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Richard Norman Henriksen

Richard Henriksen

Professor Emeritus

he/him/his

Emeriti

Physics, Engineering Physics & Astronomy

Arts & Science

henrikr@queensu.ca

613-530-0482

People Directory Affiliation Category
Astronomy, Astrophysics & Relativity
Emeriti

Degree

PhD from Manchester, UK, 1965

Research Interests

My interests have ranged widely over the field of astrophysics. At present a major theme is the attempt to construct a detailed model of the birth of stars. We should remember that the stars provide the light and heat of our Universe and as such are probably its dominant characteristic. We know that star birth occurs mainly in the cold molecular clouds of galaxies, but we do not understand fully the processes that lead to intense beams of matter that are ejected in diametrically opposed directions as the star forms and proceeds through its early evolution. Nor do we understand the way in which the enormous magnetic flux and angular momentum associated with the diffuse material that eventually forms the star is reduced to values compatible with the existence of the star. It is likely however that this reduction is what is happening when the beams are formed in conjunction with the giant X-ray flares that also seem to be associated with the birth of young stars.

I have studied evolution of molecular clouds towards 'star-birth' by studying the nature of what might be called 'Ballistic Turbulence'. Fluid turbulence is thought to decay too quickly to support the cloud over its lifetime, but a structure made up of tidally interacting clouds in an n-body structure might be better. Another dominant theme is the study of the relaxation of Dark Matter halos around galaxies and clusters of galaxies. This material can only be detected indirectly through its gravitational effects, but it consistently appears as the most massive component of the Universe. Thus the distribution in phase space of the constituent particles is important for the understanding of the dynamics of the visible 'normal' matter. These systems are also intriguing theoretical systems since the dark matter particles seem to be collisionless, and so they form an n-body system of the simplest kind. We can therefore hope to use a combination of theoretical analysis and numerical simulation to study the relaxation of such systems and find perhaps a universal distribution in energy space.

Existing results have been published and I hope to extend the previous researches to include angular momentum, non-spherical symmetry and a novel method of coarse graining. With a Ph D student I would like to explore the relativistic n-body problem using the same techniques. This is a particularly pure problem in general relativity since the equation of state of the matter is almost as elegant as the geometrical representation of gravity! But we also hope to make a contribution to the understanding of near 'black hole' evolution. This problem involves both analytical and numerical work.

In addition I continue my traditional interests in relativistic astrophysics. Pulsars remain as a puzzling physical problem and Higgins and I (see II below) have made some of the few predictions of gamma ray activity. I continue to be intrigued by the magnetic interactions between central 'objects' and the surrounding disc/halo material generally. These include phenomena ranging from protostars to Quasars. Most recently I have been developing models for galactic magnetic fields as produced by classical magnetic dynamos. This is in collaboration with Dr J. Irwin, Alex Woodfinden and the CHANG-ES team, who are actually measuring galactic magnetic fields. At present we are trying to validate the models by fitting them to the data on distant galaxies as well as to our own Milky Way (in collaboration with Dr J. West of the Dunlap Institute). Student or collaborative interest is welcomed but funding is not readily available.

Interests outside of research

Hiking, travelling, Marksmanship, pondering the puzzles of the day.

Publications and Files

Recent Selected Publications

Please note the acronyms used for publications journals:

MNRAS = Monthly Notices of the Royal Astronomical Society (London)
A&A = Astronomy and Astrophysics
ApJ = Astrophysical Journal

  1. Henriksen, R.N., 2022, A&A, 658, 101, "Galactic magnetic X fields"
  2. Henriksen, R.N.; Irwin, J.A.; 2021, ApJ, "Turbulent Magnetic Dynamos with Halo Lags, Winds, and Jets"
  3. Woodfinden, A.; Henriksen R.N.; Irwin J.A.; Mora-Partiarroyo, Silvia Carolina, 2019, MNRAS, 487,1498, "Evolving galactic dynamos and fits to the reversing rotation measures in the halo of NGC 4631"
  4. Henriksen, R.N., 2019, Galaxies, 7,53, "Solar and Galactic Magnetic Halo Structure: Force-Free Dynamos?"
  5. Henriksen,R.N., 2018, Rotating Magnetic Spiral Arms from Dynamo Theory, Presented at The 6th Annual CHANG-ES Collaboration Meeting, Calgary
  6. Henriksen, R.N.; Woodfinden, A.; Irwin, J.A.; 2018, Arxiv:1802.07689 v1; "Exact spirally symmetric galactic dynamos"
  7. Irwin, J.A.; Henriksen, R.N.; Wezgowiec, M.; Damas-Segovia, A.; Wang, Q. D.; Krause, M.; Heald, G.; Dettmar, Ralf-Juergen; Li,Jiang-Tao; Wiegert, Theresa; and 11 coauthors; 2018, MNRAS.tmp..442I, "CHANG-ES XI: circular polarization in the cores of nearby galaxies"
  8. Henriksen, R.N.; Woodfinden, A.; Irwin, J.A.; 2018, MNRAS, 476,635, "Exact axially symmetric galactic dynamos"
  9. Irwin, J.A.; Schmidt, Philip; Damas-Segovia, A.; Beck, Rainer; English, Jayanne; Heald, George; Henriksen, Richard N.; Krause, Marita; Li, Jiang-Tao; Rand, Richard J.; and 5 coauthors; 2017, MNRAS, 464,1333, "CHANG-ES VIII, Uncovering hidden AGN activity in radio polarization"
  10. Perlman, Eric, S.; Meyer, Eileen, T.; Wang, Q. Daniel; Yuan, Qiang; Henriksen, Richard N.; Irwin, Judith; Krause, Marita; Wiegert, Theresa; Murphy, Eric, J.; Heald, George; Dettmar, Ralf-Juergen; 2017, ApJ, 842,126, "Compact Resolved Ejecta in the nearest Tidal Disruption Event"
  11. Henriksen, R.N.; 2017, MNRAS, 469,4806, "Magnetic spiral arms in galaxy haloes"
  12. Henriksen, R.N.; Irwin, J.A.; 2016, MNRAS, 458,4210, "Magnetized galactic haloes and velocity lags"
  13. Irwin, Judith A.; Henriksen, Richard N.; Krause, Marita; Wang, Q. Daniel; Wiegert, Theresa; Murphy, Eric J.; Heald, George; Perlman, Eric; 2015, ApJ, 809, 172," CHANG-ES V: Nuclear Outflow in a Virgo Cluster Spiral after a Tidal Disruption Event"
  14. Irwin, J.A.; Brar,R.S.; Sakia, D.J.; Henriksen, R.N., 2013, MNRAS, 433, 2958, "The 617 MHz-lambda 850 micron correlation (cosmic rays and cold dust) in NGC 3044 and NGC 4157"
  15. Le delliou, M.; Henriksen, R.N.; MacMillan, J.D.;2011, A&A, 526,13, "Black Holes and Galactic Density Cusps"
  16. Henriksen, R.N., 2009, ApJ, 690,102, "Nature and Nurture in Dark Matter Halos"
  17. Henriksen, R.N.,2007, ApJ, 671, 1147, "Central Relaxation of Dark Matter Halos"

Past Selected References/Publications

Henriksen, R.N. 2006, "Power-laws and non-Power-laws in Dark Matter Halos"

Astrophysical Journal, 653, Dec. 20. MacMillan, J.D., Widrow, L.M. \& Henriksen, R.N., 2006, "On Universal Halos and the Radial Orbit Instability"

Astrophysical Journal, 653, Dec. 10. Henriksen, R.N. 2005, " Isolated and non-isolated dark matter halos and the NFW profile"

Mon. Not. R. astron. Soc. 366, 697. Henriksen, R.N. 2004, "Coarse graining the distribution function of cold dark matter-II"

Mon. Not. R. Astron. Soc. 355, 1217=1236. Le Delliou, M. and Henriksen R.N. 2003, "Non-radial Motion and the NFW Profile"

Astronomy and Astrophysics, 408, 27-38. Merrall T.E.C. and Henriksen R.N. 2003, "Relaxation of a Collisionless System and the Transition to a new Equilibrium"

Astrophysical Journal, 595, 43-58. Lery T. Henriksen R.N., Fiege J.D., Ray T.P., Frank A., Bacciotti F. 2002, "A Global Jet/Circulation Model for Young Stars"

Astronomy and Astrophysics, 387, 187 Henriksen R.N. and LeDelliou M. 2002, "Coarse Graining the Distribution Function of Cold Dark Matter"

Mon. Not. R. Astron. Soc, 331, 423-434. MacMillan J.D. and Henriksen R.N. 2002, "Black Hole Growth in Dark Matter and the Mbh-Sigma Relation"

ApJ, 569, 83. Aburihan Mahmoud, Fiege J.D., Henriksen, R.N. and Lery, T. 2001, "Protostellar Evolution during Time Dependent, Anisotropic Collapse"

Mon. Not. R. Astron. Soc., 326, 1217-1227. Lery T., Henriksen R. N. and Fiege J.D. 1999, "Magnetized Protostellar Bipolar Outflows"

A&A 350, 254. Henriksen, R.N. and Widrow, L.M. 1999, "Relaxing and Virializing a Dark Matter Halo"

Mon. Not. R. Astron. Soc. 302, 321. Higgins M.G. and Henriksen R.N. 1997, "The Deutsch field gamma-ray pulsar-I. The model basics"

Mon. Not. R. Astron. Soc. 292,934. Higgins M. G. and Henriksen R.N. 1998,"The Deutsch field gamma-ray pulsar-II. Application of the model"

Mon. Not. R. Astron. Soc 295, 188. Henriksen R.N. 1997, "Multi-dimensional self-similarity, and self-gravitating N body systems", in "Scale Invariance and Beyond", Dubrulle,Graner and Sornette,eds, Springer, EDP Sciences.

Books

1. Henriksen, R.N.; 2011, Practical Relativity: From first Principles to the Theory of Gravity, Wiley, Chichester, U.K.

2. Henriksen, R.N.; 2015, Scale Invariance: Self-Similarity of the Physical World, Wiley-VCH, Weinheim, Germany

Maple Files and Scripts

• Exact axially symmetric galactic dynamo, maple script (see Henriksen, Woodfinden & Irwin 2018, MNRAS, 476, 635). File Size is 1MB.

• Exact spirally symmetric galactic dynamo, maple script (see Henriksen, Woodfinden & Irwin 2018, arXiv180207689). File Size is 1MB.

Maple scripts above are executable and readable in MAPLE 16 or higher.

Please note, if you don't have MAPLE software, you can download Maple Player to read the files. Maple Player is free for anyone to download.

PDF Files

A Continuum Approach to the Distribution of Plasma in a Pulsar Magnetosphere by Julian Faust (Undergraduate Research Thesis)