By the mids the plasma density of the magnetosphere had been probed remotely using lightning-generated, very-low-frequency waves. Nevertheless, the beginning of space physics as a discipline was marked by the discovery of the Van Allen radiation belt and the in situ exploration of Earth's magnetosphere and its interaction with the solar wind made possible with the advent of rockets and satellites in the late s and s.
The data gathered in space-based observations are collected by sets of 3 to perhaps 10 different sensors positioned on Earth-orbiting satellites or interplanetary probes. A typical satellite might carry a magnetometer to detect slowly changing magnetic fields and a separate sensor to measure magnetic oscillations; a device to record electric fields and waves; plasma analyzers often a coordinated set of sensors to measure the fluxes of charged particles as functions of their mass, energy, and direction of motion; and one or more sensors to measure high-energy charged particles.
The data consist of time sequences of the sensors' outputs. When possible, similar or complementary data are collected by other satellites in different locations in space.
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In addition, data gathered simultaneously from ground-based instruments are used to examine phenomena such as disturbances in the geomagnetic field as detected by arrays of ground-based magnetometers , changes in the ionospheric density as indicated by radar, riometer, and rocket-based observations , enhancements in atmospheric emissions signifying excitation by energetic particles as shown in images from photometers and all-sky cameras , and activity on the Sun as shown by, e. Data on particles and fields are now often augmented with images of Earth's atmosphere in the visible, ultraviolet, or x-ray regions of the electromagnetic spectrum, thus enabling space physicists to relate observed high-altitude phenomena to ground-based observations.
The data matrices produced by space- and ground-based instruments thus include many different kinds of measurements often taken at widely separated sites, but often with good but differing time resolution. A challenge in analyzing and interpreting the data is to combine and compare them so as to deduce a global picture of the behavior of the magnetospheric system.
Combining and analyzing these various data sets and types both require extensive electronic communications, including electronic mail and network transfer of data and text files, between the home institutions sometimes international of the many investigators involved. Space plasma physicists use a combination of analytical and numerical methods to interpret and understand data, as well as to assist in the planning of observational campaigns. These methods can range from the use of simple linearized equations to model the early time evolution of plasma waves to the use of extensive multidimensional codes that attempt to simulate the full complexity of these nonlinear systems.
The simulations can consist of calculations of the locations and motions of many millions of individual charged particles, together with the electric and magnetic fields that they generate, or they can be solutions of simultaneous partial differential equations that describe the plasma as a ''fluid.
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The amount of numerical "data" generated is so great that if one were to attempt to keep it all, it would far exceed the capacity of even the largest computers. Even after pruning, the files that are kept necessitate good reliable and fast network communications between the. Simulations are now becoming a common part of space physics projects because the models are becoming sufficiently realistic to warrant direct comparisons with the measurements.
Indeed, one of the greatest challenges in a number of current programs is the synthesis of models and measurements through coordinated displays and analyses. Thus, manipulation and display of diverse data sets from both numerical modeling and a wide range of experiments are a focus for computational and telecommunications activities in space physics. Also discussed are the Solar-Terrestrial Energy Program, NSF's Geospace Environment Modeling Program, and the International Solar-Terrestrial Physics program, which provide additional evidence of the increasingly important role of collaboration in the space physics community.
The Space Physics Data System, envisioned as an aid for individual researchers and a first step toward building a broad-based system for handling space physics data, is outlined as an approach whose potential utility has been acknowledged within the community of researchers. In September members of the space plasma physics science community from more than three dozen institutions met to discuss what steps were needed to provide a more coordinated approach to solving many data access and analysis problems.
There was then, and still remains today, a strong need to better utilize existing and diverse space physics databases through collaborations with remotely distributed space scientists. This initial working group recognized that the technology existed to interconnect distributed computer systems that would provide the "enabling environment" for remotely accessing databases at a low cost Greenstadt and Green, It was quickly realized that a computer-to-computer communication system could be achieved which satisfied many of the desired objectives even though significant funding was not available by making maximum use of existing computers, equipment, and facilities at the remotely distributed sites.
Almost immediately, many scientists became involved in previously impossible collaborative activities such as simply comparing data on the same time scale Green et al. The network relied explicitly and to an unprecedented degree on the active involvement of its users. A scientific oversight group, the Data Systems Users Working Group, guided the entire effort, meeting approximately every 9 months see, for example, Baker et al.
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The actual operation of. This approach linked the users and developers in a tightly coupled feedback loop and enabled the network to meet many of the users' highest-priority needs, greatly enhancing many NASA and non-NASA space science programs Green and King, ; Thomas and Green, ; and Winterhalter, SPAN succeeded far beyond the dreams of its initial developers. Its success was recognized both by participants and by those responsible at NASA for electronic communication.
The CDAW's purpose was to bring together all available magnetospheric data for specific periods of time to determine how a particular magnetospheric process worked. Nine CDAWs have been held to date. Recent workshops have focused on global-scale solar-terrestrial physics problems requiring diverse data sets and a variety of modeling skills.
CDAWs in general have involved a broad cross-section of the space physics community especially the solar wind-magnetosphere-ionosphere community. The initial phase of a CDAW effort is selection of the problem to be addressed; relevant data are then identified and collected from multiple as many as 10 spacecraft and from scores of ground-based facilities. The resulting databases have often included literally hundreds of individual data sets for selected analysis intervals.
Those who contributed data are then invited to gather at a common site and jointly analyze aspects of the problem at hand. Early CDAWs were "paper" workshops—participants simply brought data records plotted on a common time scale for comparison with other data. The more recent workshops have utilized a common database accessed by interactive computer systems used during the workshops, held normally at the NSSDC but also at other locations such as Stanford University and Toyokawa, Japan.
After the workshops, the participants return to their home institutions to prepare joint oral and written papers on their results. A major aspect of CDAWs has been the cooperative sharing of expertise.
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Such sharing has been facilitated by the face-to-face workshop format, which allows scientists who sometimes have very different views of the physics involved to discuss alternative interpretations of the same data sets. Perhaps an even more significant aspect of CDAWs has been the open sharing of data prior to publication obtained from many different instruments. One of the major difficulties associated with CDAWs is the large overhead cost involved in assembling the infrastructure needed for the collaboration, including the assembling of the data and the coordinating of meetings and people.
Thus far fewer workshops have been held than the space physics community would find most beneficial. It carried five scientific instruments that made measurements of the electric and magnetic fields and plasmas in Earth's magnetosphere. The CCE was designed to measure the ions of barium and lithium that entered the magnetosphere from releases in the solar wind and the magnetotail.
This unique experiment indicated that barium was being released from a large portion of Earth's surface. This central facility produced raw data from spacecraft telemetry, provided these data and information about spacecraft position to all remote institutions, and processed and distributed survey data products. Remote institutions accessed the data through dedicated telephone lines and SPAN, allowing individual scientists to further process data both at the central facility and at their home institutions.
Thus, those with access to the database could work with others without incurring the overhead costs involved in contacting many institutions.alexacmobil.com/components/hyzogyxeb/tudy-whatsapp-intercettare-conversazioni.php
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This mission was successful because it provided almost effortless access to a reasonably well funded, well-managed central data facility, as well as access to a relatively small number of dedicated scientists who understood individual instrument performance and were interested in scientific collaboration, and the freedom to analyze data remotely using tools available at home institutions rather than depend solely on the standard analysis routines provided by the central facility.
Several existing ground-based observatories, such as the Sondre Stromfjord Observatory in Greenland and the numerous stations in Antarctica used to study upper-atmosphere and space physics, offer only limited access because they are located in remote regions of the world. The space physics community and other researchers would benefit enormously if these instruments could be operated remotely via computer networks, thus improving access to real-time data.
The Sondre Stromfjord Observatory in Greenland is currently being used as a testbed for enabling collaborative research. The facility has many attributes that make it an excellent choice for a collaboratory project: it is remote, the user community is distributed and manageable in size, and it already has a modest networking infrastructure in place.
The real-time viewing of data obtained at the Sondre Stromfjord Observatory will allow scientists to perform experiments that previously required on-site decision making, allowing those not present at the remote observatory to respond, for example, to rarely occurring geophysical phenomena such as solar proton events, which affect ozone depletion and represent a hazard to aircraft flying on transpolar routes. Also, the use of computer networks will enable more experimenters to be involved simultaneously in research at the remote facility, thus enhancing decision making and productivity.
The possibility of remotely adapting preplanned experiments to existing geophysical conditions is also an exciting prospect.
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The worldwide community of solar-terrestrial scientists has embarked on an exciting and intellectually rewarding project: to understand quantitatively the linkages from the Sun through the interplanetary medium and into the depths of the surrounding geospace. The variety and complexity of the physical processes involved in these linkages have challenged our ability to understand the total system.
Now, through a concerted global effort, the Solar-Terrestrial Energy Program STEP has begun to use remarkable new observational tools and modeling capabilities to achieve an unprecedented comprehension of our solar-terrestrial system. STEP was approved by the Scientific Committee of Solar-Terrestrial Physics in and launched in ; the International Council of Scientific Unions gave its formal endorsement in and recently extended the program through The main scientific goal of STEP is to advance the quantitative understanding of the coupling mechanisms responsible for the transfer of energy and mass from one region of the solar-terrestrial system to another; the main practical goal is to improve the ability to predict the effects of the variable components of solar energy and mass flows on the terrestrial environment, on technological systems in space and on Earth, and on the biosphere.
A well-coordinated ground- and space-based observing program is essential to accomplish these goals. Basic in situ measurements will be obtained by the various spacecraft missions approved by the Inter-Agency Consultative Group as a cooperative project of the world's four major space agencies. In parallel with these efforts, STEP will coordinate the use of specially designed ground-based instruments and aircraft, balloon, and rocket experiments and will promote theory development, modeling, and simulation studies on an international scale.
Crucial to the success of STEP are the dedicated information and data systems that allow scientists from all participating countries to improve communications among themselves and facilitate the coordination and standardization of measurements, as well as the interchange and analysis of data. These systems include those operating at satellite situation centers and coordinated data-handling facilities, at new ground-based observation situation centers and computer simulation centers, and during coordinated data analysis workshops. These facilities should provide sufficient support at present for the active programs, but the problem of accessing and studying data from older missions remains.
Toward the end of the STEP mission, when the data acquisition phase is complete, this problem will apply also to currently active programs. Geospace encompasses the regions from Earth's upper atmosphere to the Sun. The Geospace Environment Modeling GEM program at NSF is an effort to study the near-Earth portion of geospace ranging from the lower ionosphere to the environment where Earth interacts with the solar wind.
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