TABLE OF CONTENTS
The Space Physics Group (SPG) studies the chain of energy transport from the surface of the sun to its eventual arrival in planetary stratospheres. It is using interplanetary measurements to investigate the structure of coronal mass ejections and their evolution in space. It is using Galileo observations to understand energy and mass transport in the jovian magnetosphere, and the secular variation of the jovian magnetic field. It is studying the data received from the Cassini mission on its way to Saturn and the NEAR mission in orbit about the asteroid 433 Eros. It is using Polar observations in the high altitude magnetosphere to understand how the solar wind couples to the Earth's magnetosphere. It is using measurements from the FAST mission to determine how the magnetosphere couples to the ionosphere. It is studying magnetic pulsations both to determine their origin and to use them as diagnoses of the state of the magnetosphere and it is using numerical simulations both as an extrapolation of localized data and as a tool to investigate magnetospheric behavior. It also has been using the data from the FORTE and Alexis missions to study terrestrial lightning. The SPG is also preparing the data dissemination system for the IMPACT investigation on the STEREO mission to be launched in 2005. The Space Physics Group also plays a vital role in the community in disseminating the observations from current and past space missions, maintaining communications within the field, educating students of space physics through textbooks and software, interacting with visitors and training students. In the sections below we discuss the achievements of the SPG over the period July 1999 to July 2000 in the areas of instrumentation, research, dissemination of data, communication, education, visiting scientists and students.
The Australian government is planning to launch a microsatellite to celebrate their 100th anniversary and to demonstrate their scientific and technical prowess. Brian Fraser, the principal investigator for the magnetometer has asked us to build the magnetometer for this mission and we have done so. The engineer units and flight unit have been assembled and now await testing and integration on the spacecraft.
The SPG has developed an inexpensive, high precision and accurately timed magnetometer for terrestrial ground based studies. These magnetometers have been deployed in four different "arrays". The first array is the Sino Magnetic Array at Low Latitudes that will ultimately consist of 16 or more magnetometers in a 2-D array across China. In the last year six more (for a total of fourteen) magnetometers were sent to China to complete the array. The second array is a chain of seven magnetometers that are being installed by M. Moldwin along the eastern seaboard of the U.S. in the MEASURE array. The third array is the IGPP/LANL array that is intended to ultimately cover the western U.S. At present there are five operating stations in San Gabriel, CA; Los Alamos, NM; the Air Force Academy; Colorado Springs, CO; Boulder, CO; and at Teoloyucan, Mexico. The latter site has a less sensitive magnetometer that will be replaced later. Finally there is a loose-knit global array with sites in Jicamarca, Peru; and Crete, Greece. These magnetometers have now been used in innumerable studies including sounding the density of the plasmasphere, sudden impulse propagation and Pi2 timing of substorms.
The SPG has also developed a sensitive searchcoil magnetometer that can measure both pulsations and lightning generated Schumann resonances. Ultimately these units will be time tagged with GPS timing.
The electronics laboratory acquired through a grant from the IGPP a vapor-phase soldering station. This device will allow the fabrication of state of the art, low-mass instruments for flight on the microsatellite missions of the 21st century.
Interplanetary Coronal Mass Ejections (ICMEs) are being studied using the solar cycle long data base obtained from Pioneer Venus and using multipoint datasets obtained from chance encounters of Pioneer Venus, ISEE, NEAR, Wind and ACE spacecraft. With a single spacecraft one can invert the structure of ICMEs using an assumed cylindrical symmetry but clearly ICMEs are not cylindrically symmetric. Thus we have altered our inversion routine to simultaneously fit ropes seen at two spacecraft. We find that an ICME can extend over 45 degrees in azimuthal but still retain its rope-like character, albeit it is much thinner along the Earth-Sun line than it is wide perpendicular to it. We have also shown that the axis of the ropes is controlled by the neutral line on the magnetic source surface in the corona.
The Space Physics Group is presently involved in two planetary magnetospheric missions: Galileo that has been in orbit about Jupiter since December 1995 and Cassini on its way to Saturn for an arrival in 2004. The NEAR mission, with which we are also involved, will attempt to determine if the asteroid 433 Eros has an intrinsic magnetic field, but a strong magnetic field capable of producing a magnetosphere is not expected to be present. The activities associated with the Cassini mission consisted principally of software development and mission planning. The Galileo activities, however, resulted in major increases in our understanding of the jovian magnetosphere. In a series of papers we were able to show that the mass addition of Io leads to a radial outward flow of plasma that moves slowly outward at first but then accelerates as it moves outward. Signatures seen near Europa indicate that the flow is moving at close to 500 m/s there. At about 25 jovian radii this has increased to about 10 km/s and at 50 radii about 50 km/s. The plasma then flows down the magnetotail but does not take the magnetic flux with it because reconnection takes place episodically. These reconnection events create magnetic islands that transport no net magnetic flux but do transport ions. The ions on these islands are lost from the tail of the magnetosphere and the emptied magnetic flux tubes return to the inner magnetosphere. They appear to move inward because they are buoyant, being empty, and centrifugal force pulls the heavier full flux tubes outward. These empty flux tubes appear also to be small and to move inward relatively rapidly.
In 1999 the Galileo spacecraft finally returned to Io again and in a series of passes mapped out the region of ion cyclotron wave growth. This pattern indicated that cross field transit by neutrals must play an important role in the emplacement of the ions of the Io torus. A simulation of this process has been developed that enables us to test assumptions about the mass addition process and determine their consequences. These observations also revealed the presence of SO in the upper atmosphere of Io.
The study of the terrestrial magnetosphere is centered principally around the POLAR mission with some retrospective studies of ISEE measurements. On POLAR we have concentrated on understanding the formation of the polar cusp and how the polar cusp is controlled by the conditions in the solar wind, as the tilt of the Earth's dipole axis to the solar wind flow. Most recently, we showed that the pressure in the cusp plasma is directly controlled by the solar wind dynamic pressure incident along the normal to the surface of the cusp. When the solar wind pressure drops to low values the magnetosphere becomes dipolar and the fluctuations cease but the field aligned currents remain constant.
Using Polar data, we have also examined effects of the equatorial ring current and the magnetopause current in the magnetic field observations in the magnetosphere. A preliminary map of the depression in the magnetosphere field at varying Dst levels and as a function of radius and latitude and local time has been created from databases of ISEE, CCE and POLAR data. In a separate study we have examined the effect of pressure changes in the solar wind on the magnetosphere. We have found that the magnetic field does not increase everywhere but that near noon principally off the equator and on the dayside the magnetic field decreases when the solar wind compresses the magnetosphere. ULF waves are also frequently amplified when these compressions occur.
The Space Physics Group has continued to analyze the particles and fields data from the Fast Auroral Snapshot (FAST) Explorer. Our research efforts have encompassed two quite diverse topics. The first is the investigation of the stresses applied to the polar ionosphere, as evidenced by the deviations in the Earth's magnetic field. These "delta-B's" indicate, for example, where reconnection at the Earth's magnetopause and the tailward transport of high latitude field lines cause the polar cap field-lines to also bend tailward. The second topic under investigation is the generation of Auroral Kilometric Radiation (AKR). We have shown that AKR is generated in deep density cavities, where the energetic electrons dominate the wave dispersion. Furthermore, the effect of the acceleration by parallel electric fields and the magnetic mirror force results in a "horseshoe"-shaped electron distribution, which can generate AKR quite efficiently.
Research on magnetic pulsations emphasizes two major directions: measuring the mass density of the plasma in the magnetosphere during storms and studying the propagation of sudden impulses through the magnetosphere. These are also two of the major scientific objectives for the establishment of a ground station network as described in the "Instrumentation" section.
Magnetic Pulsations for studying magnetic storms - We continued the analysis of the plasma mass density during the September 1998 magnetic storm by using the gradient technique of magnetic pulsations. Magnetometer data at middle and high latitudes (collected by the Canadian CANOPUS Project) show that more plasma was found in the trough region during the first two days of the storm, associated with the enhanced ion outflow from the ionosphere. Enhanced broadband ULF wave power was also found during the storm, enabling the gradient method to be applied on the magnetometer data at very low latitudes (collected by the Circum-pan Pacific Magnetometer Network), where we find that the phase change across the resonant shell has an opposite sense compared to what is found elsewhere in the magnetosphere. This implies that the frequency of field line resonance decreases with decreasing L-value due to the rapid increase of density toward the ionosphere.
Sudden Impulses - The Preliminary Impulses (PI) associated with the arrival of interplanetary shocks at the magnetospheric boundary has been known to occur almost simultaneously at high latitudes and at the equator. For many years the Earth-ionosphere waveguide model has been widely accepted for explaining such rapid propagation of signals. We analyzed the data from several magnetometer arrays to study the occurence time of the PI's associated with the Sudden Commencement on September 24, 1998. The high- resolution data with GPS accuracy in time enables us to identify the small time delays among the PI signatures seen at different stations. The results clearly indicate that the propagation of PI can in fact be interpreted by MHD wave propagation.
Global simulations of Earth's magnetosphere and ionosphere are used to investigate basic magnetospheric processes, to supplement experimental studies, and to investigate the feasibility of magnetospheric multiprobe missions. Jimmy Raeder has been asked to serve on the Draco constellation study team to assist them in this latter regard. Jimmy has also been asked to serve on the Geospace Management Operations Working Group.
We continue to improve the UCLA MHD code. In collaboration with Tim Fuller Rowell of NOAA, Jimmy Raeder has coupled the UCLA MHD code to the NOAA Coupled Thermosphere Ionosphere Model. He is also working with LLNL to incorporate their adaptive mesh (SAMRAI code) in the MHD model so that the plasma depletion layer can be studied. His testing of the effects of resistivity on code results has called into question previous simulation results. This has resulted in some controversy. He has also worked with Oleg Vaisberg to probe magnetospheric convection under conditions of large By and northward Bz, and resolved along standing problem of mapping.
In collaboration with scientists at the Los Alamos National Laboratory the Space Physics Group has continued to analyze radio frequency (RF) signals observed by the ALEXIS spacecraft. The signals, known as Trans-Ionospheric Pulse Pairs (TIPPs), were originally thought to be generated by lightning. Our work has shown that TIPPs are generated by a specific type of lighting: intracloud lightning. Furthermore, TIPPs have the same general diurnal and geographic variation as lightning, although TIPPs appear to occur later in the day than normal lightning. We have also shown that TIPPs occur in pairs because of reflection from the ground, rather than being an intrinsically double-pulsed phenomenon, and we have shown that they arise in thunderstorms. One series of strong TIPPs was shown to arise at high altitudes in a hurricane system. This effort has now ended as the student involved has finished his studies.
Due to our long involvement in Space Physics research, we have built a tremendous data base of measurements of the solar terrestrial system. As part of NSF's Global Environmental Measurement program and later in cooperation with the Space Physics Data System, we set up systems for the dissemination of those data to the community. We originally set up an on-line data base of IMP-8 data. We then developed a web-based distribution system for this effort. Now we have added POLAR magnetometer data to this system, as well as Wind and ACE magnetometer and solar wind data, and now provide on-line access to the ground-based magnetometer data obtained during the IMS (1977+) to the ISEE1 and 2 magnetometer data and also all the 1- second ground based data.
The Space Physics Group has taken the lead in fostering communication in the discipline as part of the NSF's Global Environment Modeling (GEM) program as well as for the American Geophysical Union's (AGU) Space Physics and Aeronomy section. Guan Le serves as editor for the electronic and hard copy newsletters, the GEM Messenger and the GEMstone. These appear about once a month and semiannually respectively. Guan Le also serves as the editor of AGU/SPA's electronic newsletter, SPA News, which appears twice a week on average. She has been the editor of the SPA web pages that provide access to information on meetings, publications and links to other members of the community. In 1998, Bob Strangeway was appointed the SPA editor for AGU's weekly newspaper EOS. His term expires in 2001.
There are four major developments in education from the Space Physics Group. First there is its development of the interactive Space Physics educational software, also known as Xspace. We continue to update and distribute this package. Some of the exercises have been converted to JAVA and can now be used over the internet. Second, we continue to participate in the International Space Physics Education Consortium that is fostering and coordinating computer-based instruction in Space Physics. Third, C. T. Russell is the Director of UCLA's branch of the California Space Grant activities. Fourth, the book Introduction to Space Physics, edited by M. G. Kivelson and C. T. Russell continues to sell well. In fact, it is now in its third printing.
In 1999-2000 C. T. Russell taught ESS9, the solar system general education course, using Web CT software. This software presented to the students all homework assignments, quizzes, midterms and finals. The software provides instant feedback to the students on their answers and assigns grades. It was well received.
Hua Zhau spent a year with us beginning May 1999 studying magnetic pulsations from the Chi mag chain. Hannes Schwarzl, a graduate student from the Technical University in Graz, Austria visited us for 6 months from April 1999 to October 1999. Xochitl Blanco-Cano from UNAM visited for three two-week intervals as part of her joint UCMEXUS research effort with C. T. Russell and R. J. Strangeway to study the generation of ULF waves at Jupiter. Other visitors for shorter periods included M. Gedalin from Ben Gurion University, Beer Sheva, Israel, N. Tsyganenko from Goddard and Brian Fraser from Newcastle University in Australia.
During the period 1999/2000 there were seven continuing graduate students: G. J. Fowler, T. Mulligan, J. Newbury, Y. L. Wang, Z. J. Yu, X. M. Zhou and R. S. Zuelsdorf. One student, R. S. Zuelsdorf, successfully completed his requirements for the MS degree and left the group and one J. Newbury successfully completed her requirements for the Ph.D. degree and now is employed by Hughes.
The SPG staff consists of students, engineering staff, programmers, computer operators and student assistants, clerical help and researchers. The researchers and graduate students have been listed above. The other staff members are as follows:
C. T. Russell, The jovian magnetospheric engine, presented at IUGG XXII General Assembly, Birmingham, U.K., July, 1999.
C. T. Russell, Solar wind interactions with magnetospheres: A tutorial update on phenomenology and physics, presented at IUGG XXII General Assembly, Birmingham, U.K., July, 1999.
C. T. Russell, The dynamics of planetary magnetospheres, presented at the Magnetospheres of the Outer Planets Symposium, Paris, August 1999.
C. T. Russell, ISEE 1 and 2: Discoveries and lessons, presented at the Cluster II Workshop on Multiscale/Multipoint Plasma Measurements, London, September 1999.
C. T. Russell, The polar cusp, presented at the Cluster II Workshop on Multiscale/Multipoint Plasma Measurements, London, September, 1999.
C. T. Russell, Solar wind and interplanetary magnetic field: A tutorial, presented at AGU Chapman Conference on Space Weather, Clearwater Florida, March, 2000.
C. T. Russell and R. L. McPherron, The near-Earth neutral point model of substorms, ISTP Science Workshop, Goddard Space Flight Center, Greenbelt, MD, March, 2000.
C. T. Russell, Reconnection in planetary and interplanetary environments, ISTP Science Workshop, Goddard Space Flight Center, Greenbelt, MD, March, 2000.
C. T. Russell, Solar-Terrestrial linkages and solar cycle variations, presented at NSF/SHINE meeting, Lake Tahoe, NV, June, 2000.
C. T. Russell, Geoeffectiveness of solar wind transients, presented at Ninth Annual GEM Meeting, Snowmass, CO, June, 2000.
Raeder, J., The auroral acceleration region in global MHD simulations, IUGG 22nd General Assembly, Birmingham, UK, July 1999.
Raeder, J., The magnetosphere under northward IMF: Models and simulations, IUGG 22nd General Assembly, Birmingham, UK, July 1999.
Raeder, J., Y. Wang, J. Brittnacher, L. A. Frank, D. Lummerzheim, G. K. Parks, J. B. Sigwarth, Global Modeling and Auroral Imaging, AGU Fall Meeting, San Francisco (EOS, vol. 81, no. 46), 1999.
Raeder, J., Y. Wang, and T. Fuller-Rowell, Global modeling of substorms and storms in Earth's magnetosphere-ionosphere-thermosphere system, AGU Chapman Conference on Space Weather: Progress and Challenges in Research and Applications, Clearwater, Florida, March 2000.
Raeder, J., Y. Wang, and T. Fuller-Rowell, Global modeling of Earth's magnetosphere-ionosphere-thermosphere geospace environment, European Geophysical Society XXV Assembly, Nice, France (EGS Newsletter, no. 74, 239), April 2000.
Raeder, J., Y. Wang, and T. Fuller-Rowell, Predictive capabilities of global magnetosphere-ionosphere-thermosphere modeling, NOAA Space Weather Week, Boulder, CO, May 2000.
Strangeway, R. J., R. E. Ergun, and C. W. Carlson, FAST Wave observations in the Earth's auroral zone, International Union of Radio Science, XXVI General Assembly, Toronto, Canada, p. 513, 1999.
Strangeway, R. J., Magnetosphere/Ionosphere coupling: Reconnection driven ion outflows, Earth and Space Sciences Seminar, University of California, Los Angeles, March 2000.
Strangeway, R. J., R. C. Elphic, E. E. Dors, and C. W. Carlson, FAST observations of the auroral field-aligned current carriers, Eos, Trans. AGU, 81 (19), Supplement, S375, American Geophysical Union Spring Meeting, Washington, DC, 2000.
Strangeway, R. J., Outstanding Issues in magnetosphere-ionosphere coupling: the three-dimensional ionosphere, GEM 2000 Snowmass Workshop, June 2000.
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