Returning to Givet

Years ago I left the small town of Givet, France as I pursued studies and a career in science. But last month, I returned to Givet… as a space scientist!

Givet is a small town in the northeastern part of France, close to the Belgian border. It is from where I am, it is where most of my family lives, and it is where I spent the first eighteen years of my life. Nothing changes as fast as in big cities there. My teacher from 1994-1995 (more than 20 years ago!) invited me to return to my primary school, l’école Saint-Hilaire, to meet her and her current class of 9 year old students. She asked me if I could tell the kids about my job as a space scientist in Berkeley, California. I was delighted to accept. But I had no clear idea what a 9 year old could be interested in. The oldest kid I know in my private circle is my godson and he is only 3.

A side note: This particular teacher was one of the first to introduce us to the English language. And, being there, I could still remember the songs we sang (Head and shoulder knees and toes; Old Mac Donald has a farm; …) and the Muzzy movie we watched oh so religiously that year.

Preparing the visit: iron filing and tinsel flying

Electric and magnetic fields are at the core of my job. But they are usually introduced in an abstract way. I set out to design a few simple experiments to help the students see some electromagnetic forces at play.

I spent a Saturday afternoon at the Exploratorium in San Francisco, in search of some cool science ideas that would illustrate my work. At the end of that day, I decided that (1) we would play with some magnets and iron fillings, to visualize some magnetic field lines, and that (2) we would make a tinsel fly, to show the action of electro-static forces. The tinsel flying experiment consists of rubbing a piece of Styrofoam with wool, and to use it to (slightly) charge an aluminum pie pan. As one drops a tinsel above the charged pan, the electrostatic force compensates gravity and the tinsel levitates! For those of you interested in doing that too: I would recommend a few hours to half-day of preparation and get-to-know the experiment before going public. I had spent some time testing the night before, as I had no tinsel, so I created my own loops out of thin aluminum tied into tiny loops. Here is a video of me practicing to become a tinsel flying champion.


In parallel, the students were preparing for the visit too. They were learning about the solar system, and about the auroras. I had recommended two Japanese mangas, one about the magnetic field and one about the auroras, translated from English to French by Pr. Fabrice Mottez (merci!), and available on his website.

The encounter

The day we met, the students were ready with questions for an interview. They were the best: curious, fun, excited, interested! We had a blast.

Here is a few of the questions that were asked to me:

  • How did you become scientist?
  • Is it a difficult job?
  • Have you ever seen auroras? (they knew I had spent some time close to the Arctic Circle, in Kiruna, Sweden)
  • Is there a chance that we will ever see an aurora in Givet?
  • Have you ever met Donald Trump? (true story)

Then, as an aside:

  • “ Have you ever met some stars?”
  • (Me, proudly): “yes, I went to a Ben Harper concert”
  • [Look of incomprehension]
  • (Me, trying again to be cool): “I saw Erykah Badu once”
  • [Look of incomprehension]
  • (Me, giving up): “…”
  • No, but I mean: have you ever met Rihanna for example?
  • (Me, feeling not cool anymore): “well, no I am sorry I have not”
  • “…”

Back on task, we dissected the word “geostationary” and we discussed the “midnight sun” phenomenon. We concluded with the experiments. First, I gave some glass jars filled with a mixture (oil + iron fillings), together with some magnets. I did not tell them what they were. I asked them to gather in groups, think about it, and then to tell me what was going on. The only rule of the road was that they could not open the jars. Instinctively, they did what scientists do: they made observations, they built a theory, they discussed it with peers, they questioned themselves, they thought of ways to test their theory, and then they made new observations. At some point, their views converged and they ended up agreeing: they told me what they were looking at the magnetic field of the magnets in the jars. I was very impressed. We concluded with some tinsel flying and let me tell you: that was a mega hit!

For more:

  • Access to all you need to know about the flying tinsel experiment [here]
  • Download the magnetic field manga (in French) [here]
  • Download the aurora manga (in French) [here]

First Full Mapping of Near-Earth Plasma Transport Achieved, Thanks to the Van Allen Probes

Maps are developed to best describe what surrounds us. That is true on the ground, and it is also true in space. There, the most interesting maps are maps of traffic conditions, i.e., maps that tell us how fast transport is, and in what the direction the flow is, depending on location. The only slight difference is that in space we are dealing with plasma transport, ions and electrons, rather than flows of cars and trucks.

To detail traffic in space, we must know both the magnetic field and the electric field: how strong are they? In what direction are they pointing? But unlike the magnetic field, the electric field is very difficult to measure, especially close to Earth! To circumvent this challenge, scientists have made assumptions and used theoretical considerations, rather than observations, to draw a simple picture of what they think the electric field should be around Earth.

This simple picture implies that the traffic conditions are as if the cold plasma was riding a giant merry-go-round, with the Earth in the center. In other words, the cold plasma is thought to rotate at the same speed as the Earth’s rotational speed, i.e., to be in corotation with the planet. Yet, this has not been proven experimentally. In fact, some sporadic particle measurements have already indicated that the merry-go-round picture was not quite right.

Using data from the Van Allen Probe satellites, we managed to make the first ever comprehensive observations of plasma transport due to the electric field close to Earth. This is a technical feat that allows us to test our 50 year old theories, at last! And the results are exciting!

Based on an analysis of more than 2 years of data, we confirmed that the cold plasma was not simply riding along a merry-go-round. In particular, we found that the speed and direction at which the plasma was drifting depended on the time of the day (or, in other words, that they depended on the location with respect to the Sun). We also found that, on average, the rotational speed of the cold plasma was 5 to 10% slower than that of the Earth. We must now understand why!

In short, our observations offer new context to existing theories; theories that merit reviews in our ongoing quest to better understand near Earth space!


For more information on that topic, you can:

  • Access the article [here]
  • Access the article by Forrest Mozer on electric field measurements in space [here]