Guest CalleB Posted February 9, 2014 Share Posted February 9, 2014 Hey All(-mighty scientists)! Yesterday Kiruna magnetometer showed a 500 nt drop. For me, living in Sweden, looking at that, equals auroras in approx. half our country. And - i Ã…re there was nothing. Abisko, way up north, turned green, but nothing south of that. So, question is. How much can I trust the magnetogram? For what I've learned, magnetograms is "observations of auroras, real time". Am I wrong, and what do I miss? Cheers! Link to comment Share on other sites More sharing options...
Marcel de Bont Posted February 9, 2014 Share Posted February 9, 2014 Hey Calle, I am posted more from personal experience as aurora watcher rather than any magnetometer knowledge (which is rather limited, perhaps someone else can shed more light on that) but my experience is, is that the oval doesn't expand or contract in an instant if you see the magnetometer dive or climb. A magnetometer does however indicate that there is a disturbance in the magnetosphere at that moment. I am at 65N and have seen aurora south of my location even with Kiruna being fairly quiet. That was on March 17, 2013 when activity was high all day but Kiruna was fairly quiet when I was outside. I also remember one time that I was watching the aurora overhead and Kiruna was also fairly quiet, but the aurora got much more intense when Kiruna started to suddenly drop, this happened very sudden but the oval didn't expand much towards the north or south as far as I remember. I suspected that was a sub storm. Did you had a clear view to the north? Åre has a lot mountains, but I suspect you would absolutely be able to see something towards your north yesterday. You're lucky you didn't had clouds, I have complete cloud cover for days now. I'm in Skellefteå. Link to comment Share on other sites More sharing options...
Guest PetaFlux Posted February 10, 2014 Share Posted February 10, 2014 The magnetometer is a good indicator for auroras but it is not bullet proof, it is a complex system where the nT on the ACE also has to point sharply south for hours, to increase the odds of auroras. Worst of all, it can sometimes be auroras out of the blue, without any indicators whatsoever. Let us know if you find a way to predict auroras, you will probably become famous. Link to comment Share on other sites More sharing options...
Vancanneyt Sander Posted February 10, 2014 Share Posted February 10, 2014 magentometer is the last step. With weak disturbances you'll have to have a prolonged southward directed IMF, very strong storms require not that much. And substorms are the hardest to predict indeed ;-) Link to comment Share on other sites More sharing options...
Guest CalleB Posted February 10, 2014 Share Posted February 10, 2014 Thanks for clarifying things up a bit I'll post a longer reply and some observation on the matter tomorrow. Link to comment Share on other sites More sharing options...
Guest Harry Twinotter Posted February 11, 2014 Share Posted February 11, 2014 I have to disagree. If a ground based magnetometer reacts, then it means there is a disturbance in the magnetosphere, no matter how it came about. It is happening in real time. If aurora can't be seen it might be you are too far south of the auroral oval. Link to comment Share on other sites More sharing options...
Marcel de Bont Posted February 11, 2014 Share Posted February 11, 2014 I agree that a magnetometer indicates real time disturbances but my own knowledge purely based on watching the aurora, the oval did not seem to immediately expand southward as soon as a magnetometer plunges. Of course I alone am only able to watch a small part of the sky but I didn't get the feeling the oval responds as instantaneously as magnetometers would suggest. They can drop 100's of nT in just minutes suggesting the aurora would suddenly show up at much lower latitudes. Does that really happen? I would seriously love to hear observations from other aurora watchers about this.Btw, Calle should absolutely have been able to see something considering his magnetic latitude is similar to Macquarie Island, okay, just north of Macquarie Island but you get the point. :) Link to comment Share on other sites More sharing options...
Guest CalleB Posted February 11, 2014 Share Posted February 11, 2014 Marcel, I´m not in Åre myself. I´m running (together with a Aurora-nerd) a Facebook-page "Norrskensverige", trying to reach out and get people more interested in to see the lights, and give folks a heads up. (the more, and more I think about this, the more interested I get). I´m living in Visby (at 58 N) and I´ve been trying to forecast auroras since living in Umeå in 2008-2010. Anyway. Interesting thoughts from you all. Just let me expelling this to myself: When the nt drops, (say -500) the aurora-oval doesn´t have to "expand or grow south". As Petaflux mentioned, looking at magnetometers isn´t a bulletproof way of telling wether auroras are visible or not. Too bad.. However, when over all conditions is mediocre or high, say from a CME or a fast moving solar wind from a CH, then It´s more likely that the magnetogram is indeed a correct "aurora-meter". Basically.. Picking up on Marcel´s last sentence, "Btw, Calle should absolutely have been able to see something… " I agree. Conditions looked favorable for auroras in Åre, and also south of that. With observers out in the night (because I told fooled them out… ) during this weekend, and yesterday night, I know nothing was happening. They gladly told me… Well, I know this auroras-stuff isn´t easy and even a great forecast (the X-flare with the fast moving CME) is likely to be wrong To sum things up.. This weekend the Bz was south-oriented (well, not always) and the magnetometer i Kiruna showed nice drops around -500, -300 and nothing showed in the areas around Åre. For me, that´s a new lesson to be learned Link to comment Share on other sites More sharing options...
Marcel de Bont Posted February 11, 2014 Share Posted February 11, 2014 Ahh okay, Visby, I assumed you were in Ã…re. Visby is too far south I'd say for the activity of this weekend. Anyway...Perhaps your friend in Ã…re was out at the wrong time or didn't look north? I am not sure how experienced he is with aurora watching but even during high activity, that doesn't mean the aurora is out there every single minute of the evening. I have seen aurora displays lasting for hours but also displays that came fast, were there for 15 minutes and then they were gone again. Aurora watching can be a waiting game.But yeah, space weather is not easy to predict and neither is auroral activity bit that makes it so interesting to follow. It is however easy to get disappointed if the data is good but there is no green in the sky. Link to comment Share on other sites More sharing options...
Vancanneyt Sander Posted February 11, 2014 Share Posted February 11, 2014 I have to disagree. If a ground based magnetometer reacts, then it means there is a disturbance in the magnetosphere, no matter how it came about. It is happening in real time. If aurora can't be seen it might be you are too far south of the auroral oval.I'm not a high latitude watcher ;-) for middle latitude watchers like me it is realy the last step ;-) here in the middle latitude we have to account much more data into it to know what the real chance is. For high latitudes the magnetometer itself would be sufficient indeed. Link to comment Share on other sites More sharing options...
Guest CalleB Posted February 11, 2014 Share Posted February 11, 2014 Last night a guy was up from 00-02 (CET) and didn't´ saw nothing, in Östersund. Meanwhile in Åre, my friend took some pictures of the sky - and nothing. Link to comment Share on other sites More sharing options...
Marcel de Bont Posted February 11, 2014 Share Posted February 11, 2014 At midnight Swedish time, Kiruna did show strong deviations so it's weird that they didn't capture anything around that time. It would make sense to to say based on Kiruna there was a chance at midnight but later on activity did seem to decrease quickly. Sundsvall only showed a K-indice of 1.http://www.spaceweatherlive.com/community/uploads/monthly_02_2014/post-94-0-01897100-1392125296.pnghttp://www.spaceweatherlive.com/community/uploads/monthly_02_2014/post-94-0-73074700-1392125339.pngOh and seriously... is everyone except me having clear skies or something?! :( Link to comment Share on other sites More sharing options...
Guest Harry Twinotter Posted February 11, 2014 Share Posted February 11, 2014 Maybe a good geomagnetic storm and aurora takes a while (hours) to build up? Perhaps if the disturbance is too short you won't see much, regardless of activity on the magnetometer. Link to comment Share on other sites More sharing options...
Marcel de Bont Posted February 11, 2014 Share Posted February 11, 2014 Maybe a good geomagnetic storm and aurora takes a while (hours) to build up? Perhaps if the disturbance is too short you won't see much, regardless of activity on the magnetometer.Exactly my thoughts! Link to comment Share on other sites More sharing options...
Guest Australis Posted February 12, 2014 Share Posted February 12, 2014 A magnetometer is not a good instrument to use for aurora alerts. You only get aurora, when the auroral ovals has enough energy in it. For aurora in the Netherlands, we need at least 100 GigaWatts electrical power in the northern oval. This happend only when the IMF turns long enough southwards, if the solarwind blows fast enough to fill the auroral ovals durning this time. A disturbance on the magnetometer shows only changes in the magneticfield when a plasma cloud arrives, or magnetic changes in the solarwinds. A better indicator is the K factor. If this factor has value between 7 - 9 , it's prettig good aurora indicator. Link to comment Share on other sites More sharing options...
Vancanneyt Sander Posted February 12, 2014 Share Posted February 12, 2014 Euhm Australis... aren't the K-indices based on the readings of the magnetometer stations? Like the Kiruna station they have for that particular location specific local K-indices based on the deflection in the horizontal X component. It's the same with the personal magnetometer SAM which does the same. Aurora hunters always use the magnetometer data for their aurora chasing. You are right indeed with the energy in the ovals but there is no real-time monitor for that. Ok Ovation model does take it into account but as there is no real-time measurements we deal with magnetometers which are the fastest and real-time. NOAA POES only passes every +1h the poles so that is not very real-time. Or do you know a satellite that transmits it in real-time? Link to comment Share on other sites More sharing options...
Guest Australis Posted February 13, 2014 Share Posted February 13, 2014 A magnetometer (Kiruna example) is only a usable instrument for people who are familiar with : how the spaceweather works. I advised other people to forget this tool soon as possible! This is the reason why; We have 2 situations here, A] the Bz dropped down for 3 hours to -20nT and the solarwind has a speed of 1000km/sec B] the Bz dropped down for 10 hours to -10nT with a solarwindspeed of 600km/sec. Which situation has the biggest chance on aurora ? Propable situatie B, because the bz is much longer negative and the auroral oval has more time to fill with energy. If the solarwind speed in situation B were 400km/sec, then situation A has the best numbers. We never know it for sure, it depends of a much of triggers. In both situations the Kiruna magnetometers shows a negative dip in the graphs. Only a magnetometer says nothing at all ! ' Or do you know a satellite that transmits it in real-time?' '> @ your service ! Link to comment Share on other sites More sharing options...
Guest Stephane Mabille Posted February 19, 2014 Share Posted February 19, 2014 Incredible ! BZ south + 8 h Link to comment Share on other sites More sharing options...
Guest CalleB Posted February 19, 2014 Share Posted February 19, 2014 And! Clouds for 24 h+... Awesome. Not. Looks like it's going to subside before european darkness anyways. Or what do you think? Link to comment Share on other sites More sharing options...
Waldo Hazeleger Posted February 19, 2014 Share Posted February 19, 2014 Awesome. Geomagnetic activity (Kp=6). According to solarham due to an unexpected CME shock passage. '> Does anyone know what happend so that we have missed it? Due to what flare has this occured? Has this been visible on ACE EPAM ? Link to comment Share on other sites More sharing options...
Marcel de Bont Posted February 19, 2014 Share Posted February 19, 2014 And! Clouds for 24 h+... Awesome. Not. Looks like it's going to subside before european darkness anyways. Or what do you think? It will likely calm down a bit before it get's dark in Europe but active (Kp4) conditions will very much be possible unless the IMF goes strong north for a while now. If the Bz goes south we might see another period of G1 storming. We will have to wait and see! Awesome. Geomagnetic activity (Kp=6). According to solarham due to an unexpected CME shock passage. '> Does anyone know what happend so that we have missed it? Due to what flare has this occured? Has this been visible on ACE EPAM ? It was an unexpected CME passage. Our alert system picked it up, be sure to follow us on Twitter for the automated alerts: Weak #CME impact - Speed 504.7km/sec - IMF Bt (strength): 14.8nT. - Follow live on http://t.co/Gj5cI2OO1z pic.twitter.com/VcmWeI2iJK— SpaceWeatherLive (@_SpaceWeather_) February 19, 2014 There are a few suspects but I can not give you an definitive answer, this one truly flew under the radar. EPAM hardly budged even during the arrival of the CME at ACE, it's truly a stealthy CME. Anyway, there is another CME on-route so more geomagnetic storming is possible the coming days! Link to comment Share on other sites More sharing options...
Guest Australis Posted February 21, 2014 Share Posted February 21, 2014 @ Waldo A big filament on the west side of the sun was erupted, this storm wasn't unexpected. This type of eruptions has no hight escape speed, so it will follow the Parker spiral easily. Filement eruptions are more powerfull as an middle klass CME, especally when the filament was north-south orientated. Link to comment Share on other sites More sharing options...
Waldo Hazeleger Posted February 21, 2014 Share Posted February 21, 2014 Thank you for your explanation. So, if I understand this correctly: Normally, an eruption near the west limb will not be earth directed, but because this was a big filament eruption, this one has more chance to be earth directed. Link to comment Share on other sites More sharing options...
Guest Australis Posted February 22, 2014 Share Posted February 22, 2014 Almost right; a CME who's escaped with an hight speed from the west side of the sun, can drifted out of the Parkerspiral en passed the earth westwards. Of the CME will hit the earth in this situation, depends of the CME escape velocity. An filament has mostly low escape velocity and will follow the Parkerspiral a much easier. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.