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Post by rbateman on May 11, 2009 5:32:53 GMT
Enjoy the show on the MDI Magnetogram, Doc.
It's the only show in town.
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Post by vukcevic on May 11, 2009 21:09:46 GMT
The is a graph of the Polar Cap Magnetic Activity Index - PC North link www.geocities.com/vukcevicu/PC-North.gifAs recorded from ftp.dmi.dk/pub/wdcc1/indices/pcn/Horizontal scale is in minutes while signal is the one averaged over 15 min periods. Is there an explanation for most of the pulses lasting in of order of 4-5 hours ? Description from the website: The Polar Cap index PC (Troshichev et al, 1989) measures geomagnetic disturbances at the polar cap which are due to ionospheric and field-aligned currents. It is calculated separately for both hemispheres, from only one station in each (Thule and Vostok). The PC index was designed to measure the part of the ionospheric current system that is due to magnetospheric field line convection. As this is assumed to correlate with the solar wind input, the index measures the energy inflow from the solar wind into the Earth's magnetosphere. For example, it has been shown that the index gives the same information - but much easily - as the low altitude polar satellites measuring the diameter of the polar cap! It has been shown to agree fairly well with AE-index in the wintertime (Vassiliadis et al., 1996), although it cannot see substorms the same way. This is because the field-aligned currents are more dominant at winter time. PC indices are available from 1975 onward. You can get them from the WDC C1, Copenhagen, or from the NGDC server. |
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Post by lsvalgaard on May 11, 2009 21:28:01 GMT
The is a graph of Polar Cap Magnetic Activity Index - PC North Horizontal scale is in minutes while signal is the one averaged over 15 min periods. Is there an explanation for most of the pulses lasting in of order of 4-5 hours ? Yes, the timescale of the 'convection' is determined by how long an interplanetary field line stays connected to the Earth's magnetic field as it is streaming past the Earth's magnetotail. The tail is 1000 Earth radii long or 6,400,000 km [on average]. Solar wind speed of 400 km/sec yields then a time scale of 6,400,000/400 = 16,000 seconds or 4.44 hours. These numbers are highly variable and so is the time scale. |
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Post by vukcevic on May 11, 2009 21:36:05 GMT
Thank you !
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Post by vukcevic on May 12, 2009 14:43:08 GMT
Yes, the timescale of the 'convection' is determined by how long an interplanetary field line stays connected to the Earth's magnetic field as it is streaming past the Earth's magnetotail. The tail is 1000 Earth radii long or 6,400,000 km [on average]. Solar wind speed of 400 km/sec yields then a time scale of 6,400,000/400 = 16,000 seconds or 4.44 hours. These numbers are highly variable and so is the time scale. Dr. Svalgaard I have done more data plotting and appear that this particular period just under five hours is the most prominent, although there are many about twice as long. Is the above one of your observations and are there papers on this matter ? |
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Post by sizzler on May 23, 2009 21:05:34 GMT
Hello Dr Svalgaard,
I'm new to this site, and have only recently taken an interest in solar activity and the current minimum.
I would like to know what coronal holes are, and is there a reason why they seem to disappear when there are sunspots and other active areas visible on the solar disk.
Sam
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Post by lsvalgaard on May 23, 2009 21:19:49 GMT
Hello Dr Svalgaard, I'm new to this site, and have only recently taken an interest in solar activity and the current minimum. I would like to know what coronal holes are, and is there a reason why they seem to disappear when there are sunspots and other active areas visible on the solar disk. Sam The corona is permeated by magnetic fields. If these fields are strong [as over sunspots] the trap the coronal material which will then stay close to the Sun. The corona is a million degrees hot and the matter moves very fast, and if the magnetic field is weak [such as away from sunspots] the field is not strong enough to hold back the very fast moving matter [temperature is just a measure of how fast the atoms move - faster = hotter]. So, the strong magnetic fields from sunspots simply keeps the corona 'at home' close to the Sun, while the weak fields away from sunspots allow the corona 'to boil away' into space and to form the solar wind. Coronal holes are then simply where matter has left the Sun. The story is much more complex than this, but at least you got a first cut at an answer. |
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Post by lsvalgaard on Jun 3, 2009 4:00:31 GMT
Dr. Svalgaard, Were Drs. Livingston & Penn able to get any readings on sunspot 1019 and if they did where does if fall on their 2015 prediction line? I ask because sunspot 1019 is one of the few which has been persistent enough and large enough to be useful in some time now. Mike I've asked, so we'll know shortly. answer: Bill did not have telescope time for that one. Next observing window is 13-18 June. Let's hope there is some activity by then. |
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Post by waynelim on Jun 3, 2009 19:10:02 GMT
Dr. Svalgaard,
An unrelated question. Some time ago, in the context of discussing a sunpot region visible on the STEREO behind images but not yet rotated to an Earth-facing view, you said the LASCO images indicated to you that it was an active region because it disrupted the radial streamers that are typically visible. You then went on to give a basic explanation of what that was so, but I can't find where you posted that information. The LASCO images at that time showed almost no streamers from the side of the sun where the sunspot region was about to rotate into view.
Would you mind going over this a little more detail, or posting a link to where I can find that information? I'm interested in what things would catch the eye of a solar scientist like yourself.
Thanks.
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Post by pochas on Jun 3, 2009 19:43:29 GMT
Leif, This paper by Tlatov and Markarov studies the variation in rotation periods of the solar surface. www.solarstation.ru/TL/PDF/tl_22.pdfIt seems that at Rmax of even solar cycles the low latitude photosphere speeds up and the mid-latitude photosphere slows down. In odd numbered cycles the low latitude again speeds up but to a lesser degree, and the mid-latitude also speeds up. What do you make of this? By the way, thanks for posting the Babcock 1961 paper on your website. edit: Had "odd" and "even" reversed. Fixed. |
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Post by lsvalgaard on Jun 3, 2009 19:53:08 GMT
Dr. Svalgaard, An unrelated question. Some time ago, in the context of discussing a sunpot region visible on the STEREO behind images but not yet rotated to an Earth-facing view, you said the LASCO images indicated to you that it was an active region because it disrupted the radial streamers that are typically visible. You then went on to give a basic explanation of what that was so, but I can't find where you posted that information. The LASCO images at that time showed almost no streamers from the side of the sun where the sunspot region was about to rotate into view. Would you mind going over this a little more detail, or posting a link to where I can find that information? I'm interested in what things would catch the eye of a solar scientist like yourself. Thanks. That there was no streamer is the 'disruption' I was talking about. Without the region there 'would' have been a streamer. Now, it is a bit more complicated than that because there often is a streamer associated with an active region, so one has to be careful about precisely one is talking about. There is a 'belt' of streamers associated with the large-scale boundary between magnetic polarities. This belt is visible in the outer corona and and continues into the Heliospheric Current Sheet that we observe in interplanetary space, e.g. near the Earth. That belt can be 'upset' by an active region. Then there are the 'helmet streamers' often sitting just above the active region. Those are different from the 'belt' streamers. Here is more on this: www.iop.org/EJ/article/0004-637X/485/2/875/35781.text.htmlSee especially section 5 that deals with the distortion of the belt by an active region. |
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Post by lsvalgaard on Jun 4, 2009 23:07:11 GMT
I've asked, so we'll know shortly. answer: Bill did not have telescope time for that one. Next observing window is 13-18 June. Let's hope there is some activity by then. Dr. Svalgaard, Thank you for making the inquiry. Needless to say, I am very disappointed that telescope time could not be rescheduled do accommodate Dr. Livingston’s observations. I know that telescope time is scheduled in advance and I am sure that there are other ongoing experiments which also require access to the instruments. Let us hope that a sunspot appears between the 13 and 18 of June. Given how cantankerous the Sun as been of late we should expect absolutely nothing. Just out of curiosity, what are the setup, breakdown and actual observation time which Dr. Livingston requires to collect the data he needs? Is there anything which can be done to give Dr. Livingston’s research a higher priority? Mike The observation basically requires the full telescope for a few hours, so it is really hard to 'fit it in'. Also, there is a fairly long drive from Tucson to Kitt Peak [an hour or so] so it is a day trip. If Bill is right there will be more spots to come, we just have to be a bit patient. All in good time... |
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Post by francisco on Jun 12, 2009 17:42:42 GMT
Dr. Svalgaard, Thank you for publishing the daily graph of TSI, Flux, MF and SSN on your website. link for those who haven't seen it: www.leif.org/research/TSI-SORCE-2008-now.pngQuestion: what source is your standard for the SSN? I notice that your chart only shows 2 or 3 spotless days in June, whereas I believe that NOAA has called June 6,7,10 and 11 as spotless. Also, do you show one daily datapoint for each parameter, or more? Thanks |
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Post by sonomaca on Jun 12, 2009 17:59:05 GMT
Dr. Svalgaard, Thank you for publishing the daily graph of TSI, Flux, MF and SSN on your website. link for those who haven't seen it: www.leif.org/research/TSI-SORCE-2008-now.pngQuestion: what source is your standard for the SSN? I notice that your chart only shows 2 or 3 spotless days in June, whereas I believe that NOAA has called June 6,7,10 and 11 as spotless. Also, do you show one daily datapoint for each parameter, or more? Thanks This chart hasn't been updated in awhile. I'd be interested to see if the curves have continued to rise as pictured. |
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Post by francisco on Jun 12, 2009 18:14:09 GMT
@ sono,
Are you sure you aren't looking at an old (cached?) version? I see the last SSN datapoint plotted at about 2009.44 along the x-axis, which corresponds to today 6/12.
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