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Recently I was asked to summarize my career and highlight how the Van Allen Probes have shaped it to date. Here is my reply:

3 Research Highlights of Solène Lejosne’s Early Career

1. Offering New Visibility on Plasma Transport in Subauroral Geospace in the Form of a Unique Database of Electric Drift Measurements (ExB/B²)

Together with Pr. Mozer, S. Lejosne has pioneered techniques to analyze RBSP-EFW data close to perigee. She demonstrated that the instruments onboard the Van Allen Probes were accurate enough to deliver reliable electric field measurements even very close to Earth (below 3 Earth radii). This database provides much-needed ground truth in a region of space historically deprived from in-situ electric field measurements due to the technical challenge that this represents. Her studies underscore the importance of magnetosphere-ionosphere coupling in the subauroral region. It often consists of examining features of the electric drift data (SAPS, ionosphere wind dynamo, disturbance dynamo, prompt penetration electric fields), and studying their consequences in terms of trapped particle drift dynamics.  

Relevant publication DOIs: 10.1002/2016GL069875, 10.1002/2016JA023613, 10.1002/2017GL074862, 10.1002/2017GL074985, 10.1029/2018GL077873, 10.1029/2018EA000550

2. Pursuing Pioneering Research on the Earth’s “Zebra Stripes”

The Van Allen Probes mission has provided unprecedented amounts of high quality data on near equatorial electric fields and energetic particle fluxes, enabling systematic empirical analyses of the “zebra stripes”. After teaming with Pr. J.G. Roederer to propose a theory for zebra stripe generation, S. Lejosne designed an algorithm to automatically detect and analyze the multitude of “zebra stripe” patterns observed by the RBSPICE instruments onboard the Van Allen Probes. The resulting statistical analysis has provided experimental information on the geomagnetic conditions usually associated with the generation, structure and evolution of the “zebra stripes”. Together with Pr. Mozer, she also reported and interpreted the 1^st observations of zebra stripe pattern inversions in the Earth’s slot region.

Relevant publication DOIs: 10.1002/2015JA021925, 10.1029/2020JA027889, 10.1029/2020GL088564

3. Rejuvenating Radial Diffusion Research

S. Lejosne dedicated her ph.D studies to radial diffusion in the Earth’s radiation belts. To celebrate the 60^th anniversary of radial diffusion research in 2019, she worked with an international team of early career researchers to write a scientific review on “Radiation Belt Radial Diffusion at Earth and Beyond” (now published in Space Science Reviews). She has highlighted the necessity to question several assumptions underlying current radial diffusion models. She has also suggested new approaches to radial diffusion quantifications. Her most recent work includes a 20 year time series of electromagnetic radial diffusion coefficients with a one-minute time resolution, based on an analysis of the solar wind immediate time history. Future work includes analyzing Van Allen Probes field and particle data to quantify electrostatic radial diffusion in the Earth’s inner radiation belt and slot region.

Relevant publication DOIs: 10.1029/2019JA026786, 10.1007/s11214-020-0642-6,10.1029/2020JA027893

I have prepared a short (< 5 min) video presentation that walks you through it all. You can check it out here!

 

My very first post on this website was on the “zebra stripes”, an intriguing feature present in electron energy spectrograms measured in the Earth’s inner radiation belt and slot region. A lot of research remains to be done on this topic, and I am happy to share some of the most recent findings.

1) Zebra stripes are usually created during substorm onset, a time at which prompt penetration electric fields are present in the plasmasphere.
For more info on the method and findings, there is now JGR Space Physics article on this! [access here]

2) The zebra stripe pattern can be disrupted and inversed in the slot region.
The first observations of this remarkable feature are presented and interpreted in our latest Geophysical Research Letter [access here]

In summary: the “zebra stripes” visible at Earth (and also Saturn!) are an exciting research topic containing a wealth of information on trapped particle dynamics.

More to come! Feedback, questions, collaborations welcome.

Sharing a bit of good news in these strange times! Recently Wiley informed me that that two of my latest works were among the top 10 % downloaded papers published in Journal of Geophysical Research: Space Physics between January 2018 and December 2019.

Interestingly, both papers provide brief reviews on a particular topic in radiation belt research:
1) adiabatic invariant theory, and
2) radial diffusion

The first paper is entitled “Coordinates For Representing Radiation Belt Particle Flux”. It is authored by Juan G. Roederer and myself. It insists on the importance of adiabatic invariant theory when it comes to analyzing measured particle fluxes, and it provides a brief review on the history of radiation belt parameterization.

The second paper, entitled “Analytic Expressions for Radial Diffusion”, discusses existing theoretical formulas to quantify radial diffusion. Unfortunately, there were many unexplained errors during the production process, and many misprints were present in the first published version of the article. The issue is now fixed.  All of this is to say: make sure you have downloaded the latest version of the paper!

I prepared the latter article while I was working with Peter Kollmann and others on a big scientific review on “Radial Diffusion at Earth and Beyond” that is now published in Space Science Reviews. Don’t hesitate to have a look if you are interested in learning more about adiabatic theory and radial diffusion! You can also navigate the website and scroll through the various seminar slides on the topic.

Thanks again for your interest in the works! and thanks all for the clicks!

 

“Synthesis is an important task in science, because it can often lead to a paradigm change” Akasofu, S.-I., 2007, preface of the second edition of “Exploring the Secrets of the Aurora”

Motivation

At the very beginning of my phD studies, my supervisor asked me to work on radiation belt radial diffusion. For months, I felt bewildered.

It took me a lot of time to find clarifications, and to answer my own questions – Why is the process diffusive? What are the drivers of this diffusion? What ingredients does one need to quantify the process?

Because radial diffusion is one of the oldest research topics of radiation belt science, its understanding evolved over time. I think that is one of the reasons why this concept can be so difficult to grasp.

As time went on, I realized that I was far from the only one facing this radial diffusion challenge. That is what motivated the writing of this review.

A Team Project

I was excited at the idea of writing a review. Yet, I could not do this on my own.

I want to say THANK YOU to Sarah, Adnane, and Peter, the early career researchers who agreed to get involved with this project. They all dedicated countless hours to help. I am also grateful to all the experienced researchers who answered my emails and helped me submit the review. To all, thanks for caring!

Objective

I hope that this review will be useful for our community … and perhaps – who knows! – lead to a paradigm shift.

So please go ahead, give it a try, and let me know what you think! All significant contributions will be acknowledged in the revised version of the manuscript – currently under review for publication in Space Science Reviews -. Merci 🙂

[Access here]