WORLD DATA CENTER A for Solar-Terrestrial Physics NUMERICAL MODELING OF IONOSPHERIC PARAMETERS FROM GLOBAL IMS MAGNETOMETER DATA FOR THE CDAW-6 INTERVALS November 1983 World Data Center A consists of the Coordination Office and the following eight Subcenters: COORDINATION OFFICE World Data Center A National Academy of Sciences 2101 Constitution Avenue, NW Washington, D.C. 20418 USA [Telephone: (202) 334-3559] GLACIOLOGY (Snow and Ice) World Data Center A: Glaciology (Snow and Ice) Cooperative Inst. for Research in Environmental Sciences University of Colorado Boulder, Colorado 80309 USA Telephone: (303) 492-5171 MARINE GEOLOGY AND GEOPHYSICS (Gravity, Magnetics, Bathymetry, Seismic Profiles, Marine Sediment, and Rock Analyses): World Data Center A for Marine Geology and Geophysics NOAA, E/GC3 325 Broadway Boulder, Colorado 80303 USA Telephone: (303) 497-6487 METEOROLOGY (and Nuclear Radiation) World Data Center A: Meteorology National Climatic Data Center NOAA, E/CC Federal Building Asheville, North Carolina 28801 USA Telephone: (704) 259-0682 OCEANOGRAPHY World Data Center A: Oceanography National Oceanographic Data Center NOAA, E/OC 2001 Wisconsin Avenue, NW Page Bldg. 1, Rm. 414 Washington, D.C. 20235 USA Telephone: (202) 634-7510 ROCKETS AND SATELLITES World Data Center A: Rockets and Satellites Goddard Space Flight Center Code 601 Greenbelt, Maryland 20771 USA Telephone: (301) 344-6695 ROTATION OF THE EARTH World Data Center A: Rotation of the Earth U.S. Naval Observatory Washington, D.C. 20390 USA Telephone: (202) 254-4547 SOLAR-TERRESTRIAL PHYSICS (Solar and Interplanetary Phenomena, Ionospheric Phenomena, Flare-Associated Events, Geomagnetic Variations, Aurora, Cosmic Rays, Airglow): World Data Center A for Solar-Terrestrial Physics NOAA, E/GC2 325 Broadway Boulder, Colorado 80303 USA Telephone: (303) 497-6323 SOLID-EARTH GEOPHYSICS (Seismology, Tsunamis, Gravimetry, Earth Tides, Recent Movements of the Earth's Crust, Magnetic Measurements, Paleomagnetism and Archeomagnetism, Volcanology, Geothermics): World Data Center A for Solid-Earth Geophysics NOAA, E/GC1 325 Broadway Boulder, Colorado 80303 USA Telephone: (303) 497-6521 World Data Centers conduct international exchange of geophysical observations in accordance with the principles set forth by the International Council of Scientific Unions. WDC-A is established in the United States under the auspices of the National Academy of Sciences. Communications regarding data interchange matters in general and World Data Center A as a whole should be addressed to World Data Center A, Coordination Office (see address above). Inquiries and communications concerning data in specific disciplines should be addressed to the appropriate subcenter listed above. WORLD DATA CENTER A for Solar-Terrestrial Physics Report UAG-88 NUMERICAL MODELING OF IONOSPHERIC PARAMETERS FROM GLOBAL IMS MAGNETOMETER DATA FOR THE CDAW-6 INTERVALS by Y. Kamide, H.W. Kroehl, B.A. Hausman, R.L. McPherron, S.-I. Akasofu, A.D. Richmond, P.H. Reiff and S. Matsushita November 1983 U.S. Department of Commerce National Oceanic and Atmospheric Administration National Environmental Satellite, Data, and Information Service Boulder, Colorado, USA 80303 # TABLE OF CONTENTS | Section | Page | |------------------------------------------------------------------------|------| | INTRODUCTION | 1 | | THE PROCEDURE | 1 | | THE METHOD | 2 | | Current Function | 2 | | Ionospheric Conductivity | 6 | | Electric Potential | 6 | | Ionospheric Currents and Field-Aligned Currents | 7 | | Joule Heating Rate | 7 | | MAGNETIC ACTIVITY DURING THE CDAW-6 INTERVALS | 7 | | 0600 - 1800 UT on March 22, 1979 | 7 | | 1200 March 31 - 0600 April 1, 1979 | 7 | | EXAMPLES | 8 | | ACKNOWLEDGEMENTS | 12 | | REFERENCES | 13 | | APPENDIX I: Data Plots for 0600 - 1800 on March 22, 1979 | 15-87 | | APPENDIX II: Data Plots for 1200 March 31 - 0600 April 1, 1979 | 89-198| NUMERICAL MODELING OF IONOSPHERIC PARAMETERS FROM GLOBAL IMS MAGNETOMETER DATA FOR THE CDAW-6 INTERVALS Y. Kamide¹,², H.W. Kroehl³, B.A. Hausman³, R.L. McPherron⁴, S.-I. Akasofu⁵, A.D. Richmond¹, P.H. Reiff⁶ and S. Matsushita⁷ INTRODUCTION The purpose of this technical report is to present the results of modeling efforts to estimate the distribution of ionospheric electric potential, ionospheric and field-aligned currents, and Joule heating rate from ground-based magnetic records for two intervals; (1) 0600-1800 UT on March 22, 1979, and (2) 1200 UT on March 31 to 0600 UT on April 1, 1979. This global modeling study constitutes one of the major contributions to the Coordinated Data Analysis Workshop (CDAW-6) sponsored by the National Space Science Data Center, NASA. The CDAW series has been, and will continue to be, focused on large, cooperative analyses of multiple satellite and other platform data recorded during the International Magnetospheric Study (IMS, 1976-1979); see e.g., Roederer (1976) and Manka (1976) for the concept of the IMS. The purpose of the Analysis Phase of the IMS is to improve our understanding of the transport of energy, mass and charge through the solar terrestrial environment utilizing the most comprehensive and extensive bases obtained from space and ground-based instruments. In this report, we briefly describe the algorithm of our numerical modeling and the characteristics of the two intervals. In Appendices I and II we show at 10-minute intervals the results of applying this algorithm to the compiled data as plots of the global distribution of the equivalent current, the electric potential, the ionospheric current, the field-aligned current and Joule heating rate. We hope that these data products provide the scientific community with new insights into our understanding of magnetospheric and ionospheric processes associated with substorms. THE PROCEDURE Figure 1 outlines the steps required to prepare a motion picture of the derived parameters from the digital values of the magnetic variations. The practical procedures of each step are summarized as follows: 1) We started with digital values of the magnetic variations recorded every 5 minutes in magnetic coordinates (H and D) or geographic coordinates (X and Y). Approximately 70% of the data used were received directly from NSSDC as contributions to the CDAW-6 data base while the remaining 30% were digitized from analog records to fill gaps in the spatial coverage. A typical quiet day's values were removed to eliminate Sq-type currents. In this case we used March 12, 1979, as the quiet day, since the 8 Kp values were 1-, 1-, 0+, 0+, 0+, 0+, 1 and 1 and $\varepsilon Kp=5$. The resulting values were then transformed into the corrected geomagnetic coordinate system of Gustafsson (1969) and labeled $X_m$ and $Y_m$. 2) In view of the fact that this data base is one of the most extensive data sets ever assembled from ground-based magnetometers, we constructed the auroral electrojet indices, AE, AU and AL, from the $X_m$ values recorded at stations between 50° and 75° in corrected geomagnetic latitude. For the first interval, 57 stations met the latitude requirements and for the second interval 58 station data were used. Substorm activity described by these indices is presented later in this report. 3) The equivalent current function is calculated by fitting a magnetic potential function to the observed data estimating the portion of this potential which results from overhead currents. 1. Space Environment Laboratory, NOAA, Boulder, CO 80303 2. On leave of absence from Kyoto Sangyo University, Kyoto 603, Japan 3. National Geophysical Data Center, NOAA, Boulder, CO 80303 4. Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90024 5. Geophysical Institute, University of Alaska, Fairbanks, AK 99701 6. Department of Space Physics and Astronomy, Rice University, Houston, TX 77251 7. High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307 (sponsored by the National Science Foundation) Figure 1. Required steps followed to generate the 35mm microfilm used to create the movie. 4) The ionospheric electrical potential is calculated for every 1° in latitude and 1 hour of local time. This process requires extensive computer computation to numerically solve a 2-dimensional, second-order, partial differential equation. A suitable model of the ionospheric conductivity, which is given as a function of the AE index, must be assumed. 5) Ionospheric current vectors are computed at each grid point from the electric field and the ionospheric conductivity. 6) The field-aligned current distribution is defined as the divergence of the ionospheric current. 7) The Joule heating rate is defined as the scalar product of the ionospheric current and electric field vectors. 8) The above parameters are computed for every 5 minutes of data. A movie was made by interpolating 15 times between the computed values, and plotting the results on a 35-mm master microfilm which was used to create the 16-mm color film. THE METHOD Magnetic records from a total of 107 stations in the Northern Hemisphere (except for two which are in the Southern Hemisphere but close to the equator) are used in this project. Those stations are listed in Table 1, and their distribution in corrected geomagnetic coordinates are plotted on an orthogonic projection in Figure 2. Details of the computations at each step outlined in Figure 1 are described in the following: Current Function The observed magnetic data from the stations were fitted to a magnetic potential function $V$ which is represented by a spherical harmonic series with longitudinal wave numbers $m$ from 0 to 6 and order $n=m$ to 56, as expressed by the standard form: $$V(\theta, \lambda) = \sum_{m=0}^{6} \sum_{n=m}^{56} (a_n^m \cos m\lambda + b_n^m \sin m\lambda) P_n^m (\cos \theta)$$ where $\theta$ and $\lambda$ are colatitude and east longitude (measured from midnight), respectively, in the corrected geomagnetic coordinate system. All terms involving associated Legendre polynomials $P_n^m$ with even $(n-m)$ are omitted from the series, except the $n=m$ term, as the odd terms alone are basically sufficient to represent the Northern... | Station Name | Geographic, deg Latitude | E. Longitude | Corrected Geomagnetic, deg Latitude | E. Longitude | |-----------------------|--------------------------|--------------|-----------------------------------|--------------| | **Alaska Chain** | | | | | | 1. Mould Bay | 76.2 | 240.6 | 80.6 | 263.5 | | 2. Johnson Point | 72.5 | 241.7 | 78.0 | 275.7 | | 3. Cape Parry | 70.2 | 235.3 | 74.6 | 273.5 | | 4. Inuvik | 68.3 | 226.7 | 71.1 | 268.2 | | 5. Artic Village | 68.1 | 214.4 | 68.4 | 258.3 | | 6. Fort Yukon | 66.6 | 214.7 | 67.0 | 260.1 | | 7. College | 64.7 | 211.9 | 64.9 | 259.7 | | 8. Talkeetna | 63.3 | 209.9 | 61.9 | 259.8 | | **Alberta Chain** | | | | | | 9. Resolute Bay | 74.7 | 265.1 | 84.1 | 304.3 | | 10. Cambridge Bay | 69.1 | 255.0 | 77.8 | 299.7 | | 11. Yellowknife | 62.5 | 245.5 | 69.9 | 294.4 | | 12. Fort Providence | 61.4 | 242.6 | 68.2 | 291.7 | | 13. Hay River | 60.8 | 244.2 | 68.0 | 293.6 | | 14. Fort Smith | 60.0 | 248.0 | 68.2 | 299.3 | | 15. Uranium City | 59.6 | 251.5 | 68.3 | 304.3 | | 16. Fort Chipewyan | 58.8 | 248.0 | 67.3 | 302.6 | | 17. Fort McMurray | 56.7 | 248.8 | 65.1 | 302.1 | | 18. Meanook | 54.6 | 246.7 | 62.6 | 300.9 | | 19. Leduc | 53.3 | 246.6 | 61.2 | 301.6 | | **Fort Churchill Chain** | | | | | | 20. Pelly Bay | 68.5 | 270.5 | 79.6 | 329.3 | | 21. Baker Lake | 64.3 | 264.0 | 75.1 | 320.1 | | 22. Rankin Inlet | 62.8 | 267.7 | 74.2 | 327.5 | | 23. Eskimo Point | 61.1 | 265.9 | 72.4 | 325.1 | | 24. Fort Churchill | 58.8 | 265.9 | 70.3 | 326.0 | | 25. Back | 57.7 | 265.7 | 69.2 | 326.0 | | 26. Gillam | 56.9 | 265.6 | 68.4 | 326.1 | | 27. Thompson | 55.0 | 263.0 | 66.8 | 321.2 | | 28. Island Lake | 53.9 | 265.3 | 65.5 | 326.5 | | 29. Whiteshell | 49.8 | 264.8 | 61.4 | 326.5 | | **Greenland Chain** | | | | | | 30. Thule | 77.5 | 290.8 | 86.8 | 39.2 | | 31. Upernavik | 72.8 | 303.8 | 81.0 | 44.8 | | 32. Umanak | 70.7 | 307.8 | 78.6 | 46.0 | | 33. Godhavn | 69.3 | 306.5 | 77.6 | 41.6 | | 34. Sondre Stromfjord | 67.0 | 309.3 | 75.2 | 42.6 | | 35. Godthab | 64.2 | 308.3 | 72.9 | 38.4 | | 36. Frederikshab | 62.0 | 310.3 | 70.5 | 39.3 | | 37. Narssarssuaq | 61.0 | 314.6 | 68.9 | 44.0 | | **Scandinavia Chain** | | | | | | 38. Nord | 81.6 | 343.3 | 80.8 | 111.7 | | 39. Ny Alesund | 78.9 | 12.0 | 75.9 | 114.7 | | 40. Bjornoya | 74.5 | 19.2 | 71.3 | 110.5 | | 41. Skarsvag | 71.1 | 25.8 | 67.6 | 111.0 | | 42. Kunes | 70.4 | 26.5 | 66.9 | 110.8 | | 43. Kevo | 69.8 | 27.0 | 66.3 | 110.6 | | 44. Marttil | 67.5 | 28.3 | 63.9 | 109.8 | | 45. Kuusamo | 65.9 | 29.1 | 62.4 | 109.2 | | **IZMIRAN Chain** | | | | | | 46. Heiss Island | 80.6 | 58.0 | 74.8 | 144.4 | | 47. Cape Zhelania | 77.0 | 68.6 | 71.5 | 147.4 | | 48. Karmakuly | 72.3 | 52.5 | 67.7 | 131.8 | | 49. Belyy Island | 73.0 | 71.1 | 68.2 | 145.9 | | 50. Tambei | 71.5 | 71.9 | 66.6 | 146.5 | | 51. Kharasayey | 71.1 | 66.8 | 66.3 | 142.2 | | 52. Seyakha | 70.2 | 65.4 | 65.4 | 146.6 | | 53. Anderma | 69.7 | 61.6 | 65.1 | 136.5 | | Station Name | Geographic Latitude | E. Longitude | Corrected Geomagnetic Latitude | E. Longitude | |-----------------------|---------------------|--------------|-------------------------------|--------------| | SIBIZMIRAN Chain | | | | | | 54. Golomjanny | 79.9 | 91.2 | 73.6 | 165.1 | | 55. Isanchenko Island | 77.2 | 89.5 | 71.3 | 163.1 | | 56. Sterlegova | 75.4 | 89.0 | 69.8 | 162.2 | | 57. Ust-Tareja | 73.3 | 90.5 | 68.0 | 163.0 | | 58. Kresty | 70.9 | 89.9 | 65.9 | 162.0 | | 59. Igarka | 68.3 | 87.8 | 63.6 | 159.6 | | 60. Turkuhansk | 65.8 | 88.4 | 61.3 | 159.9 | | UK Network | | | | | | 61. Eskdalemuir | 55.3 | 356.8 | 54.6 | 79.0 | | 62. Durness | 58.6 | 355.2 | 58.3 | 79.4 | | 63. Faroes | 62.5 | 353.0 | 62.6 | 80.0 | | 64. York | 54.0 | 358.9 | 52.9 | 80.0 | | 65. Lerwick | 60.1 | 358.8 | 59.4 | 82.9 | | 66. Kiruna | 67.8 | 20.4 | 64.8 | 104.2 | | 67. Tromso | 69.7 | 18.9 | 66.8 | 104.8 | | AFGL Network | | | | | | 68. Sudbury | 42.2 | 288.8 | 55.2 | 2.3 | | 69. Lompoc | 34.4 | 239.7 | 40.2 | 300.9 | | 70. Rapid City | 44.1 | 256.9 | 54.1 | 317.4 | | 71. Camp Douglas | 43.6 | 269.8 | 55.8 | 334.6 | | 72. Tampa | 27.6 | 277.7 | 40.3 | 345.4 | | 73. Mount Clemens | 42.4 | 277.5 | 55.4 | 345.7 | | Other Stations | | | | | | 74. San Juan | 18.1 | 293.8 | 31.4 | 5.5 | | 75. St. John's | 47.6 | 307.3 | 57.6 | 29.1 | | 76. Leirvogur | 64.2 | 338.3 | 66.8 | 69.6 | | 77. Daneborg | 74.3 | 339.8 | 75.9 | 84.3 | | 78. Danmarkshavn | 76.8 | 341.4 | 77.6 | 91.7 | | 79. M'Bour | 14.4 | 343.0 | 10.7 | 57.7 | | 80. Almeria | 36.8 | 357.5 | 33.5 | 73.8 | | 81. Furstenfeldbruck | 48.2 | 11.3 | 45.0 | 87.8 | | 82. Minsk | 54.1 | 26.5 | 50.3 | 101.9 | | 83. Odessa | 46.7 | 30.9 | 42.3 | 103.7 | | 84. Tbilisi | 42.1 | 44.7 | 37.4 | 115.3 | | 85. Alert | 82.5 | 297.5 | 86.8 | 124.3 | | 86. Sverdlovsk | 56.7 | 61.1 | 52.7 | 132.5 | | 87. Tashkent | 41.3 | 69.6 | 37.2 | 139.6 | | 88. Dixon Island | 73.5 | 80.6 | 68.3 | 154.7 | | 89. Cape Chelyuskin | 77.7 | 104.3 | 71.6 | 174.2 | | 90. Irkutsk | 52.3 | 104.3 | 48.3 | 175.0 | | 91. Tixie Bay | 71.6 | 129.0 | 65.8 | 195.5 | | 92. Kanoya | 31.4 | 130.9 | 25.7 | 200.8 | | 93. Kakioka | 36.2 | 140.2 | 29.9 | 209.9 | | 94. Memambetsu | 43.9 | 144.2 | 37.4 | 213.7 | | 95. Guam | 13.6 | 144.9 | 6.9 | 213.7 | | 96. Magadan | 60.1 | 151.0 | 53.9 | 217.4 | | 97. Wake Island | 19.2 | 166.7 | 14.1 | 234.1 | | 98. Cape Wellen | 66.2 | 190.2 | 62.5 | 242.6 | | 99. Honolulu | 21.3 | 202.0 | 21.7 | 267.6 | | 100. Victoria | 48.5 | 236.6 | 54.1 | 292.4 | | 101. Newport | 48.3 | 242.9 | 55.4 | 299.4 | | 102. Tucson | 32.3 | 249.2 | 39.9 | 311.4 | | 103. Boulder | 40.1 | 254.8 | 49.5 | 315.7 | | 104. Fort Severn | 56.2 | 271.5 | 68.4 | 335.9 | | 105. Fredericksburg | 38.2 | 282.6 | 51.5 | 352.7 | | 106. Great Whale River| 55.3 | 282.2 | 68.0 | 353.7 | | 107. Ottawa | 45.4 | 284.4 | 58.5 | 356.1 | 1 Denotes stations data was used for the first event only. 2 Denotes stations data was used for the second event only. Figure 2. A view of the northern hemisphere in corrected geomagnetic coordinates and plotted on an orthogonic projection, i.e. the plotted distance between latitude circles varies as a sine function in colatitude. Hemisphere potential. The choice of these maximum \( n \) and \( m \) values is based on trial and error tests with a variety of values. There are in total 358 coefficients, \( a_n^m \) and \( b_n^m \), to be determined in the harmonic series (1). In seeking an appropriate potential function \( V \), it is required here that the potential vary smoothly in space between stations. For details of the practical method of the calculation, see Kamide et al. (1982). The root-mean-square difference between computed and observed magnetic perturbations is typically 15%. However, at certain times the discrepancy rises above 20%. It is then assumed that there is a relatively small internal contribution to the magnetic potential caused by a perfectly conducting layer 300 km below the Earth's surface. The remaining external potential \( V(e) \) is extrapolated to 110 km altitude and converted to an equivalent ionospheric current function by the standard procedure: \[ \Psi_n = \frac{1}{\mu_0} \frac{2n+1}{n+1} \left( \frac{a}{R_E} \right)^n V_n(e) \] where \[ a = R_E + 100 \text{km} \] \[ \mu_0 = 4\pi \times 10^{-7} \text{ H/m}. \] Ionospheric Conductivity At present there is no way to monitor continuously the global distribution of the ionospheric conductivity. Several conductivity models have been developed based on radar measurements of electron and ion density and temperature and satellite measurements of precipitating electrons and protons. In this report it is assumed that the conductance, that is, the height-integrated ionospheric conductivity, has two components: one is a background and is of solar ultraviolet origin and the other simulates an enhancement presumably due to substorm associated particle bombardment. We may call the former the quiet time conductance and the latter auroral enhancement conductance. For the background conductance, we follow the quiet time distribution for equinoctial months, as described in equations (19) and (20) of Kamide and Matsushita (1979). For the auroral enhancement, we use an empirical model based on the work of Spiro et al. (1982) with updated improvements. In their work the height-integrated Hall and Pedersen conductivities (\( \Sigma_H \) and \( \Sigma_P \)) are tabulated at every 1-2° (in latitude) and 1 hour (in MLT) for each level of auroral electrojet activity measured by the AE index. Data of precipitating particle energy flux and characteristic electron energy obtained from the Atmosphere Explorer satellites (AE-C and AE-D) were used along with the dependence of the conductivities on the characteristic energy of precipitating electrons obtained by Vickrey et al. (1981). It should be noted, however, that at two instants with the same value of the AE index, the auroral distribution and the conductivity distribution, as well as the current patterns in the polar region, may be significantly different. In our modeling the following adjustment is employed in the use of the conductivity model: by assuming that the latitude of the maximum equivalent current strength coincides with the latitude of the highest Hall conductivity, a latitudinal shift is made for the entire conductivity distribution whenever a difference between the two latitudes of the maxima is found. Electric Potential During the last several years, different techniques have been developed to analyze global magnetometer data in order to infer the three-dimensional distribution of electric currents around the Earth (e.g., Kisabeth, 1979; Mishin et al., 1980; Kamide et al., 1981). These methods take the distribution of magnetic perturbation vectors observed on the Earth's surface as the input and try to estimate the distribution of ionospheric and field-aligned currents and other related quantities as outputs for a given model of ionospheric conductivities. In this report, we employ an improved version of the computer algorithm developed by Kamide et al. (1981). The height-integrated ionospheric current can be considered to consist of two elements. The toroidal (solenoidal) current \( J_T \) is related to the equivalent current function \( \Psi \) as \[ J_T = -\frac{\partial \Psi}{a \sin \theta \partial \lambda} \] \[ J_T = \frac{\partial \Psi}{a \partial \theta} \] The other part, the poloidal current \( J_P \) can be considered as a closing current for field-aligned currents \( j_\parallel \). (Note that \( j_\parallel = \text{div } J_P \) and \( \text{div } J_T = 0 \) by definition and \( j_\parallel \) and \( J_P \) together produce no ground magnetic variation under the assumption that magnetic field lines penetrate vertically into the horizontal ionosphere). The associated electric field \( E \) is derivable from an electrostatic potential \( \Phi \). A partial differential equation for \( \Phi \) in terms of \( \Psi \) can then be written in the form \[ A \frac{\partial^2 \Phi}{\partial \theta^2} + B \frac{\partial \Phi}{\partial \theta} + C \frac{\partial^2 \Phi}{\partial \lambda^2} + D \frac{\partial \Phi}{\partial \lambda} = F(\Psi, \theta, \lambda) \] where coefficients \( A, B, C, D \) and \( F \) are given by the conductivities and their spatial gradients; see Kamide et al. (1982). The above differential equation (4) is to be numerically solved with approximate boundary conditions: \[ \Phi(0, \lambda) = 0 \text{ at the pole} \] \[ \frac{\partial \Phi(\pi/2, \lambda)}{\partial \theta} = 0 \text{ at the equator} \] Once the electrostatic potential is obtained, the electric field \( E \) is derivable from the potential \( \Phi \) as \[ E = -\text{grad } \Phi. \] Practically, we solve (4) numerically by a finite difference scheme over a network of grid points spaced 1° in \( \theta \) and 15° in \( \lambda \). It was assumed in deriving (4) that the magnetic contributions of the magnetospheric ring currents and tail currents to \( \psi \) can be neglected and geomagnetic field lines are effectively radial. The breakdown of these assumptions at lower latitudes probably invalidates the calculated potential values at low latitudes. **Ionospheric Currents and Field-Aligned Currents** Once the electric field is determined, it is possible to derive the ionospheric current vector \( J \) from \[ J = \sum_{P} E + \sum_{H} E \times n_r \] where \( n_r \) is a unit radial vector. From the requirement that the three-dimensional current be divergence free, the field-aligned current density \( j_H \) (positive downwards) can be calculated as \[ j_H = \text{div } J = \text{div } J_p \] **Joule Heating Rate** The height-integrated Joule heating rate is defined by \[ u_J = J \cdot E = \sum_{P} E^2 \] The Joule heating rate in the entire Northern Hemisphere ionosphere \( U_J \) can then be obtained by integrating \( u_J \) as \[ U_J = \int \int u_J a^2 \sin \theta \, d\theta d\lambda \] **MAGNETIC ACTIVITY DURING THE CDAW-6 INTERVALS** Figures 3a and b show auroral electrojet activity as described by the AE(57) and AE(58) indices for the first and second CDAW-6 intervals, respectively. The upper envelope, AU, depicts the maximum magnetic variation and the lower envelope, AL, describes the minimum magnetic variation. The distance between the two indices is another index, called AE. **0600-1800UT on March 22, 1979** Mid-latitude magnetic records indicate that this interval spanned a very quiet period, a storm sudden commencement at 0826 UT and the initial and main phases of a medium-size magnetic storm as Dst reached -74 nT during the 17th hour on March 22nd. From the auroral electrojet indices, we note two major substorms identified as relatively isolated enhancements in auroral electrojet activity. In the first sequence, an AE enhancement began at 1020 UT and was followed by the major expansion onset noted in the auroral zone as AL reached -1000 nT and at mid-latitude by positive bays in the H-component and by Pi2 pulsations, all beginning at 1055 UT. This major onset was marked with a decrease in the strength of the eastwest electrojet as the majority of the auroral zone is engulfed in westward current which reached its maximum intensity around 1130 UT. Soon after the recovery of the first major substorm, both the AU and AL values intensify at 1325 UT. At 1435 UT another major expansion onset was recorded. This substorm reached its maximum intensity of about 2000 nT in AE at 1450 UT. **1200 March 31-0600 April 1, 1979** The interval is best characterized by continuous activity of the auroral electrojets. At mid-latitudes, the Dst index bounced between -22 and -35 nT and \( K_p \) was fairly stable at the level of 3. Unlike the previous interval, this interval shows almost continuous auroral activity from 0100 to 2000 UT which was followed by sharp substorm developments at 2150 and 0300 UT. The maximum phases of these latter substorms reach relatively large values of -1000 nT at 2320 UT and -740 nT at 0315 UT as recorded in the AL index. Figure 3. Nonstandard AU and AL indices showing the maximum positive and negative excursions in the $X_m$ component at 57(a) and 58 (b) stations between 50° and 75° corrected geomagnetic latitude. **EXAMPLES** In Figures 4a-j, we show some of the outputs from the extensive calculation for, as an example, 1125 UT on March 22, 1979, which was near the maximum epoch of the first intense substorm. Figure 4a shows the distribution of the equivalent ionospheric current vectors which are essentially the observed magnetic perturbation vectors rotated clockwise by 90°. Data below 50° in corrected geomagnetic latitude are not shown in this diagram. One can notice that the intense westward electrojet flows in a wide local time span, from the noon sector to the premidnight sector, and maximizes in early morning hours. Unfortunately, there is a large gap in the distribution of magnetometers over eastern Siberia. In Figures 4b and 4c, we show the distribution of isointensity contours of calculated external current function (the so-called equivalent ionospheric current system) and of the associated equivalent current vectors, respectively. The current vectors are plotted at our grid points every 1° (in latitude) and 1 hour (in magnetic local time). Comparing Figures 4a and 4c, one must be cautious in interpreting the derived equivalent currents in regions where there is an absence of measurements. In particular, the large gap in the distribution of surface magnetometers over eastern Siberia can produce significant uncertainties. Our fitting algorithm generates a northward turning of the westward electrojet toward the polar cap through this data gap in 2000-2300 MLT sector. It is impossible to state definitely whether or not this pattern corresponds well with reality. These uncertainties must be kept in mind when interpreting the results of our subsequent outputs. Isocontours of the height-integrated Pedersen and Hall conductivities assumed for this particular time are displayed in Figure 4d. Note the different contour intervals used for the two conductivities. Figure 4e shows isocontours of the electric potential calculated for the combined set of the current function (Fig. 4b) and the conductivity model (Fig. 4d), and Figure 4f shows the corresponding electric field computed at our grid points. The potential pattern consists essentially of twin vortices in high latitudes with the highest and lowest potentials existing in the early morning and early afternoon sectors, respectively. However, there can exist many local deformations. It is important to point out that in many earlier works, the pattern of the electric potential has been assumed to be identical to that of the equivalent current system. By comparing Figures 4e and 4b, it is noticeable that the potential pattern is significantly different from the equivalent current system at and near auroral latitudes. Such a difference is caused simply by the nonuniform distribution of the ionospheric conductance. It is also pointed out that because of vertical magnetic field lines in the potential calculation, the electric potential in subauroral latitudes, say below 60° is unrealistically large. Figure 4g shows the distribution of the calculated ionospheric current vectors. One can notice by comparing the equivalent and 'true' ionospheric currents, that although the gross distributions of the two currents are similar, there are significant differences both in current direction and strength. The major portions of the equivalent currents flow nearly in an east-west direction, but the 'true' ionospheric currents have a considerable north-south component. For example, the westward electrojet in the morning sector has a significant southward component as well, and the eastward electrojet in the evening sector is actually flowing northeastward. In Figure 4h, we compare the Pedersen and Hall currents separately. It is evident that the Hall currents are remarkably similar to the equivalent currents. However, a significant difference can be found in the polar cap, where the Hall current is very small. This indicates that the main source of the polar cap magnetic perturbations are field-aligned currents, at least during substorms. Figure 4i shows isocontours of the calculated field-aligned currents. There is a great variability in the field-aligned current distribution in comparison with the statistical pattern obtained by averaging a number of satellite measurements. Finally, in Figure 4j, we show the distribution of the Joule heat production rate associated with the auroral electrojets. In the left-bottom corner, the total Joule heating integrated over the entire polar ionosphere (from the North Pole to 50° latitude) is indicated in the unit of watts. ACKNOWLEDGEMENTS The total CDAW-6 list of participants exceeds the scope of this report though we would like to express our appreciation to R.H. Manka, the organizer, and J.I. Vette, our most gratious host. This project represents a major effort of the magnetic fields subgroup. This report results from the cooperation of many people in numerous institutions in the world as the data were recorded at remote sites, processed at home institutes, sent to NSSDC, entered into the CDAW-6 data base, and sent directly to us. Special contributions were received from W. Baumjohann, P. F. Fougere, E. Friis-Christensen, V. I. Mishin, G. Rostoker, W. F. Stuart, J. K. Walker and A. N. Zaitzev. We also wish to give a special note of thanks to the staff of Sigma Data supported by NASA/NSSDC, M. Teague, D. Sawyer and E. Teague. Parts of this study were supported by the following grants received from the Atmospheric Science Division of the National Science Foundation; ATM 80-17316, ATM 80-20376 and ATM 81-08994; from NASA; NGR-44-006137 and NSG-7-447; and from ONR; N00014-82-K-0031. The data plots and the 16-mm movie could not have been completed without the use of the computer resources made available to us by NCAR. REFERENCES Gustafsson, G., 1969; A revised corrected geomagnetic coordinate system, Kiruna Geophysical Observatory Report No. 694, Royal Swedish Academy of Science. Kamide, Y. and S Matsushita, 1979: Simulation studies of ionospheric electric fields and currents in relation to field-aligned currents, 1, Quiet periods, J. Geophys. Res., 84, 4083-4098; 2, Substorms, J. Geophys. Res., 84, 4099-4115. Kamide, Y., A. D. Richmond and S. Matsushita, 1981: Estimation of ionospheric electric fields, ionospheric currents, and field-aligned currents from ground magnetic records, J. Geophys. Res., 86, 801-813. Kamide, Y., B-H. Ahn, S.-I. Akasofu, W. Baumjohann, E. Friis-Christensen, H. W. Kroehl, H. Mauer, A. D. Richmond, G. Rostoker, R. W. Spiro, J. K. Walker and A. N. Zaitzev, 1982: Global distribution of ionospheric and field aligned currents during substorms as determined from six IMS meridian chains of magnetometers: Initial results, J. Geophys. Res., 87, 8228-8240. Kisabeth, J. L., 1979: On calculating magnetic and vector potential fields due to large-scale magnetospheric currents systems and induced currents in an infinitely conducting earth. In Quantitative Modeling of Magnetospheric Processes (W. P. Olson, ed.), American Geophysical Union, Washington, D.C., 473-498. Manka, R. H., 1976: US program for the IMS, EOS Trans. American Geophysical Union, 57, 63. Mishin, V. M., A. D. Bazarzhapov and G. V. Shpynev, 1980: Electric fields and currents in the earth's magnetosphere. In Quantitative Modeling of Magnetospheric Processes (W. P. Olson, ed.), American Geophysical Union, Washington, D.C., 249-268. Roederer, J. G., 1976: IMS 1976-1979: New concept in international scientific cooperation, EOS Trans. American Geophysical Union, 57, 6. Spiro, R. W., P. H. Reiff and L. G. Maher, Jr., 1982: Precipitating electron energy flux and auroral zone conductances - An empirical model, J. Geophys. Res., 82, 8215-8227. Vickrey, J. F., R. R. Vandrak and S. J. Matthews, 1981: The diurnal and latitudinal variations of auroral-zone ionospheric conductivity, J. Geophys. Res., 86, 65. APPENDIX I Data Plots for 0600-1800 on March 22, 1979 Out of the various output plots shown in Figures 4a-j, we have chosen to show 5 polar plots (equivalent ionospheric current system, electrical potential, ionospheric current vectors, Joule heating rate and field-aligned current density) as well as the distribution of the observed magnetic perturbation noted as equivalent currents. The plots are reconstructed every 10 minutes for the 12-hour interval. The outermost circle is 50°N in corrected geomagnetic coordinates, with other circles spaced 10°. Date and UT are marked on each diagram. Note that all of the scales change at 1020 UT. APPENDIX II Data Plots for 1200 March 31-0600 April 1, 1979 Out of the various output plots shown in Figures 4a-j, we have chosen to show 5 polar plots (equivalent ionospheric current system, electrical potential, ionospheric current vectors, Joule heating rate and field-aligned current density) as well as the distribution of the observed magnetic perturbation noted as equivalent currents. The plots are reconstructed every 10 minutes for the 12-hour interval. The outermost circle is 50°N in corrected geomagnetic coordinates, with other circles spaced 10°. Date and UT are marked on each diagram. Fewer than four UAG Reports are published at irregular intervals each year. Copies of these publications may be purchased through the NATIONAL GEOPHYSICAL DATA CENTER, Solar-Terrestrial Physics Division (E/GC2), 325 Broadway, Boulder, Colorado 80303, USA. A $4.00 handling charge per order will be added to the single-copy price, if any, listed below. Please note, too, that some reports are available on microfiche only. Orders must include check or money order payable in U.S. currency to the Department of Commerce, NOAA/NGDC. UAG-1 IQSY NIGHT AIRGLOW DATA, by L.L. Smith, F.E. Roach, and J.M. McKennan, ESSA Aeronomy Laboratory, Boulder, CO, July 1968, 305 pp, $1.75. UAG-2 A REEVALUATION OF SOLAR FLARES, 1964-1966, by Helen W. Dodson and E. Ruth Hedeman, McMath-Hulbert Observatory, University of Michigan, Pontiac, MI, August 1968, 28 pp. UAG-3 OBSERVATIONS OF JUPITER'S SPORADIC RADIO EMISSION IN THE RANGE 7.6-41 MHZ, 6 JULY 1966 THROUGH 8 SEPTEMBER 1968, by James W. Warwick and George A. Dulk, University of Colorado, Boulder, CO, October 1968, 35 pp. UAG-4 ABBREVIATED CALENDAR RECORD 1966-1967, by J. Virginia Lincoln, Hope I. Leighton and Dorothy K. Kropf, ESSA now NOAA, Aeronomy and Space Data Center, Boulder, CO, January 1969; 170 pp, $1.25. UAG-5 DATA ON SOLAR EVENT OF MAY 23, 1967, AND ITS GEOPHYSICAL EFFECTS, compiled by J. Virginia Lincoln, World Data Center A, Upper Atmosphere Geophysics, ESSA now NOAA, Boulder, CO, February 1969, 120 pp. UAG-6 INTERNATIONAL GEOPHYSICAL CALENDARS 1957-1969, by A.H. Shapley and J. Virginia Lincoln, ESSA Research Laboratories, now NOAA, Boulder, CO, March 1969, 25 pp. UAG-7 OBSERVATIONS OF THE SOLAR ELECTRON CORONA: FEBRUARY 1964 - JANUARY 1968, by Richard T. Hansen, High Altitude Observatory, NCAR, Boulder, CO, and Kamuela, HI, October 1969, 12 pp. UAG-8 DATA ON SOLAR-GEOPHYSICAL ACTIVITY OCTOBER 24 - NOVEMBER 6, 1968, Parts 1 and 2, compiled by J. Virginia Lincoln, World Data Center A, Upper Atmosphere Geophysics, ESSA now NOAA, Boulder, CO, March 1970, 312 pp, $1.75 (includes Parts 1 and 2). UAG-9 DATA ON COSMIC RAY EVENT OF NOVEMBER 18, 1968, AND ASSOCIATED PHENOMENA, compiled by J. Virginia Lincoln, World Data Center A, Upper Atmosphere Geophysics, ESSA now NOAA, Boulder, CO, April 1970, 109 pp. UAG-10 ATLAS OF IONOGRAMS, edited by A.H. Shapley, ESSA Research Laboratories now NOAA, Boulder, CO, May 1970, 243 pp, $1.50. UAG-12 SOLAR-GEOPHYSICAL ACTIVITY ASSOCIATED WITH THE MAJOR GEOMAGNETIC STORM OF MARCH 8, 1970, Parts 1, 2 and 3, compiled by J. Virginia Lincoln and Dale B. Bucknam, World Data Center A, Upper Atmosphere Geophysics, ESSA now NOAA, Boulder, CO, April 1971, 466 pp, $3.00 (includes Parts 1-3). UAG-13 DATA ON THE SOLAR PROTON EVENT OF NOVEMBER 2, 1969, THROUGH THE GEOMAGNETIC STORM OF NOVEMBER 8-10, 1969, compiled by Dale B. Bucknam and J. Virginia Lincoln, World Data Center A, Upper Atmosphere Geophysics, ESSA now NOAA, Boulder, CO, May 1971, 76 pp. UAG-14 AN EXPERIMENTAL, COMPREHENSIVE FLARE INDEX AND ITS DERIVATION FOR 'MAJOR' FLARES, 1955-1969, by Helen W. Dodson and E. Ruth Hedeman, McMath-Hulbert Observatory, University of Michigan, Pontiac, MI, July 1971, 25 pp. UAG-16 TEMPORAL DEVELOPMENT OF THE GEOPHYSICAL DISTRIBUTION OF AURORAL ABSORPTION FOR 30 SUBSTORM EVENTS IN EACH OF IQSY (1964-65) AND IASY (1960), by F.T. Berkey, University of Alaska, Fairbanks, AK; V.M. Driatskiy, Arctic and Antarctic Research Institute, Leningrad, USSR; K. Henriksen, Auroral Observatory, Tromson, Norway; D.H. Jelly, Communications Research Center, Ottawa, Canada; T.I. Shchuka, Arctic and Antarctic Research Institute, Leningrad, USSR; A. Theander, Kiruna Geophysical Observatory, Kiruna, Sweden; and J. Yliniemi, University of Oulu, Oulu, Finland, September 1971, 131 pp, $1.50 (microfiche only). UAG-17 IONOSPHERIC DRIFT VELOCITY MEASUREMENTS AT JICAMARCA, PERU (JULY 1967 - MARCH 1970), by Ben B. Balsley, NOAA Aeronomy Laboratory, Boulder, CO, and Ronald F. Woodman, Jicamarca Radar Observatory, Instituto Geofisico del Peru, Lima, Peru, October 1971, 45 pp, $1.50 (microfiche only). UAG-18 A STUDY OF POLAR CAP AND AURORAL ZONE MAGNETIC VARIATIONS, by K. Kawasaki and S.-I. Akasofu, University of Alaska, Fairbanks, AK, June 1972, 21 pp. UAG-19 REEVALUATION OF SOLAR FLARES 1967, by Helen W. Dodson and E. Ruth Hedeman, McMath-Hulbert Observatory, University of Michigan, Pontiac, MI, and Marta Rovira de Miceli, San Miguel Observatory, Argentina, June 1972, 15 pp. UAG-21 PRELIMINARY COMPILATION OF DATA FOR RETROSPECTIVE WORLD INTERVAL JULY 26 - AUGUST 14, 1972, by J. Virginia Lincoln and Hope I. Leighton, World Data Center A for Solar-Terrestrial Physics, NOAA, Boulder, CO, November 1972, 128 pp. UAG-22 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES (AE) FOR 1970, by Joe Haskell Allen, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, November 1972, 146 pp. UAG-23 U.R.S.I. HANDBOOK OF IONOGRAM INTERPRETATION AND REDUCTION, Second Edition, November 1972, edited by W.R. Piggott, Radio and Space Research Station, Slough, UK, and K. Rawer, Arbeitsgruppe fur Physikalische Weltraumforschung, Freiburg, GFR, November 1972, 324 pp, $1.75. UAG-23A U.R.S.I. HANDBOOK OF IONOGRAM INTERPRETATION AND REDUCTION, Second Edition, Revision of Chapters 1-4, edited by W.R. Piggott, Radio and Space Research Station, Slough, UK, and K. Rawer, Arbeitsgruppe fur Physikalische Weltraumforschung, Freiburg, GFR, November 1972, 135 pp, $2.14. UAG-24 DATA ON SOLAR-GEOPHYSICAL ACTIVITY ASSOCIATED WITH THE MAJOR GROUND LEVEL COSMIC RAY EVENTS OF 24 JANUARY AND 1 SEPTEMBER 1971, Parts 1 and 2, compiled by Helen E. Coffey and J. Virginia Lincoln, World Data Center A for Solar-Terrestrial Physics, NOAA, Boulder, CO, December 1972, 462 pp, $2.00 (includes Parts 1 and 2). UAG-25 OBSERVATIONS OF JUPITER'S SPORADIC RADIO EMISSION IN THE RANGE 7.6-41 MHZ, 9 SEPTEMBER 1968 THROUGH 9 DECEMBER 1971, by James W. Warwick, George A. Dulk and David G. Swann, University of Colorado, Boulder, CO, February 1973, 35 pp. UAG-26 DATA COMPILATION FOR THE MAGNETOSPHERICALLY QUIET PERIODS FEBRUARY 19-23 AND NOVEMBER 29 - DECEMBER 3, 1970, compiled by Helen E. Coffey and J. Virginia Lincoln, World Data Center A for Solar-Terrestrial Physics, NOAA, Boulder, CO, May 1973, 129 pp. UAG-27 HIGH SPEED STREAMS IN THE SOLAR WIND, by D.S. Intriligator, University of Southern California, Los Angeles, CA, June 1973, 16 pp. UAG-28 COLLECTED DATA REPORTS ON AUGUST 1972 SOLAR-TERRESTRIAL EVENTS, Parts 1, 2 and 3, edited by Helen E. Coffey, World Data Center A for Solar-Terrestrial Physics, NOAA, Boulder, CO, July 1973, 932 pp, $4.50. UAG-29 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES AE(11) FOR 1968, by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, October 1973, 148 pp. UAG-30 CATALOGUE OF DATA ON SOLAR-TERRESTRIAL PHYSICS, prepared by NOAA Environmental Data Service, Boulder, CO, October 1973, 317 pp, $1.75. Supersedes catalogs UAG-11, 15 and 20. UAG-31 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES AE(11) FOR 1969, by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, February 1974, 142 pp. UAG-32 SYNOPTIC RADIO MAPS OF THE SUN AT 3.3 MM FOR THE YEARS 1967-1969, by Earle B. Mayfield, Kennon P. White III, and Fred I. Shimabukuro, Aerospace Corp., El Segundo, CA, April 1974, 26 pp. UAG-33 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES AE(10) FOR 1967, by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, May 1974, 142 pp. UAG-34 ABSORPTION DATA FOR THE IGY/IGC AND IQSY, compiled and edited by A.H. Shapley, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO; W.R. Piggott, Appleton Laboratory, Slough, UK; and K. Rawer, Arbeitsgruppe fur Physikalische Weltraumforschung, Freiburg, GFR, June 1974, 381 pp, $2.00. UAG-36 AN ATLAS OF EXTREME ULTRAVIOLET FLASHES OF SOLAR FLARES OBSERVED VIA SUDDEN FREQUENCY DEVIATIONS DURING THE ATM-SKYLAB MISSIONS, by R.F. Donnelly and E.L. Berger, NOAA Space Environment Laboratory; Lt. J.D. Busman, NOAA Commissioned Corps; B. Henson, NASA Marshall Space Flight Center; T.B. Jones, University of Leicester, UK; G.M. Lerfeld, NOAA Wave Propagation Laboratory; K. Najita, University of Hawaii; W.M. Retallack, NOAA Space Environment Laboratory and W.J. Wagner, Sacramento Peak Observatory, October 1974, 95 pp. UAG SERIES OF REPORTS (Continued) UAG-37 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES AE(10) FOR 1966, by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, December 1974, 142 pp. UAG-38 MASTER STATION LIST FOR SOLAR-TERRESTRIAL PHYSICS DATA AT WDC-A FOR SOLAR-TERRESTRIAL PHYSICS, by R.W. Buhmann, World Data Center A for Solar-Terrestrial Physics, Boulder, CO; Juan D. Roederer, University of Denver, Denver, CO; and M.A. Shea and D.F. Smart, Air Force Cambridge Research Laboratories, Hanscom AFB, MA, December 1974, 110 pp, $1.50. UAG-39 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES AE(11) FOR 1971, by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, February 1975, 144 pp, $2.05. UAG-40 H-ALPHA SYNOPTIC CHARTS OF SOLAR ACTIVITY FOR THE PERIOD OF SKYLAB OBSERVATIONS, MAY 1973 - MARCH 1974, by Patrick S. McIntosh, NOAA Space Environment Laboratory, Boulder, CO, February 1975, 32 pp. UAG-41 H-ALPHA SYNOPTIC CHARTS OF SOLAR ACTIVITY DURING THE FIRST YEAR OF SOLAR CYCLE 20 OCTOBER 1964 - AUGUST 1965, by Patrick S. McIntosh, NOAA Space Environment Laboratory, Boulder, CO and Jerome T. Nolte, American Science and Engineering, Inc., Cambridge, MA, March 1975, 25 pp. UAG-42 OBSERVATIONS OF JUPITER'S SPORADIC RADIO EMISSION IN THE RANGE 7.6-80 MHZ, 10 DECEMBER 1971 THROUGH 21 MARCH 1975, by James W. Warwick, George A. Dulk and Anthony C. Riddle, University of Colorado, Boulder, CO, April 1975, 49 pp. UAG-43 CATALOG OF OBSERVATION TIMES OF GROUND-BASED SKYLAB-COORDINATED SOLAR OBSERVING PROGRAMS, compiled by Helen E. Coffey, World Data Center A for Solar-Terrestrial Physics, NOAA, Boulder, CO, May 1975, 159 pp, $3.00. UAG-44 SYNOPTIC MAPS OF SOLAR 9.1 CM MICROWAVE EMISSION FROM JUNE 1962 TO AUGUST 1973, by Werner Graf and Ronald N. Bracewell, Stanford University, Stanford, CA, May 1975, 183 pp, $2.55. UAG-45 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES AE(11) FOR 1972, by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, May 1975, 144 pp, $1.50 (microfiche only). UAG-46 INTERPLANETARY MAGNETIC FIELD DATA 1963-1964, by Joseph H. King, National Space Science Data Center, NASA Goddard Space Flight Center, Greenbelt, MD, June 1975, 382 pp, $1.95. UAG-47 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES AE(11) FOR 1973, by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, June 1975, 144 pp, $1.50 (microfiche only). UAG-48A SYNOPTIC OBSERVATIONS OF THE SOLAR CORONA DURING CARRINGTON ROTATIONS 1580-1596 (11 OCTOBER 1971 - 15 JANUARY 1973), [Reissue of UAG-48 with quality images], by R.A. Howard, M.J. Koomen, D.J. Michels, R. Tousey, C.R. Detwiler, D.E. Roberts, R.T. Seat, and J.D. Whitney, U.S. Naval Research Laboratory, Washington, DC, and R.T. Hansen and S.F. Hansen, C.J. Garcia and E. Yasukawa, High Altitude Observatory, NCAR, Boulder, CO, February 1976, 200 pp, $4.27. Supersedes UAG-48. UAG-50 HIGH-LATITUDE SUPPLEMENT TO THE URSI HANDBOOK ON IONOGRAM INTERPRETATION AND REDUCTION, edited by W.R. Piggott, British Antarctic Survey, c/o Appleton Laboratory, Slough, UK, October 1975, 294 pp, $4.00. UAG-51 SYNOPTIC MAPS OF SOLAR CORONAL HOLE BOUNDARIES DERIVED FROM HE II 304A SPECTROHELIOGRAMS FROM THE MANNED SKYLAB MISSIONS, by J.D. Bohlin and D.M. Rubenstein, U.S. Naval Research Laboratory, Washington, DC, November 1975, 30 pp. UAG-52 EXPERIMENTAL COMPREHENSIVE SOLAR FLARE INDICES FOR CERTAIN FLARES, 1970-1974, by Helen W. Dodson and E. Ruth Hedeman, McMath-Hulbert Observatory, University of Michigan Pontiac, MI, November 1975, 27 pp. UAG-53 DESCRIPTION AND CATALOG OF IONOSPHERIC F-REGION DATA, JICAMARCA RADIO OBSERVATORY (NOVEMBER 1966 - APRIL 1969), by W.L. Clark and T.E. Van Zandt, NOAA Aeronomy Laboratory, Boulder, CO, and J.P. McClure, University of Texas as Dallas, Dallas, TX, April 1976, 10 pp. UAG-55 EQUIVALENT IONOSPHERIC CURRENT REPRESENTATIONS BY A NEW METHOD, ILLUSTRATED FOR 8-9 NOVEMBER 1969 MAGNETIC DISTURBANCES, by Y. Kamide, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO; H.W. Kroehl, Data Studies Division, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO; M. Kanamitsu, Advanced Study Program, National Center for Atmospheric Research, Boulder, CO; Joe Haskell Allen, Data Studies Division, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO; and S.-I. Akasofu, Geophysical Institute, University of Alaska, Fairbanks, AK, April 1976, 91 pp, $1.50 (microfiche only). UAG SERIES OF REPORTS (Continued) UAG-56 ISO-INTENSITY CONTOURS OF GROUND MAGNETIC PERTURBATIONS FOR THE DECEMBER 16-18, 1971, GEOMAGNETIC STORM, Y. Kamide, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, April 1976, 37 pp, $1.39. UAG-57 MANUAL ON IONOSPHERIC ABSORPTION MEASUREMENTS, edited by K. Rawer, Institut fur Physikalische Weltraumforschung, Freiburg, GFR, June 1976, 302 pp, $4.27. UAG-58 ATS6 RADIO BEACON ELECTRON CONTENT MEASUREMENTS AT BOULDER, JULY 1974 - MAY 1975, by R.B. Fritz, NOAA Space Environment Laboratory, Boulder, CO, September 1976, 61 pp. UAG-59 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES AE(11) FOR 1974, by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, December 1976, 144 pp, $2.16. UAG-60 GEOMAGNETIC DATA FOR JANUARY 1976 [AE(7) INDICES AND STACKED MAGNETOGRAMS], by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, July 1977, 57 pp. UAG-61 COLLECTED DATA REPORTS FOR STIP INTERVAL II 20 MARCH - 5 MAY 1976, edited by Helen E. Coffey and John A. McKinnon, World Data Center A for Solar-Terrestrial Physics, Boulder, CO, August 1977, 313 pp, $2.95. UAG-62 GEOMAGNETIC DATA FOR FEBRUARY 1976 [AE(7) INDICES AND STACKED MAGNETOGRAMS], by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, September 1977, 55 pp. UAG-63 GEOMAGNETIC DATA FOR MARCH 1976 [AE(7) INDICES AND STACKED MAGNETOGRAMS], by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, September 1977, 57 pp. UAG-64 GEOMAGNETIC DATA FOR APRIL 1976 [AE(8) INDICES AND STACKED MAGNETOGRAMS], by Joe Haskell Allen, Carl C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO, February 1978, 55 pp. UAG-65 THE INFORMATION EXPLOSION AND ITS CONSEQUENCES FOR DATA ACQUISITION, DOCUMENTATION, PROCESSING, by G.K. Hartmann, Max-Planck-Institut fur Aeronomie, Lindau, GFR, May 1978, 36 pp. UAG-66 SYNOPTIC RADIO MAPS OF THE SUN AT 3.3 MM 1970-1973, by Earle B. Mayfield and Fred I. Shimabukuro, Aerospace Corp., El Segundo, CA, May 1978, 30 pp. UAG-67 IONOSPHERIC D-REGION PROFILE DATA BASE, A COLLECTION OF COMPUTER-ACCESSIBLE EXPERIMENTAL PROFILES OF THE D AND LOWER E REGIONS, by L.F. McNamara, Ionospheric Prediction Service, Sydney, Australia, August 1978, 30 pp, $1.50 (microfiche only). UAG-68 A COMPARATIVE STUDY OF METHODS OF ELECTRON DENSITY PROFILE ANALYSIS, by L.F. McNamara, Ionospheric Prediction Service, Sydney, Australia, August 1978, 30 pp, $1.50 (microfiche only). UAG-69 SELECTED DISTURBED D-REGION ELECTRON DENSITY PROFILES. THEIR RELATION TO THE UNDISTURBED D REGION, by L.F. McNamara, Ionospheric Prediction Service, Sydney, Australia, October 1978, 50 pp, $1.50 (microfiche only). UAG-70 ANNOTATED ATLAS OF H-ALPHA SYNOPTIC CHARTS FOR SOLAR CYCLE 20 (1964-1974) CARRINGTON SOLAR ROTATIONS 1487-1616, by Patrick S. McIntosh, NOAA Space Environment Laboratory, Boulder, CO, February 1979, 327 pp, $3.50. UAG-71 MAGNETIC POTENTIAL PLOTS OVER THE NORTHERN HEMISPHERE FOR 26-28 MARCH 1976, A.D. Richmond, NOAA Space Environment Laboratory, Boulder, CO; H.W. Kroehl, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO; M.A. Henning, Lockheed Missils and Space Co., Aurora, CO; and Y. Kamide, Kyoto Sangyo University, Kyoto, Japan, April 1979, 118 pp, $1.50. UAG-72 ENERGY RELEASE IN SOLAR FLARES, PROCEEDINGS OF THE WORKSHOP ON ENERGY RELEASE IN FLARES, 26 FEBRUARY - 1 MARCH 1979, CAMBRIDGE, MASSACHUSETTS, U.S.A., edited by David M. Rust, American Science and Engineering, Inc., Cambridge, MA, and A. Gordon Emslie, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, July 1979, 68 pp, $1.50 (microfiche only). UAG-73 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES AE(11-12) FOR JANUARY - JUNE 1975, by Joe Haskell Allen, Carl C. Abston, J.E. Salazar and J.A. McKinnon, National Geophysical and Solar-Terrestrial Data Center, NOAA, Boulder, CO, August 1979, 114 pp, $1.75. UAG SERIES OF REPORTS (Continued) UAG-74 ATS-6 RADIO BEACON ELECTRON CONTENT MEASUREMENTS AT OOTACAMUND, INDIA, OCTOBER - JULY 1976, by S.D. Bouwer, K. Davies, R.F. Donnelly, R.N. Grubb, J.E. Jones and J.H. Taylor, NOAA Space Environment Laboratory, Boulder, CO, and R.G. Rastogi, M.R. Deshpande, H. Chandra and G. Sethia, Physical Research Laboratory, Ahmedabad, India, March 1980, 58 pp, $2.50. UAG-75 THE ALASKA IMS MERIDIAN CHAIN: MAGNETIC VARIATIONS FOR 9 MARCH - 27 APRIL 1978, by H.W. Kroehl and G.P. Kosinski, National Geophysical and Solar-Terrestrial Data Center, Boulder, CO; S.-I. Akasofu, G.J. Romick, C.E. Campbell and G.K. Corrick, University of Alaska, Fairbanks, AK; and C.E. Hornback and A.M. Gray, NOAA Space Environment Laboratory, Boulder, CO, June 1980, 107 pp, $3.00. UAG-76 AURORAL ELECTROJET MAGNETIC ACTIVITY INDICES AE(12) FOR JULY - DECEMBER 1975, by Joe Haskell Allen, Carl C. Abston, J.E. Salazar and J.A. McKinnon, National Geophysical and Solar-Terrestrial Data Center, NOAA, Boulder, CO, August 1980, 116 pp, $2.50. UAG-77 SYNOPTIC SOLAR MAGNETIC FIELD MAPS FOR THE INTERVAL INCLUDING CARRINGTON ROTATIONS 1601-1680, MAY 5, 1973 - APRIL 26, 1979, by J. Harvey, B. Gillespie, P. Miedaner and C. Slaughter, Kitt Peak National Observatory, Tucson, AZ, August 1980, 66 pp, $2.50. UAG-78 THE EQUATORIAL LATITUDE OF AURORAL ACTIVITY DURING 1972-1977, by N.R. Sheeley, Jr. and R.A. Howard, E.O. Hulbert Center for Space Research, U.S. Naval Research Laboratory, Washington, DC and B.S. Dandekar, Air Force Geophysics Laboratory, Hanscom AFB, MA, October 1980, 61 pp, $3.00. UAG-79 SOLAR OBSERVATIONS DURING SKYLAB, APRIL 1973 - FEBRUARY 1974, I. CORONAL X-RAY STRUCTURE, II. SOLAR FLARE ACTIVITY, by J.M. Hanson, University of Michigan, Ann Arbor, MI; and E.C. Roelof and R.E. Gold, The Johns Hopkins University, Laurel, MD, December 1980, 43 pp, $2.50. UAG-80 EXPERIMENTAL COMPREHENSIVE SOLAR FLARE INDICES FOR 'MAJOR' AND CERTAIN LESSER FLARES, 1975-1979, compiled by Helen W. Dodson and E. Ruth Hedeman, The Johns Hopkins University, Laurel, MD, July 1981, 33 pp, $2.00. UAG-81 EVOLUTIONARY CHARTS OF SOLAR ACTIVITY (CALCIUM PLAGES) AS FUNCTIONS OF HELIOGRAPHIC LONGITUDE AND TIME, 1964-1979, by E. Ruth Hedeman, Helen W. Dodson and Edmond C. Roelof, The Johns Hopkins University, Laurel, MD 20707, August 1981, 103 pp, $4.00. UAG-82 INTERNATIONAL REFERENCE IONOSPHERE - IRI 79, edited by J. Virginia Lincoln and Raymond O. Conkright, National Geophysical and Solar-Terrestrial Data Center, NOAA, Boulder, CO, November 1981, 243 pp, $4.50. UAG-83 SOLAR-GEOPHYSICAL ACTIVITY REPORTS FOR SEPTEMBER 7-24, 1977 AND NOVEMBER 22, 1977, Parts 1 and 2, compiled by John A. McKinnon and J. Virginia Lincoln, World Data Center A for Solar-Terrestrial Physics, NOAA, Boulder, CO, February 1982, 553 pp, $10.00. UAG-84 CATALOG OF AURORAL RADIO ABSORPTION DURING 1976-1979 AT ABISKO, SWEDEN, by J.K. Hargreaves, C.M. Taylor and J.M. Penman, Environmental Sciences Department, University of Lancaster, Lancaster, UK, July 1982, 69 pp, $3.00. UAG-85 CATALOG OF IONOSPHERE VERTICAL SOUNDINGS DATA, edited by Raymond O. Conkright and H. Irene Brophy, National Geophysical Data Center, NOAA, Boulder, CO, July 1982, 107 pp, $3.50. Supersedes UAG-54. UAG-86 INTERNATIONAL CATALOG OF GEOMAGNETIC DATA, compiled by J.H. Allen and C.C. Abston, National Geophysical Data Center, NOAA, Boulder, CO; E.P. Kharin and N.E. Papitashvili, Academy of Sciences of the USSR, World Data Center B2, Moscow, USSR; and V.O. Papitashvili, IZMIRAN, Moscow Region, USSR, November 1982, 191 pp, $4.00. Supersedes UAG-35 and 49. UAG-87 CHANGES IN THE GLOBAL ELECTRIC FIELDS AND CURRENTS FOR MARCH 17-19, 1978, FROM SIX IMS MERIDIAN CHAINS OF MAGNETOMETERS, by Y. Kamide, Kyoto Sangyo University, Kyoto, Japan; H.W. Kroehl, National Geophysical Data Center, NOAA, Boulder, CO; and A.D. Richmond, NOAA Space Environment Laboratory, Boulder, CO, November 1982, 102 pp, $3.50. UAG-88 NUMERICAL MODELING OF IONOSPHERIC PARAMETERS FROM GLOBAL IMS MAGNETOMETER DATA FOR THE CDAW-6 INTERVALS, by Y. Kamide, Kyoto Sangyo University, Kyoto, Japan; H.W. Kroehl, National Geophysical Data Center, NOAA, Boulder, CO; and B.A. Hausman, National Geophysical Data Center, NOAA, Boulder, CO, November 1983, 196 pp, $4.00. * U.S. GOVERNMENT PRINTING OFFICE: 1983-776-034/1001