I've been aware of and watching solar Coronal Mass Ejections for years, but something I've never heard of, called a "Cannibal CME," arrived late on November 3rd Coordinated Universal Time (UTC) according to SpaceWeather.com. 20:00 hours UTC is 4:00 PM EDT. It kicked off a geomagnetic storm.
CME IMPACT SPARKS STRONG GEOMAGNETIC STORM: A cannibal CME, described below, hit Earth's magnetic field on Nov. 3rd at approximately 20:00 UT. Solar wind data from the DSCOVR spacecraft show a stairstep structure indicative of two or more CMEs pressed together. A strong G3-class geomagnetic storm is underway now.
The clue to what exactly a cannibal CME is can be found in that line about the DSCOVR spacecraft. A cannibal CME is the second CME after a first ejection that travels faster than the first and slams into it, enlarging the mass in the ejection. The resulting mix of CMEs contains tangled magnetic fields and compressed plasmas that can do a good job sparking geomagnetic storms. The graph they're referring to in that paragraph is this:
Cycle 25 has been off to a faster and stronger start than predicted, and activity is above the predicted levels, which can be seen here.
The current (21:00 EDT November 3rd; also called 0100 UTC November 4th) solar-terrestrial indices are Solar Flux Index 94. A index 21 and K index 7. The sunspot number is 42. The A and K indices show that a solar storm is taking place, and it's rated at G3. That's not a particularly dangerous storm down here on the surface of the planet, although it can affect satellites. Solar Flares are rated by an alphabetical scale, with the lowest intensity flares rated A1 and the as intensity goes up, they go through A2 to A10 before becoming B1 flares. The pattern repeats through B, and then C before progressing to M level flares. Finally, as M is used up, we get to X class flares. The flare behind this CME was a low M class flare: M1.7.
These solar flares and mass ejections are not very intense and only people who are playing in the HF radio spectrum (or using it professionally) are likely to notice anything. The auroral oval hasn't come far south in the country. Once or twice in a strong solar cycle, a flare might happen that will cause aurora displays as far south as Florida. To get auroras into the deep south requires X9 flares or stronger and they have to point directly at the planet. That's a rare combination and I'm aware of only once in my life that auroras were visible into Florida.
The wild card in that assessment of impact is that Earth's magnetic field is going through some changes. The magnetic field protects us from some of the energetic particles a mass ejection throws into space. If the field is weakening, that will affect what gets through.
The bright spot almost exactly in the middle of the sun is the November 2nd CME that started this.
We know that Earth's magnetic field has gone through changes in the past and that magnetic north wanders a bit. Do we know what caused the BIG changes - not just a weakening, but a flip?
ReplyDeleteNot that I know of.
DeleteWe know that movements of the poles happen with some regularity. Having some knowledge of how they determine the time when the poles flipped, I don't see how they could determine if the poles wandered lots - like 30 to 45 degrees - and then wandered back in a short span of time ("short" to geologists, like a human lifetime). Since we're dealing with fluid mechanics here, my guess is that some times the poles are doing their wandering and some sort of change of state happens and it goes from the one stable state to the other with north and south reversing.
There's a guy on YouTube who's favorite topic is a roughly 12,000 year cycle of catastrophes and a cyclic magnetic field weakening is one of things he pushes. Is he right? I don't know.
I can tell you that HF propagation started to die in a hurry about 2030 EDT last night. I was playing FT8 and had a pipeline to California (from North Carolina) on 17m. 17 died and I moved to 20, which quickly died. Moved to 30 and it died. By 2050 I was on 40 and it died about 2100. Amazing thing to see in action.
ReplyDeleteSounds like what's commonly called a Sudden Ionospheric Disturbance (SID). They're primarily from the D layer of the ionosphere getting too dense, and shut down from the highest frequencies down to the lowest.
DeletePretty common in geomagnetic storms, so I should have mentioned that.