I I, I I I I’ Department of Physics and Astronomy STATE UNIVERSITY OF IOWA Iowa City, Iowa A STUDY OF THE AURORA AUSTRALIS IN CONNEC'I'ION WITH AN ASSOCIATION BmwEEN WEHISS AND AUROW ARCS AND BANDS OBSERVED AT SOUTH GEOGRAPHICAL POI& 1960 Henry M. Morozumi . A thesis submitted in partial fhlfillment of the requirements for the degree of Master of Science in the Department of Physics and . Astroncmy in the Graduate College of the State University of Iowa Chairman: Professor Brian J. O'Brien . ACKNOWLEDGEMENTS The observational equipment was provided by the Air Force Cambridge Research Laboratory (AFCRL) and the State University of Iowa (SUI), Department of Physics and Astronomy. I am indebted to Dr. Helliwell of Stanford University for his permission to use the W equipment. Hiss audio spectra were provided by the Radioscience Laboratory, Stanford University. I wish to thank Messrs. Morse of National Bureau of Standards (NBS), Flowers of United States Weather Bureau (USWB), Oliver of AFCRL, and Goodwin of United States Coast and Geodetic Survey . (USC and GS) for making the data available . I wish to thank Professor Gartlein of the World kta Center A (WE-A), Cornell University, for proposing the IPN analysis. I am particularly indebted to Dr. Sprague for his many suggestions and help in IBM operation and the computation of Tables I and 11. Mrs. Clark of Cornell University kindly provided Figures 4, 5, and 6 from her thesis. The research was done at AFCRL, Cornell WDC-A, and the State University of Iowa. Discussions with Messrs. B. Sanford, T. Obayashi, R. Gallet, B. MaeNwn, and many associates in this ii university were valuable in improving this material. I am greatly indebted to my advisor, Dr. B. J. O'Brien, for his many suggestions. It is my pleasure to acknowledge Dr. J. A. Van Allen's interest in this thesis project at this university. The author also wishes to thank Mrs. &Long, MI-. Jump, and Miss Van Dusen of WE-A, and Mrs. Robison of SUI for their assistance. Most of the research was supported by the Arctic Institute of North America, and partly by the State University of Iowa and USARP, National Science Foundation. iii TABU OF COIITENTS Chapter I . INTRODUCTION ................................. 1 I1 . INS!I!RUMEN!FATION FOR THE OBSERVATION .......... 5 1. Program in General ...................... 5 2 . Visual Program .......................... 6 3 . All Sky Camera .......................... 7 4 . Photmeter .............................. a 5 . vI;F Equipment ........................... 11 6 . Magnetometer ............................ 12 111 . SUMMARY OF THE DATA OBTAINED ................. 13 IV. DATA CODIFICATION AND REDUCTION .............. 15 V . ANALYSIS OF THE RESUmS ...................... 19 VI. THEOFUES OF RADIO WAVE EMISSION FROM PLASMA AND ASSOCIATED PHE"A ..................... 29 VI1. DISCUSSION AND CONCLUSION .................... 42 iv TABU OF FIGURES Figure No . 1. Aurora-Airglow Program instrumentation ............ 55 2 . heation of various instruments on the tower roof ............................................. 56 3 . Orientation of the aurora tower relative to the magnetic and Greenwich meridian .............. 57 4 . Alidide card for visual observations ............. 58 5 'Phe relationship between angular and linear distance of aurora ............................... 59 6 . Auroral isochasm ................................. 60 7 . Spectrograph integrator circuit modification ..... 61 8 . Spectrograph photmeter cathode follower ......... 62 9 . Directional photmeter circuit diagram ........... 63 10. bgarithmic amplifier calibration curve .......... 64 11 . All-Slry photmeter circuit diagram ............... 65 12 . All-slry photaeter parer supply .................. 66 13 . W clipper circuit .............................. 67 14 . Block diagram of VUmonitor system .............. 68 15. Electronic magnetmeter circuit diagram .......... 69 16. Synoptic data sheet .............................. 70 V TABU3 OF FLGURES (continued) Figure No. 17. Diurnal variation of various events ............. 71 18. Typical 24-hm photmeter data . .. .. 72 19. Relationship between the mwnetic, VU, and aurora data ..................................... 73 20. All-Sky camera data ............................. 74 21. All-Sky camera data ............................. 75 22. All-Sky camera data ............................. 76 23. Audio spectrum of auroral hiss .................. 77 24 . VIP-Aurora intensity variation (Brush) .......... 78 25 . VLF-Aurora intensity variation (E. A.) .......... 79 26. VLF-Aurora intensity variation (Brush) e a a a 80 27. All-Sky camera data ............................. 81 28. my type aurora ................................. 8e 29. my type aurora ................................. 83 30. "he relationship between the visual aurora and the magnetic data ........................... 84 Vi TABLE OF ILLUSTRATIONS Illustration NO I. Directional Photometer *.. 85 11. All-Sky Photometer .. .. .. 86 111. Kiss Pattern on the Scope .. .. 87 TABLE OF TABLE3 Table No . me I. Diurnal Variation of Various Events .. .. 20 11. Variuus Events as a Function of K ............. 22 1st. Characteristics of Two Aurora Peaks .. 45 viii ABSTRACT Observations of auroras and vI;F hiss were made during the dark months of 1960 at the South Pole. About one thousand hours of auroral observations were made. The data were analyzed statis- tically on the IEPJI 101 computer from 3432 cards. In the analysis detailed studies were also made of more than three thuusand hours of data from photmeters, magnetmeters, an all sky camera, and a VIE receiver. A close association between hiss and auroral arcs and bands was fuund, which had a diurnal occurrence peak at a few hours before the magnetic midnight. Ikss identifiable long ray type aurora diurnal peak was found at around a few hours before the magnetic noon. These two types of auroras were markedly different in various aspects. The differences are discussea in this thesis. A brief theoretical consideration on the vI;F emission mechanism is given. ix 1 I. INTRODUCTION Although the existence of naturally occurring audio- frequency electranagnetic waves had been reported by several authors, Burton and Boardman E9317 appear to be the first to have observed any correlation between such emissions and various geo- physical disturbances . Bey reported a correlation between atmospherics and auroral activity. The frequency range of their receiving equipment was 150 to 4000 cps. Various researchers have studied atmospherics and cosmic radio noises since then. Such radio emissions were found to be distributed mer a wide spectral range, not only in the kilocycle range but up to several megacycles or higher. Sme workers investigated the nature of noise in the megacycle region /rShain, 1954; Ellis, 1956; and Ellis, 19577. me origklal pziiose of researches in the megacycle region, however, was mainly the study of radio galaxies ,&hklovsky, l9q. Menzel and others developed their theories and observed the phenomena in ELF-VLF region, seeking correlation between the lar frequency radio emission and changes in the earth's magnetic field, etc. @oris et al., 1953, 1956; Menzel et al., 1948; and Willis, 194y. The work of Storey identified sane of the audio-frequency signals as whistlers, inferring the electromagnetic wave emission frm 2 lightning, which propagated through the exosphere by means of a quasi-longitudinal mode. There are other types of emissions which are independent of thunderstorm activity [mis, 1959; and Gallet, 1957, such as stated by Burton and others. A close correlation was found between activity and the electro- I solar magnetic emission of a second type in the frequency range between 2 and 10 kc/s @lis, 19q. Such radio wave emission is generally called WE, very low frequency emission. No widely accepted definitions of V", ELF, and micropulsation frequency ranges are in use. However, we are tending to use lcps as the upper fre- quency of micropulsations and 1 - 3000 cps for the EIJ? range, and 3000 - 30,000 cps for the VIP range Belliwell, 19627. Among the many kinds of VLFE ,&rons, 1956, 1960; Ellis, 1957; Gallet, 1959; Martin et al., 1960; and Allcock, 195v a certain type of emission identified as "hiss" has received attention recently fiatts, lg5r. Sme evidence has been found on associa- tions between hiss and variaus geophysical phenmena kens, 1960; Ellis, 1960a and 196Ob; Martin et al., 1960; Watts, 1957; and Helliwell, et al., 1962q. Watts reported his observation of "hiss" on March 3, 1956, recorded at Boulder, Colorado, as follows: An observer arrived at the field station to find another signal which was different fran whistlers and 3 choruses, a loud hissing noise, being recorded, The energy was obviously enormous, since the needle of the tape recorded level meter, normally near zero end of the scale except for the atmospherics, was pinned continuously against the top stop. Such noise lasted more than twelve huurs. Gallet observed more than ten hours’ hiss; however, he found the average duration to be 1.6 haurs for I22 distinct cases (is5g. A relationship was found between 2130 kc/s cosmic noise and Es [ais, 19577. Ellis found appraximately 50 per cent of isolated noise bursts may be correlated with magnetic bays Luis, 196Ov. Correlations between the WEand magnetic phenumena are reported elsewhere ,&tts, 195F. !be physical dimension of the audio-electrcsnagnetic wave emitter was measured recently Luis, 19a. Simultaneous observations of sub-visual aurora and radio noise on 4.6