SOLAR GAMMA-, X-, AND EUV RADIATION d Golub L. S. Kahler A. Krieger Z. Svcslka S. de Miceli D. Rust UnderwooJ. T. Gegerly J. Vorphal 8) 9) 0) 1) 2) 3) 4) 5) 6) 223333333 (((((((( n Culhane J. Sa hade J. G. Doschek R. Marabini de Feiler L. H. S. Hudson R. Hutcheon P. Pye H. ParkinsoJ. 9) 0) 1) 2) 3) 4) 5) 6) 7) 122222222 ((((((((( G. Brueckner R. Ramaty T. Paneth T. Gosling J. P. R. Lin C. Y. Fan T. Takakura D. Dallowe C. Jordan 10) II) 12) 13) 14) 15) 16) 17) 18) ((((((((( Seibold J. M. FOnlenla J. H. S. Ghielmetti S. Yousef H. Molnar G. M. Simnet c.-c. Cheng W. N. Glencross M. Machado I) 2) 3) 4) 5) 6) 7) 8) 9) ((((((((( ® ® ® ® © © ® ® ® @ © ® ® © ® ® @ ® ® ~ ® E)® ® e ® e 6 ® ® 6e ® 8® INTERNATIONAL ASTRONOMICAL UNION UNION ASTRONOMIQUE INTERNATIONALE SYMPOSIUM No. 68 HELD IN BUENOS AIRES, ARGENTINA, 11-14 JUNE 1974 ORGANIZED BY THE IAU IN COOPERATION WITH COSPAR SOLAR GAMMA-, X-, AND EUV RADIATION EDITED BY SHARAD R. KANE Space Sciences Laboratory, University of California, Berkeley, Calif, U.S.A. D. REIDEL PUBLISHING COMPANY DORDRECHT-HOLLAND / BOSTON-U.S.A. 1975 Library of Congress Cataloging in Publication Data Main entry under title: Solar gamma-, X-, and EUV radiation. (Symposium - International Astronomical Union; no. 68) Includes bibliographies. 1. Solar radiation - Congresses. I. Kane, Sharad R. II. International Astronomical Union. III. International Council of Scientific Unions. Com mittee on Space Research. IV. Series: International Astronomical Union. Symposium; no. 68 QB531.S57 523.7'2 75-6545 ISBN-13:978-90-277-0577-8 e-ISBN-13:978-94-010-1802-9 DOl: 10.1007/978-94-010-1802-9 Published on behalf of the International Astronomical Union by D. Reidel Publishing Company, P.O. Box 17, Dordrecht, Holland All Rights Reserved Copyright © 1975 by the International Astronomical Union Sold and distributed in the U.S.A., Canada, and Mexico by D. Reidel Publishing Company, Inc. 306 Dartmouth Street, Boston, Mass. 02116, U.S.A. No part of this book may be reproduced in any form, by print, photoprint, microfilm, or any other means, without written permission from the publisher TABLE OF CONTENTS PREFACE IX LIST OF PARTICIPANTS XI PART 1: GENERAL SOLAR ACTIVITY, CORONAL HOLES AND BRIGHT POINTS R. W. NOYES, P. V. FOUKAL, M. C. E. HUBER, E. M. REEVES, E. J. SCHMAHL, J. G. TIMOTHY, J. E. VERNAZZA, and G. L. WITHBROE; EUV Observations of the Active Sun from the Harvard Experiment on A TM 3 w. M. GLENCROSS; Holes in the Solar Corona 19 L. GOLUB, A. S. KRIEGER, J. K. SILK, A. F. TIMOTHY, and G. s. VAIANA; Time Variations of Solar X-ray Bright Points 23 R. 1. THOMAS; Solar Activity Observed in X-Rays and the EUV from OSO 7 25 PART 2: ACTIVE REGIONS J. H. PARKINSON; X-Ray Spectra of Solar Active Regions 45 J. P. PYE, R. J. HUTCHEON, J. H. PARKINSON, and K. A. POUNDS; X-Ray Spec- troscopy of Solar Active Regions During the Third Sky lab Mission 65 R. C. CA TURA, L. W. ACTON, E. G. JOKI, C. G. RAPLEY, and J. L. CULHANE; Spatially Resolved X-Ray Spectra of Coronal Active Regions 67 R. J. HUTCHEON; Classification of New Spectral Lines of Fe XVII Observed in Solar Active Regions 69 s. YOU S EF ; Statistical Methods in the Identification and Prediction of the Solar X-Ray Spectral Lines 71 A. B. C. WALKER, JR.; Interpretation of the X-Ray Spectra of Solar Active Regions 73 D. H. BRABBAN, E. B. DORLING, W. M. GLENCROSS, and J. R. H. HERRING; Soft X-Radiation from Single Active Regions 101 A. S. KRIEGER, R. C. CHASE, M. GERASSIMENKO, S. W. KAHLER, A. F. TIMOTHY, and G. s. VAIANA; Time Variations in Coronal Active Regions 103 G. E. BRUECKNER; Flare-Like Ultraviolet Spectra of Active Regions 105 c. JORDAN; The Structure of Solar Active Regions from EUV and Soft X-Ray Observations 109 VI TABLE OF CONTENTS PART 3: SOLAR FLARES G. E. BRUECKNER / Ultraviolet Emission Line Profiles of Flares and Active Regions 135 K. G. WIDING / Fe XXIV Emission in Solar Flares Observed with the NRL/ATM XUV Slitless Spectrograph 153 G. A. DOSCHEK / X-Ray and EUV Spectra of Solar Flares and Laboratory Plas- mas 165 P. R. SENGUPTA / Association of X-Ray Flares with Solar Coronal Active Regions 183 s. W. KAHLER, A. S. KRIEGER, J. K. SILK, R. W. SIMON, A. F. TIMOTHY, and G. s. VAIANA / Studies of the Dynamic Structure and Spectra of Solar X-Ray Flares 185 1. CRAIG / On the Thermal Structure of the Flare-Produced Plasma 187 D. W. DATLOWE / The Relationship between Hard and Soft X-Ray Bursts Observed by OSO 7 191 D. W. DA TLOWE and H. s. HU DSON / Relationship between Hard and Soft Solar X-Ray Sources Observed by OSO 7 209 s. W. KAHLER / Thermal and Nonthermal Interpretations of Flare X-Ray Bursts 211 P. HOYNG, J. C. BROWN, G. STEVENS, and H. F. VAN BEEK / High Time Reso- lution Analysis of Solar Flares Observed on the ESRO TD-IA Satellite 233 J. A. VORPAHL and T. TAKAKURA / Rise Time of Hard X-Ray Bursts 237 J. C. BROWN and H. F. VAN BEEK / Determination of the Height of Hard X-Ray Sources in the Solar Atmosphere by Measurement of Photospheric Albedo Photons 239 D. M. RUST / Inference of the Hard X-Ray Source Dimensions in the 1972, August 7, White Light Flare 243 J. C. BROWN / The Interpretation of Spectra, Polarization, and Directivity of Solar Hard X-Rays 245 L. D. DE FElTER / Solar Flare X-Ray Measurements and Their Relation to Microwave Bursts 283 T. T AKAKURA / Relation of Microwave Emission to X-Ray Emission from Solar Flares 299 R. TALON, G. VEDRENNE, A. S. MELIORANSKY, N. F. PISSARENKO, V. M. SHAMOLIN, and o. B. LIKIN / X- and y-Ray Measurements during the 1972, August 2 and 7 Large Solar Flares 315 E. L. CHUPP, D. J. FORREST, and A. N. SURI / High Energy Gamma-Ray Radia- tion above 300 keY Associated with Solar Activity 341 R. KOGA, G. M. SIMNETT, and R. S. WHITE / Measurements of a Gamma-Ray Burst above 1 MeV 361 R. RAMATY and R. E. LINGENFELTER / Gamma-Ray Lines from Solar Flares 363 TABLE OF CONTENTS VII R. P. LIN / Fast Electrons in Small Solar Flares 385 c. Y. FAN, G. GLOECKLER, and D. HOVESTADT / Nuclei of Heavy Elements from Solar Flares 411 c. C. CHENG and D. S. SPICER / Implications of NRL/ATM Solar Flare Obser- vations on Flare Theories 423 H. S. HUDSON, T. W. JONES, and R. P. LIN / Nonthermal Processes in Large Solar Flares 425 z. 8VESTKA / On the Acceleration Processes in Solar Flares 427 PREFACE The symposium on 'Solar Gamma-, X- and EUV Radiation' was held at Buenos Aires, Argentina, from 11 June to 14 June 1974. It was sponsored jointly by the Inter national Astronomical Union (IAU) and the Committee on Space Research (COSPAR). The Organization Committee responsible for the program consisted of Drs K. A. Anderson (Chairman), J. L. Culhane, G. Elwert, B. B. Fossi, S. L. Mandel s'tam, W. M. Neupert, V. K. Prokofiev, and J. Sahade and representatives of COSPAR, Drs H. Friedman and Z. Svestka. During the symposium Dr Svestka kindly represented the chairman of the Organizing Committee who was unable to attend the symposium. The local arrangements in Buenos Aires were made by Drs J. Sahade (Chairman), H. S. Ghielmetti, M. J. Gulich, H. Molnar, J. J. Tasso and N. Martinez Riva de Tropper. This symposium brought together the observational and theoretical aspects of the Solar Gamma-, X-, and EUV Radiation and other related solar emissions such as radio and energetic particles. There were three specific topics for the symposium, viz. X-ray and EUV emissions from solar active regions, EUV, X- and Gamma-emissions from solar flares, and mechanisms of hard photon emissions. The large improvement in our understanding of the physical processes in the active regions and flares, made possible by the various spacecraft and ground-based observations during the past few years could be clearly seen from the papers presented during the Symposium. Al though only a fraction of the Skylab observations were analyzed at that time, several Skylab experimenters discussed their measurements related to the active regions and flares as well as the newly discovered solar features such as coronal holes and bright points. The order in which the papers are included in these proceedings is somewhat differ ent from the order in which they were presented during the symposium. Most of the papers submitted for publication were specifically related to either active regions or flares. These are included in Parts 2 and 3 respectively of these proceedings. The few papers which dealt with several aspects of solar activity or discussed coronal holes or bright points are included in Part 1. It is hoped that this organization of the proceed ings will help to bring into focus the physical process occurring in the two major forms of solar activity, viz. the active regions and flares. The excellent work done by the Organizing Committee in preparing a good program for the meeting can be clearly seen from the large number of new results presented during the symposium. About sixty scientists from twelve different countries partici pated in the Symposium. A total of forty-five papers were presented indicating the large amount of research currently being done in the various aspects of the Solar Gamma-, X-, and EUV Radiations. x PREFACE An important part of the proceedings of a symposium is the edited transcripts of the discussions following each paper. Dr Sahade made a great effort to record on magnetic tapes the discussions that followed the presentations of the various papers. However, due to technical difficulties, it was not possible to make transcripts which could be reproduced in these proceedings. Publication of proceedings, such as these, is possible only with the cooperation and help from many people. I am particularly thankful to Dr K. A. Anderson, Chairman of the Organizing Committee and Dr Edith A. Miiller, Assistant General Secretary of the IAU, for keeping me informed about the various aspects of the program and proceedings of the symposium. Material related to the list of participants, a photo graph of the participants and tapes and transcripts of the discussions were kindly provided by Dr J. Sahade. Ms Carol Legge helped with a large part of the clerical work needed in the organization of the program and the preparation of the manus cript for publication. Finally, thanks are due to Mr J. F. Hattink of D. Reidel Pub lishing Company for his help in bringing the proceedings to the present published form. Space Sciences Laboratory SHARAD R. KANE University of California Berkeley, Calif., U.S.A.