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Sunspots ahoy!

Over on our sister site, the Old Weather team are digitising ship’s logs from first world war Royal Navy vessels in order to capture the valuable meteorological information that the fleet collected. These records also contain information that can be surprisingly useful for a whole host of other reasons.

One such example was identified by HebesDad and brought to our attention over at Solar Stormwatch by Caro.

Log_and_zoom

In the log of H.M.S. Hilary on Saturday February 10th 1917, the observer wrote;
“at noon aTS observed spots near centre of sun like this [diagram] it appeared to be two with a narrow passage between them, I make this note, for although I have seen sun spots before, I have never seen such large ones”

This is an unusual sighting and, if observed with the naked eye, (something you should never try to do as you risk damaging your eyes) the spots must have been very large indeed.

I consulted my colleagues at the UK Solar System Data Centre at the Rutherford Appleton Laboratory and they were able to confirm that this observation was indeed correct. Photographs taken from the Dehra Dun observatory show quite clearly that on that day, and on the days leading up to the 10th, a large sunspot group was indeed observed almost exactly as the observer on H.M.S. Hilary described.

Feb_1917_sunspots

My colleague Dr David Willis, an expert on historical sunspot observations, informs me that the accepted limit above which sunspots can be seen with the naked eye is taken to be when a sunspot exceeds an area of 500 millionths of the Sun’s visible hemisphere. On my screen, the Sun has a diameter of 220mm while the spots are around 10 mm. Using the formula for the area of a circle (3.14 x [radius squared]), I estimate that the area of each of these spots is around 6195 millionths of the total area of the Sun. These sunspots are clearly above the threshold to be viewed with the naked eye!

David also provided information from the Greenwich observatory publication “Sunspots and Geomagnetic-Storm Data Derived From Greenwich Observations 1874-1954” (HM Stationary Office, 1955). In a list of the 55 greatest sunspots in the interval 1874-1954 this sunspot group (number 7977) recorded the 8th largest maximum area.

The reason we are so interested in observation of sunspots is that these regions are closely linked with solar mass ejections – vast eruptions of material from the Sun’s atmosphere. If one of these eruptions comes towards Earth, it can generate spectacular auroral displays, disturb the Earth’s magnetic field – leading to anomalous compass bearings, deplete the ionosphere (the electrically charged layers in the Earth’s upper atmosphere) – leading to disruption of radio communications, and cause surges of electricity along any long cables such as power and communications networks.

Matthew Wild at the UKSSDC generated a plot of the aa index for February 1917. The aa index is a measure of the variability in Earth’s magnetic field. This index compares the measurements made by two magnetic observatories on opposite sides of the World in the UK and Australia. Measurements started in 1868. Originally the UK measurements were made at Kew in London but they are now made at Hartland in the UK while the Australian measurements are made in Canberra. Large values of aa represent a disturbed magnetic field.

191702_aa

Looking at the aa index for February 1917 we can see that the values around the 10th were not particularly high but that on the 15th February, aa levels increased from around 20 to over 150! It is likely that this is a result of the Earth being hit by a solar storm launched from this enormous sunspot group. It is difficult to say how big or fast this storm was since we have no record of when it was launched but these storms travel at speeds between 400 and 2000 km per second, reaching Earth in 1-3 days. It would be interesting to see if any ships reported erratic compass bearings during this time as the cloud of solar material buffeted the Earth’s magnetic field in space. Variable magnetic fields set up electrical currents that heat the Earth’s upper atmosphere, depleting the ionisation there. As a consequence, wireless operators, using the ionosphere to reflect their wireless signals around the world, would also have noticed a weakened signal strengths in the days that followed the arrival of the solar storm at Earth. The Greenwich publication noted a ‘small’ geomagnetic storm on the 15th and rather curiously relates it to the much smaller sunspot group number 7990 though there seems to be no conclusive proof of this.

So, there you have it. A rare observation of a large sunspot group visible with the naked eye recorded with precision by a diligent observer who presumably knew the potential impact that such an observation could have to both the ship’s navigation and radio communication (if it was equipped with such modern technology).

Sunspot_photo_and_drawing

If you are interested in finding out more about the Sun and solar storms feel free to join us over at solar stormwatch where you can even help predict the arrival of solar storms at Earth. Meanwhile please keep us posted on any sightings of aurora, sunspots, erratic compass needles or poor wireless reception. They are all clues about the activity of the Sun in a time long before spaceflight.

My thanks to Matthew, Sarah and David at the Rutherford Appleton Laboratory for helping to piece this story together. If you would like more information about the UK Solar System Data Centre and the records it contains, visit http://www.ukssdc.ac.uk. Solar images are under Crown Copyright.

Chris.

Storms, data-analysis and fruitcake

Thanks to everyone who helped track the most recent bunch of solar storms. Several of them came by Earth but their magnetic fields were mostly the same polarity as Earth’s and when this happens, just like in the school experiment, the two magnetic fields just bounce off each other. I was amazed that we could track an Earth-directed storm at all from where the spacecraft are now, particularly with the gaps now appearing in the data coverage in incoming-traceit. You are really showing us what the limits are on our mission! Keep tracking the real-time events though. Even if we can’t track them to Earth very easily we can still test out our tracking skills by watching them go by other planets. We have spacecraft around all the inner planets at the moment:- Messenger at Mercury, Venus Express at Venus, the sister-craft to Mars Express which (amongst others) is orbiting Mars.

Thanks to your efforts we now have two publications that used your clicks to help track storms and dust. The next task we’re aiming to do is to analyse the huge amount of data you have processed in the trace-it archive. With this dataset we hope to track each storm in detail as it expands out into the solar wind. Experts like Solar Stormwatch’s own Neel Savani can turn your clicks into a comprehensive survey of all the storms we have seen. Not only will this analysis tell us how fast and how big each storm was, it should also reveal how much it was distorted by the solar wind into which it was expanding – vital information in tracking their progress towards our planet.

So, please keep clicking on trace-it archive data too. The real time stuff may be the most exciting but the careful consideration of the archived data will be an important part of the Solar Stormwatch legacy too.

And the fruitcake? Ah… I appear to have eaten the last photograph of one that Jules posted to the forum… sorry.

Thanks once again for all your enthusiasm, time and efforts. It really is a privilege working with you all.

Chris.

Real science, real progress

Hi Stormwatchers! The science team may have been a bit quiet on the Stormwatch forum of late but that doesn’t mean we’re not still involved. You may have seen the announcement in the forum pages of our first Stormwatch related paper, published in the Monthly Notices of the Royal Astronomical Society. This focussed on the detection of interplanetary dust from particle trails seen in HI images. If you want to see how your efforts translated to real science, a preview of the paper can be found at; http://arxiv.org/abs/1111.4389 thanks to everyone who spent the time looking at dust! There is a second paper, this time using Stormwatch identifications of solar storms to remove them from the data so that we could look at the effects of high speed solar wind streams arriving at Earth. This paper has been submitted to the Space Weather journal and is currently under review (it is sent to fellow scientists for their comments to ensure that we’re not saying anything incorrect or outrageous). I’ll let you know when I hear more about this. So, we have two publications on the go, with real science informed by your efforts. Thank you so much, we really appreciate your time and efforts but it won’t stop there. Currently we have scientists lined up to take a look at the Stormwatch real-time forecasts generated by you in incoming! and incoming trace-it, and also someone who will be looking at the comet data. This is potentially really exciting as we’re hoping to use observations of the absorption of starlight as the tail drifts across distance starts to tell us something about the particle sizes in the comet tail. Comparing these with observations made in the infra-red by the Herschel spacecraft will hopefully provide some insight into the generation of the very material that we have seen hitting the STEREO spacecraft!

You may also have seen that there was an earth-directed storm that arrived at Earth today without us being able to make a prediction from your clicks. This may have been due to unfortunate gaps in the telemetry from the spacecraft or simply that the spacecraft are now sufficiently far from Earth that making such forecasts for our planet are becoming more challenging. Please keep clicking though, any storm tracked in the science and real-time data is providing us with valuable information on what we will need if we are to accurately predict these storms in future. There is plenty of information left to be mined from our data and we simply wouldn’t be able to do it without you all. Thank you once again for your enthusiasm, efforts and time. It’s such a privilege to be working with you all.

Chris.

Astronomy Photographer of the Year 2011 – the solar selection

Last month I attended the Astronomy Photographer of the Year awards, held at the Royal Observatory Greenwich, with fellow Solar Stormwatch forum moderator ElisabethB (Els) and fellow Moon Zoo forum moderator Geoff. The overall winner was an amazing photo of Jupiter, Io and Ganymede by Damian Peach showing detail on the two moons  – well worth pouring over in high resolution. Some solar astrophotos made the final list this year. In particular Dani Caxete’s photo of the ISS crossing the Sun was one of our favourites as this required nerves of steel to click the shutter at the precise moment.

Here are the solar related photos that made it through to the finals.

“Earth and Space” category runners up:

Divine Presence
by Ole C. Salomonsen (Norway)

high resolution version
Volcanic Aurora
by Örvar Atli Þorgeirsson (Iceland)

high resolution version

“Our Solar System” category runners up:

May 7th Hydrogen-Alpha Sun
by Peter Ward (Australia)


high resolution version
ISS and Endeavour crossing the Sun
by Dani Caxete (Spain)


high resolution version

And here are some that didn’t make the final:

Another ISS transit
by Thierry Legault
Entitled “solar keyhole”
by Steven Christenson
A different kind of transit
by astronominsk
A fabulous sunset
by Stefano De Rosa
A sun halo
by Niki Giada

More photos and information on the APOTY website and the Flickr APOTY pool.


Clicks to Predictions I – Incoming trace – Identify Storms

Every four hours we pull all the data from incoming trace-it from the database, this give us a massive file with lines looking like.

20110601_014721_hiB_jmap_999,99437,2455712.838797814:43.66942148760331,2455712.707650273:40.36363636363637,2455712.5765027324:36.09366391184573,2455712.2996357013:29.757575757575758,2455712.0956284152:25.074380165289255,2455711.87704918:19.56473829201102,2455711.5710382513:14.46831955922865,2455711.3233151184:9.096418732782368

This is broken down as follows:-

  • 20110601_014721_hiB_jmap_999 – the name of the jmap – identifies the latest data in the jmap, the camera and in this case that the data is for the ecliptic plane.
  • 99437 – the code number for the user
  • 2455712.838797814 the date [as a julian date] here 2011/05/31 08:7:52 GMT
  • 43.66942148760331 the elongation angle measured from the image

These last two fields repeat as a pair for the entire profile.

The first process is some simple housekeeping where the result set in each profile is ordered in time and where people have clicked on two traces the line is split into two separate entries; there is a potential pitfall here if two profiles overlap in time and contributors are discouraged from doing this but this process at least allows this data to go forward.

The profiles are then collected into sets arranged by the earliest time in the profile, if from less that 10 degrees elongation, rounded to the nearest hour and split by spacecraft ahead or behind.

The next process counts the number of profiles in each of these bins, but also introduces the concept of a “good” profile that must have a least 3 points and span an elongation range of at least 5 degrees. A 7 hour running window is then computed over the count of good assets. Intervals are then identified where there are more than 10 profiles and the largest value in that range is then identified as an event.

For each event all results meeting the “good” criteria in a 7 hour running window are gathered together into a single file for the fitting process.

The plot shows for August 2010 in red the total number of profiles, in green the total number of “good” profiles and in blue the running total and shows three distinct events on the behind spacecraft and two on ahead.
Number of storm watch traces August 2010

In my next post I will discuss taking the clicks for a single profile and producing speeds and directions.

Steve

First results from trace-it!

Now that you have been analysing the data for some time, we can now start to look at the results that are coming out from your anayses. First off, thank you all for your efforts. I’m genuinely humbled that so many of you have taken time to click on our data.

We have been using the information you have provided via the spot! videos to identify storms and give preliminary values of the their speeds and directions where we can. Jackie has used these numbers to identify the start-times of storms in the jmaps we show you in trace-it (this tells us where to put that pesky blue bar on the jmap to show you which line we are interested in!).

Recently, I’ve been looking at your clicks from Trace-it and thought you’d like to see the preliminary results.

First off is a plot showing the speeds of storms from HI-A;

Velocity_histogram_STEREO-A

Here N is the number we see at each speed, so the taller the column, the more storms we see with that particular speed. This distribution certainly is a picture of a quiet solar wind! Most storms are travelling with speeds around 350 km/s but there are a few faster ones…

If we look at the distribution of speeds of storms seen in HI-B we see much the same picture;

Velocity_histogram_STEREO-B

Again, most with a relatively slow velocity (350 km/s) while a few have much faster velocities (for comparison, the famous Carrington storm of 1859 travelled at around 2,500 km/s reaching Earth in 17 hours).

So, what do your results tell us? Well, for one thing, it certainly is true that storms can occur at any time of the solar activity cycle. We were amazed to see so many with STEREO at a period when the Sun was quieter than at any time in the last century! The fact that storms still occur means that there are still changes occuring in the Sun’s magnetic cycle. Some scientists think that solar storms are the mechanism by which the magnetic field continues to evolve on the Sun. Even if the field is so weak on the solar disk that there are no obvious sun-spots. The fact that we can see storm activity during this period of extreme quiet is interesting evidence for this continued evolution. The fact that most were no faster than the solar wind would have meant that without spacecraft like STEREO and ACE they would probably have gone largely undetected.

I also plotted out the angles of the storm trajectories with respect to the Earth for HI-A;

Angle_histogram_STEREO-A

We have seem storms over a wide variety of angles, as we’d expect (they should be emitted in random directions as the Sun doesn’t pick on the Earth out of spite!). The fact that the distribution peaks at an angle of zero (headed Earthward) is likely to be due to the evolving geometry of the mission as the spacecraft head away from Earth. The distribution for HI-B looks similar;

Angle_histogram_STEREO-B

So, what do these first results tell us? Well, for starters it confirms that you are doing a fantastic job! It also confirms that there have been few spectacularly fast storms. Our next steps will be to compare the data from both spacecraft to see if they agree with each other (!) and update the speed and directions for the storms you have already identified in ‘Spot’ but for which we couldn’t estimate the speed. Then we can pick out (say) the Earth-directed ones and take a look at them in more detail.

We could still use your help in trace-it though so please keep looking at our data. The more clicks we have, the more accurately we can determine each storm’s characteristics. Eventually we hope to learn how fast each storm expands into space in all directions, how it is slowed or accelerated by the solar wind and how we can use these corrections to better predict the arrival of such storms at Earth.

Thanks again for all your time, effort and enthusiasm. Without you we would not be learning as much as we are nor learning it as fast.

Chris.

HI ho, HI ho, it’s off to work we go!

We’ve been meeting with various people lately who are all interested in using your data analysis in their research. As a result, I thought I’d update you on our plans.

Firstly, thanks to everyone who has been contributing to the real-time forecasting of space-weather events. With the spacecraft now heading towards the far side of the Sun from the Earth, I don’t know how much longer we will be able to forecast Earth-impacting storms so it’s great that we are able to hone our prediction skills while we can! This is all very useful information and will provide valuable insight into designing the follow-on solar missions that will attempt to provide on-going space-weather forecasts. In order to assess how successful we have been with our real-time forecasts, researchers at Imperial College in London will be scrutinising your clicks and comparing our predictions with those from the higher resolution science data. The real-time beacon is much lower in resolution than the science data (used in the trace-it and spot games) and we want to know if that affects our ability to make accurate forecasts. If it does, that is a strong argument to improve the resolution of future real-time space-weather missions. If not, then we can save money by sticking with what we have! Either way, we want to learn what we can from your analysis of the STEREO real-time data.

In addition to the real-time analysis, Neel Savani, one of our Stormwatch regulars, is going to analyse the science data from trace-it and produce some catalogues of the storms we have seen so far. With all your efforts, we should be able to not only provide estimates of speeds and directions but also look at how each storm expands as it travels out from the Sun.

… and what about the dust impacts? I hear you cry. Well, that paper is very close to being submitted but we’re still trying to understand exactly what’s going on there. I will be sure to let you know as soon as we find out!

Meantime, it looks like Neel could win the race for the fist stormwatch paper to be submitted. those of you who have been looking at the forum will have seen that Neel set up a mini-project asking you to look out for perfectly circular storms. Well, it seems he’s been busy preparing a publication on that too.

I haven’t mentioned some of the games here but don’t think that means we’re not using the data from them. We’re just starting to pick through the mountain of information. We’ll get to the others in good time.

In the next few months, we will see the fruits of your labours being put out to the sceintific community for scrutiny. Thank you all so much for your efforts, however much you have been able to do. It’s all much appreciated and we couldn’t have done any of this without you.

Chris.

Solar storm has arrived at Earth: Congratulations Stormwatchers!

As Stormwatch team-member Steve commented to us a couple of days ago, solar storms are like buses. None for ages and then three turn up at once. This time however, we were ready for them and thanks to all of you who took the time to click on our data we were able to predict the arrival time to within 7 hours – our closest prediction yet! The Stormwatch alert warned of a storm heading in a direction that would take it within 3 degrees of Earth and that it would arrive at around 9 UT (GMT) on the 18th February.

At around 01:00 UT on the 18th, the ACE spacecraft (which sits around a million miles upstream of the Earth in the solar wind), saw a simultaneous increase in magnetic field strength, solar wind speed, density and temperature. A classic signature of a CME as detailed by Christian on this very blog a few days ago. You need to add on about an hour to these times to get the arrival time at Earth.

The ACE data for the 18th looked like this;

CME arrival at Earth as seen by ACE 18/02/2011

The heliospheric imagers on the STEREO spacecraft ‘see’ a solar storm by imaging sunlight that is scattered off the hot cloud of plasma. The more particles there are in the solar wind, the brighter it looks in our cameras. The leading edge of the storms we observe therefore corresponds with the sudden jump in solar wind density seen by ACE at around 01:00.

We are currently asking you to scale the middle of the storm trace in ‘Trace It – Incomming’ (keep doing this, it’s the best thing to do!) as it is the easiest part to track. We need to get a few more storms under our belt before we know exactly how much lead time we need to add to improve our predictions but it’s looking like 7-12 hours based on two events.

So, will this storm cause any auroral activity? Well I’d be surprised if there wasn’t anything. The efficiency with which the solar wind can dump energy into our atmosphere depends on the orientation of the solar wind’s magnetic field with respect to the Earths. If it has a northward component (Bz is positive or greater than 0) then the solar wind and Earth’s fields are similar and, like laboratory magnets, like poles repel each other and not much interaction occurs (there may be some if the magnetic field is complex, I’m just talking about the idealised situation here). If there is a southward component however (Bz negative, less than 0) the two fields can connect (space scientist call this magnetic reconnection) allowing the solar wind to enter the Earth’s magnetic field over the north and south poles where it accelerates particles into the Earth’s atmosphere, exciting the gasses there which then glow – generating the aurora.

The longer and more extreme the period of southward Bz, the more likely there is to be auroral activity and the further equatorward this activity is likely to occur.

If you look back at the snapshot of data from the ACE spacecraft (top panel, red line), you will see that initially the storm had a northward component (+ve Bz) but that this subsequently swung southwards indicating that there may be auroral activity. Keep an eye on the real-time feed at;

http://www.swpc.noaa.gov/ace/MAG_SWEPAM_24h.html

if you want to know how conditions evolve from now on.

The skies above Oxfordshire are once again their uniform grey colour so if you have clear skies, let us know if you see any aurora in the next few days. Midnight is a good time to be looking since this is when you will be closest to the energetic particles being thrown into the upper atmosphere by the Earth’s magnetic tail as it snaps back after being stretched to breaking point by the solar wind.

Congratulations on a very successful prediction. Let’s hope we have a few more before the STEREO spacecraft move too far from the Earth. We want to hone our skills before we start making space weather predictions for Venus, Mars Jupiter and Saturn later in the mission, but more about that later… 😉

Thanks once again for all you time, efforts and enthusiasm,

Chris.

Gone with the (solar) wind …

Now that we’re trying to forecast Earth-directed solar storms, I’ve been attempting to explain how we know whether our prediction has been any good or not. This involves looking at data from a NASA spacecraft called ACE (the Advanced Composition Explorer) that sits a million km upstream of Earth and measures the Earth–directed solar wind as it blows by. The ACE data are presented as a series of wiggly lines that require an experienced eye to interpret so I was very pleased when one of the world’s experts in such data, Dr Christian Mostl from the University of Graz in Austria, agreed to give us all a lesson in how to understand what’s going on with the solar wind by studying these wiggles. So, without further delay, I will hand you over to Christian (a team can never have too many Chris’s – Chris);

What’s the solar wind doing at the moment?

Dear Stormwatchers,

Here is a little tutorial for you to understand better what is going on in the solar wind around Earth at this very moment in time. After going through this text, you will able to check for yourself in real time if the next prediction which we will issue with your help was excellent, good, bad or utterly horrific!
As pointed out earlier, this is the site to see the current space weather environment around Earth – this is one of our “weather stations” in space:

http://www.swpc.noaa.gov/ace/MAG_SWEPAM_7d.html

These strange, wiggly lines tell you the state of the solar wind for the last 7 days, observed by the Advanced Composition Explorer or ACE spacecraft, situated about 1.5 Million kilometers away from the Earth, in the sunward direction. So, first question: why are these lines so freakishly trembling? Answer: the solar wind is just a very turbulent medium. Even the “slow solar wind” (by definition around 400 kilometers per second – that’s over 1 million kilometers per hour!) is flowing away from the Sun so fast that its velocity always exceeds its own speed of sound by about a factor of 5. This makes it a constantly supersonic flow, and thus much, much more turbulent than, say, a wild river. By the way: why exactly the solar wind is so fast is one of the great mysteries of astrophysics!

Most of the time, the ACE plot will show you plain, normal, slow solar wind. I summarize here some of its parameters, which are shown in the plot, from top to bottom:

Magnetic field:
Bt (its total magnitude): around 5 nT, but always less than 10 nT.
Bz (its north-south component): between +/- 5 nT; be aware that this parameter is like the on/off button for Earth’s magnetosphere: the more southward or negative it is, the more energy will be transferred to the magnetosphere, resulting in auroras and magnetic storms. In contrast, for a positive or northward Bz, very little happens.

lets skip the next panel for simplicity, so lets go to…

N is the number density: between 1 and 10 protons/ccm. On the plot, there actually are two horizontal dashed lines at these levels, so you can easily spot outsiders. Don’t worry about data points which are below 1 p/ccm, this happens quite often. But be aware that this is a logarithmic scale, so the y-axis goes up all the way to 100, and intervals which appear slightly above 10 p/ccm can actually indicate much higher density!

V is the solar wind speed: between 300 and 450 km/s. Note that the solar wind flow points all the time almost perfectly in the direction away from the Sun.

T is the temperature: most of the time the protons have less than 100 000 K – again there is a horizontal line to guide the eye.

Now, if there is a slow solar wind, there must be a fast one too, right? Every few weeks on average, a gust of high speed solar wind, between 500 – 800 km/s, will hit Earth. They are strong enough to produce minor magnetic storms and are very good at creating beautiful auroras, but they usually lack the punch of a strong solar storm (a CME) to knock out any technological infrastructure. You can identify a high speed stream from these parameters:

Bt, Bz: a peak of 10-25 nT followed by values around 5 nT.
N: a peak of 10-20 p/ccm followed by low values of 1-5 p/ccm.
V: 500-800 km/s.
T: greater than 100 000 K, so hotter than slow solar wind.

Also, the magnetic field should be very wiggly throughout the interval where the speed is high.
Usually, N will peak first, followed by B, T, and V. This order is a consequence of a fast stream compressing the slow wind ahead of it.

Now, I have a little exercise for you: can you spot whats going on in the plot below?

Mag_swe_7d

The answer is: There is a long interval of slow solar wind followed by a high speed stream, starting on day 31. Great!

Finally, we come to the cherry on the cake: An “interplanetary coronal mass ejection” or ICME is the name given to a solar storm or coronal mass ejection (CME) you have been tracking in Solar Stormwatch when it is observed directly, on-spot or in situ by a spacecraft in the solar wind like ACE. ICME parameters are in principle elevated compared to the slow solar wind, but their signatures can vary greatly from one to another. Also, there are different regions inside an ICME. So to make it as simple as possible, watch out for intervals where B, N, V and T are much higher than normal, and yes – this can be difficult to distinguish from a high speed stream. Here is an example:

icme_realtime_3

On day 06 there is a very abrupt and strong upward jump in all the parameters – this signals the arrival of the shock wave driven by the CME! That’s the time which should be compared to the forecast which was issued by Solar Stormwatch with your help.

While not well seen in the example above, there can be intervals following the shock wave, where the Bz is very smoothly changing and T is very low. With this we can identify an ICME with certainty, and this part of it is called a “magnetic cloud”. It signals that a CME hit Earth’s magnetic field head on! Most scientists think of “magnetic clouds” being at the core of many, if not all, ICMEs, and there the magnetic fields are the strongest, giving rise to the strongest geomagnetic storms.

So, now you should be able to spot for yourself if a solar storm has just hit Earth. But beware! Often it is easy to identify a shock wave driven by the ICME by very abrupt and strong upward jumps in all the parameters, but to see if a magnetic cloud has hit Earth you will have to wait for sometimes up to at least another day. Slow ICMEs do not drive a shock and can often be identified with certainty only in retrospect.

Further questions?

http://twitter.com/chrisoutofspace

The Sun, the whole Sun and nothing but the Sun

Has it really been over four years since I watched the STEREO spacecraft rocket into the sky over Florida? The two spacecraft used lunar swing-bys to put them into Earth-like orbits, one drifting away ahead of the Earth and one behind, each retreating from the Earth at an angle (with respect to the Sun) of 22.5 degrees per year.

On Sunday February 6th 2011, just after 17:08 GMT the two spacecraft will have drifted to the point where they are on exactly opposite sides of the Sun from each other. This is a momentous moment as it will be the first time we have been able to see the entire Sun. All very interesting you may think, but why is that important? Well, it is true that the the Sun rotates just like a planet, taking around 27 days to complete one rotation so we could just wait for it to roll past. Unlike a planet however, the Sun is a continuously churning magnetic fluid that rotates at different rates at different locations. The up-shot of all this motion is that the magnetic fields get stretched, tangled and knotted, causing the vast eruptions that solar stormwatch has been designed to study. These magnetic fields connect different regions of the Sun and, while we have been able to image the Earth side of the Sun since the start of the space-age, we have never been able to image changes on the far side that may trigger eruptions towards Earth.

While the two STEREO spacecraft will image the whole sun for a fleeting moment, as they continue on their paths towards the far side of the Sun from the Earth, Earth-orbiting spacecraft like the Solar Dynamic Observatory will fill in the gap and allow at least 8 years of observations of the entire Sun.

It’s going to be a fascinating time and, by participating in Solar Stormwatch, you will be helping us to understand the complex and mysterious life of the Sun, which in turn will help us to understand the many millions of stars that adorn the night’s sky.

Thanks again for all your time, effort and enthusiasm.

Chris.