Welcome to my web site which contains information about my research activities. Most of my research centres on solar physics, mostly interpretation of solar spacecraft data but more recently I have led a team to look for fast oscillations in the visible-wavelength solar corona with an instrument called SECIS (Solar Eclipse Coronal Imaging System) which consists of a pair of fast-frame CCD cameras, a computer system to grab and store the images, and various optical components. I also do research into nearby solar-type stars as their properties can often be deduced from what the sun does. I am particularly interested in the X-ray and ultraviolet regions of the spectrum, and do a lot of work in spectroscopy and atomic physics, especially line ratios as a means of determining the physical conditions of emitting gases in the solar corona, flares, stellar coronae, and laboratory plasmas such as those produced in fusion devices like JET.
I was interested in solar astronomy as a schoolkid (my first sunspot drawing was when I was 12, made on July 5, 1958) and from there progressed to a Bachelor's degree at University College London, my Prof. being C. W. Allen (author of Astrophysical Quantities). I went on to do a Ph.D. in space science at the Mullard Space Science Laboratory, then held postdoctoral fellowships at the NASA Goddard Space Flight Center (Greenbelt, Maryland) and the University of Hawaii. I returned from the U.S. in 1976 to take up an appointment at the Rutherford Appleton Laboratory. I took early retirement from RAL in 2002 and took up my present US National Research Council Senior Research Associateship, awarded to me earlier that year.
I wrote Guide to the Sun published by Cambridge University Press in 1992 (PB published in 1995) which covers most aspects of solar astronomy, solar physics and even solar energy. I have over 200 papers in the literature, roughly half in refereed journals, and several book contributions. I wrote a cover-story article on the solar corona's high temperature for the June 2001 Scientific American with my colleague Bhola Dwivedi which has also appeared in the Japanese, German, Polish and other foreign language versions of the magazine. It was recently (Sept. 2003) updated in a Special Issue of Scientific American. I have had several successful grant applications which have funded both my research and travel and that of some of my colleagues.
If you are interested in anything you see here, I can supply more details if you e-mail or write to me (see address at foot of page).
NRC Senior Research Associate, NASA Goddard Space Flight Center
I have been a Senior Research Associate in the US National Research Council's Program since October 2002. I work at the NASA Goddard Space Flight Center, Greenbelt, Maryland, USA, in the group dedicated to science from the Reuven Ramaty High Energy Solar Spectroscopic Imager or RHESSI, a NASA solar spacecraft that has been in earth orbit since February 2001. It views the sun in X-rays and gamma-rays over the energy range 4 keV to 17 MeV, getting spectra and imaging through a modulation collimator technique (modulation collimators in front of its nine detectors). It has observed thousands of flares since its launch on a Pegasus rocket. My colleague and supervisor Brian R. Dennis leads this group. Over the period of my first year, I have worked with data from RHESSI and the RESIK instrument on the Russian Coronas-F spacecraft. In work with Polish colleagues who built RESIK and Enrico Landi at US Naval Research Laboratory, I determined abundances of the elements K, Ar, and S from some long-duration flares seen by RESIK and RHESSI, and more recently did some work on the diagnostic capabilities of the 4--10 keV part of the flare spectrum that RHESSI detects, the so-called thermal spectrum, emitted at temperatures of about 20 MK (1MK = 1 million Kelvins). This includes the Fe-line feature at 6.7 keV that is made up of Fe XXV lines, Fe XXIV satellites, and at very high temperatures (> 30 MK) the Fe XXVI lines. RHESSI also sees a feature at 8 keV which is due to a mixture of Fe and Ni lines, known as the Fe/Ni-line feature. The observation of these features should lead to routine measurement of the Fe/H abundance in flare plasmas, and to a resolution of whether the Fe/H abundance is more coronal than photospheric -- current evidence points to variability, perhaps as a function of flare type.
One of my main interests over the past few years is searching for fast changes or oscillations in the visible solar corona's intensity using fast CCD cameras. Details are given below.
My team and I went on a highly successful trip to Zambia to see the eclipse on June 21, 2001. The weather was perfect and all our equipment worked fine. Take a look at these 2 images, from the 1000th frame of the data. The SECIS web site has some great movies in both the white-light and green-line channels of our instrument. There was a bright active region and prominence on the sun's NE limb, clearly visible in our images. We had information before the eclipse provided by the TRACE and SOHO spacecraft. My team was on BBC2 TV on July 6, 2001 (00.30), programme Final Frontier .
We previously had a successful trip to Bulgaria for the eclipse on August 11, 1999. Our equipment worked perfectly then too! We have been analyzing the results in some detail. You can view a movie from both channels, thanks to my colleague David Williams at QUB who got it running. The white light channel (left hand panel) shows the prominences as well as the coronal structures, while the green line (filter at 530.3nm) channel shows only the coronal features. The last frame is when the photosphere just starts to peep through. Each movie is made up of every 100th frame of the total of 6364 images each channel over the 2 minutes 20 seconds of totality. Check out our publications on the web site above. See Robin Barnsley's web site for pictures of the 1999 eclipse site and people.
The SECIS experiment had lots of media coverage before and after the 1999 eclipse. We were featured on the BBC1 6 o'clock news on August 9, and there was coverage on the Discovery TV and UK Today channels which went out worldwide. SECIS was also featured on Radio 4's `Material World' programme on two occasions (1.7.99 and 23.9.99), as well as BBC News24 and other TV and radio events. The Daily Telegraph had two big write-ups on SECIS (it even featured in The Sun!!) while there was also coverage in articles in Issues of New Scientist, New Electronics, and Physics Today. Peter Gallagher and I have items in the BBC's eclipse web site.
It was a great honour to get a Group Award from the University of Wroclaw, Poland, in February 2001, kindly arranged by our colleagues Pawel Rudawy and Bogdan Rompolt. They have become very good friends over the years, together with other colleagues at Wroclaw. Pawel and his colleague Adam Buczylko were at the 2001 eclipse with their heliostat which worked perfectly.
My article entitled "Why is the Sun's Corona so hot? Views from SOHO, Yohkoh, and solar eclipses", which features the SECIS instrument (published in Plasma Physics and Controlled Fusion, 42, 113-126 ) was the second most popular on the electronic version of the journal in 2000, being downloaded 1562 times. The article was based on an invited talk I gave to the IoP Plasma Physics meeting in Pitlochry, Scotland, in 1999. See the IoP journals web site (click on Journal Archiving) for further details and downloading information.
Some other details are on the Total Solar Eclipses item.
I chaired a panel visiting astronomy research establishments in Estonia -- our panel made its deliberations and gave its very favourable report to the Estonian Higher Education Accreditation Centre, Tallinn. Interest in this was shown by Mr Lembit Opik who is MP for Montgomershire, Wales, as he is grandson of the famous astronomer Ernst Opik who was Director of the Armagh Observatory, Northern Ireland, for many years. Also, one of the panel members, Dr Claes-Ingvar Lagerkvist, who is a minor planet astronomer at Uppsala, Sweden, kindly arranged for each panel member to have a minor planet named after him. Mine is Minor Planet No. 13991 (1993 FZ6, discovered at the European Southern Observatory on March 17, 1993).
Left is my certificate showing kenphillips' orbit and orbital parameters. See
citation for 13991 Kenphillips.
RECENT PRESENTATIONS etc.
Several presentations at the COSPAR conference, Paris, July 2004, including:
"Thermal and Nonthermal Contributions to the Solar Flare X-ray Flux" (B. R. Dennis et al.)
"High Time Resolution Observations of Solar Flare H-alpha Emission" (K. Radziszewski et al.)
"Temperature-sensitive Line Ratio Diagnostics based on Si Satellite-to-Resonance Line Ratios" (K. J. H. Phillips et al.)
"RHESSI, RESIK and GOES Observations of the Solar Flare Thermal Spectrum", Presentation at the AAS/SPD meeting, Denver, June 3, 2004
"New Insights into Solar X-ray Flares", Seminar at the Laboratory for Solar and Astrophysics", GSFC, May 6, 2004
"The Sun, our Star", Presentation at the Montgomery Study Circle, Greenbelt, Maryland, August 2003.
"Solar Flare Abundances of K, Ar, and S", AAS Solar Physics Division Meeting, July 2003.
"The Fe-line Feature in RHESSI Solar Flare Spectra", RHESSI Workshop, July 2003.
"Searching for Rapid Changes in the Solar Corona during the 2001 Eclipse", Presentation in SOHO/RHESSI Seminar Series, October 2002.
``Flare Temperatures from Fe XXV and Ca XIX: Improved Atomic Data'', Paper by KJHP and others, presented by Louise Harra at Tenth Anniversary of Yohkoh Meeting, Hawaii, January 21/25, 2002.
Interview on nature of Sunspots with Louise Harra on BBC Radio 4 Material World programme with Quentin Cooper, November 20, 2001.
Invited talk ``Looking for the Coronal Heating Mechanism with the SECIS Instrument'', Totality Day Eclipse conference, Open University, August 11, 2001.
Talk to 700 students, schoolchildren, teachers and lecturers at the Sports Hall, University of Zambia, June 19, 2001 on viewing the June 21, 2001 eclipse.
Contribution to the Learning Edge BBC Radio 4 programme, June 21, 2001 -- interviewer Geoff Watts.
``Results from the SECIS experiment''. Talk given at the NAM conference (UK Solar Physics session), April 2-5, 2001, Cambridge, UK.
``Why is the Solar Corona so Hot? Results from SECIS''. Seminar given at UCL, February 12, 2001.
I have been doing solar physics research for more than 30 years, principally in the
areas of solar flares, X-ray and UV spectroscopy, coronal heating
and diagnostics of hot
coronal plasmas. My PhD (Mullard Space Science Laboratory, University
College London, 1972) was on soft X-ray emission from solar flares using
data from the OSO-4 spacecraft. I held postdoctoral fellowships at NASA
Goddard Space Flight Center (1972--75) and at the University of Hawaii
(1975--76). From 1977 to 2002, I worked at RAL (originally
the Astrophysics Research Division, Appleton Laboratory), in the Space Science and
Technology Dept where I was Leader of the Solar Research Group, and
one of the four Co-Applicants of the Space Science PPARC Rolling Grant over several years. I had honorary appointments at Queen's University, Belfast
Some of my collaborators include Dr Louise Harra (MSSL), and Dr Pawel Pres (who was at RAL in 1998 on a Royal Society/NATO postdoctoral fellowship I successfully applied for). I had British Council-funded collaborations with the Astronomical Institute, University of Wroclaw, Poland (including Professor Jerzy Jakimiec, Prof. Bogdan Rompolt, Dr Pawel Rudawy etc.) and the SRON Laboratory for Space Research, Utrecht (Dr Rolf Mewe). I also collaborate with several other groups in the U.K., Europe, and the U.S. (notably US Naval Research Laboratory and Lawrence Livermore Laboratory).
A good friend of mine, Dr Wolfgang Ihra, who does work, among other things, on e- and e+ impact ionization beyond the Wannier theory, has a nice web site. He is presently at the Max Planck Institut, Freiburg. Another good friend, Brian Thomas, runs the educational programmes and excellent web site of The Marine Society, often mentioned in the press and recently highlighted in respect of the Mozambique airlift. My relative Brian Phillips is MD of Integrated Electronics in Wraysbury, Middx., and some years ago supplied equipment for Rutherford Appleton Laboratory.
GUIDE TO THE SUN AND BOOK CONTRIBUTIONS
I am the author of the book
`Guide to the Sun', published in hard bound (1992)
and paperback (1995) by
Cambridge University Press
(ISBN 0 521 39483X hbk, 0 52139788 X pbk). The book covers
all major aspects of solar astronomy and physics, including a historical
chapter, one on the solar interior including the solar neutrino problem
and helioseismology, the solar atmosphere, solar activity, relation of the
Sun to other stars and the interplanetary
medium, and a final chapter on observing the Sun with ground-based
telescopes and spacecraft. There are sections on the Sun's influence on the
earth's climate, and also global warming and the
depletion of the ozone layer. It has sold about 3600 copies world-wide, and has
been adopted as a course book at a number of US and UK universities and
colleges. It received a 5-star rating in the
amazon.com web-based book store.
I contributed the solar and radiation entries for the `Oxford Dictionary of Astronomy' (ed. Ian Ridpath), widely available at bookshops worldwide (ISBN 0-19-211596-0 pbk, 1997).
`The Many Faces of the Sun', a summary of the Solar Maximum Mission satellite that flew in the 1980's, has a review chapter by me on Spectroscopy and Atomic Physics (ch. 13). The book is published by Springer-Verlag (New York, Berlin, and Heidelberg: ISBN 0-387-98481-X 1998).
I contributed one of the entries (`Sun as a Star') in the Encyclopedia of Astronomy and Astrophysics' which appeared in September 2000 and had a big launch party at the IAU General Assembly in Manchester in August 2000.
A new book, Dynamic Sun(CUP), on recent solar physics results, has a chapter `Probing the Sun's Hot Corona' by me and Bhola Dwivedi, appeared in Spring 2003.
Studies of the Quiet Sun with the Solar and Heliospheric Observatory.
I am involved in many collaborations in studies of especially the quiet Sun
using data from the SOHO spacecraft, launched in December 1995. With my colleagues
Peter Gallagher and
at MSSL, I
completed a major study of quiet Sun properties using data from
the Coronal Diagnostics Spectrometer (CDS), including brightness, area,
fractal index, contrast and other properties of the network -- one of our basic
findings is that the network appears most ``contrasty" in transition region
lines, but can be traced in coronal lines. It is more blurred-looking
in the chromospheric He I and II lines but we show in our work that this is
probably due to the high optical thickness of these lines.
I successfully applied for Dr Pawel Pres to come to RAL on a Royal Society/NATO-funded postdoctoral fellowship in 1998. He and I did a study of a quiet Sun region observed simultaneously by SOHO and Yohkoh in 1997. Magnetogram observations from the SOHO MDI instrument show the presence of converging and diverging bipoles which show up in Yohkoh data as X-ray bright points. Pawel found a fascinating correlation of the energy in the photospheric magnetic field, the EUV emission from the bright coronal Fe XII line, and the X-ray brightness as measured by the Yohkoh SXT instrument. The magnetic field energy is approximately (to a factor 2) the same as the conductive and radiative losses, so that the magnetic energy seems to supply the entire energy of the bright point. This is the case for the 6 bright points in an initial study (paper published in Ap. J. Letters -- see below) and for most of more than 20 cases which are being analyzed right now for a more extended work. We also noted the occurrence of several tiny X-ray ``network flares" similar to what has been seen by other observers. Pawel also gave a poster on this work at the Brendan Byrne Memorial Symposium (Armagh, September 1998) -- see the Proceedings (PASP Special Publication). We are now working on a more extensive paper to be submitted to Astr. Astrophys. where a much larger number of coronal bright points are studied, along with data from the CDS experiment on SOHO.
In another major study involving Peter and Louise, we looked at small network brightenings. We used a SOHO CDS study in which the NIS slit is held in one position on the Sun, with features slowly drifting past by solar rotation. There are literally hundreds of tiny brightenings which can be identified in any one observation (typically two hours long). We have devised statistical methods of identifying and categorising them. We recently had a paper published (Gallagher et al.: Astr. Astrophys.) on velocities associated with these brightenings: it appears that there is a strong correlation of brightenings with downflows of 20km/s or so, with a tendency for semi-periodic behaviour as shown in a wavelet analysis that Peter carried out.
I gave a summary of some of the above work at the Cospar conference in Nagoya, Japan (in July 1998), at the Brendan Byrne Memorial Symposium at Armagh in Sept. 1998, and at the IOP Plasma Physics conference at Pitlochry, March 1999 (this invited review appeared in Plasma Physics and Controlled Fusion [IOP]).
Synthesis of X-ray line spectra for comparison with spectra of solar active regions and flares observed by the Solar Maximum Mission and Yohkoh satellites. These include helium-like magnesium, silicon, sulphur, argon, iron and some other solar-abundant elements. The lines of He-like ions are sensitive to electron density for low-Z elements. Dielectronic satellites which occur near by are sensitive to electron temperature. He-like spectra are therefore useful ways of remotely diagnosing solar plasmas. See Phillips et al. (ApJ , 419, 426) for work on Ar XVII, Harra-Murnion et al. (A&A , 306, 670) for work on S XV. Mark Phillips (no relation!), a PhD student at QUB, and I have started work on Mg XI for determination of flare densities, continuing work of Dr Caroline Greer who worked with me a few years ago.
Benchmark Study of the MEKAL code with SMM Spectra. The SMM data (from the Flat Crystal Spectrometer especially) are the highest-resolution X-ray spectra ever obtained in the 1--20 Angstrom range, and are an excellent resource for benchmarking atomic codes. Recognizing this, I set up a collaboration with the SRON Laboratory for Space Research, Utrecht, with funds from the Joint Scientific Research Programme of the Netherlands Organization for Scientific Research (NWO) and the British Council, Amsterdam. We even got an extension of this funding till March 1999, which I am told is quite unusual. Dr Rolf Mewe and Dr Jelle Kaastra (SRON), Dr Louise Harra (MSSL) and I were involved in a study in which we compared observed flare spectra from the FCS instrument with theoretical spectra using the MEKAL code that Drs Mewe and colleagues have developed over the years. The comparison has enabled improvements in the MEKAL and associated codes to be made which will be useful for looking at spectra from the XMM and AXAF (Chandra) missions. The paper appeared in Astr. Astrophys.
The British Council in Amsterdam featured us in a forthcoming brochure to illustrate their work in funding joint projects.
Rolf has been very hard at work doing figures and tables that summarize our fits. You can get one such version showing the comparisons between the SMM spectra with the MEKAL before and after line wavelength adjustments -- this can be viewed clicking here (the plots on the bottom two panels are the deduced emission measure distribution).
High values of electron densities in flare plasmas. I collaborated with Queen's University Belfast, Mullard Space Science Laboratory (UCL), Royal Holloway University of London, Goddard Space Flight Center who have supplied atomic data or helped me with running atomic codes (principally the Cowan HFR code). Although we often found that flare densities were less than the low-density limit imposed by the atomic physics, we found from a study of Fe XXI and Fe XXII lines that the electron density in a very impulsive flare was 2 or 3 times 1012 cm-3 at its peak, exceptionally high compared with most previous estimates, leading to the possibility that the emitting volumes are very small and that at flare maximum cooling is by radiation, at least for a time (see below).
work on Fe XVII (Astrophysical Journal Letters), click here (file length =
178K) for a postscript file of the paper with
encapsulated figures. The work is based on some SMM spectral scans of the
intense Fe XVII lines emitted by solar active regions and flares. One of the
lines is marginally optically thick, which enables the path length Ne x l
to be determined for the emitting regions. This combined with the emission
measure Ne2 x L gives separately the electron density and
path length L. This
has application to the dimensions of small bright points which are being seen
by the SOHO EIT and other instruments and to active regions on RS CVn and
other binary star systems in which one or both members are chromospherically
Studies of X-ray flares
from Yohkoh. I did some extensive analysis of
morphologies and time characteristics of flares with Dr Uri Feldman, at NRL. We found that the bright loop-top
sources which are often seen and which have temperatures of up to 20MK
most likely lose energy by radiation, not conduction to the cool chromosphere
(where the temperature is 104 K). Equating the e-folding time for the
temperature decay to the radiation loss time leads to very high densities,
of order 1012 cm-3, in support of spectroscopic
findings (see above). My colleague
George Hanoun and I
worked on static loop models for flares and George has come up with some
elaborate graphics to represent the cooling of flare loops after impulsive
heating with various spatial dependence. You can view these on his web site. In
a later development, there is a fine TRACE image of a flare in the 192A
band which includes emission from an Fe XXIV line showing a whole set of
loop-top sources, which is great as it completely dispels the sceptics who
denied the existence of them, explaining them as a optical effect. I thank
George Doschek who recently pointed this out to me. With Uri and Louise Harra, I am just about to complete an analysis of six long-duration Yohkoh flares and a seventh, in 1999, seen by Yohkoh and SOHO SUMER, where I looked into nonthermal velocities measured from BCS Ca and S spectra. It's clear from the SXT data that the very large velocities are in reality due to the spatial extent of the flare in soft X-ray flares. I hope to elaborate on this soon.
Collaboration with the Astronomical Institute, University of Wroclaw, Poland.
In a 3-year exchange programme, my Polish colleagues Jerzy
Jakimiec, Michal Tomczak, and Robert Falewicz, together with Andrzej
Fludra (RAL), we studied bright loop-top sources
(see preceding paragraph). We
developed an idea that Jerzy has been working on for some years that the kernel
is due to a region of tangled magnetic field, with continual reconnections
occurring that keep this part of the flaring loop energized and thus visible in
soft X-rays. The work has been published in Astronomy and
Astrophysics (A&A, 334, 1112, 1998 -- click here for a postscript file
(file length = 178K).
I gave a summary of this work at the Cospar conference in 1998; it eventually
appeared in Adv. Space Res., vol. 26 (2000).
-- are a major topic in solar physics -- it is
widely believed that the coronal abundances are different from the photospheric
by factors of up to 3 or 4 for some elements, this depending on the value of
the first ionization potential (FIP). I have determined a number of element
abundance ratios which may or may not support these assertions, but some work I did a few years ago concerns the direct measurement of the coronal
to photospheric abundance of Fe, using X-ray lines which are formed
collisionally in a coronal (flare) plasma and in the photosphere, by
fluorescence. Analyses have been done using Yohkoh data (Phillips et
ApJ, 435, 888) and SMM data. The conclusion was that this
ratio is one. However, more recent work on data from the RESIK instrument (PI Dr Janusz Sylwester, Space Research Centre, Wroclaw, Poland) on the Coronas-F spacecraft (published in ApJ (Letters), 2003, 589, L113) agrees with a FIP effect such that low-FIP elements are enhanced by a factor 3 in the corona, high-FIP elements are approximately the same as photospheric abundances.
I gave an invited review of this and other work at
the 1996 COSPAR Scientific Assembly (Adv. Space Res. , 20(1), 79).
Jacques Dubau at Meudon Observatory, Louise Harra, and John Rainnie (QUB
PhD student at AEA Culham Laboratory), I worked on revising collisional rate coefficients for Fe XXV and Ca XIX X-ray lines seen by Yohkoh and SMM/XRP, so updating software. Jacques
calculated recombination rates for us for the S XV theoretical line spectra
which we didn't include in our A&A paper (Harra-Murnion et al. 1995, A&A., 306,
670). We finally finished this project in August 2003, when we submitted our write-up to Astronomy and Astrophysics. John used this as part of his PhD thesis which he successfully defended -- on a fateful day, September 11, 2001. We found
that, although the differences in the
w, x, y, and z line intensities are not very large, but there will be slight
differences in temperatures derived from the ratio of the j or k dielectronic
satellites to the w line -- this has been one of the main ways in which solar
flare plasmas have been diagnosed with spacecraft in the past. I am very grateful to Jacques who put a lot of work into this on
a visit we all made to Meudon in July 1998. He was also an excellent host,
taking us to every conceivable sight in Paris of interest!
TOTAL SOLAR ECLIPSES
The SECIS (Solar Eclipse
Coronal Imaging System)
Although observations from the Yohkoh, SOHO, and other spacecraft give
us a great deal of information about the Sun's atmosphere, in particular the
solar corona, it is not generally possible to get coronal images at very high
frequency, so there may be a range of phenomena occurring, like periodic
intensity modulations, without our knowing it. In recent years, investigators
like Prof. Jay Pasachoff (Williams College, Mass., USA) have been observing the
Sun's white-light corona at high frequency to search for evidence that the
corona is heating by short-period waves. Theory suggests that fast-mode MHD
waves with periods of a few seconds or less are likely to be candidates for the
corona's high temperature (of about 1 million K). I proposed
instrumentation (SECIS, Solar Eclipse Coronal Imaging System)
that would be able to do the same kind of investigation in which the
white-light corona would be imaged with very fast CCD cameras, operating at
30Hz. The experiment has funding from RAL under the
Facilities, Studies, and Technology (FTS) line.
A schematic of the experiment can be viewed by clicking here .
Our award-winning Eclipse WWW site gives some details of this experiment. George Hanoun has done a fine job designing this site.
We have collaborated with Prof. Bogdan Rompolt and Dr Pawel Rudawy at the Astronomical Institute, University of Wroclaw, Poland, who have funding from the Polish Science Funding Council, KBN, to build a high-precision heliostat. We provided the rest of the instrument (lens, green-line filter, CCD cameras, computer). Some of our Bulgarian colleagues kindly arranged for us to observe the eclipse from Shabla, on the Bulgarian coast of the Black Sea just north of the resort of Varna.
A preliminary version of the experiment was taken out to the Caribbean for the total eclipse on 1998 February 26. Peter Gallagher and I went to Guadeloupe (French West Indies), and conducted the experiment with a group of other experimenters including Dr Serge Koutchmy. We used a CCD camera that had been used for other purposes at RAL, and a lens of very high quality kindly lent to us by Dr Francisco Diego (Optical Sciences Laboratory, University College London). A specially adapted PC, from Messrs Carr-Crouch (Maidenhead), was used to grab and store the more than 3000 frames of data that we expected to capture during the 2-minute-long period of totality. Unfortunately we were unable to get any results because of a loss of power, almost literally at the last minute.
In August 1998, we went to the National Solar Observatory/Sacramento Peak with this equipment to test it out and make useful scientific observations with the 40cm Evans Solar Facility (ESF) coronagraph there. This was done at the suggestion of Dr Ray Smartt at NSO. Peter was delighted to get funding from NSO on a Summer Scholarship program, so he spent August and September 1998 there. I gave a presentation while at Sac Peak about our activities. We had taken delivery of improved CCD cameras from EEV (Cambridge) just prior to this trip; these are the ones we will use for the 1999 eclipse. Although we were troubled by cloudy weather, Peter managed to get some nice images towards the end of the allocated time on the ESF. The data were stored on tape.
Peter has a movie on his Web site for the ESF coronagraph data. It shows an active region on the solar limb associated with a large sunspot group that had been followed for the previous few days. The data set consists of 200 images, taken in the green line at a rate of about 60 frames a second. Take a look also at this image which is one formed by co-adding 1000 images of this sequence (about 15s long), and even better click here for a really nice comparison between the Sac Peak green line image, Yohkoh SXT, and TRACE that Peter has done. You can see exactly where the footpoints of the Sac Peak coronal loops emerge from with the TRACE image which was taken a couple of days (Sept. 5) before.
As a result of my collaborations with the Astronomical Institute, University of Wroclaw in Poland, my colleagues Dr Pawel Rudawy and Professor Bogdan Rompolt and others have built an extremely high-precision heliostat for the experiment. Click here for a picture of the hardware (without mirror). The heliostat is computer-controlled and adjustable for any latitude. We did some tests in Wroclaw on both the sun and full moon in late May 1999 when we brought our hardware across to them.
We put together the experiment for final tests in June and July then shipped it to Bulgaria where, with the kind assistance of Prof. Vlado Dermendjiev and his colleague Dr Maria Madjarska at the University of Sofia, we arranged to set up our equipment on a Bulgarian Army Base in Shabla, on the Black Sea coast, NE Bulgaria. Our Wroclaw colleagues transported their heliostat also. We had a nail-biting time waiting for the SECIS kit to get across Europe and into Bulgaria but just made it for the day before the eclipse. It was a nightmare at the time, but on the day itself, August 11, the weather couldn't have been better. We did our alignment and other tests with the heliostat in the hours before the eclipse, then everything worked like magic for the eclipse itself. The sky remained cloudless, the slight breeze that might have caused some slight problems died away completely, and all our equipment worked perfectly! We played back the movie on the PC that grabbed the data and found to our intense delight that there were nice images in both channels, white-light and green-line. Some 12728 images (6364 for each channel) were obtained in the 2m 22s of totality, which occurred at about 11:11 UT (14:11 local time).
We have now completed a lot of analysis. David Williams at QUB led a paper published in MNRAS on possible 6-s oscillations in a particular coronal loop, while Pawel Rudawy and I have articles in the extremely well-organised conference on 1999 eclipse results, held in Varna, Bulgaria in September 2000. Pawel's final write-up was submitted in July 2003 to Astronomy & Astrophysics.
I have no connection with the following paper on SECIS results: Katsiyannis et al. (2003), Astr. Ap., 406, 709.
We have a movie from both channels. The ``white light" channel (left hand panel) shows the prominences as well as the coronal structures, while the ``green line" channel shows only the coronal features. The last frame is when the photosphere just starts to peep through. Each movie is made up of every 100th frame of the total of 6364 images each channel over the 2 minutes 20 seconds of totality. David's wavelet analysis for just a small portion of the green line images (top of a coronal loop) over a 44-second interval shows possible temporary periodicity -- click here for the figure that shows this. The paper I wrote with colleagues on the instrument and preliminary results finally appeared (after a long, inexplicable delay) in Vol. 193 of Solar Physics -- I will send preprints on request (see contact details below).
In the movie, you can see the sun's west limb, with north at the bottom right. There is a curious prominence apparently suspended just off the south-west limb which most photos and movies managed to catch. Speaking to someone at the recent Eclipses et Couronne Solaire conference in Paris (April 2000) I found that the prominence is in fact in the form of a small loop that perceptibly changed orientation between the time we saw it during the Bulgarian eclipse and the time Serge Koutchmy and colleagues saw it during the Iranian eclipse, an hour later. Another small prominence on the north-west limb comes into view towards the end of the totality period as the moon's disk slides across the sun. It's possible that one of the prominence systems we recorded on the west limb is a post-flare loop system -- if so the flare occurred just over the sun's west limb.
As mentioned above, you can see pictures of the eclipse and expedition on Robin Barnsley's web site.
It was a great shock to hear, just after the New Year 2001, that Prof. Vlado Dermendjiev, who was so instrumental in getting our equipment into Bulgaria and who became a close friend, died suddenly of a heart attack. I was very grieved by this news. I am sure many friends, colleagues and of course his family will miss him a very great deal. He did a wonderful job in organising the Varna conference in September 2000. What a loss to solar physics! The Proceedings of the Varna conference will be dedicated to him.
A full report of our 1998 eclipse expedition is available by clicking here (128K). Don't forget to check out our award-winning web site which George Hanoun has designed. This contains some nice ``fly-through" movies of our equipment which he and Barry Kellett have done with a webcam. I wrote a light-hearted account of our 1999 eclipse experiences for the December 1999 issue of the Salford Astronomical Society journal -- click here to see it.
There were a couple of articles in the Daily Telegraph and even The Sun! I have made a few TV and radio broadcasts on this experiment (Radio 4 interviews with Trevor Phillips -- one-time London Mayor candidate and again no relation! [1.7.99, 23.9.99], UK Today TV, Discovery Channel) and have done magazine interviews (New Scientist [end of May], New Electronics, Physics Today, Scientific Computing (IOP) ). Peter Gallagher and I are featured on the BBC Online Web site.
An article on coronal heating -- ``The Paradox of the Sun's Hot Corona'' -- has just appeared in the June 2001 issue of Scientific American, written by me and Bhola Dwivedi, my friend and colleague at the Banaras Hindu University in Varanasi, India. It is the cover story for this issue of Scientific American. The Editors of the magazine have done a wonderful job in including imagery of the corona from the SOHO, TRACE and Yohkoh spacecraft.
Incidentally, some of our time at Sac Peak in August/September 1998 was spent using the Vacuum Tower Telescope to observe the photospheric filigree in a collaborative project with the TRACE spacecraft. Peter achieved some magnificent images of a gigantic erupting prominence associated with a moderate-sized flare -- see Peter's web site for them. We wrote up the results of this in a Solar Phys. paper. It appears that much of the flare energy went into mass motion rather than radiation. I hope we can do further analysis some time, before I retire!
The above has to be updated quite a bit -- when I get some time I will describe our trip to Zambia for the 2001 eclipse in more detail. Meanwhile watch this space!
Flare stars are cool, M-type stars that show sudden brightenings in optical and
other spectral regions which appear to be related to solar flares. Emission
lines in the optical and UV strongly imply the existence of a solar-type
chromosphere and transition region, and X-rays imply that there is corona.
I worked with Gordon Bromage (University of Central Lancashire) and others on a project in 1991/92 to study the origin of the UV continuum that appears in IUE SW spectra of dMe stars in a flaring state. The continuum is definitely real, not instrumental, and is particularly strong at wavelengths longer than 1500A. There is an analogous continuum emitted in the quiet sun which is strongly enhanced in flares, as has been seen with the NRL spectrometer on Skylab. In the solar case the continuum is due to free--bound transitions in Si II, with excitation occurring by intense UV lines such as the C IV doublet at 1550A. These lines are even more intense in the case of dMe stars, especially in a flaring state, and so the excitation of Si recombination radiation is much enhanced. This leads to an approximately proportional relation between line and continuum emission expressed as a power (erg s-1), as is shown in our paper to exist for flares of various magnitudes on a number of dMe stars.
More recently, I have been working with colleagues at Queen's University Belfast (Mihalis Mathioudakis etc.) on HETGS spectra of Capella from the Chandra (formerly AXAF) spacecraft. We investigated optical depth effects and electron densities. A paper analyzing a Chandra HETGS X-ray spectrum of Capella as well as near-simultaneous spectra from the EUVE satellite was published in MNRAS (not my choice of journal! I would have preferred A&A or ApJ where the refereeing would have been less predictable than with the same old cronies who edit MNRAS). In it we included a comparison of the Chandra spectrum in the 8--20 A range with the equivalent spectrum from the decaying stage of an M-class solar flare as seen with the SMM spacecraft. Click here for a figure showing this. Notice how similar the line intensities are, as well as the spectral resolution at wavelengths greater than 13A. The Fe XVII 15A and 17A lines are prominent in both, as is the O VIII Ly-alpha line at 18.97A. Although it appears that the intensity ratios are different, they are not in fact -- there is a strong wavelength-dependent FWHM in the Chandra spectrum. So I believe the solar and Capella abundances are quite similar which argues against the so-called FIP effect which I don't think has much evidence going for it in spite of the hype. A differential emission measure analysis indicates that much of the material in both Capella and the decaying solar flare is at a temperature of about 6MK. More details will follow soon. The electron density from O VII ratios and the relatively small emission measure leads to extremely small volumes. I feel this is an indication that there is in fact no significant corona on either of the components making up Capella -- rather, that there is an intra-stellar source that somehow retains its identity, perhaps through magnetic field confinement. If not, the corona of either star must consist of just a few loops, but then it's puzzling why there is no significant rotational modulation (one component rotates very rapidly).
There was a meeting to commemorate the life and work of the late Dr Brendan
Byrne (Solar and Stellar Activity: Similarities and Differences)
in Armagh, September 2--4, 1998, at which I gave a review of solar flares.
The Proceedings were published by the Astronomical Society
of the Pacific (ed. by John Butler and Gerry Doyle).
Brendan was a good friend of mine and I miss his infectious humour and
enthusiasm for his subject. It was sad to hear of his tragic death.
Click here for a shot of me (on right) with colleagues at the great dinner we had at Castle Leslie (just across the border in the Republic)!
My article on "SOHO: our New View of the Sun" was in the April 2000 issue of
Astronomy Now magazine which came complete with a SOHO CD-ROM.
For my other publications, I will eventually have a complete list which will be
viewable from this site. Meanwhile, you can get
postscript files of some of my publications from . There is an out-of-date
list of my publications you can get by clicking here.. I will get this updated as soon as possible.
Here is a list of some papers that are referred to above -- preprints available as postscript files in some cases:
Last modified - November 9, 2004