HAO 2010 PROFILES IN SCIENCE: Dr. Michael Wiltberger
Dr. Michael Wiltberger is a Scientist III in the High Altitude Observatory of the National Center for Atmospheric Research. His main research interest is modeling and analysis of magnetospheric processes using global scale magnetohydrodynamic simulations. Specific areas of interest include coupling between the magnetosphere and ionosphere, structure and dynamics of ultra-low frequency waves and their impacts of radiation belt particles, and coupling between the magnetotail and the inner magnetosphere during storms and substorms.
Figure 1: A comparison of the magnetospheric configuration for a run (left) without and (right) with O+ outflow: (top) the configuration during the first substorm interval, and (bottom) formation of a second substorm which is only seen in the SFE9 outflow simulation.
Influence of cusp O+ outflow on magnetotail dynamics in a multifluid MHD model of the magentosphere
Wiltberger, M., W. Lotko, J. G. Lyon, J. Geophys. Res., 115, A00J05, doi:10.1029?2010JA015579.
Using the recently developed Multi-fluid version of the LFM MHD magnetospheric model, a series of simulations were carried out to study the impact of oxygen ions flowing from the dayside cusp region of the ionosphere into the magnetotail. The right-side images of Figure 1 show results from a baseline simulation without any outflow under idealized steady southward interplanetary magnetic field. Under these conditions the simulation has a single magnetospheric substorm (which refers to explosive release of stored energy) before entering a quasi-stable configuration. The images on the left show the oxygen ions flowing out of the cusp region into the magnetotail. Since the flow does not reach the reconnection region prior to the first substorm the initial evolution is not dramatically affected. However, once these ions reach the magnetotail they reduce the local magnetic reconnection rate, preventing the simulated magnetosphere from entering a quasi-stable state, and resulting in a second substorm event. Wiltberger and his colleagues are working to understand the details of this interaction and to develop causally driven models for the outflow so that these important effects can be included in space weather forecasts.