Hi all, thanks for all your hard work tracing storm fronts so far; we’re now over a third of the way there!
Back in September, I wrote a blog post explaining why we wanted your help with Solar Stormwatch II. Since then I’ve been using the data from Solar Stormwatch II to look at how solar storm fronts change shape and distort as they travel through the heliospheric imager field of view.
In this blog post, I explain how we combine all the storms fronts that you trace into a single consensus storm front (or two) in each image, allowing the fronts of a solar storm to be studied over the whole field of view.
Differenced images of solar storms are uploaded to Solar Stormwatch II. This image shows a solar storm from May 2010, and all the images in this post are of this same storm.
Every image of a solar storm is shown to 30 people, who each draw around the outermost and brightest fronts they see in each image. Each colour represents a different front drawing.
The points from the 30 front drawings are split into two groups. We use the coordinates of the outer front in the previous image to determine which points are likely to represent the same front. These points are shown in red, and the remaining points are shown in blue.
We first look at the red points as shown in the previous step. To combine all the points and find a consensus storm front profile, we use a process called kernel density estimation. This finds the areas of the image with the highest density of points; these areas are shown in black. The largest area corresponds to the storm front.
Using the storm front area found in the previous step, we can find the expected location of the storm front (solid red line) and calculate uncertainties from the distribution of the points in this area (dashed red lines).
The previous two steps are repeated for the second set of points shown in blue. There isn’t a second front in every image, so this stage involves a check to see whether the blue points show a storm front or not.
This method is repeated for every image of a solar storm, allowing us to examine how the shape of the storm changes throughout the field of view. The animation shows the outermost storm fronts found for this solar storm as it travels away from the Sun.
I’ve been looking at several solar storms to see how the shape of the storm front compares to the solar wind speed across the front; I hope to update you on this soon!
In the meantime, we are grateful for your continued support tracing storm fronts, and if you want to help with even more space weather research, we (the Solar Stormwatch II team) have recently released another project in collaboration with the Science Museum, see here: Protect our Planet from Solar Storms.