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CIR and CH HSS impacting?


Sam Warfel

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I don't know.  Stealth CME?  The latest prediction of a glancing blow from a southerly CME isn't expected to impact Earth until Dec 3rd.  We do have two coronal holes (as seen in AIA 193) rotating into geoeffective position, one south of the solar equator, the second along the equator, but we shouldn't be seeing CH HSS from those for a few days yet.  I'm not sure where the spike in solar wind density came from, but maybe we're seeing some early leading edge winds from the first of these corona holes?  In any event, the negative Bz (which cannot be predicted) is facilitating and enabling these current KP4 active conditions.

Edited by Drax Spacex
3rd not 2nd
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9 minutes ago, Drax Spacex said:

I don't know.  Stealth CME?  The latest prediction of a glancing blow from a southerly CME isn't expected to impact Earth until Dec 3rd.  We do have two coronal holes (as seen in AIA 193) rotating into geoeffective position, one south of the solar equator, the second along the equator, but we shouldn't be seeing CH HSS from those for a few days yet.  I'm not sure where the spike in solar wind density came from, but maybe we're seeing some early leading edge winds from the first of these corona holes?  In any event, the negative Bz (which cannot be predicted) is facilitating and enabling these current KP4 active conditions.

Make that G1 Storm. Spaceweather.com says it’s probably a CIR

I doubt it’s a CME, there was no sudden increase in solar wind speed or density or imf, and the lack of one, especially in the speed, means it looks much more like a CIR than a CME

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From SWPC:

Forecast Discussion :Issued: 2021 Dec 01 0030 UTC

# Solar Wind .24 hr Summary... The solar wind environment was disturbed. Analysis of real-time solar wind data from the DSCOVR satellite suggests the arrival of a CH HSS, which had not been anticipated. This HSS would have likely originated from an extension from the northern crown that has since rotated out of view. Total field peaked at 15 nT and Bz dropped to -13 nT for a time. More recently winds began to climb from around 350 km/s to near 475 km/s. The phi angle oscillated some through the day, but switched to a positive orientation with the onset of the HSS.

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1 hour ago, Drax Spacex said:

From SWPC:

Forecast Discussion :Issued: 2021 Dec 01 0030 UTC

# Solar Wind .24 hr Summary... The solar wind environment was disturbed. Analysis of real-time solar wind data from the DSCOVR satellite suggests the arrival of a CH HSS, which had not been anticipated. This HSS would have likely originated from an extension from the northern crown that has since rotated out of view. Total field peaked at 15 nT and Bz dropped to -13 nT for a time. More recently winds began to climb from around 350 km/s to near 475 km/s. The phi angle oscillated some through the day, but switched to a positive orientation with the onset of the HSS.

Looks like I thought, although I still can’t remember where the CH was 😂

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43 minutes ago, Christopher S. said:

I was checking LASCO and saw a mini CME Earth-directed occur maybe 48-60 hours ago? It might have had its speed enhanced and what we're seeing is a result of high speed, not high mass

You mean the CME to the south from the filament eruption?  Or was that more recent than 48-60 hours?

Anyway, how could it have been a result of high speed when we are not seeing any particularly high speeds?  The speeds are much more in line with a CH HSS.

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1 hour ago, Christopher S. said:

I was checking LASCO and saw a mini CME Earth-directed occur maybe 48-60 hours ago? It might have had its speed enhanced and what we're seeing is a result of high speed, not high mass

SWPC has modeled the Nov 29th mostly southerly CME to arrive with a glancing blow midday Dec 3rd.

As for possible CME correlation to today's G1 conditions, I do see a launch of ejecta starting about 2021-11-26 00:00 on both Stereo Cor 2 RD and faintly on LASCO C2, perhaps even with a partial halo, which may have been earth-directed.  Cross-reference SDO AIA 193 explosion in NE quadrant at about that same time with visible shockwaves and/or coronal dimming.

Edited by Drax Spacex
Sdo cf
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1 hour ago, Drax Spacex said:

SWPC has modeled the Nov 29th mostly southerly CME to arrive with a glancing blow midday Dec 3rd.

As for possible CME correlation to today's G1 conditions, I do see a launch of ejecta starting about 2021-11-26 00:00 on both Stereo Cor 2 RD and faintly on LASCO C2, perhaps even with a partial halo, which may have been earth-directed.  Cross-reference SDO AIA 193 explosion in NE quadrant at about that same time with visible shockwaves and/or coronal dimming.

 But no x-ray Solar flare was recorded?

That is odd, but it still seems like a CIR/CH HSS and not a CME due to the actual data as it arrived at Earth (I.e. the slow increase in solar wind speed, not a sudden jump, and the density spike)

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Flares elevate X-Ray flux, but CMEs can occur from a filament eruption without any flare.  Looking at SDO/AIA 304 wavelength imagery, there is definitely a filament eruption from that explosion in the NE quadrant on 2021-11-26 00:00 UT.  The explosion occurred in the same region as the coronal hole with northern crown extension.  So it may be difficult to decouple the CME from the CH HSS to say which is the root cause of the G1.

Edited by Drax Spacex
AIA 304
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13 minutes ago, Jesterface23 said:

The 26th to the entry of the higher proton density is in excess of 4 days. In terms of a CME velocities it would result in values of around 350km/s or less.

That was approximately the same velocity of the Nov 24 CME that arrived Nov 27.  I assume these are travel times not solar wind speed measured upon arrival.

Minor CME impact - Speed 383km/sec - IMF Bt (strength): 14nT. Follow live on https://spaceweather.live/l/aurora
 
 
Image
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The 350km/s would be solar wind velocities at DSCOVR. The 24th CME had a far shorter travel time of ~80 hours compared to 96+. The solar wind velocities reached around 390-400km/s(a few hours into the CME), which is reasonable for that travel time. The longest travel time that I even have noted down is 90 hours at 340km/s.

Edited by Jesterface23
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7 minutes ago, Jesterface23 said:

The 350km/s would be solar wind velocities at DSCOVR. The 24th CME had a far shorter travel time of ~80 hours compared to 96+. The solar wind velocities reached around 390-400km/s, which is reasonable for that travel time. The longest travel time that I even have noted down is 90 hours at 340km/s.

Thank you for that clarification.  You make a good case that today's G1 storm was not a CME arrival but was indeed a CH HSS.  I appreciate your patient and cogent explanation.  And as Orneno noted, the increase in solar wind speed and density today was gradual while there was an abrupt stairstep increase for the Nov 24 CME.  In my limited experience I had not yet observed a G1 storm to be caused by a CH HSS, though I understand that it can and does happen, and that's most likely what we saw here.

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6 hours ago, Drax Spacex said:

Thank you for that clarification.  You make a good case that today's G1 storm was not a CME arrival but was indeed a CH HSS.  I appreciate your patient and cogent explanation.  And as Orneno noted, the increase in solar wind speed and density today was gradual while there was an abrupt stairstep increase for the Nov 24 CME.  In my limited experience I had not yet observed a G1 storm to be caused by a CH HSS, though I understand that it can and does happen, and that's most likely what we saw here.

Not just a CH HSSS, but a CIR can indeed cause G1 storms. It’s often described as being like a mini-CME

A CH HSS can too. Check out this article I remembered from a while back. This CH HSS caused not just G1, but even G2! https://www.spaceweatherlive.com/en/news/view/432/20210303-geomagnetic-storming-coronal-hole.html

Edited by Orneno
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@Drax Spacexso ye, between the article I sent and what Jester said, CIR and CH HSS can definitely cause geomagnetic storming!

6 hours ago, Drax Spacex said:

Thank you for that clarification.  You make a good case that today's G1 storm was not a CME arrival but was indeed a CH HSS.  I appreciate your patient and cogent explanation.  And as Orneno noted, the increase in solar wind speed and density today was gradual while there was an abrupt stairstep increase for the Nov 24 CME.  In my limited experience I had not yet observed a G1 storm to be caused by a CH HSS, though I understand that it can and does happen, and that's most likely what we saw here.

It’s also important to note that the somewhat unusual stair-step shape in the solar wind speed on this CME was due to it being a cannibal CME that absorbed other CMEs. We can be sure that wouldn’t be the case with any possible CME for this activity, because there were no slower, preceding CMEs


This made it look more like a gradual increase, kind of like what happened last night, but it was still a CME, with those very sharp large increases in solar wind speed. A more typical CME would spike almost immediately to a value near maximum, instead of slowly ramping up (or stepping up in the case of a cannibal CME).

Edited by Orneno
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