Solar Orbiter

[MinYoongi]

Does that mean the CME will impact with -40BZ? Or will it weaken on its way to earth? Im not familiar with Solar Orbiter. 

 

@Jesterface23 @Philalethes maybe this is interesting for you  

[Jesterface23]

48 minutes ago, MinYoongi said:

Does that mean the CME will impact with -40BZ? Or will it weaken on its way to earth? Im not familiar with Solar Orbiter. 

It will decline exponentially over time, and the Solar Orbiter is a little under half way between us and the Sun. I'd just have a guesstimation of an IMF total strength of 15nt in the flux rope once it reaches L1. ACE's solar wind velocities are around 370km/s and possibly declining at this point in a weak CH, so we should see a CME arrival.

 

I was wondering if I should bring this up. They did release a new low latency MAG data plot.

.............

Also for Solar Orbiters position,

https://solarorbiter.esac.esa.int/where/

(satellite not to scale)

[MinYoongi]

14 minutes ago, Jesterface23 said:

It will decline exponentially over time, and the Solar Orbiter is a little under half way between us and the Sun. I'd just have a guesstimation of an IMF total strength of 15nt in the flux rope once it reaches L1. ACE's solar wind velocities are around 370km/s and possibly declining at this point in a weak CH, so we should see a CME arrival.

 

I was wondering if I should bring this up. They did release a new low latency MAG data plot.

.............

Also for Solar Orbiters position,

https://solarorbiter.esac.esa.int/where/

(satellite not to scale)

Is that the Same Data as in the Tweet i shared? or why did you say you did not know if you should talk about it?

So what do you think could the BZ be when it arrives at earth?

[Jesterface23]

2 minutes ago, MinYoongi said:

Is that the Same Data as in the Tweet i shared?

Yep.

2 minutes ago, MinYoongi said:

or why did you say you did not know if you should talk about it?

It is a new source of data, but it isn't always right in front of Earth.

6 minutes ago, MinYoongi said:

So what do you think could the BZ be when it arrives at earth?

No idea

[MinYoongi]

6 minutes ago, Jesterface23 said:

Yep.

It is a new source of data, but it isn't always right in front of Earth.

No idea

I don’t think it could reach -40 bz. People on twitter said it will weaken because of the distance, but I still thought asking on here will bring the best answers 😎☺️

[Jesterface23]

4 minutes ago, MinYoongi said:

I don’t think it could reach -40 bz.

I'm only guessing an IMF total strength of 15nT once it reaches us. The Bz rotation could be similar to the SO or it could be completely different.

[MinYoongi]

4 minutes ago, Jesterface23 said:

I'm only guessing an IMF total strength of 15nT once it reaches us. 

4 minutes ago, Jesterface23 said:

I' The Bz rotation could be similar to the SO or it could be completely different.

 

Thank you for the "guesstimate" 🙂  

Altough im still puzzled about the Bz rotation - youre probably speaking about the way it goes from negative to positive (i.e in what order, etc) ? Yeah, it will likely change, it still has a way to go 🙂  But what i meant was the raw value of -40 BZ.

 

[Jesterface23]

7 minutes ago, MinYoongi said:

But what i meant was the raw value of -40 BZ.

The absolute values of Bx ,By, and Bz can never be higher then B. The square root of (Bx^2+By^2+Bz^2) = B

Edited March 20 by Jesterface23

[Philalethes]

3 hours ago, MinYoongi said:

Does that mean the CME will impact with -40BZ? Or will it weaken on its way to earth? Im not familiar with Solar Orbiter. 

 

@Jesterface23 @Philalethes maybe this is interesting for you  

That's really cool, and a neat coincidence that SolO happened to be passing by right as this fairly slow CME makes its way towards us. Possibly even cooler that SolO's magnetometer has its own dedicated X account in the first place.

But yeah, I see Jesterface has already provided a fair amount of good information about it. At those speeds one wouldn't expect much of a deflection angle, so the fact that it hits SolO when it's radially aligned with our perspective is something I'd interpret as a good indicator that we'll register it here too.

As you can probably tell the data is provided in RTN coordinates, where B_N doesn't necessarily correspond exactly to Bz; and as noted the potential rotation (or other movement) of the rope itself would still make it difficult to translate from those coordinates to what it'll be like when it hits us. That being said, it would be interesting to have it in GSM coordinates just as a reference, because then we could potentially get some valuable information about whether or not or the extent to which the flux rope has changed direction on its way.

It does certainly look like a clear flux rope signature at the very least. I guess if we just hand-wave a bit and consider B_R, B_T, and B_N to correspond to Bx, By, and Bz respectively (with B_T being in the opposite direction as By, if I'm not mistaken), then we'd be looking at an SWN rope (or SEN for those of us who prefer using cardinal directions in more standardized ways). If we were to extend this to the strength, then we'd have to compare against a guess of how much weaker it will be when it hits us; using Jesterface's estimate of a Bt of 15 nT when it hits us and considering the absolute strength of around 50 nT, we can in fact just scale down each component by the same factor (as you can extract the square of that factor for the total), and in this case that factor is 50 nT / 15 nT = 3.33, so in that hypothetical scenario we'd expect a Bz of 40 nT / 3.33 = 12 nT.

I guess we'll find out more when it actually reaches us, presumably late this day or early tomorrow, UTC of course.

Edited March 20 by Philalethes
typo

[AndrewB]

Nearly 15 hours after the CME arrival we've had in total only ~3 hours of southward Bz at longest period - that's a joke and extremely different conditions from those observed by SolO ☹️  Now we've exit from second slightly prolonged period with south Bz but values near -10nT was still pathetic. Philalethes has done a pretty good job of estimating Bt/Bz values. For me, the scale of CME weakening over the distance from 0.4 to 1 AU is impressive, comparing DSCOVR and SolO data.

Regards

Andrew

Edited March 21 by AndrewB