Density greyscale of an axisymmetric simulation (top half only shown) of a propagating jet (M=10, η=0.1) from left to right with: (top) passive magnetic field; (middle) strong toroidal field (β=0.2); and (bottom) strong poloidal field (β=0.2) all after the same propagation time. In 2-D, a toroidal field enhances propagation speed, a poloidal field impedes it.

 

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The maiden AZEuS simulation showing the Alfvénic Mach number (colours) and magnetic field lines of a protostellar jet with eight levels of refinement. This is the first simulation to follow a magnetocentrifugally launched jet (at resolution 0.00625 AU) to observational scales (2,000 AU) where the jet takes on its familiar bow-shock led morphology. See Ramsey & Clarke for details.

 

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Line-of-sight integration of the pseudo-synchrotron emission of two ZEUS-3D simulations of supersonic (M=10), light (η=0.1) jets with: (top) a trace magnetic field; and (bottom) a strong (β=0.2) toroidal magnetic field. Jet propagation is from left to right.

 

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Line-of-sight integration of  ∇ · v  in a jet launched magnetocentrifugally from the left face (red ring with orange centre). The jet propagates from left to right and follows a helical path as it succumbs to higher-order modes of the Kelvin-Helmholtz instability. Details in Ouyed, Clarke, & Pudritz.

 

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Line-of-sight integration of the magnetic energy density in a supersonic (M=10), super-Alfvénic turbulent medium using the Consistent Method of Characteristics (CMoC) in dzeus36 on a 256³ grid.

 

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Teaching resources

^*Course no longer part of the curriculum.

Official department curriculum

In 2007, the department curriculum was revised and fully documented. Expectations and outcomes for each course were defined, described, and placed on the web for faculty and student reference. I encourage students to review the course curriculum of each course they take, and to hold their professors accountable to its content.

Research interests

I am the developer and curator of the widely used magnetohydrodynamics (MHD) computer code, ZEUS-3D. With it, I and my students perform multi-dimensional simulations of fluid phenomena such as astrophysical jets.

 

You can read more about my research interests here, consider graduate student projects here, and see a partial list of my publications here.

 

Research-related web sites

	ZEUS-3D website for gallery, description, user/installation guides, and downloading the code (version 3.6).
	AZEuS (AMR+ZEUS-3D) website for gallery and description. The code is not yet ready for distribution.
	EDITOR is my source-code manager for ZEUS-3D and AZEuS. Version 2.2 and user manual available for download.

 

Past and present students and PDFs: Where are they now?

 

I am pleased to say that every student who finished their degree with me moved on successfully to the next logical stage of their academic career.

Early in my career, I dabbled in radio astronomy using the VLA to observe radio galaxies such as 3C 219 (above left; image courtesy Alan Bridle, NRAO). You might imagine my surprise when, about ten years later, I happened upon our data immortalised in tile on the Hayden Planetarium floor (insert; image courtesy of Jodi)!

Undergraduate research mini-symposia

Links to the programmes (PDF files) for the department's annual summer student mini-symposium that I've organised over the years.

Graduate Record Examinations (GRE).

Senior undergraduates considering applying to graduate schools in the US must determine whether taking the GRE is necessary. Some non-US schools may also require the exam as part of the application.

The exam is administered locally by Prometric Testing Centre; 6440 Quinpool Rd.; 422-8378 whom you should contact to schedule the time of your test. Exams should be taken at least four weeks before application deadline to US schools, and 6-8 weeks before deadlines to non-US schools.

As of September, 2013, the fee for the general exam is US$185, and for the subject (physics) exam, US$150, which includes delivery of your results to four institutions. Additional institutions are US$25 each. Obviously, check with the targeted school if the GREs are even required before scheduling, studying, taking, and paying for them!

University Committees

National Committees/Panels

All codes are bundled into compressed tarballs. Once downloaded and placed in the desired directory, issue the command: tar xvzf ---.tar.gz, then follow the directions in the README file in the newly created directory.

DC's personal page

Despite my background in algorithm development and supercomputer simulations, I remain a bit of a luddite. I'm not a blogger, I don't do Facebook, and I most certainly don't tweet. This web-page, then, represents my first and likely only foray into "social media".

Background

Born in Charlottetown, Prince Edward Island to Sheila (née Davison; Charlottetown) and Alan Clarke (Halifax) in 1958, I was raised in Ontario and did my B.Sc. at Queen's University at Kingston (Honours Physics, 1981). My M.Sc. (Thesis: "Two-Dimensional Collapse of a Rotating Interstellar Cloud", 1984) was also from Queen's under Dick Henriksen. My Ph.D. (Dissertation: "A Search for the Effects of Active Magnetic Fields in Extragalactic Radio Sources", 1988) was from the University of New Mexico under Jack Burns and Mike Norman (LANL, NCSA).

I was a post-doctoral fellow at the NCSA (U. Illinois) from 1988–1992 under Mike Norman, and a post-doctoral research associate at the Harvard-Smithsonian CfA from 1992–1993 under Ramesh Narayan.

In 1993, I was appointed an assistant professor at Saint Mary's University, promoted to associate professor in 1995, gained tenure in 1996, and promoted again to full professor in 2003. During my 2000–2001 sabbatical leave, I was appointed astronome invité at l'observatoire de Grenoble. You can view my CV here.

Family

I went to the U.S. in 1984 single, came home in 1993 with a family. My wife of 34 years (as of Oct. 2021), Jodi Asbell-Clarke, hails from North Haven, CT and is currently a senior science curriculum developer at a non-profit in Cambridge MA. My son, Dane, born in Albuquerque NM in 1989, received his BIT from Carleton/Algonquin in 2011 and is a graphic artist (check out his webpage!) while my daughter, Alison, born in Urbana IL in 1992, completed her political science degree from the University of Guelph in 2014. Both live in Halifax.

Both of my parents have passed. I have two brothers; Peter Clarke lives in the Toronto area with his wife Mayr, and Gordon Macdonald lives on Vancouver Island with his wife Nicky. My step-mother, Adaline O'Gorman, lives in Victoria.

Whimsy

I offer here a few snippets of "pre-historic" comedy, all from well before most of our students were born! They're timeless, they're clean, and they're fun; enjoy!

My favourite comic of all time, Dennis Wolfberg died in 1994 at the age of 48. If you have 27 minutes and can tolerate a few split sides, indulge yourself with these three You-Tube links.

Part 1: "His name was Marvin; I certainly learned that much! And his first name was More. More Marvin, more Marvin!" Part 2: "If we had a daughter, my wife wanted to name her Sue, which is a lovely name but for Jews is generally a verb!" Part 3: "...which is somewhat akin to telling someone in the path of a tidal wave: you might experience moisture!"

Many from my generation remember the Carol Burnett Show as a one-of-a-kind. In the few years SNL has been great, it has occasionally come close. A few of my favourite sketches include...

Harvey Korman trying not to laugh as Tim Conway fills himself with novacaine. "Stroke!...Stroke!...I think I'm having a...Stroke!" "Thank you, I saw it in the window, and I just couldn't resist it." (Part 1, Part 2)

And speaking of SNL, here are a few of my favourite characters: Dana Carvey's "Church lady", Martin Short's "Ed Grimley", and Kristen Wiig's "Kathie Lee Gifford".

Dana Carvey on Church Chat: "Well, isn't that special." Martin Short's Ed Grimley: "Gimme a break, I must say." Snippets of Kristen Wiig's Kathie Lee Gifford.

One of my Dad's all-time favourites was Victor Borge (1909-2000). His "phonetic punctuation" sketch is a classic.

"Phonetic Punctuation" "Hands Off" Victor Borge, the duet

Quotable quotes

All the world's daft, save thee and me. And lately I've been wondering about thee.

If, in the last few years, you haven't discarded a major opinion or acquired a new one, check your pulse. You may be dead.

Brag of your country. When I am abroad, I brag of everything that Nova Scotia is, has, or can produce and, if they beat me at everything else, I say: `How high do your tides rise?'.

Figure out who you are, then do it on purpose.

You don't really understand something until you can compute it.

Numquam ponenda est pluralitas sine necessitate; Plurality must never be posited without necessity.

If I have seen further than others, it is by standing upon the shoulders of giants.

I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.

The most incomprehensible thing about the Universe is that it is comprehensible.

He must be a dull man who can examine the exquisite structure of a comb, so beautifully adapted to its end, without enthusiastic admiration.

We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture.

Prediction is very difficult, especially about the future.

Those who are not shocked when they first come across quantum theory cannot possibly have understood it.

I cannot seriously believe in quantum theory because it cannot be reconciled with the idea that physics should represent a reality in time and space, free from spooky actions at a distance.

I have stated previously that the arrow of time should follow the arrow of universal expansion, and if the universe should start to collapse, we'd all start getting younger. I was wrong.

Only two things are infinite: the universe and human stupidity, and I'm not sure about the former.

To hell with the expense; give the canary a second seed!

I haven't an inkling, and it takes a thousand inklings to make a clue!

Freedom has to be armed no worse than tyranny.

And I find it kinda funny, I find it kinda sad; the dreams in which I'm dying are the best I've ever had; I find it hard to tell you, 'cause I find it hard to take; when people run in circles, it's a very very mad world, mad world.