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Early September Aurora Lights Up The Sky

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Northern Lights Now – A long duration geomagnetic display gave aurora hunters a treat on the first three nights of September. Space weather conditions, under the influence of a large coronal hole on the Sun, were favorable for aurora borealis from late August 31st through September 3rd. KP reached G2 (moderate) storming levels for four 3-hour periods during that time. Strong storming is expected to continue for another 6-12 hours

Storm Origins

September’s solar storm was caused by strong solar wind buffeting Earth. The solar wind is the stream of charged particles constantly flow outward from the Sun into the Solar System. At Earth, that stream travels at about 350-400 km/s under normal conditions. This weekend it has been flowing at 600-750 km/s. The magnetic fields of those particles interact with, and push on, the magnetic fields of Earth. Solar wind becomes enhanced as the result of CMEs or when coronal holes are pointed towards Earth.

The current enhanced solar winds are from a very large coronal hole in the northern hemisphere of the sun. It is visible as the dark area from AIA211 images taken by the SDO satellite:

Large Coronal hole pointed towards Earth on August 31st
Large Coronal hole pointed towards Earth on August 31st

Long durations

Also visible in the above photograph is the longitudinal extent of the hole. As the Sun rotates, it takes about 14 days for a feature to move from the east lime (left side) to the west limb, the different portions of the hole are pointed towards earth. The longer portions of the hole are pointed towards Earth, the longer high solar wind speeds will impact earth and the longer the potential storm is. In today’s DSCOVR solar wind chart, notice that wind speeds have now been above 500km/s for over 48 hours, and above 650 km/s for over 6 hours:

Solar wind speeds have been strong for over two days
Solar wind speeds have been strong for over two days

The result of that long duration wind stream has been an epic solar storm. Over the last three days there have been four 3-hour periods where Boulder KP readings exceeded G2 storm levels, nine periods exceeded G1 levels and just 4 periods of KP less than three.

Three days of extrodinary aurora storming as measured by SWPC in Boulder Co.
Three days of extrodinary aurora storming as measured by SWPC in Boulder Co.

The Good Stuff

Below find several of our favorite tweets of pictures from this storm

A back of cam pic from the beginning of the storm in Finland:

The next night in Wisconsin:

Tasmania!

This Full sky display from over Lake Superior:

And of course, this author went out hunting in Colchester VT because we had clear skies:

More To Come

The official forecast shows this storm slowly decreasing in strength over the next 6-12 hours. There is still plenty of possibility for yet another night of display for Europe and the Eastern half of N. America. As long as wind speeds main enhanced, any disturbance traveling on the high speed wind stream could set off another substorm.

Happy Hunting

Coronal Hole High Speed Stream Now Impacting Earth – Live Updates

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Northern Lights Now – The Coronal Hole High Speed Wind Stream (CH HSS) that prompted the Jan 6, 2016 G1 #aurora watch started arriving at Earth just past Midnight GMT On Jan 6. Rather than updating the original article, NLN will be posting updates to this blog post instead, please come back soon for more updates!

13:44 UTC January 7, 2015 (08:45AM EST)

Solar winds are now gradually subsiding. This period shows too much variability in the Bz to produce wide-spread aurora.

23:45 UTC January 6, 2015 (18:15PM EST)

Around 21:45 UTC the Bz shifted softly to the south with measurements in the -2 to -4nT range at the ACE satellite. This is very mildly south, but it lasted for about 75 minutes. It was enough to start an aurora show in Finland. Here’s a skycam framegrab taken from the Sodankylä Geophysical Observatory from about an hour after the negative Bz was measured at Earth:

Aurora skycam from Sodankylä Geophysical Observatory in Finland
Aurora skycam from Sodankylä Geophysical Observatory in Finland

17:15 UTC January 6, 2015 (12:15PM EST)

Solar wind speeds have decreased slightly over the last 12 hours to around 525-550 km/s. In the last 2 hours readings have become more volatile. The Bz has stayed consistently north. As such, there have not been any signs of aurora. It is still possible that any transients or small CMEs traveling along the wind stream could push the Bz one way or the other. If that happens, there will be about 45 minutes of lead time.

04:15 UTC January 6, 2015 (11:15PM EST)

Just after midnight UTC solar wind speed started increasing. Reading moved up from 450km/s to 625km/s at the same time there was a 90 minute period of south point Bz. Together, these events pushed ground based KP monitors to register a KP of 4.67 (G1) for the 00:00 – 03:00 period. Wing KP responded by over-estimating the predicted 60 minute KP with a reading of 5.67 even though the Bz subsequently shifted to the north. The is expected to be a long duration high solar wind speed event, so there are ample opportunities for more aurora over the next 24-36 hours. Here’s the ACE data from SWPC with the increase in wind speed annotated:

Annotated ACE satellite date show increase in solar wind speed around midnight UTC
Annotated ACE satellite date show increase in solar wind speed around midnight UTC
WingKP registered a short term forecast of KP=5.67 around 03:45 UTC which was likely an over-estimate of actual conditions
WingKP registered a short term forecast of KP=5.67 around 03:45 UTC which was likely an over-estimate of actual conditions

Through this, there was a brief period where we’d have expected to see Aurora at lower latitudes. During that window this tweet came in from Scotland marking the first photographed aurora from this storm: