SPE 06/2024 (Solar Proton Event) S3

[Ingolf]

We had a S3 SPE the last days and I have some questions, I can't find the answer here at SWL.

What I know: The SPE take place when eruptions occur. Flares can have CME or mostly when impulsive without CME. CME and Protons have nothing in common, two different things. Protons are highly energized particles and they travel extreme fast. Parker spiral can speed them up. The "snow" in LASCO is caused by protons when they hit the sensor. 

What I don't know:

When will protons eject from the sun? We had so many big eruptions in May with no SPE. Where are the protons located, are they somewhere inside the sun or around the sun? 

Can someone explain this in a hopefully not too scientific way? 

[Parabolic]

Particle acceleration from CME shock and magnetic reconnection is part of the mechanism. They are sometimes associated with type ii - type iii radio bursts as well. I'm not sure if an exact cause has been agreed upon though.

[Ingolf]

43 minutes ago, Parabolic said:

Particle acceleration from CME shock and magnetic reconnection is part of the mechanism. They are sometimes associated with type ii - type iii radio bursts as well. I'm not sure if an exact cause has been agreed upon though.

Thank you. This means for a SPE it is necessary that there is a CME? The CME shockwave accelerates the particles. Is this right? I imagine it with an explosion of a grenade for example. The grenade explodes and the "Shockwave" accelerates all the dust around it away from the explosion center. 

Why is there not always a SPE when we have a CME?  Aren't those protons not there all the time? 

 

Edit: 

The protons are in the solarwind and the shockwave accelerate them? So this is the reason why sometimes we have SPE and sometimes not, it depends of when the CME happens. Is the Parker spiral in reach or a coronal hole is/was near the protons will be accelerate, if there is no solarwind we just have the CME?

Edited June 9 by Ingolf

[SpaceWeather5464]

2 hours ago, Ingolf said:

Thank you. This means for a SPE it is necessary that there is a CME? The CME shockwave accelerates the particles. Is this right? I imagine it with an explosion of a grenade for example. The grenade explodes and the "Shockwave" accelerates all the dust around it away from the explosion center. 

Why is there not always a SPE when we have a CME?  Aren't those protons not there all the time? 

 

Edit: 

The protons are in the solarwind and the shockwave accelerate them? So this is the reason why sometimes we have SPE and sometimes not, it depends of when the CME happens. Is the Parker spiral in reach or a coronal hole is/was near the protons will be accelerate, if there is no solarwind we just have the CME?

You need a fast CME to produce a SPE event. Slow CME’S cannot cause a proton event. Every single fast CME that has hit our planet like the 2003 Halloween solar storms or the 1972 Solar storm caused an extreme proton event.

[Ingolf]

3 hours ago, SpaceWeather5464 said:

You need a fast CME to produce a SPE event. Slow CME’S cannot cause a proton event. Every single fast CME that has hit our planet like the 2003 Halloween solar storms or the 1972 Solar storm caused an extreme proton event.

Ahhhh, thank you, that was the missing piece in the puzzle. Okay, the CME speed is the factor if we get a proton event or not. Is there a threshold or experience what speed is necessary? 

Edit:

Deleted nonsense I wrote

Edited June 10 by Ingolf

[Philalethes]

On 6/10/2024 at 6:02 AM, Ingolf said:

Okay, the CME speed is the factor if we get a proton event or not. Is there a threshold or experience what speed is necessary? 

I don't know what the exact threshold is, but from what I've seen it's typically only the biggest eruptions that produce significant particle events; if I were to take a guess I'd say events with CME speeds of 800+ km/s are necessary to make the higher-energy protons move, although the 10+ MeV protons do move a bit from time to time even at lower speeds.

Looking into it a bit more I found this where the relationship is investigated, and they write:

Quote

Figure 12 presents the logarithm of the SEP proton peak fluxes in different integral energies with respect to the speed of the associated CME. The correlation of proton peak fluxes with CME speed has been established in several studies of gradual SEP events (Reames 1999; Kahler 2001).

Fig. 12 looks like this:

For the two highest-energy protons on the bottom it looks like around 800 km/s is indeed where you start to see most of the particle events (all of them for the 100+ MeV protons as far as I can tell), while the lower-energy ones rise frequently with slower events too; but in all cases there seems to be a general relationship between speed and proton flux (not as clear for the 100+ MeV ones I guess, due to the scarcer data).

Another one I found was Relationship between Solar Energetic Particles and Properties of Flares and CMEs: Statistical Analysis of Solar Cycle 23 Events, where they seem to make several interesting findings:

Quote

A strong rise of this probability is observed for increasing flare intensities, more western locations, larger CME speeds and halo CMEs. [...] The results show that the correlation between the proton peak flux and the CME speed decreases with energy, while the correlation with the flare intensity shows the opposite behavior. Furthermore, the correlation with the CME speed is stronger than the correlation with the flare intensity below 15 MeV and becomes weaker above 20 MeV.

The first statement there seems to confirm that particle event strength is indeed associated with CME speed, but also with flare intensity (which also tends to be correlated with CME speed, but as we know it's not always the case). The parts about location and halo are not really about the characteristics of the CME itself, but is naturally also part of the extent to which a particle event will be registered here.

The second statement is also interesting, as it seems to indicate that the exact speed doesn't necessarily matter that much for the highest-energy events, so maybe that explains the 100+ MeV in the figure above, at least partially; and maybe a bit surprisingly the intensity of the flare seems to be associated more at the highest energies, which I wouldn't have guessed. For lower energies they conclude the opposite, with CME speed being more important, which we see rather clearly in the figure.

Quite interesting indeed.

Edited Saturday at 09:45 AM by Philalethes
typo

[Ingolf]

1 hour ago, Philalethes said:

Another one I found was Relationship between Solar Energetic Particles andProperties of Flares and CMEs: Statistical Analysisof Solar Cycle 23 Events, where they seem to make several interesting findings:

The first statement there seems to confirm that particle event strength is indeed associated with CME speed, but also with flare intensity (which also tends to be correlated with CME speed, but as we know it's not always the case). The parts about location and halo are not really about the characteristics of the CME itself, but is naturally also part of the extent to which a particle event will be registered here.

The second statement is also interesting, as it seems to indicate that the exact speed doesn't necessarily matter that much for the highest-energy events, so maybe that explains the 100+ MeV in the figure above, at least partially; and maybe a bit surprisingly the intensity of the flare seems to be associated more at the highest energies, which I wouldn't have guessed. For lower energies they conclude the opposite, with CME speed being more important, which we see rather clearly in the figure.

Quite interesting indeed.

 

Thank you very much for the quotes and links, and yes, it is pretty interesting. The second statement makes sense to me when I read it against the last SPE we had.

The CME was very fast but the intensity was low -> 10 MeV were on the rise , 50 MeV just a little and 100 MeV was not impressed by the CME speed. Do you know a CME in the past when the speed was low and intensity was high? Is this possible? I would think that as higher the intensity as higher the speed, so if 100 MeV is rising the lower energies will always rise, too. 

   

Edit: I checked it with 28th of October just for visualization. Seems that there should need X20 or more to move the higher protons significant. Interesting: The X14 Flare at the next day had not that big impact to the ongoing solarstorm.  

Edited June 10 by Ingolf
Additional information

[Philalethes]

14 minutes ago, Ingolf said:

Do you know a CME in the past when the speed was low and intensity was high? Is this possible?

If you're referring to the proton flux intensity in general, then I don't think that's possible, at least not for the higher-energy protons; as seen above only 2-3 events in the 60+ MeV range came from CMEs slower than 800 km/s, and none for 100+ MeV below that same speed. For the 10+ MeV the chances seem to be better, but even there only a handful of events seem to have reached S2-levels from below 800 km/s.

If you were referring to flare intensity, then I'd say that does happen every now and then, intense flares aren't necessarily always associated with fast CMEs.

18 minutes ago, Ingolf said:

I would think that as higher the intensity as higher the speed, so if 100 MeV is rising the lower energies will always rise, too. 

In general flare intensity and CME speed are correlated, but you get some fast CMEs without strong flaring, and vice versa; but while the correlations they have to proton flux differ, I don't think you'll ever get a situation where the pfu is higher for certain higher-energy protons than it is for lower-energy ones. I think you'll always see them separate out in bands according to energy level, like for the most recent event:

I'd love to see any evidence to the contrary if it exists.

[Ingolf]

44 minutes ago, Philalethes said:

I'd love to see any evidence to the contrary if it exists.

I'm pretty sure I am not the one bringing the evidence 🙂

Thanks again for this lesson, now I have a final question before I start to watch everything closer and learn.

There are flare possibilities shown for every AR, I know they are not very reliable. It depends on the configuration of the AR and its history. Logically a delta config has a higher potential for bigger flares. But... there ist always the probabillity of a proton event beside the flare probabillity. Is the proton event probabillity in % in correlation to a higher X flare probabillity in % ? Or is there something visible in HMIIF / HMIBC that causes the proton event % ?  Is it possible that there is a X at 10% and proton at 30%? I don't think so. 

[Philalethes]

2 minutes ago, Ingolf said:

There are flare possibilities shown for every AR, I know they are not very reliable. It depends on the configuration of the AR and its history. Logically a delta config has a higher potential for bigger flares. But... there ist always the probabillity of a proton event beside the flare probabillity. Is the proton event probabillity in % in correlation to a higher X flare probabillity in % ? Or is there something visible in HMIIF / HMIBC that causes the proton event % ?  Is it possible that there is a X at 10% and proton at 30%? I don't think so. 

If you're talking about the predictions SWPC publish daily then I'd say they're indeed not very reliable. And particle events are even rarer, so I think trying to predict that would probably be even less reliable. But you're right, if they were to make such predictions I strongly doubt they'd ever have the chance higher for a particle event than for an X-flare happening, and there are no external signs indicating that the former might somehow be more probable than the latter that I know of; it's really just when a somewhat explosive CME occurs for the most part, which will tend to be associated with an X-flare or at the very least a strong M-flare. To predict a higher chance of a particle event you'd essentially have to find some way to predict such an explosive CME being about to happen from an M-flare or lower, which I doubt is even possible, and certainly not something we're able to do for the time being.

As an aside, you can always check DeFN for flare predictions that are produced via an automated system that uses statistics and machine learning; I still don't know how accurate it is, but I'd venture to guess that it's probably at least as reliable as the SWPC predictions.

[Ingolf]

1 hour ago, Philalethes said:

As an aside, you can always check DeFN for flare predictions that are produced via an automated system that uses statistics and machine learning; I still don't know how accurate it is, but I'd venture to guess that it's probably at least as reliable as the SWPC predictions.

Thanks a lot, this link is really useful for me. 👍 

 

[Trestan]

22 hours ago, Ingolf said:

This means for a SPE it is necessary that there is a CME?

18 hours ago, SpaceWeather5464 said:

You need a fast CME to produce a SPE event.

Not all SEP events are produced by CME shocks. Impulsive SEP events are associated with particle acceleration along open magnetic field lines near flare/jet sites (usually) without an observed CME and occur on time scales of hours; in contrast, gradual SEP events are associated with particle acceleration at CME-driven shocks and occur on time scales of days. The latter are often much stronger than the former, however, so are more important in the space weather context to my knowledge.

Reames 2013 (DOI: 10.1007/s11214-013-9958-9; https://arxiv.org/abs/1306.3608) provides a good review of both types of events and the physics involved.

[hamateur 1953]

This topic also very helpful to me wondering about “ what it really takes”  to produce a Ground Level Enhancement.  

tnx all. 

Edited Saturday at 05:28 AM by hamateur 1953