Archive | July 2011

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.