Why is Solar Wind speed high?

[Sam Warfel]

Why is the Solar Wind speed pretty high right now (~500 km/s). It looks like a CH HSS, but I can’t figure out what Coronal Hole it could have come from. 

Was it from one of the glancing blow CMEs from the M-class flares that was expected yesterday or today? I’m seeing a bit of a jump in the speed at 02:57 that could be a CME, but it’s hard to tell, it’s super weak if it is. 

[Vancanneyt Sander]

No CME signatures so that can be excluded. From SWPC reports you can read the following:

“Solar wind parameters, as measured by the DSCOVR spacecraft, were slightly elevated, possibly due to the influence of the periphery of a transient that left the Sun on 21 Dec.”

[Sam Warfel]

3 minutes ago, Vancanneyt Sander said:

No CME signatures so that can be excluded. From SWPC reports you can read the following:

“Solar wind parameters, as measured by the DSCOVR spacecraft, were slightly elevated, possibly due to the influence of the periphery of a transient that left the Sun on 21 Dec.”

Hmm, I see. As I look at the data, there’s a pretty clear sudden increase in solar wind speed and density, and a southward spike in Bz (after which it seems to be more strongly magnetized).  We’re sure that can’t be a CME? So, would that then be just normal behavior of the gusty solar wind?

[Vancanneyt Sander]

26 minuten geleden, Orneno zei:

Hmm, I see. As I look at the data, there’s a pretty clear sudden increase in solar wind speed and density, and a southward spike in Bz (after which it seems to be more strongly magnetized).  We’re sure that can’t be a CME? So, would that then be just normal behavior of the gusty solar wind?

There was a slight increase but definitely not noteworthy (~30km/sec and 1nT isn’t worth speaking). Also no sudden impulse detected so no signature.

[Jesterface23]

The SWE data from DSCOVR has had some glitchy data spikes recently as well.

[Sam Warfel]

1 hour ago, Vancanneyt Sander said:

There was a slight increase but definitely not noteworthy (~30km/sec and 1nT isn’t worth speaking). Also no sudden impulse detected so no signature.

What’s a “sudden impulse”?

[Vancanneyt Sander]

17 minuten geleden, Orneno zei:

What’s a “sudden impulse”?

A sudden impulse happens when a CME arrives on Earth. So when you see a CME arrival at DSCOVR, it’s still miles away from Earth. You know when it hit Earth the moment a sudden impulse is detected by magnetometers on the ground. These will show a sudden jump in the magnetic readings indicating the arrival of a CME. 

[Christopher S.]

IMF is likely carrying these winds we've been seeing. Based on CME direction and IMF "wave" locations, I imagine it's a lot like low- and high-pressure behavior that we see on Earth in the form of winds behind a trough. The "trough" in this case is a band of dense plasma rotating around the Sun as part of the IMF, enhanced by activity maybe. 

I'm talking purely from logical hypothesis. There's likely people who know more on this particular topic, but, I'd point at that for an explanation.

[Sam Warfel]

2 hours ago, Vancanneyt Sander said:

A sudden impulse happens when a CME arrives on Earth. So when you see a CME arrival at DSCOVR, it’s still miles away from Earth. You know when it hit Earth the moment a sudden impulse is detected by magnetometers on the ground. These will show a sudden jump in the magnetic readings indicating the arrival of a CME. 

Thanks!

[Vancanneyt Sander]

the CME from the glancing blow has just arrived, clear signature:

[Jesterface23]

It might be turning out to be the entry of the dense protons of a CH similar to early last week

[Sam Warfel]

1 minute ago, Jesterface23 said:

It might be turning out to be the entry of the dense protons of a CH similar to early last week

Nah, CIRs have a different signature on the data, although they do mimic a mini CME in some ways.  Typically for a CIR, the density will spike much, much higher than it did here, and the solar wind speed will not spike at all (the HSS that comes after the CIR appears as a slow rise in speed some time after the main CIR has passed).  Only CMEs appear as a step-like increase in almost all solar wind and IMF plots.

@Sander Vancanneyt, would the spike from ground magnetometers at the time indicate that it's a CME and not a CIR, or would they register an impact in both cases? 

[Jesterface23]

The CH HSS arrived pretty much right after I entered that. The solar wind velocities were so low that it looks like a CME and I certainly have been tricked by them before during my research.

[Vancanneyt Sander]

11 minuten geleden, Orneno zei:

would the spike from ground magnetometers at the time indicate that it's a CME and not a CIR, or would they register an impact in both cases? 

Ground magnetometers registered a small sudden impulse indicating the CME arrival at Earth. CIR/CH don’t have a sudden impulse as data of speed and IMF are always slow rising and not a sudden jump.

[Jesterface23]

8 hours ago, Vancanneyt Sander said:

CIR/CH don’t have a sudden impulse as data of speed and IMF are always slow rising and not a sudden jump.

 

It is fairly rare but it can happen. Trust me on this one.

Here is an very clear one from January 8th, 2018,

Solar wind data:
https://drive.google.com/file/d/1I8lKP_wdHIcjQt7LRp2LZ6oblMMp8U7B/view?usp=sharing

Geomagnetometers:
https://drive.google.com/file/d/13z14fRroR_1C97PgWA7L48F_ULSegeCv/view?usp=sharing

 

[Drax Spacex]

On 12/25/2021 at 4:55 PM, Christopher S. said:

IMF is likely carrying these winds we've been seeing. Based on CME direction and IMF "wave" locations, I imagine it's a lot like low- and high-pressure behavior that we see on Earth in the form of winds behind a trough. The "trough" in this case is a band of dense plasma rotating around the Sun as part of the IMF, enhanced by activity maybe. 

I'm talking purely from logical hypothesis. There's likely people who know more on this particular topic, but, I'd point at that for an explanation.

"Cosmic Squall Line" could perhaps be analogous terminology for EM disturbances and intense winds ahead of the leading edge of a solar event front.  I know different terminology has been adopted for space weather.  It would make an interesting spreadsheet to correlate terrestrial weather terminology and space weather terminology where there is some relationship or equivalent, even if it is merely descriptive.

[Drax Spacex]

We've seen many stairstep jumps in the solar wind and density graphs In the past 24 hours which I doubt correspond to individual CMEs.  Solar wind gusts within a CH HSS?  Jittery data?  ACE/DSCOVR source data swapping?  I don't know.  It's difficult to ascribe a physical explanation if the data accuracy / validity is questionable.

Dec 28

[Sam Warfel]

17 minutes ago, Drax Spacex said:

We've seen many stairstep jumps in the solar wind and density graphs In the past 24 hours which I doubt correspond to individual CMEs.  Solar wind gusts within a CH HSS?  Jittery data?  ACE/DSCOVR source data swapping?  I don't know.  It's difficult to ascribe a physical explanation if the data accuracy / validity is questionable.

Dec 28

Yeah that’s odd-looking data for sure 

Is there a way to tell if the data is from ACE or DSCOVR?

Edited December 28, 2021 by Orneno

[Drax Spacex]

39 minutes ago, Orneno said:

Yeah that’s odd-looking data for sure 

Is there a way to tell if the data is from ACE or DSCOVR?

I believe you can select between ACE or DSCOVR from https://www.swpc.noaa.gov/products/real-time-solar-wind if your browser supports it. 

[Jesterface23]

I didn't forget SOHO for once, http://umtof.umd.edu/pm/. Maybe DSCOVR is using different levels of data at different times, or it's just glitched out. Even when data is correct the different parameters won't match across the different satellites though. They are each unique.

Edited December 28, 2021 by Jesterface23