Research Interests

My first ever research work was as an undergraduate summer assistant at ROE in 1966 where I used an iris diaphragm photometer to measure stellar image sizes on three colour(UBV)  plates of the several hundred stars in an open cluster, and thereby construct an HR diagram and deduce its distance and age. This work took me about 6 weeks of 8 hour days and 5 day weeks and the results led to a paper in which I got an acknowledgement. The same analysis today would take a machine less time than it takes me to type this full stop.
I subsequently spent the summers of 1967 and 1969 in the Radar Meteor Group at Harvard-Smithsonian Astrophysical Observatory (now CfA) in Cambridge Mass, working with Gerald S.Hawkins and Richard Southworth on analysing meteor echo characteristics. (HSAO Special Report No 254). This gave me a lifelong interest in meteors, comets, and orbits, on which I have since done occasional research ranging from comet-earth impacts - Brown, J.C. and Hughes, D.W.: 1977, Nature 268, No.5630, 512,- (and currently comet-sun impacts), Bode’s Law, hyperbolic meteor searches, and solar-sailed spacecraft orbits (McInnes, C.R. and Brown, J.C.: 1990, Celestial Mechanics 49, 249-264. Solar sail	Tunguska Trees Comets
By 1969, I was well into my solar physics PhD topic under the supervision pf Peter A. Sweet (of Sweet-Parker reconnection and Eddington-Sweet circulation fame).  He, being a student of Hoyle’s who was a student of Eddington’s, was a huge source of inspiration in my career and the clearest thinking mathematical physicist I have ever met – a fact not at all reflected in his minimal published output. My topic was the role of energetic electrons in solar flares. Diagnosing the properties of such particles from their radiation signatures and their heating effects in the thermal flare plasma has been a primary research interest ever since. The topic got me heavily involved with many solar space missions : ESRO TD1-A, Skylab, Solar Maximum Mission, Hinotori, YohKoh, Compton GRO and most recently the NASA Award winning RHESSI (Ramaty High Energy Solar Specroscopic Imager) on which I am a Co-Investigator. While I have published many papers in this field, my 1971 paper (Solar Physics 18,489) on electron Hard X-ray spectral diagnostics and on the Thick Target model of electron beams, proved to be a cornerstone of the subject. It is my most cited paper and interestingly its citation rate graph follows the solar activity cycle, rising with the launch of each successive solar space mission dedicated to solar activity studies. My other solar physics interests have included studies of neural networks in time series prediction of sunspot numbers.
	RHESSI
	Astronomers Watched the Launch of RHESSI from GU
The flare electron spectral analysis problem got me heavily involved in the mathematical field of inverse problems, of wide occurrence in remote sensing sciences like astronomy, meteorology etc. In these observations (e.g. HXR photon spectrum) do not yield the desired source information (e.g. electron spectrum) directly but as the integral convolution of the desired function with an kernel function (e.g. radiation cross section). Consequently, inferring  the source property requires integral deconvolution techniques combined with ‘regularisation’ methods to suppress the magnification of data noise which always occurs in this inversion solution. As emphasised in my 1986 inverse problems monograph with I.J.D. Craig, the loss of information involved has serious consequences for the uniqueness of the solutions and the value of hypothesis testing by the more usual approach forward fitting of models – limitations whose seriousness is still not widely appreciated in some areas of astronomy. My work with Craig in this area was the basis for my long standing collaboration with Bertero, Piana and Massone (Genova and Verona).
My third main research interest is in the physics of, and modelling of data on, mass loss (and inflow) of hot stars which is crucial to understanding their evolution and the structure and chemical composition of the interstellar medium on which they impact, and which is the birthplace of subsequent stellar generations. Among the more specific topics of my work in this area are : stellar winds, jets and accretion flow; mechanisms governing stellar wind speeds, mass loss rates, wind anisotropy, variability, inhomogeneity and disk formation; structure of white dwarf accretion columns. My initial work stimulated by Ian S. McLean, was on the use of light polarised by aspherical scattering as a diagnostic of the geometry of circumstellar matter and of binary orbits including a new method (Brown, McLean and Emslie 1978) of determining binary orbit inclination and hence stellar masses.
While based in Glasgow throughout my career, I have spent sabbatical leave in many labs abroad and established numerous collaborations  - see Resume pages. I have published over 250 papers – see Publication pages for full details with * against my favourites, shortly to be made available here as downloadable pdfs. My papers can also be accessed through NASA ADS http://adsabs.harvard.edu / or via the Department website (for 2001-2006) Publications: John C. Brown