Backside CME on LASCO imagery

[Newbie]

Yesterday a CME was reported by CACTus on the AIA (Atmospheric Imaging Assembly) website. It had a radial velocity of 1014 km/s. This is  a moderately powerful blast. I have noticed similar, even faster radial velocities at times. They have beenr farside events and not impacting the earth at all. 

Generally these CME's are caused by filament eruptions because of their narrow angular width, rather than by sunspots. There is no way of telling though is there? Just wait for the sun to continue its rotation. 

 

 

Edited June 24, 2021 by Vancanneyt Sander
Update topic title to make it more clear what it’s about

[Vancanneyt Sander]

this topic isn't very clear, the topic title isn't reflecting whats inside the topic so i'm a bit confused what the point is that you are trying to say? 

Yesterday there was an eruptive C-flare that occured just around the limb, the resulting CME has been detected by LASCO imagery and the CACtus software that uses the LASCO images to detect CME's. CME's can have a varying speed depending on the strength of the event and indeed from filament eruptions the speed is lower than compared with CME's.  Except from backside CME's, the source of the CME is known but we don't have much eyes on the farside so you can only guess what it caused (filament or sunspot)

 

[Newbie]

Apologies for being confusing, not my intention.

This is not about the eruptive C3 flare yesterday. I believe the CME associated with that was of a lesser speed?

There was another CME detected which travelled past the west limb of the sun at 1014 km/s. It was picked up by AIA CACTus using LASCO images. I am not sure when the explosion ocurred as the source was on the far side of the sun and no increase in flux was observed.

We have no way of telling whether this was a filament eruption or an eruptive flare from a new sunspot region do we? I note that you say filament eruptions are usually not as powerful as CMEs. I suppose if these types of eruptions were showing up regularly as higher speed CMEs it might indicate quite an active sunspot group heading our way. Would this be right? And .....

I'm happy for you to suggest a better title.

[Vancanneyt Sander]

There is no AIA CACtus, SDO has the AIA instrument on board, CACtus is software of the SIDC that processes the LASCO imagery of the SOHO satellite to detect CME’s.

I don’t find the CME you are regering too if it wasn’t the one of yesterday. It helps to say on what time and/or include an image of it  , it would make it a lot more clear for everyone what you are talking about 😉👍

[abc]

9 hours ago, Newbie said:

Yesterday a CME was reported by CACTus on the AIA (Atmospheric Imaging Assembly) website. It had a radial velocity of 1014 km/s. This is  a moderately powerful blast. I have noticed similar, even faster radial velocities at times. They have beenr farside events and not impacting the earth at all. 

Generally these CME's are caused by filament eruptions because of their narrow angular width, rather than by sunspots. There is no way of telling though is there? Just wait for the sun to continue its rotation. 

 

 

Do you mind sharing the link of the website?
 

Edited June 24, 2021 by abc

[Newbie]

No probs

sdowww.lmsal.com  for  23 June 2021

[Vancanneyt Sander]

5 uren geleden, Newbie zei:

No probs

sdowww.lmsal.com  for  23 June 2021

That’s not the cactus link 😝 and on the 23rd the only CME that was detected by cactus was from the C flare just behind the limb. 

[Newbie]

This is the link to the CME travelling at 1014 km/s. After watching the video of it, it seems to be occuring during the C3 event.

 

http://sidc.oma.be/cactus/out/CME0005/CME.html

[Vancanneyt Sander]

It’s still the CME of the C3 and nothing else to see 🤷‍♂️

[Newbie]

When a sufficiently eruptive flare occurs it can scatter plasma in every direction and at high velocities. It is called a full halo CME and is usually the result of major eruptive flares.  Partial halo CMEs scatter plasma in a sort of arc. The bulk of the plasma from the C3 flare was scattered around an arc of about 58º. I was surprised that this minor eruptive flare produced a CME of such high velocity and in a different direction to the rest of the CME. That is why I wondered if it was from another flaring that we could not observe because of its far side position.  

Thanks for your patience

All good 😃

 

[Vancanneyt Sander]

Sometimes you don’t need a huge solar flare for a significant CME 🤷‍♂️ So it was normal that you where surprised as a newbie 😉

[Newbie]

With regards to LASCO and CACTus data, I have been looking into the range of speeds of ejecta from CME's. The speed of a each CME is given as an average of scatterplot entries. Often there are high speed outliers amongst say 20 to 50 average speed entries, but when it's averaged out, their influence on speed is negligble. Sometimes however there might be only 4 entries,  perhaps 3 high speed, 1 low speed on a scatterplot, giving an inaccurate perception of the strength of the CME. 

The paper below describes statistical analysis of the periodic oscillations in LASCO CME speeds. Quite interesting. 

Unfortunately I couldn't get the link to work from here.

Michalek2016_Article_StatisticalAnalysisOfPeriodicO.pdf?dl=0

[Christopher S.]

5 hours ago, Newbie said:

With regards to LASCO and CACTus data, I have been looking into the range of speeds of ejecta from CME's. The speed of a each CME is given as an average of scatterplot entries. Often there are high speed outliers amongst say 20 to 50 average speed entries, but when it's averaged out, their influence on speed is negligble. Sometimes however there might be only 4 entries,  perhaps 3 high speed, 1 low speed on a scatterplot, giving an inaccurate perception of the strength of the CME. 

The paper below describes statistical analysis of the periodic oscillations in LASCO CME speeds. Quite interesting. 

Unfortunately I couldn't get the link to work from here.

Michalek2016_Article_StatisticalAnalysisOfPeriodicO.pdf?dl=0

 

I don't know how relevant this is for you, but @Jesterface23 has been studying and analyzing CMEs for at least a few years. Check his post 

 

[Newbie]

Thanks for this, it answered a few questions I had. Much appreciated.

The amount of research Jesterface23 did was inspiring