I am MHD, an astrophysicist with degrees (Msc, PhD) from the University of Groningen, the Netherlands.
MHD are my initials, and I have been using it as a nickname on the internet (as well as in the real world) for quite some years. Coincidentally, MHD is also an acronym for Magnetohydrodynamics, a topic in which I am far from an expert, :-)
My contributions to the English wikipedia are mostly corrections of spelling or grammar errors and expanding/correcting of Astronomy related articles. I am also active at the Dutch Wikipedia.