Unspecified geomagnetic activity

[cgrant26]

Tamitha Skov's latest Solar Storm Forecast just came out. She's thinking the Western directed CME from the 4th may give us a glancing blow due to the higher solar wind speed from the CH that's been facing us the last week or so. The prediction is mid day today through tomorrow for high to maybe mid latitude aurora. Fingers crossed!

 

 

[Philalethes]

2 hours ago, cgrant26 said:

Tamitha Skov's latest Solar Storm Forecast just came out. She's thinking the Western directed CME from the 4th may give us a glancing blow due to the higher solar wind speed from the CH that's been facing us the last week or so. The prediction is mid day today through tomorrow for high to maybe mid latitude aurora. Fingers crossed!

I'm not sure I entirely agree with her reasoning about the fast Solar wind. I've mentioned Bernoulli's principle before in similar contexts, and while there probably are some reasons why it doesn't apply perfectly to Solar wind (e.g. being somewhat compressible and electromagnetic effects) I believe the main principle still stands, i.e. that an increase in speed leads to a decrease in static pressure (the pressure exerted perpendicular to the direction the fluid is flowing); and in fact, that the Solar wind is indeed somewhat compressible and that the fast wind has a lower density than the slow one should, if I'm not entirely mistaken, only serve to exacerbate that effect.

So in other words, as far as I can tell the fast wind will do the opposite in that position, and actually lead to less deflection of the CME than if it were plain old slow wind. I do however agree that Solar wind in general will indeed tend to deflect CMEs in that direction if the CME is fast enough (presumably due to similar reasons as above, i.e. that this would mean less static pressure on the Solar wind beside it), but for slow ones the opposite can be the case. Here's a paper discussing this to some extent; quoting from the abstract:

Quote

Under the effect of the Parker spiral magnetic field, a fast CME will be blocked by the background solar wind ahead and deflected to the east, whereas a slow CME will be pushed by the following background solar wind and deflected to the west. The deflection angle may be estimated according to the CMEs'' transit speed by using a kinetic model. It is shown that slow CMEs can be deflected more easily than fast ones. This is consistent with the observational results obtained by Zhang etal. (2003), that all four Earth-encountered limb CMEs originated from the east. On the other hand, since the most of the EFHCMEs are fast events, the range of the longitude distribution given by the theoretical model is E40,W70, which is well consistent with the observational results (E40,W75).

Given that this did not appear to be a halo CME and didn't seem that fast, I'd say that makes it less likely, and if what I've mentioned so far about the change in pressure is in fact true then you'd expect that to lead to it being even less likely.

But I could certainly be wrong (maybe there's something about fluid dynamics in general or the Solar wind in particular I'm missing), and/or the CME could end up hitting us anyway. Just sharing what I think based on my understanding of a simple model of the physics involved.

Edited June 7, 2023 by Philalethes
typo

[Jesterface23]

Guess what happened to arrive at L1. Certainly not expecting much though.

I wouldn't expect velocities near 400km/s even.

[Philalethes]

9 hours ago, Jesterface23 said:

Guess what happened to arrive at L1. Certainly not expecting much though.

I wouldn't expect velocities near 400km/s even.

Yeah, looks to me like a glancing blow; at least I don't even see any clear flux rope signature (yet). The speed does indeed seem to be very low too.

[Philalethes]

This is from the CH that just passed us I take it? HSS entry?

I noted a few days ago when someone posted on Twitter about a couple of CHs that this CH had a negative polarity, and thus that it would come with an IMF toward the Solar surface, which as per the R-M effect discussed earlier would lead to increased likelihood of a negative Bz (only marginally at this part of the year, but still visibly as per the charts in the paper). The Bz isn't that stable, but the phi angle does indicate that that the Bx and By of the IMF are indeed pointing in the expected directions.

Edit:

Looks like the IMF direction isn't as stable as I would have assumed; maybe it will stabilize more deeper into the HSS.

Edited June 15, 2023 by Philalethes
grammar

[Jesterface23]

It looks to be. The HSS/CIR transition began around /15 14:00Z. Hard to say if the CIR ended yet

[Philalethes]

32 minutes ago, Jesterface23 said:

It looks to be. The HSS/CIR transition began around /15 14:00Z. Hard to say if the CIR ended yet

It's certainly interesting how the density is fairly high for those speeds, I would also have guessed that that might signify a transition between the two since the HSS itself usually comes with lower density from what I can remember having seen in the past, but maybe there's more variance there than I'm aware of.

At least it leads to quite a bit of flow pressure as discussed earlier, and a good amount of energy being dumped into the magnetosphere whenever the Bz connects. Turns out the constants in the formula could be simplified to 2*10^(-6), so multiplying that by density and velocity squared leads to a pressure of ~3.7 nPa, roughly half of what seemed to be typical for larger storms. Of course the Bz is also relevant, but the higher the pressure, the less Bz is needed (although it might not be a linear relation).

And now the Bx and By do seem to have stabilized around where was expected, but perhaps this isn't necessarily as indicative of the Bz in a HSS as it would be from the regular slow wind.

Also, G2, pretty cool how these well-placed CHs can really stir things up, even this close to the solstice.

[Isatsuki San]

12 minutes ago, Philalethes said:

It's certainly interesting how the density is fairly high for those speeds, I would also have guessed that that might signify a transition between the two since the HSS itself usually comes with lower density from what I can remember having seen in the past, but maybe there's more variance there than I'm aware of.

At least it leads to quite a bit of flow pressure as discussed earlier, and a good amount of energy being dumped into the magnetosphere whenever the Bz connects. Turns out the constants in the formula could be simplified to 2*10^(-6), so multiplying that by density and velocity squared leads to a pressure of ~3.7 nPa, roughly half of what seemed to be typical for larger storms. Of course the Bz is also relevant, but the higher the pressure, the less Bz is needed (although it might not be a linear relation).

And now the Bx and By do seem to have stabilized around where was expected, but perhaps this isn't necessarily as indicative of the Bz in a HSS as it would be from the regular slow wind.

Also, G2, pretty cool how these well-placed CHs can really stir things up, even this close to the solstice.

Yes, but I was surprised by the g2

[Isatsuki San]

It seems that the cme of the solar flare x did hit the magnetic field giving an indirect hit to the earth but the bt magnetic field is at 12 and the bz is to the south for now the activity is in kp4 maybe we will see a kp 5 for him bz to south but nothing else

[Philalethes]

22 minutes ago, Isatsuki San said:

It seems that the cme of the solar flare x did hit the magnetic field giving an indirect hit to the earth but the bt magnetic field is at 12 and the bz is to the south for now the activity is in kp4 maybe we will see a kp 5 for him bz to south but nothing else

It's a bit strange if it's the X-flare, as it happened ~100 hours ago, so for that to check out it'd need an average transit speed of ~420 km/s, and likely much slower upon arrival. I won't say anything conclusive, there could be something I haven't thought of, but I'm not sure to what extent that's possible. I suppose it'd have to be some very slow-moving component of it. Space weather is clearly very complicated, so maybe my simplistic assumptions just aren't checking out.

That being said, it does look like the signature of a flux rope on the magnetic field, at least that's what I associate that sweeping movement of the various components of it with. From looking at a diagram of the various flux rope configurations I would guess it looks like a WSE rope. I could be completely wrong about all of that, though, so take it all with a big chunk of halite.

Would be great with input from others on this for sure.

[Jesterface23]

There seems to be 2 possibilities of a CME about a day apart and looking at ACE as the primary satellite. I can't say for certain if either are CMEs though. We are in a long and weaker looking CH from SDO's AIA 211 imagery going back a few days.

Edited June 24, 2023 by Jesterface23

[Philalethes]

Ah, yes, nothing like some geomagnetic activity in the middle of the day in the middle of summer.

[CapeCodShade]

Why am I seeing University of Alaska Fairbanks predicting KP 4+ on June 12/13? Also seeing news stories about Aurora next week visible from Maryland??!!

https://www.gi.alaska.edu/monitors/aurora-forecast

News story about July 12 lights

Another news story claiming lights will be visible in Indiana July 12/13

Are they just following the NOAA 27 day outlook issued on July 3 that predicts KP 5 conditions on these dates? NOAA July 3 Outlook

Edited July 8, 2023 by CapeCodShade
Added more info/additional question

[Jesterface23]

5 hours ago, CapeCodShade said:

Are they just following the NOAA 27 day outlook issued on July 3 that predicts KP 5 conditions on these dates? NOAA July 3 Outlook

Probably. The SWPC does have Kp5-6 here, https://www.swpc.noaa.gov/products/weekly-highlights-and-27-day-forecast, just not on the other page for some reason. In the other file the Ap values are different, but Kp values are the same, so maybe that has something to do with it.

[tniickck]

On 7/7/2023 at 1:53 PM, Philalethes said:

Ah, yes, nothing like some geomagnetic activity in the middle of the day in the middle of summer.

btw in Moscow it should be at night so if anything extraordinary happens i will see it xd

[Sam Warfel]

On 7/8/2023 at 6:42 AM, CapeCodShade said:

Why am I seeing University of Alaska Fairbanks predicting KP 4+ on June 12/13? Also seeing news stories about Aurora next week visible from Maryland??!!

https://www.gi.alaska.edu/monitors/aurora-forecast

News story about July 12 lights

Another news story claiming lights will be visible in Indiana July 12/13

Are they just following the NOAA 27 day outlook issued on July 3 that predicts KP 5 conditions on these dates? NOAA July 3 Outlook

The old 27-day forecast had KP6, due to a CH from last rotation, and for some reason the news picked up on that and decided to make it into something it's not.  We can see now the CH has closed up, and don't expect any storming from that source anymore.

[CapeCodShade]

31 minutes ago, Sam Warfel said:

The old 27-day forecast had KP6, due to a CH from last rotation, and for some reason the news picked up on that and decided to make it into something it's not.  We can see now the CH has closed up, and don't expect any storming from that source anymore.

In a twist of fate we may well get geomagnetic storms on July 13 after all thanks to the recent CME’s haha. A cruel universe may vindicate our sensationalistic media **shakes fist at sky**.

Edited July 11, 2023 by CapeCodShade
Said June instead of July by accident :P

[Philalethes]

On 7/11/2023 at 5:17 AM, CapeCodShade said:

In a twist of fate we may well get geomagnetic storms on July 13 after all thanks to the recent CME’s haha. A cruel universe may vindicate our sensationalistic media **shakes fist at sky**.

Heh, I noticed that; we'll see tonight if there's any activity, would definitely be misleading for a ton of people who have gotten the impression that you can forecast aurorae weeks in advance (well, large recurring CHs are probably the best guess for that, this one just happened to close).

[Jesterface23]

The CME from the 11th has arrived at L1

Maximum velocities may reach around 500km/s.

[tniickck]

Space Weather Message Code: WARSUD
Serial Number: 204
Issue Time: 2023 Jul 14 1551 UTC

WARNING: Geomagnetic Sudden Impulse expected
Valid From: 2023 Jul 14 1549 UTC
Valid To: 2023 Jul 14 1654 UTC
IP Shock Passage Observed: 2023 Jul 14 1526 UTC

NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation

hopefully it will reach G1

[Philalethes]

39 minutes ago, Jesterface23 said:

The CME from the 11th has arrived at L1

Maximum velocities may reach around 500km/s.

Nice. This should be the sheath first, no? Doesn't look all that turbulent, but perhaps that's because it's not a very powerful CME.

[Jesterface23]

Just now, Philalethes said:

Nice. This should be the sheath first, no? Doesn't look all that turbulent, but perhaps that's because it's not a very powerful CME.

Yeah, we are in the sheath. It could take 6 or several more hours before a flux rope arrives after this arrival.

(and off to work)

[tniickck]

its cloudy in Saint Petersburg, sad

Space Weather Message Code: SUMSUD
Serial Number: 251
Issue Time: 2023 Jul 14 1633 UTC

SUMMARY: Geomagnetic Sudden Impulse
Observed: 2023 Jul 14 1622 UTC
Deviation: -28 nT
Station: Newport

NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation

Bz fell to -11.1

[tniickck]

reached Kp4

[Philalethes]

Still waiting for something to appear at L1, but nothing so far; should be 4-5 hours between the two if I'm not mistaken.