According to the various solar/geomagnetic data (collected in one convenient place by SolarHam.com; I actively support them with contributions), we are currently experiencing minor geomagnetic storming. This is likely being caused by a combination of a favorably-oriented local interplanetary magnetic field, as well as an enhanced wind stream from a coronal hole.
|This is a Solar Dynamics Observatory image |
from 23 August 2016. It depicts the coronal holes
on that date (yesterday). Holes were numbered by
SolarHam. Coronal Hole #07 likely produced the
solar wind stream creating the current geomag storming.
The planetary K-index is a NOAA Space Weather Prediction Center (SWPC) product created using magnetometers around the world. According to the SWPC, "The K-index quantifies disturbances in the horizontal component of earth's magnetic field with an integer in the range 0-9 with 1 being calm and 5 or more indicating a geomagnetic storm. It is derived from the maximum fluctuations of horizontal components observed on a magnetometer during a three-hour interval. The planetary 3-hour-range index Kp is the mean standardized K-index from 13 geomagnetic observatories between 44 degrees and 60 degrees northern or southern geomagnetic latitude. The label 'K' comes from the German word 'Kennziffer' meaning 'characteristic digit.' The K-index was introduced by Julius Bartels in 1938. SWPC has used the K-index since the forecast center began operations."
Any time the K-index reaches 5, geomagnetic storming is occurring. We have been experiencing K=5 for at least 9 hours at the time of this writing.
|K-index graph captured as of approximately 10:25pm CDT, 23 Aug 2016.|
The higher the K-index, the farther away from the geomagnetic poles the aurora can be seen, and the more effects can be seen. Generally coronal hole wind streams produce only minor storming; it takes a moderate to strong coronal mass ejection (CME) impact to reach the upper levels of the K-index.
|The NOAA SWPC Geomagnetic Storm Scale.|
We are currently experiecing a G1 Minor geomagnetic storm.
It takes something around an X-class flare producing a large, strong CME to hit an 8-9 on the K-index scale, and that's up around Carrington-event class. So we aren't going to have anything like that, but higher latitudes might have a nice aurora tonight or the next few nights.
Here are maps (posted to SolarHam, but obtained from NOAA SWPC) that will show you where aurorae are possible. Find the line marked Kp=5 for our current condition, then look from that line poleward. If you are in that region, keep a watch out for aurorae. If you are near but outside the region, keep an eye peeled poleward, just in case.
|K-index map of North America.|
|K-index map of South America/Antarctica.|
|K-index map of Eurasia.|
|K-index map of Australia/extreme South Pacific.|