D IS SERTATIO CVM NVNCIO SIDEREO III 4 PRAGAE MMVI 17. VIII. SERIES TERTIA Today's invited discourse at 6:15 p.m. in the Congress Hall Zdeněk Švestka – 40 years as an editor of Solar Physics Address of František Fárník at the yesterday’s celebratory lunch DISCOURSE The magnetic fi eld and its effects on the solar Ladies and gentlemen, dear colleagues, atmosphere in high resolution I was honored by the suggestion of Lídia to say a few words about Zdeněk during INVITED Alan Title, Stanford-Lockheed Institute for Space Research this occasion, focusing on his contribution to solar physics in general. It is a pleasure S ' in the fi rst place but, at the same time, a very diffi cult task for me. I am sure that To resolve the effects of the magnetic fi eld it is necessary to image the interior and speaking about Zdeněk’s scientifi c work for a group of solar physicists is like “carrying TODAY measure its rotation and fl ow systems; track the responses of the magnetic fi elds to fl ows in the surface; and to follow the coals to Newcastle”. Therefore, allow me to be brief about science and to add some personal reminiscences too. Because I am one generation younger, I came to our OF evolution of structures in the corona. Because the Sun is dynamic, both high spatial and temporal resolution are essential. Since the Sun’s magnetic fi eld effects encompass the entire spherical exterior, the entire surface and outer atmosphere Institute in Ondřejov after Zdeněk had to emigrate in 1971 and that’s why we met for must be mapped. And because the magnetic fi eld is cyclical, high-resolution observations must be maintained over multiple the fi rst time when Zdeněk was nearly 56 years old – the reason is clear : Traveling to the West and, even more diffi cult, visiting emigrants was almost impossible in those cycles. BSTRACT years. This made a division – situation before we met and after. When returning to A The last 15 years has been a revolutionary period in solar physics because of the development of new observatories the beginning, I have to describe a long and fruitful period of Zdeněk’s stay at the on the ground and in space, advances in numerical simulations, and adaptive optics and post processing techniques. Ondřejov Observatory which I know from the literature and from the stories told by 24/7 monitoring of the full Sun has allowed helioseismologists to determine the temperature, density, equation of state my older colleagues only. It may sound like a joke that the fi rst contract which Zdeněk of the solar interior, and velocity structure of the solar interior. New adaptive mirrors and post processing techniques received in July 1948 at the observatory was offi cially as a gardener. Nevertheless, have allowed 0.1 arc second imaging with Strehl ratios of 0.9 over fi elds of view of 60 arc seconds and more. As a result shortly afterwards a group of newly recruited young scientists started to study a the temperature structure of the photosphere and chromosphere are much better understood. brand-new fi eld in Ondřejov – solar physics. Since the very beginning Zdeněk focused These observations are critical to understanding how the surface magnetic fi elds are connected himself on optical spectroscopy, especially when using the H-alpha data from the to the transition region and corona. Coronal observations show that magnetic fi elds on smaller local spectroheliograph. During the fi fties, when Zdeněk was already head of the scales interact with and deliver energy to larger magnetic structures i. e., scale mixing. It now Solar Department, a unique multi-channel optical spectrograph was built in Ondřejov. appears that much, if not most, of the heating of the corona is due to magnetic fi elds that are The idea to build this spectrograph was suggested by Zdeněk and Milan Bláha and generated by local magnetic processes. the successful observations with the new instrument made Ondřejov one of the leading solar observatories in the world. Results of the Zdeněk’s analysis of many The almost universal commitment of observatories and Principal Investigators to open data optical spectra of solar fl ares were published in a lot of papers and are summarized in policies coupled with fast internet connections has allowed the international community of solar Zdeněk’s book “Solar Flares”. Here I have to mention also an important contribution physicists, astrophysicists, plasma physicists, and fl uid dynamicists to participate in the data of his wife Lída and some other colleagues from Ondřejov. Later on, Petr Heinzel analysis process. and his collaborators reconstructed this instrument and after Petr met Zdeněk at NASA in 1986, they worked on new spectra taken in Ondřejov. Zdeněk was again the source of inspiration for us. The successful and happy “Ondřejov” period was broken by the Russian invasion in 1968. Zdeněk, already a distinguished scientist, Imagine . was invited to work in ESTEC in 1970. The political situation quickly deteriorated and Zdeněk had to stay abroad, to emigrate against his will. He spent a short period Imagine that you can only see the solar corona above the limb, that you have never heard about coronal in Freiburg and then two years in American Science and Engineering in Cambridge, mass ejections traveling through interplanetary space, or about coronal holes, and that your only USA, where he participated on the Skylab X-ray telescope and its data analysis. He knowledge in the fi eld of helioseismology are the 5-minute oscillations. slowly changed his fi eld of study from the optical region to X-rays. He moved from the USA to the Netherlands and from 1977 he worked in SRON, Space Research Zdeněk Švestka Organization of Netherlands, the director of which was Professor C. de Jager at that That was the situation in solar physics when the IAU met Observatories and with Space Vehicles” and Commission time. Here, Zdeněk was involved in the development, observations and data analysis the last time in Prague – in the year 1967. I was president 10 endorsed the COSPAR resolution to organize a of the Dutch hard X-ray telescope, HXIS, which fl ew onboard the SMM satellite. The of Commission 10 on solar activity at that time, mainly due symposium on “Solar Flares and Space Research” one year historical overview approached the moment when I met Zdeněk for the fi rst time, at to successful observations and interpretations of spectra later, in 1968, in Tokyo. Still, one could hardly envisage at a workshop in Annecy in 1981. This is also the moment when I would like to mention of chromospheric fl ares in our unique fl are spectrograph at that time the quality of the future achievements in solar one, very important, thing: Zdeněk has (and always had) a very cordial relation to Ondřejov. Nowadays we know that what we observed and space experiments: Could anybody in 1967 imagine the his “home observatory” in Ondřejov and he tried as much as he could to help by all analyzed at that time were actually only footprints of enormous unbelievable images of coronal structures obtained by the possible ways. That’s why, when I told him that I am interested in observations invisible coronal fl are dinosaurs in the chromosphere. TRACE, with one-arc-second resolution, 30 years later? and analysis of solar X-rays, he suggested a possibility that I could spend some time Only six years later, Skylab revealed the solar corona all Of course, this outstanding progress in observational in SRON in Utrecht where we could analyze together data from HXIS. Since 1983, over the disk, showing its loop-like structure, the occurrence techniques would not have been possible without extremely when I spent 3 months in SRON, our close cooperation continued until the moment, when he decided to retire from science a few years ago. Under Zdeněk’s guidance of bright points and coronal holes, and the existence of fast development of highly sophisticated computers. Just in we mainly studied large coronal structures observed in hard (HXIS) and later, when coronal transients, later renamed coronal mass ejections. the year when the previous IAU Assembly in Prague was the Yohkoh satellite started observations, in soft X-rays. Among the studied topics And two more years were needed before the rich structure taking place, the Ondřejov Observatory got its fi rst computer were bright surges, fl aring arches, rising and stationary post-fl are giant arches, post- of the 5-minute oscillations was fi rst resolved, thus founding – and it occupied a whole, large, newly built building. fl are streamers, wind streams from fl aring active regions, interconnecting loops and the prolifi c fi eld of helioseismology. Nowadays a little box on my d esk performs incomparably others. It is impossible to describe even the most relevant results during this short Also in that year, 1967, the fi rst two volumes of the better than that monster installed 40 years ago. presentation. journal “Solar Physics” appeared which, since that time, has This progress in solar physics and, of course, in the whole Besides many scientifi c papers (ADS gives 285 papers of which Zdeněk is the published more than 8,000 scientifi c articles studying the fi eld of astronomy, is certainly encouraging. However, it also main author or one of co-authors) he wrote the already mentioned book on solar Sun and solar-terrestrial relations. As solar physicists are produces some concerns, because it is not refl ected by any fl ares, published in 1976. One of his most important activities, I mean the founding meeting this year again here in Prague, Volume 237 will be comparable development in the minds of mankind.