Has anybody been watching the big K index figures over the past few days... and yet the there has been no significant flares, what is going on?
-David - VK3KCX
K index
Re: K index
There some sort of magnetic thing last night again
Us were complaining about it on 40m
Us were complaining about it on 40m
Re: K index
David,
The K index is a measure of Geomagnetic activity, not a measure of flare activity.
Often one associates flare activity with the K index, but that is usually because when there are a large number of flares, there will often result in large CME's (Coronal mass ejections) which ultimately impinge on the earth's magnetic field some 36 or so hours later.
Remember the flare results in large amounts of UV radiation (read 8 minutes to get to us from the sun), whereas the CME is slow moving protons which take around 36 hours to arrive.
If you look at http://www.spaceweather.com/ you will see up to date graphs of K and A indices.
Cheers
Peter VK3QI
The K index is a measure of Geomagnetic activity, not a measure of flare activity.
Often one associates flare activity with the K index, but that is usually because when there are a large number of flares, there will often result in large CME's (Coronal mass ejections) which ultimately impinge on the earth's magnetic field some 36 or so hours later.
Remember the flare results in large amounts of UV radiation (read 8 minutes to get to us from the sun), whereas the CME is slow moving protons which take around 36 hours to arrive.
If you look at http://www.spaceweather.com/ you will see up to date graphs of K and A indices.
Cheers
Peter VK3QI
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VK3KCX
Re: K index
Thanks for the link Peter, I'm familiar with the usual relationship and the time delays involved, I think this line contains the answer - "How can such a display occur while solar activity is so low? The answer has to do with the interplanetary magnetic field (IMF). On Sept. 7th, the IMF tilted south, opening a crack in Earth's magnetosphere. Solar wind (which exists even during times of quiet) poured in to fuel the auroras."
Very interesting, on the two occasions I'm aware of this cycle when it may have been possible to see the Southern lights from near Melbourne the visibility has been very poor, I hope there will be another chance.
- David Pratt
VK3KCX
Very interesting, on the two occasions I'm aware of this cycle when it may have been possible to see the Southern lights from near Melbourne the visibility has been very poor, I hope there will be another chance.
- David Pratt
VK3KCX
Re: K index
David,
As a general rule, auroral displays tend to occur during the cycle peaks and on the trailing parts of the solar cycle. It may well be that as the cycle diminishes, the interplanetary magnetic field is more susceptible to changes and consequent opportunities for auroral displays to occur further north (or south) than usual.
A pity about the poor visibility with the recent events. I was down in Ocean Grove for one of the recent events and the view south over the ocean was quite impressive.
Cheers
Peter (notcb)
As a general rule, auroral displays tend to occur during the cycle peaks and on the trailing parts of the solar cycle. It may well be that as the cycle diminishes, the interplanetary magnetic field is more susceptible to changes and consequent opportunities for auroral displays to occur further north (or south) than usual.
A pity about the poor visibility with the recent events. I was down in Ocean Grove for one of the recent events and the view south over the ocean was quite impressive.
Cheers
Peter (notcb)