Drop in solar wind densitiy preceeding a CME hitting earth.

[HalfFeralHuman]

I've noticed a pattern several times now whereby before a CME hits, the solar wind density drops in a way that's perhaps analogous to the way a tsunami's wave is usually preceeded by a drop in water levels. Density levels have dropped rather low now, and the densest blast of wind I've seen this cycle is expected tomorrow if predictions are right. [edit: Mentioned prediction was NOAA's WSA-ENLIL, which turned out to be rather off. the 'blast' did happen, but wasn't anything to write home about at all.]

Is this a known thing, or is this just probably just one of those observational bias things.

If this is a thing, can anyone explain the mechanism? To me, I'd kind of expect the opposite effect as in theory particles of similar electric charge would repel and try to spread out.

Edited April 14, 2022 by HalfFeralHuman
Clarifying that predicted event was much weaker than I expected.

[MinYoongi]

I do think thats unrelated, but I'm interested in looking into it further!

 

Only thing I know thats confirmed is that Ace EPAM rises before a CME arrives.

[HalfFeralHuman]

13 hours ago, MinYoongi said:

Only thing I know thats confirmed is that Ace EPAM rises before a CME arrives.

Now I'm confused, am I missing something, but isn't EPAM just measuring the same stuff, but just splitting it down into particles of specific charge and energy?

But I'm not really seeing the same pattern on EPAM, only DSCOVR and SOHO. Yep, I'm definitely confused now 🤔!

[Drax Spacex]

If the trough of the tsunami wave reaches the coast first, this causes a phenomenon called drawdown, where it appears that sea level has dropped considerably.  Drawdown is followed immediately by the crest of the wave which can catch people observing the drawdown off guard.  

Inflow bands or feeder bands in meteorology are winds that move into or toward a storm.

I'm not sure if either of these terrestrial phenomenon can be applied analogously to CMEs or if we are collecting the type of sensor data that might indicate such correspondence. 

 

 

 

 

Edited April 14, 2022 by Drax Spacex

[ron]

Such an observation is interesting. The more observation that takes place to confirm or refute this observation will only solidify the meaning of this observation.

[Vancanneyt Sander]

Op 13/4/2022 om 17:58, HalfFeralHuman zei:

I've noticed a pattern several times now whereby before a CME hits, the solar wind density drops in a way that's perhaps analogous to the way a tsunami's wave is usually preceeded by a drop in water levels.

Of all CME impacts I’ve seen I don’t see that happening with most of the CMEs so I rather think it’s more a confidence than fact as it doesn’t happen with each CME.

In the following example you’ll see two CME impacts in one day where there is no drop before the impact:

And a second example (also of a double impact), also no drop in solar wind before CME arrival (same with density).

[HalfFeralHuman]

@Vancanneyt Sander It's particularly the density, not the speed that I'm looking at. What year are those from?

This prompted me to look for DSCOVR archive data though, this is the kind of pattern I'm talking about (the one in the middle):

But yeah, I certainly haven't seen enough to be sure of anything other than coincidence, and I guess kind of need to know what else was happening at the time. I'm thinking if this is a phenomonem it probably isn't something that necessarily happens. I reckon it could depend on factors like whether it's a glancing hit or a direct one, or probably the shape of the CME. Anyway... I'm not sure I'd know how to go about analysing things for statistical sinificance... soo... /shrug

[Vancanneyt Sander]

4 minuten geleden, HalfFeralHuman zei:

@Vancanneyt Sander It's particularly the density, not the speed that I'm looking at. What year are those from?

I picked a few dates from the strongest geomagnetic storms page and checked those in the archive. Of the examples I’ve posted the density didn’t drop as well.

Solar wind speed is measured based on the speed the particles have when they hit the detector, the more particles the more density of the solar wind and the more accurate the solar wind speed reading is. A density of a one particle per cubic square centimeter doesn’t result in a very accurate speed reading.

in your example, I don’t see a CME signature. Speed didn’t go up, only density, no rise in temperature (it’s a drop in temperature) and no jump in total field value of IMF.

[HalfFeralHuman]

19 minutes ago, Vancanneyt Sander said:

I picked a few dates from the strongest geomagnetic storms page and checked those in the archive. Of the examples I’ve posted the density didn’t drop as well.

Ah... I forgot you had that section.

I'm confused though. In the first example you give, it is preceeded by a drop in density (without a concurrent drop in speed if that's relevant). In the second example there's no mention of a CME in the reports unless I'm missing something or got the wrong year.

What I'm confused about is why we're talking about speed, It's the density I think I'm seeing a pattern in, not speed. Am I missing a point here?

[Vancanneyt Sander]

10 minuten geleden, HalfFeralHuman zei:

Ah... I forgot you had that section.

I'm confused though. In the first example you give, it is preceeded by a drop in density (without a concurrent drop in speed if that's relevant). In the second example there's no mention of a CME in the reports unless I'm missing something or got the wrong year.

What I'm confused about is why we're talking about speed, It's the density I think I'm seeing a pattern in, not speed. Am I missing a point here?

The density of the solar wind doesn’t matter much, only for Aurora the more particles the better 😜. Density is always a lot fluctuating with several ups and downs.

in my example of august 24th 2005 there is only a density drop before the second CME impacted. But others I don’t see that behaviour, just check the top 50 page it has links to the solar wind data in our archive. 

[HalfFeralHuman]

7 minutes ago, Vancanneyt Sander said:

The density of the solar wind doesn’t matter much, only for Aurora the more particles the better 😜.

lol, unfortunately I'd need a full-on Carrington event to have an ice-cream's chance in hell of seeing the Aurora at my latitude 😛 . It's how all this stuff works in the first place that facinates me.

30 minutes ago, Vancanneyt Sander said:

in my example of august 24th 2005 there is only a density drop before the second CME impacted. But others I don’t see that behaviour, just check the top 50 page it has links to the solar wind data in our archive. 

Yeah, I reckon the shape of the CME would be all important... I'd need to go comparing things to SOHO and STEREO archives, and... yeah... well there's too little to go on to feel particularly driven to do that. I might do if I get really bored 🙃

[Jack]

I’m a little confused by what you’re asking and using as an example. Are you referring to a density drop before a CME shock arrival? And by that are suggesting an early detection prior to magnetic field disturbance or upon magnetic field disturbance?

secondly, I cannot understand why you are referring to Coronal hole wind stream effects as an example for CME density drop prior to geoeffectivity.

 

sorry just trying to clarify what you’re asking or suggesting.

from every CME Shock I’ve ever seen it is met by both a rise in density, temp and wind (though wind is dependant upon the speed prior as to whether it sees elevation or not) simultaneously with the magnetic field disturbance. Coronal hole wind streams however, tend to issue a denser leading edge before wind streams arrive.

So, I’m not sure what you’re referring to as an example unless you are suggesting some kind of insignificant dip just minutes before arrival which can be seen in some cases and not in others but, it’s never appeared significant or consistent as far as I’ve known.

 

probably using WSA-ENLIL+Cone Prediction models isn’t a very good example in actuality for how such events occur, as it is after all a Prediction model.

Do you have any examples of what you’re talking about from past events that reflect what you’re proposing so we may take a look through it?

Here’s something you can work off if it helps….

 

Edited April 18, 2022 by Jack

[HalfFeralHuman]

2 minutes ago, Jack said:

Are you referring to a density drop before a CME shock arrival?

Yeah, exactly that

3 minutes ago, Jack said:

And by that are suggesting an early detection prior to magnetic field disturbance or upon magnetic field disturbance?

Not really, I don't think it could be reliable enough or early enough to be of any use for detection. My angle is just on trying to better understand the interplay between electromagnetic fields and these flows of charged particles.

My thinking is that the movement of denser, blobs of charged particles could theoretically mess with magnetic fields in a way which pushed other charged stuff ahead of it out of the way, kinda like a parallel to the way the earth's field causes charged stuff moving towards it to circle round. I figure this could cause a minor drop in density ahead of a CME wave.

11 minutes ago, Jack said:

secondly, I cannot understand why you are referring to Coronal hole wind stream effects as an example for CME density drop prior to geoeffectivity.

I am? Certainly the initial example that caused started this thread was a CME...  Was that example from 2020-09-01 a CH HSS? I just chose a random date, I'll admit I didn't check if a CME hit Earth, but isn't that way too spiky for an HSS?

I know I said Earth and we're actually talking about L1 measurements, but I wasn't really commenting on geoeffectivity, I'm more interested in the cross-interactions going on.

[Jack]

Ok, so what do you mean by cross interactions and how does your theory run against the image I’ve provided?

I don’t truly see a consistent correlation, in fact in most scenarios quite the opposite but, perhaps you’re referring to a very minor dip just minutes to detection?

post up some imagery data to give us an idea of what you’re talking about. It would help.

I get the idea behind what you’re suggesting but, it’s not a consistent or significant fluctuation pattern to warrant a conclusion to be made of any kind.

Though I’d be happy to see some kind of consistent correlation that supports any new finding. So it’s for you to go to work on that 👍

Edited April 18, 2022 by Jack

[HalfFeralHuman]

Sorry, missed the edit.

By cross interactions I mean the plasma equivalent of a transformer's mechanism for want of a better description. Charged things moving though magnetic fields are them selves contributing to the field, but are also effected by it. As they are pushed, their change in motion results in a change to the field... that complicated back-and-forth electromagnetic field tussle. Going back to the electronics comparison, I guess I'm talking back-EMF.

About the chart you posted, I'm not sure I can show anything there. Previously though what I've seen has been quite subtle and over a longer time period. I'd need to get some idea of background levels several hours before. I can't find an archive of the same chart though.

I think it's important to be clear that I wouldn't anticipate more than a quite subtle effect.

[Jack]

The motion of Flux ropes are of course rather difficult to predict in their constitution and propagation at L1 to an exact. So in order to accurately understand what you’re proposing we’d need to be utilising data received from pre-recorded events occuring at L1. We cannot use WSA-ENLIL+Cone prediction model examples for exactly what eventuates for numerous reasons.

Without any graphic data to back it up the theory for which you are trying to discuss is especially difficult to have this conversation.

Perhaps take some recordings and snap shots over the next few CME events and collaborate some evidence. Who knows, you might find something 👍

But, for now, no data or imagery means it’s impossible to have a weighted discussion.

There is one I’ve offered already which shows the opposite occuring.

Edited April 18, 2022 by Jack

[Jesterface23]

Keep errored data in mind. Today we can get solar wind data from DSCOVR, SOHO, and ACE. Data from Wind can be spotty depending on the source.

[HalfFeralHuman]

Completely agree. Single sources aren't going to show anything, even if there is something in this. If I get anything a little more cohesive I'll bring it back.