As you go about your day, especially during the hot summer season, you probably don’t think much about the Sun other than that it makes you want to go for a quick dip in the swimming pool to cool off. After all, the Sun rises and sets every day (for those of us outside the Arctic and Antarctic Circles), and people just take it for granted without much thought.
The Sun is far more dynamic than you might think, although thankfully we don’t usually feel direct effects of its activity from Earth’s surface. The atmosphere and magnetic field of the Earth provide a nice buffer zone that protects us.
Every 11 years, the Sun completes a cycle that is fairly regular. During solar maximum, the number of sunspots is higher than usual, and during solar minimum (which we are just coming out of), it is relatively spot free.
The Sun is still coming out of solar minimum, but activity is slowly returning. At about 8:55 UTC on August 1, a measurable solar flare triggered an event known as a coronal mass ejection (CME). This is where the “atmosphere” of the Sun sends out a burst of energized plasma. In this case, nearly the entire Earth-facing side of the Sun was involved, so effects on the Earth are more likely. Here’s the X-ray signature of the solar flare that triggered the CME:
Although not particularly powerful by historical standards, it is a sign of the Sun’s increasing activity (due to peak in 2013). We won’t know until on or about August 3 whether the plasma (which typically takes several days to reach us) will have any effect (e.g. auroras). Depending on the orientation of the interplanetary magnetic field, it could bounce right off and not affect us. Or it could be oriented just right and funnel down the magnetic field of the Earth and cause the atmosphere to light up in a nice auroral display. If the z-component of the interplanetary magnetic field (IMF) is negative, it points strongly south, and this would be favorable to an auroral display. It would be like opening the window to the solar plasma. The image below shows how the z-component of the IMF looked as of this writing.
Now all we can do is wait. Watching the 3-hour Kp index when the plasma arrives will give an indication of the state of the Earth’s magnetic field. Values of 7 and higher mean likely auroras for Chicago (assuming it’s dark when this happens; otherwise you won’t see anything). The higher the value, the farther south the aurora can be seen. The image below shows how the Kp index looked as of this writing.
Even if it bounces off the magnetic field, we’ll probably see spikes in the solar wind values. The image below shows how the solar wind was behaving at the time of this writing.
This event is just a taste of things to come as we approach 2013′s solar maximum. Even if this event doesn’t produce any visible effects, sunspots are on the rise and they bring with them strong magnetic fields and lots of dynamic activity. Now you can use Wolfram|Alpha to track this activity and not be caught unaware.