimum. This shows us that in spite of decades of solar weather forecasting, we still don’t have enough knowledge about our star to predict its behaviour.
The Sun's photosphere, pictured by NASA's Solar Dynamics Observatory (SDO), with very few spots. July 22. Credit: NASA/SDO
The Sun is currently at the peak of its activity, also known as solar maximum. In this period, it emits high amounts of solar material and electromagnetic radiation through phenomena known as coronal mass ejections and solar flares. When this hot material in Sun’s chromosphere and photosphere is ejected, it makes the cooler (but still very hot) material below visible.
These regions are known as sunspots and they appear dark in contrast to hotter surrounding material, indicating the most active regions of our star. By observing the number of sunspots, astronomers can tell if the Sun is active or not.
The Sun reaches the solar maximum every 11 years and at that time, sunspots are most frequent. During the last week, however, the Sun was nearly spotless, indicating very low activity in the middle of the solar maximum.
"It is weird, but it’s not super weird," said astronomer Dr. Tony Phillips of spaceweather.com. "To have a spotless day during solar maximum is odd, but then again, this solar maximum we are in has been very wimpy."
Although we’ve learned a lot about the Sun in the last couple of decades, it is a relatively short period to solve all of its riddles. We are fairly certain in predicting when the solar maximum will occur, because since earliest observations, periods with increased number of sunspots have come and gone every 11 years. Quiet periods during the solar maximum are not unheard of, but they make us wonder how much do we actually know about our star.
"It all underlines that solar physicists really don’t know what the heck is happening on the Sun," said Dr. Phillips. "We just don’t know how to predict the Sun, that is the take away message of this event."
After stormy couple of months at the beginning of this year, solar inactivity is good news for radio communications on Earth, as well as for satellites in orbit. Protons, electrons and electromagnetic radiation are ejected at high velocities and if they hit the Earth, they can disrupt our satellites. Earth’s magnetic field and atmosphere protect living organisms, but there can be disruptions in radio communication due to disturbances in ionosphere.