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View Full Version : No big solar wind, no CME, why is there an aurora?



beskeptical
2005-Mar-15, 06:51 AM
Twice now there has been a G1 or G2 auroral activity spike as seen on the SEC site, (not a visible aurora here but I'm assuming one could have seen it in north of here). With both of these instances the solar wind wasn't remarkable on the ACE gage. There weren't any CMEs. There have been a couple CMEs on the non-Earth facing side of the Sun but I think if we had gotten a glancing blow, one, spaceweather would have noted it, and two, we still should have seen a solar wind gust or high density protons but none of those things happened.

So folks, what causes auroral activity besides particles from the Sun hitting the magnetosphere? Or which particles are hitting us that aren't monitored on the usual gages?

http://www.sec.noaa.gov/rt_plots/satenv.html
See Mar 14 if you get a later page on the link.
It does show electrons hitting the satellite monitors.

There's a lot of other data on the site but I can't easily make sense of any of it.

Lance
2005-Mar-15, 01:28 PM
I've been watching some beautiful aurora on the Aurora Web Cam in Alaska (http://salmon.nict.go.jp/live/aurora_cam/live_aurora_cam_e.html) for a while now. It's beginning to fade.

beskeptical
2005-Mar-15, 11:13 PM
So where/what is the source?????

frogesque
2005-Mar-15, 11:52 PM
It's all very quiet at the moment. I might have caught a proton aurora on 8/9th March but nothing since. I've got to stress the jury's not in yet on this pic (http://frogesque.com/aurora/proton%20aurora3a.jpg) I've seen the Kp take a few hikes into the red during the past few days(nowhere near the 6.5 min I need) and there was a 6.0 spike about the time I took that. I need to go back to the same location and get a reference photo with similar conditions but without aurora present for comparison. To let you understand my caution there is some pretty awful sodium light pollution hereabouts but I could definately see that diffuse red skyglow.

What I have noticed is that we can sometimes get a minor sub-storm here after conditions have been stable for a while. It's as if the ionosphere gradually builds up a magnetic flux and then some lines snap releasing the energy. That idea probably belongs in ATM by the way and I've no theory to back it. :lol: It's just an observation.

Other than that I'm fresh out of ideas so I just keep lookin at the indicators and watch the sky any time I'm out.

publiusr
2005-Mar-16, 07:30 PM
Some say it was HAARP, and/or some sounding rocket with chemicals aboard.

beskeptical
2005-Mar-19, 10:16 AM
Some say it was HAARP, and/or some sounding rocket with chemicals aboard.No way. One rocket causing a widespread aurora? Kind of hard to imagine.

Anyway, there was another G1 storm tonight. I noted a solar 'breeze'. So I am going to have to guess it is solar wind unless someone more knowledgeable chimes in here. We haven't gotten too many folk's attention to the thread.

frogesque
2005-Mar-19, 11:23 AM
Spaceweather have an item up about March being the best time to get aurora due to the Earth's tilt and magnetic orientation. Unfortunately our weather has been very erratic here and it's been some time since I've been able to get out when indicators have been even moderate.

SarahMc
2005-Mar-19, 09:11 PM
In addition to what Frogesque mentioned, Coronal holes will also increase the speed and density of the solar wind, causing an auroral display under good conditions. This past week we had such an occurance. The other event which can cause aurora would be a prominence eruption (which would be similar to a CME, but usually much slower moving).

um3k
2005-Mar-19, 11:43 PM
I was outside last night, the sky looked green. But, I'm at 41 degrees north, and I don't think an aurora would be visible here. So I was either hallucinating or it was light pollution or something. I did see Jupiter though. :D

beskeptical
2005-Mar-20, 12:54 AM
In addition to what Frogesque mentioned, Coronal holes will also increase the speed and density of the solar wind, causing an auroral display under good conditions. This past week we had such an occurance. The other event which can cause aurora would be a prominence eruption (which would be similar to a CME, but usually much slower moving).There were no coronal holes. I said that in the OP. There were no coronal mass ejections. I said that in the OP.

Actually, if you played the GIF movies at the bottom of the SOHO page (http://sohowww.nascom.nasa.gov/data/realtime-images.html) on both the LASCO C2 and C3 there were no Earth directed ejections. There were some ejections from the far side of the Sun, but no mention of 'glancing blows' on the http://www.spaceweather.com page. The fact spaceweather say this is aurora season has to do with the Earth's magnetic field position, but without solar wind or ejections there is nothing to spark the aurora.

Eroica
2005-Mar-20, 09:14 AM
There were no coronal holes. I said that in the OP.
You did? I must have missed it.

frogesque
2005-Mar-20, 09:23 AM
I think that's the whole deal with aurora. You can have all the indicators screaming at you and yet see nothing of any note and other times they just appear like from nowhere. Prediction is far from a given as yet and to me that's part of their mystery and appeal.

In reply to um3k, there was a brief spike on the Kp index (about 5 IIRC) on Saturday so you may have seen something. You say you are 41N, is that geographic or magnetic?

Edit: Yep, Kp 5 about 01.30 UTC on 19th March (http://www.sec.noaa.gov/rt_plots/kp_3d.html) (each bar on the graph covers 3 hours)

SarahMc
2005-Mar-20, 03:03 PM
There were no coronal holes. I said that in the OP. There were no coronal mass ejections. I said that in the OP.

See this page (http://www.dxlc.com/solar/coronal_holes.html) for the last few months of coronal hole history, including this past week.


Actually, if you played the GIF movies at the bottom of the SOHO page (http://sohowww.nascom.nasa.gov/data/realtime-images.html) on both the LASCO C2 and C3 there were no Earth directed ejections. There were some ejections from the far side of the Sun, but no mention of 'glancing blows' on the http://www.spaceweather.com page. The fact spaceweather say this is aurora season has to do with the Earth's magnetic field position, but without solar wind or ejections there is nothing to spark the aurora.

Streams from coronal holes aren't going to be visible on LASCO C3 images unless the streams aren't geoeffective. You can see them off to the sides as "helmet streamers", but once they rotate in line with us they're next to impossible to see.

You are correct that there were no geoeffective CME's. There was however, a very prominent solar wind for the entire week (http://www.sec.noaa.gov/ace/MAG_SWEPAM_7d.html), in which there were three instances where the IMF went southerly, allowing for minor geomagnetic storming and auroral displays to occur at higher latitudes. One instance was from high particle densities, the other two from increased solar wind speeds from CH152 - a recurrent coronal hole which had rotated into geoeffective position on the 14th.

um3k
2005-Mar-20, 03:16 PM
In reply to um3k, there was a brief spike on the Kp index (about 5 IIRC) on Saturday so you may have seen something. You say you are 41N, is that geographic or magnetic?

Edit: Yep, Kp 5 about 01.30 UTC on 19th March (http://www.sec.noaa.gov/rt_plots/kp_3d.html) (each bar on the graph covers 3 hours)
Geographic. I didn't even realize there was such thing as magnetic coordinates! It makes sense that there is, though.

It was a hazy night and there's a lot of light pollution around here, so I'm still kind of doubtful that it was an aurora that I saw.

beskeptical
2005-Mar-21, 07:23 AM
There were no coronal holes. I said that in the OP.
You did? I must have missed it."the solar wind wasn't remarkable "

If one has a coronal hole, the solar weather results when they reach us is solar wind. I'm sorry, my brain merged the two facts and I see where not everyone else would have done so.

Thank you for requesting a clarification.

beskeptical
2005-Mar-21, 07:26 AM
I think that's the whole deal with aurora. You can have all the indicators screaming at you and yet see nothing of any note and other times they just appear like from nowhere. Prediction is far from a given as yet and to me that's part of their mystery and appeal.

In reply to um3k, there was a brief spike on the Kp index (about 5 IIRC) on Saturday so you may have seen something. You say you are 41N, is that geographic or magnetic?

Edit: Yep, Kp 5 about 01.30 UTC on 19th March (http://www.sec.noaa.gov/rt_plots/kp_3d.html) (each bar on the graph covers 3 hours)Frog, the aurora is not magic. It has to have an underlying cause, I am asking about which particles/phenomena are the underlying cause when an aurora doesn't originate from a CME or solar wind.

However, I am not clear if there was solar wind and I missed seeing it on the ACE gauge. In that case then I'm curious about the wind dynamics when there isn't a coronal hole or CME.

Eroica
2005-Mar-21, 08:03 AM
Thank you for requesting a clarification.
And thank you for providing it. 8)

beskeptical
2005-Mar-21, 08:04 AM
There was however, a very prominent solar wind for the entire week (http://www.sec.noaa.gov/ace/MAG_SWEPAM_7d.html), in which there were three instances where the IMF went southerly, allowing for minor geomagnetic storming and auroral displays to occur at higher latitudes. One instance was from high particle densities, the other two from increased solar wind speeds from CH152 - a recurrent coronal hole which had rotated into geoeffective position on the 14th.Using the archive index on the right hand side of the Spaceweather page (http://www.spaceweather.com/index.cgi), one can look back at coronal hole reports:
Mar 4 A solar wind stream flowing from this coronal hole could reach Earth on March 7th or 8th.
Mar 10 Earth is inside a solar wind stream flowing from the indicated coronal hole.
Mar 11, 13, 14, 15 There are no big coronal holes on the Earth-facing side of the sun today.
Mar 18 A new coronal hole is emerging over the sun's eastern limb. A solar wind stream flowing from this hole could reach Earth on or about March 24th. For the coronal hole in position on Mar 10th, it is confusing because we had Kp 5-6 on 6th - 8th of Mar but nothing higher than 4 until the 14th.

http://www.sec.noaa.gov/ftpdir/plots/2005_plots/kp/20050308_kp.gif
March 6th Kp 5, 7th Kp 6, 8th Kp5

http://www.sec.noaa.gov/ftpdir/plots/2005_plots/kp/20050315_kp.gif
Mar 14 Kp5

Then with no holes until the 18th which don't affect us until the 24th we still had a Kp of 5 on the 19th.

http://www.sec.noaa.gov/ftpdir/plots/2005_plots/kp/20050319_kp.gif
Mar 19 Kp5

My head is spinning trying to keep track, but I think the problem is the spaceweather data is only on large coronal holes. Your data seems to be more detailed. I think that explains it.

beskeptical
2006-Jan-26, 09:33 PM
Well this reinforces what our very knowledgeable member SarahMc said.

http://www.spaceweather.com/

AURORAS! Last night, for no particular reason, the interplanetary magnetic field (IMF) near Earth tipped south. This caused a hole to open in Earth's magnetic field, allowing solar wind energy to slip through.

I started this thread a while back when we had a moderate incident of auroras despite no solar wind from a coronal hole and no CME striking Earth. And I knew when we had those two things, the fact the Earth's magnetic field tipped south made for much bigger auroras.

Here is the explanation, just tipping south alone is enough to get an aurora with normal background solar wind levels.