Craig DeForest

Heliophysicist

 
 

I am interested in the formation of the solar magnetic field, solar corona, and solar wind -- and the tools we use to probe them.  The magnetic field links every aspect of the solar system, from the star’s deep interior to the environment in deep space and planetary neighborhoods, to the dimensions of our local bubble in interstellar space.  This system is large and complex, and each element of it has become the subject of an entire scientific specialty.  We are on the cusp of a new era of integrated heliophysics, when the entire system can be understood and studied as a single system rather than many isolated parts. 


In broad brushstrokes: nuclear fusion in the Sun’s interior produces mechanical energy in the Sun’s outer layers.  Convection and dynamo action transform some of that energy into a rich, complex magnetic field.  In turn, the magnetic field forms, shapes, and heats the solar corona, giving rise to a supersonic solar wind and, ultimately, “space weather” near Earth.  The exact mechanisms of magnetic energy storage and release, and even how magnetic structure in the lower corona couples to the solar wind itself, are not (yet) well understood.  Probing them requires developing new types of instrument and new data analysis techniques.


I am leading the PUNCH Small Explorer mission in order to understand the connection between the corona and the solar wind itself.

Current research topics and interests

Deep-field imaging of the young solar wind: Using the rather excellent data sets available from the STEREO mission, we were able to extract images of the Thomson-scattered light from solar wind in the heliosphere, quite far from the Sun.  These images are made by separating out the faint reflected sunlight from free electrons in the interplanetary void.  You can download two early presentations here in PowerPoint format [AAS/SPD 2011 (204 MB); Boulder Solar Day 2012 (582 MB)].  Since then, this imaging has become the focus of much of my research.  You can see my papers page for more details. results.


MHD modeling: Magnetic reconnection and its consequences are critical to understanding the solar corona.  Magnetohydrodynamics is too complex to be addressed analytically in nontrivial cases, so everyone uses numerical simulation to understand it.  Numerical codes have specific, well-known limitations -- which demand huge amounts of processing power.   We’ve been exploring a different approach to MHD modeling --  fluxon modeling -- that allows simulation of certain systems in the complete absence of unwanted magnetic reconnection with, with much less computing power.  Current efforts focus on adapting the code for space weather prediction, an application that requires a balance between physical fidelity and computing feasibility.



Open source scientific computing: I am a strong advocate of open source computing for science.  For nearly 20 years, I’ve been a developer for the Perl Data Language.  In recent years, it has become increasingly clear that Scientific Python, in particular the Numpy, Scipy, and Sunpy packages, has the traction to become a mainstream replacement to proprietary packages.  We are moving toward adopting Python as the official analysis language for PUNCH.

Karen Harvey’s Dissertation: “Magnetic Bipoles on the Sun”

Karen Harvey was a pioneer of solar magnetic image analysis, and much beloved within the solar physics community.  In 2002, I found that her important dissertation had become nearly unavailable.  Mandy Hagenaar lent me her copy of the dissertation, and I scanned it for posterity.  With permission from Jack Harvey, here is a copy of the complete dissertation, as a PDF: kharvey_dissertation.pdf (420MB)