This is a five year project led by the John Hopkins University Applied Physics Laboratory (JHU APL) to establish a facility to provide a global measurement of the field-aligned Birkeland electric currents that flow between the Earth?s magnetosphere and ionosphere. Field aligned currents are a fundamental aspect of the coupling between the magnetosphere and ionosphere but our current ability to measure these is severely limited by lack of adequate data coverage. This proposal will remedy this situation in a spectacular and highly efficient fashion. It will provide the first ever global, continuous observations of the Birkeland currents over both the northern and southern Polar Regions with sufficient time resolution Global coverage is provided by utilizing the existing Iridium constellation of more than 70 satellites in low altitude (780 km), polar (86 degree inclination) orbits evenly distributed among six equally spaced orbit planes. This commercial satellite network is operated to provide global communication services. It is owned by Iridium Satellite LLC (ISLLC) and is operated by Boeing Service Company (BSC) out of their Satellite Network Operations Center in Leesburg, VA. As part of their attitude control system the satellites all carry vector magnetometers that provide on-board magnetic field measurements of ~30nT accuracy at below second cadence. Currently, however, the magnetic field data are sub-sampled and bundled in a large engineering data packet for transmission to the ground only once every 200 seconds on average. This corresponds to latitude spacing between measurements of ~12 degrees and as a result data have to be collected for ~2hours to obtain global maps of field-aligned current estimates at ~1degree latitude resolution. This project will perform an upgrade to the Iridium satellites flight software and ground data systems that will send 10 to 100 times more magnetometer data to the ground to yield continuous, near real-time measurements of the global Birkeland currents with a latitude resolution of ~0.12 to ~1.2 degrees and a re-visit interval of just 9 minutes. In addition to the flight software modifications and development of an additional AMPERE satellite operations ground system that will be carried out in collaboration with BSC and ISLLC, an AMPERE science data center will be established at JHU APL for routine data processing, science product generation, providing community data services, and offering real-time monitoring. The new observational data set will enable investigation of a large number of important outstanding science questions and, thus, will transform the field of magnetosphere-ionosphere system science.
The new facility will serve a wide section of the space physics community and will enable and enhance a wide range of space physics research project, both observational and theoretical. In addition, the project has broader societal benefit in that it provides a valuable observational asset for space weather monitoring and forecasting as well as for space weather model validation and data assimilation. The project exploits and expands a unique partnership between scientists and commercial satellite operators that is certain to inspire and open the door for similar initiatives in the future.
The Earth’s magnetic field interacts with the supersonic solar wind of charged particles from the Sun to create the magnetosphere. The magnetosphere is the high altitude extension of Earth’s magnetic field, and spans the region of space where the geosynchronous satellites orbit the Earth. Our magnetosphere responds dramatically, even violently, to solar storms resulting in geomagnetic storms and drives the electric currents that cause aurora borealis and intensify the Van Allen radiation belts. The electric currents that flow between Earth’s uppermost atmosphere and the high-altitude magnetosphere are a mirror of the state of the entire region of Earth’s space environment and their measurement allows us to study the system. The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) is the first ever system providing continuous, global measurments of these central electric currents and their dynamics as Earth’s magnetosphere responds to solar storms. Where these currents are strong, they heat the atmosphere at heights of about 60 to 70 miles, ten times higher than thunderstorms. This heating is strong enough that it causes increased drag on satellites orbiting as high and even higher than the space station and shuttle. AMPERE measures these currents by collecting the magnetic field data from all of the Iridium satellites, sampling the field from each satellite once every 20 seconds. There are 66 satellites in the Iridium constellation and AMPERE acquired data 24/7 from every single one. With AMPERE we now have a system in place to provide continuous 24/7 pictures of what is really happening to near-Earth space, much like weather radars track the actual progress of weather fronts and major storms systems. The Iridium satellites are not a government facility and were not funded by NASA, but are totally private sector constellation of satellites, owned by Iridium Communications and operated for Iridium by the Boeing Service Company. To implement AMPERE, we forged a first-of-its-kind partnership between the commercial space sector (Iridium and Boeing) and the university research community (The Johns Hopkins University Applied Physics Laboratory, JHU/APL) under National Science Foundation sponsorship to achieve something that the federal government could not have accomplished on its own. The Iridium satellites include instruments that measure the magnetic field, magnetometers, but the satellite software was not designed to save the data rapidly enough to measure the auroral electric currents. Under AMPERE, new software was written, tested, and transmitted up to the Iridium satellites to acquire the necessary magnetic field data. In addition, the AMPERE Science Data Center was created at JHU/APL to receive the new AMPERE data and process it to derive global maps of the auroral electric currents which are available at http://ampere.jhuapl.edu. The system resulted in the first ever global, continuous record of these currents from over three years, from January 2010 through May 2013, including over two dozen geomagnetic storms. These new data are already transforming our understanding of Earth’s interaction with near-space and increasing our ability to cope with the effects of solar storms on our communications, navigation, and transportation systems which are so heavily dependent on satellites and space technologies.
