Why is Solar wind speed so high?

[Sam Warfel]

Why is the solar wind speed so high (600km/s)? Is this possible from a CH HSS? If so, I didn’t know they could go to 600km/s…

I don’t see any other enhancements to the solar wind or IMF, doesn’t seem to be a CME

[MinYoongi]

Yes, very well possible. Why shouldnt a CH HSS not be able to deliver more than 400-500 km/s winds? I already told you about one exceeding 700-800 in 2019 when there were literally no flares or CMEs.

[Sam Warfel]

29 minutes ago, MinYoongi said:

Yes, very well possible. Why shouldnt a CH HSS not be able to deliver more than 400-500 km/s winds? I already told you about one exceeding 700-800 in 2019 when there were literally no flares or CMEs.

I didn't say it's not able, I just had never seen one do that before, so it surprised me, and I sought confirmation that it's just a CH HSS

[HalfFeralHuman]

8 hours ago, Orneno said:

I didn't say it's not able, I just had never seen one do that before, so it surprised me, and I sought confirmation that it's just a CH HSS

From what I could tell, both a small CME and the HSS arrived together.

I did see what looked like an earth-directed CME on SDO imagery, but there was that huge CME on the reverse side so I had no idea what was what on SOHO. My guess though is that this is was some kind of interaction between a small CME and the HSS.

This kind of interaction could maybe explain why NOAA's WSA-ENLIL model tends to get stuff wrong when HSSs and CMEs coincide, I guess it would certainly be a complicated thing to simulate if it is a thing.

[KW2P]

On 4/15/2022 at 10:58 PM, Orneno said:

Why is the solar wind speed so high (600km/s)? Is this possible from a CH HSS? If so, I didn’t know they could go to 600km/s…

I don’t see any other enhancements to the solar wind or IMF, doesn’t seem to be a CME

Thanks for posting this question. A couple days ago I too was puzzling over the high wind speed

[Drax Spacex]

The solar wind speed could be augmented by the northern extension that is connected to the equatorial coronal hole from which this solar wind emanates.  This northern extension is best seen in AIA 193 - the dark crevasse that extends from the coronal hole at the equator up to the Sun's north pole.  Incidentally, there was a filament eruption just before the formation of this northern extension.

AIA 193 2022-04-15

Edited April 18, 2022 by Drax Spacex
added image

[KW2P]

Once the answer was pointed out I felt kind of dumb because I had the answer in my hand earlier. Around Tuesday or so I noticed the equatorial corona hole coming around and thought, "Gee, that's a big corona hole and it's going to be pointed right at us."  By Thursday/Friday, I was focused on sunspots and flaring, puzzling over the wind speed and forgetting about the corona hole. Hah.

"Wake up and pay attention, Phil."

[KW2P]

Well, now I'm puzzled again. Why did the wind speed jump from 290 to 480 and what's up with Kp=5?  There's nothing significant going on that I can see. No flares for a while.  The two questions probably have the same answer but high wind speed doesn't always result in high Kp.  Hmm.

[Newbie]

29 minutes ago, KW2P said:

Well, now I'm puzzled again. Why did the wind speed jump from 290 to 480 and what's up with Kp=5?  There's nothing significant going on that I can see. No flares for a while.  The two questions probably have the same answer but high wind speed doesn't always result in high Kp.  Hmm.

Hello KW2P, there was a CIR (boundary between the ambient slow moving solar wind and the fast moving solar wind from a Coronal Hole. CIR's are well known for creating a shock wave, disturbing the Earth's magnetic field. Should the CME from a few days ago deliver a glancing blow later on today it may further impact the magnetic field and enhance storm conditions. 

I was surprised how low the Dst index went.

There is actually a good description of CIR's and how they impact the magnetic field in the help section of SWL home page.

Newbie

[KW2P]

Thank you very much!  I only recently learned a little about CIRs and imagined they were rare oddball events.  A CIR never crossed my mind.  I'll have to change that attitude.

I searched forecasts and analyses from NOAA etc. for quite a while seeking an answer and found no explanation before I posted here.

Can you suggest a source for analyses that would have mentioned the CIR?  Current data and forecasts are easy to find, which is great because I'm usually looking for forecasts. But explanations of what's happening now are hard to find for some reason -- explanations after the fact.

[Newbie]

Hello KW2P,

When a solar storm appears out of nowhere, so to speak, the culprit is often a CIR. At the moment there is an Earth facing Coronal Hole. Please note that storms produced this way are not major storms. 

So while the solar wind flowing from the Sun doesn't always impact the Earth in such a way, if it is a particularly fast stream it can catch up with the slower solar wind and cause a shock at the interface between the two. If the conditions are right a crack will open up in the Earth's magnetic field allowing solar particles to flow in.

Two sites that I know: spaceweather.com and solarham report this occasionally, they did today.

The behaviour of the Sun and its impact on the Earth are very hard to predict. 

Having just spoken about CIR's I have heard in the past of the odd sneaky CME that went undetected, impacting the Earth's magnetic field causing unexpected solar storms.

Newbie

 

1 hour ago, KW2P said:

Thank you very much!  I only recently learned a little about CIRs and imagined they were rare oddball events.  A CIR never crossed my mind.  I'll have to change that attitude.

I searched forecasts and analyses from NOAA etc. for quite a while seeking an answer and found no explanation before I posted here.

Can you suggest a source for analyses that would have mentioned the CIR?  Current data and forecasts are easy to find, which is great because I'm usually looking for forecasts. But explanations of what's happening now are hard to find for some reason -- explanations after the fact.

 

Edited May 28, 2022 by Newbie

[KW2P]

Thank you very much!

[KW2P]

On 5/28/2022 at 3:42 AM, Newbie said:

Hello KW2P,

When a solar storm appears out of nowhere, so to speak, the culprit is often a CIR. At the moment there is an Earth facing Coronal Hole. Please note that storms produced this way are not major storms. 

So while the solar wind flowing from the Sun doesn't always impact the Earth in such a way, if it is a particularly fast stream it can catch up with the slower solar wind and cause a shock at the interface between the two. If the conditions are right a crack will open up in the Earth's magnetic field allowing solar particles to flow in.

Two sites that I know: spaceweather.com and solarham report this occasionally, they did today.

The behaviour of the Sun and its impact on the Earth are very hard to predict. 

Having just spoken about CIR's I have heard in the past of the odd sneaky CME that went undetected, impacting the Earth's magnetic field causing unexpected solar storms.

Newbie

 

 

I'm starting to get the hang of it. I've even started trying to identify sunspot configurations myself. Whoo hoo.

This weekend is an important time for ham radio enthusiasts in the USA. It's the annual Field Day, where around 35,000 of us here in the USA set up in outdoor and remote locations and spend 24 hours trying to communicate with as many others as possible. It's great fun and the practical side is that it's an exercise for setting up emergency communications.

So I checked the weather and it looks okay (no thunderstorms). Then I checked solar weather and it's not great. Right at the start of the exercise, the Kp index is expected to jump up to 4. Normally, I would have stopped there. I know what Kp=4 means for radio. But these days I ask why and took a look at the sun. Lo and behold, there's an equatorial corona hole point at us right now.  If the stream of particles is moving at 650 km/s it would get here in about 60 hours, which is about when the Kp index is expected to jump up.  So those numbers seem to make sense.

Am I on the right track here or is there something else I'm missing?

[dave]

Slightly off topic.

 

Is there really a sunspot at the South Pole? 3040.

I can not see it.

[Newbie]

44 minutes ago, KW2P said:

I'm starting to get the hang of it. I've even started trying to identify sunspot configurations myself. Whoo hoo.

This weekend is an important time for ham radio enthusiasts in the USA. It's the annual Field Day, where around 35,000 of us here in the USA set up in outdoor and remote locations and spend 24 hours trying to communicate with as many others as possible. It's great fun and the practical side is that it's an exercise for setting up emergency communications.

So I checked the weather and it looks okay (no thunderstorms). Then I checked solar weather and it's not great. Right at the start of the exercise, the Kp index is expected to jump up to 4. Normally, I would have stopped there. I know what Kp=4 means for radio. But these days I ask why and took a look at the sun. Lo and behold, there's an equatorial corona hole point at us right now.  If the stream of particles is moving at 650 km/s it would get here in about 60 hours, which is about when the Kp index is expected to jump up.  So those numbers seem to make sense.

Am I on the right track here or is there something else I'm missing?

Hi KW2P,

Spot on I would say. There are three Earth facing Coronal Holes at the moment. 

N.

 

11 minutes ago, dave said:

Slightly off topic.

 

Is there really a sunspot at the South Pole? 3040.

I can not see it.

Hello Dave, no there isn't. 3040 was located around 15ºS. last update.

Newbie

[MinYoongi]

14 minutes ago, dave said:

Slightly off topic.

 

Is there really a sunspot at the South Pole? 3040.

I can not see it.

Haha, no. Must be a glitch or some bug. I cant see anything in Suvi.