Recently a mathematical function was discovered that predicts how the solar wind couples to the magnetosphere for a wide variety of near-Earth space conditions and for a wide variety of phenomena in the magnetosphere and ionosphere. Several questions of significant geophysical interest and practical consequence arise from this discovery. One is to determine the absolute dayside magnetic merging rate (instead of a proportionality) by examining instances of unbalanced (rapid) dayside merging in two different ways. One method uses the latitude of the ionospheric cusp compared to appropriate magnetic field models, and the other examines changes in polar cap flux over an interval of rapid growth. These two predictors of solar wind driving allow the development of improved geomagnetic activity predictors. This will make it possible to produce a more physics based, operational predictor of important magnetic indices such as Kp and AE. The sensitivity of the global merging rate to the interplanetary magnetic field (IMF) cone angle will also be more fully explored.
Part of this funding will support a young,post-doctoral scientist. The project will also involve a collaboration between scientists at the Virginia Tech and JHU/APL. This will also provide partial funding for the distribution of particle precipitation data from the Defense Meteorological Satellite Program (DMSP) to the general space science community. The DMSP data, from raw data to time-energy spectrograms to various high-level data abstractions, are used by researchers around the world. Young scientists are particularly heavy users of this NSF-funded data distribution system.
We investigated how various combinations of solar wind parameters (notably the velocity, and magnitude and direction of the interplanetary magnetic field) related to the explosive increase in auroral power called "substorms." The study particularly focussed on whether certain abrupt changes in the solar wind served as the immediate trigger for substorms. This is one of the outstanding questions in the dynamics of near-Earth space. It turns out that the solar wind changes seen before substorms start are very similar to other random times. This and other evidence led to a conclusion that it is not changes in the solar wind that immediately trigger substorms. There does however have to be a period of strong driving lasting 10-15 minutes or more before a substorm can occur. We also looked at the ways in which magnetometer data from a variety of stations collected together in the international collaboration called "SuperMAG" could be used to better monitor auroral power. This turned out to work quite well. In fact, the auroral power over the entire northern hemisphere can be predicted fairly accurately even on a 1-min cadence. This work supported the work of an undergraduate at Johns Hopkins U., who later graduated and is now attending Virginia Tech. During her work at APL, she published a paper in Geophys. Res. Lett. as first author. We also updated a model called "OVATION Prime" which predicts auroral behavior from solar wind data. This upgrade added seasonal variations. The improved model is currently running at NOAA Space Weather Prediction Center, and at NASA Goddard. The improved geomagnetic indices allowing magnetometer stations to monitor aurora are available at the SuperMAG web sites, and are being used by scientists around the world for other purposes.
