As you will have seen on our Facebook page, several interesting solar developments have taken place recently and they may bring some awesome auroral displays in the coming days (hopefully!). In this blog post, we’ll run through exactly what’s happened and why we’re excited. Updates in red.
M5 solar flare – 04 September 2017
A solar flare is a sudden explosion of energy from the sun. Unlike a coronal mass ejection (CME), however, they don’t carry any plasma (charged gas) with them and so they travel through the solar system at the speed of light. This also means that, while they can cause radio black-outs and GPS issues, they won’t generate any aurora.
An M5 solar flare was released from a region of the sun known as 2673. The term “M5” is just a way to describe how strong the flare is. The smallest flares are known as A-class, then increasing to B, C, M and X. Just as with the Richter scale for earthquakes, each class is 10 times stronger than the previous class. E.g., an X-class flare is ten times stronger than an M-class and 100 times stronger than a C-class. Each class also has a scale of 1 through to 9 to describe where the flare fits in that class.
G3 geomagnetic storm watch issued – 05 September 2017
A little while after we observed the M5 solar flare, we saw that the solar region 2673 had also produced a CME. Flares quite often do this – but not always! Based on their analysis of the imagery provided by the SOHO and STEREO satellites (which orbit much closer to the Sun than the Earth), the NOAA Space Weather Prediction Center predicted that the CME would produce a G3 geomagnetic storm.
A #SOHO loop of the September 4 2017 Earth directed full halo #solarstorm – actually 2? Speed estimates ~1500 km/s for the faster one. pic.twitter.com/LyslKvSH6I
— Christian Möstl (@chrisoutofspace) September 5, 2017
Like with the flares, the term “G3” describes how strong the geomagnetic storm is likely to be. This custom NOAA SWPC scale ranges from 1 (minor) through to 5 (extreme), with G3 being a “strong” storm, roughly correlating to Kp of 7. This means that aurora might be visible from much further south than usual – including much of the UK.
Direct hit! NASA prediction model shows #solarstorm launched today hits Earth late on September 6! Expect #hamradio, #GPS issues & #aurora! pic.twitter.com/40QNDh72nT
— Dr. Tamitha Skov (@TamithaSkov) September 5, 2017
Current predictions are that this CME will arrive late this evening (06 Sept) or early tomorrow morning (07 Sept). We will update with arrival time if and when we can!
Update (0811 07 Sept 17): The CME has arrived at DSCOVR early this morning at 0008 BST (2308 UTC 06 Sept 17). Unfortunately the Bz component of the its magnetic field is positive (“northward”) – and we need it to be negative (“southward”) for good aurora. We are now seeing periods of southward Bz but this CME has yet to produce much in the way of activity – and, of course, we are now into the daylight hours for Europe.
X2 flare – 06 September 2017
Earlier today (1010 BST, 0910 UTC) a large X2 flare was observed, again coming from region 2673. X-class is the largest class of flare and caused radio black outs for large parts of the polar regions. Again, flares themselves cannot cause aurora – so it remained to be seen if there was an associated CME.
#AR12673 shoots off an X2 class flare, first X-class since 2015! #exciting #solar #flare #spaceweather via @SolarMonitororg pic.twitter.com/GkWaqPayof
— Laura A. Hayes (@laura_hayess) September 6, 2017
X9 flare – 06 September 2017
Then bam! Shortly after today’s X2 flare, another massive flare is released. This one measures as an X9 flare – the highest the scale goes! This is the largest flare of this solar cycle (11-years) and occurred at 1302 BST (1202 UTC). The flare carried on causing the radio black outs we’d been seeing with its smaller sibling. Early signs were also promising, as the flare’s radio emissions hinted that a CME might have also been released with this flare.
X9 flare associated CME – expected arrival 1300 BST 08 September 2017
The latest images from the STEREO satellites show that at least one CME has been produced alongside today’s two sibling flares (probably from the X9). We currently await the verdict from NOAA SWPC about if and when it might arrive at Earth, and what geomagnetic storm conditions it might bring. If all goes to plan, we can assume that it will bring further auroral activity in ~48hours time (ish). Further updates to come!
Update (1632 BST 06 Sept 17): CME may be heading “south” of Earth, so might only be a “glancing blow” rather than a knock-out punch which may mean lower auroral activity than first anticipated unfortunately.
Great images from STEREO-A of the #solarstorm that went off with a X9 flare – very strongly southward directed, so maybe just glancing 🌏 https://t.co/toHEGP1yOU
— Christian Möstl (@chrisoutofspace) September 6, 2017
I feel I need to dampen #aurora expectations for 2 #solarstorms from Mon / Wed, both fast, but deflected south, L1 magnetic field likely low
— Christian Möstl (@chrisoutofspace) September 6, 2017
Update (1828 BST 07 Sept 17): Well all might not be lost for the CME associated with this flare! NOAA SWPC have issued a G3 watch for 08 and 09 September 2017. Latest computer simulation suggests an arrival time of around 1300 BST (1200 UTC) tomorrow (08 Sept) but arrival times are notoriously difficult to predict.
More flares follow – 07 September 2017
Update (1558 BST 07 Sept 17): Today has seen even more flares coming from region 2673, including several M-class and one X-class flare. We will have to wait and see if an Earth-directed CME was released with this latest flare (chances are slimmer as the region moves off towards the limb, or edge of visible region, of the Sun).
More to come?
Maybe! The joint NOAA/USAF forecast currently predicts a 75% chance of an M-class flare tomorrow and Friday (07 & 08 Sept). Perhaps there’ll be another CME associated with one of those! All this comes at a time when the Sun’s activity is supposed to be at it lowest – which makes this turn of events very interesting!
Remember, seeing the aurora is never guaranteed. Even if all other conditions are perfect, you’ll need clear, dark skies with a good view of the northern horizon. Keep an eye on our alerts for the latest info.
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