How to know whether a CME is Earth-directed

[Jackson Myers]

I noticed that the SpaceWeatherLive site has a list of recent CMEs and that list includes a bunch of information including angle. Is there any way to tell if they are earth directed, for example is a CME within a range of angles earth directed? I know I can wait for an ENLIL model run but before ENLIL updates do the angles tell me anything useful about possible impact on earth?

Just curious how to best interpret this data. Thanks!

[Vancanneyt Sander]

1 uur terug, Jackson Myers zei:

I noticed that the SpaceWeatherLive site has a list of recent CMEs and that list includes a bunch of information including angle. Is there any way to tell if they are earth directed, for example is a CME within a range of angles earth directed? I know I can wait for an ENLIL model run but before ENLIL updates do the angles tell me anything useful about possible impact on earth?

Just curious how to best interpret this data. Thanks!

Of course, it’s even indicated in the column halo 😉 the only thing to consider that it can also be a backside halo 😜

[Jackson Myers]

Thank you!

The "Halo?" column doesn't give me any indication of whether is it earth directed or not, does it? It could also be a backside halo? The halo category seems to be related to the angular width. Am I correct to assume that a larger width means higher chance earth is affected?

I made myself a nice dashboard here where I can see where some of the CMEs are being directed relative to earth but I noticed it hadn't updated with data from the 22nd yet, and I just started using your site and noticed some CMEs on the 22nd so I was curious if they might bring us auroras. Turns out there's no halo so I think the answer is no.

[Jesterface23]

Part one: You can click the Play button icon to view the difference C2 imagery. Sometimes differenced C3 imagery will need to be looked at. If you see the CME go across all angles of the imagery, you have a halo. If the CME spans greater than >180 degrees in imagery, that is good too.

Part two: You need to take a look at solar imagery to see where the CME came from. If you can't find an eruptive source or filament eruption on our side of the solar disk that looks to be in decent spot compared to what the coronagraph imagery shows, it is probably a far side event. GOES SUVI solar imagery comes in handy, because you can see shocks on the edges of the disk from far side events much better than in SDO imagery. Filaments are much easier to see in GOES imagery as well. (Make sure to look at the timestamp of the coronagraph imagery and solar imagery to make sure they are close)

Part three: There can be some Earth-directed halo CMEs that come from a source closer to the limb. If the CME isn't fast enough, it may degrade in the solar wind before arriving at Earth.

[Jackson Myers]

Thank you!

[Barbean]

What does this represent?

[Vancanneyt Sander]

The asteriks are the different speed measurements and angles. From that data it tries to find the average speed range indicated by what you are circling.

[Philalethes]

21 hours ago, Barbean said:

What does this represent?

That would be a box plot. The box represents the range containing the middle 50% of the values (first quartile to third quartile), and the horizontal bar within it is the overall median of the entire set of values. The so-called whiskers on either side vary from plot to plot, where in some cases they extend all the way to the minimum and maximum values (not the case here, as you can see), while in others they extend only to a maximum range with the rest regarded as outliers; in the latter case the boundaries are commonly set at 1.5 times the length of the box itself (called the interquartile range, IQR), and that is indeed what's being done here.

Here you can read the original description of the detection system, where Appendix A describes the box plot.

[Barbean]

2 hours ago, Philalethes said:

That would be a box plot. The box represents the range containing the middle 50% of the values (first quartile to third quartile), and the horizontal bar within it is the overall median of the entire set of values. The so-called whiskers on either side vary from plot to plot, where in some cases they extend all the way to the minimum and maximum values (not the case here, as you can see), while in others they extend only to a maximum range with the rest regarded as outliers; in the latter case the boundaries are commonly set at 1.5 times the length of the box itself (called the interquartile range, IQR), and that is indeed what's being done here.

Here you can read the original description of the detection system, where Appendix A describes the box plot.

Thank you.  I'm going to try to get my head around this. Lolololololololol (Husband sound effects)