May 18, 2012, 12:00 pm - 1:00 pm
May 18, 2012, 12:00 pm - 1:00 pm, Heliophysics Director's Seminar
Simulated Ring Current Response During Periods of Dawn-Dusk Oriented Interplanetary Magnetic Field (By)
Dr. Elizabeth Mitchell,NASA Goddard Space Flight Center/NPP
Ring current formation is mainly attributed to enhanced global magnetospheric convection and particle injection. One of the indicators of enhanced global magnetospheric convection is the transpolar potential. The transpolar potential has been shown to respond to dawn-dusk oriented interplanetary magnetic field (IMF), enhancing as the IMF magnitude grows. This suggests that the ring current should respond to dawn-dusk oriented IMF. This work examines the ring current response during periods of dawn-dusk oriented IMF using the LFM and CRCM simulations, exploring the effects of global magnetospheric convection and the location of the reconnection region on the night side. This work shows that as the magnitude of the dawn-dusk oriented IMF increases, producing a corresponding increase in the transpolar potential, the ring current response increases. The response is always much less than a comparable southward IMF would produce. This lower response is due to both magnetospheric convection, which builds the ring current but at a slower rate, and flank reconnection, which allows energy to flow through the inner magnetosphere without building the ring current plasma population.
Dipolarization Fronts and Reconnection in 2D Current Sheets
Dr. Natalia Buzulukova, NASA Goddard Space Flight Center/Catholic University
Dipolarization fronts (DF's) are moving structures in the Earth's magnetotail with a sharp increase of the magnetic field component Bz normal to the neutral plane. DFs are routinely observed inside bursty bulk flows. Bursty bulk flows with DFs are the main mechanism for energy and plasma transfer in the Earth magnetotail and supply particles to the inner magnetosphere and the ring current. It is usually accepted that DFs and bursty bulk flows are reconnection exhausts. To model collisionless reconnection and DFs in the Earth's magnetotail, we use a 2D PIC code with open boundaries. We start from fully kinetic 2D equilibrium and show that the reconnection process is very sensitive to initial equilibrium. We find that equilibrium with accumulated flux in the magnetotail generates multiple DFs. In this case, DF's and bursty bulk flows are not a consequence of reconnection. Instead, it is the motion of the DF that triggers reconnection and the formation of an active X-point. We implement virtual spacecraft in our simulations and find that characteristics of simulated DFs agree very well with observations. These results will be important for the future NASA MMS mission devoted to studying the reconnection process in the Earth's magnetosphere.
Modeling Ionospheric Outflow
Dr. Alex Glocer,NASA Goddard Space Flight Center
The Earth's magnetosphere, formed by the complex interaction of the solar wind with the planet's magnetic field, has no intrinsic source of plasma. It acquires all the matter within it from the ionosphere and solar wind. Indeed, since the earliest measurements of O+ in the magnetosphere, a clear indicator of an ionospheric source, the topic of magnetospheric composition and its role in governing magnetospheric processes has been of keen scientific interest. In this study, we model the ionospheric outflow solution during the geomagnetically quiet conditions in the polar cap during solar maximum. We directly compare our simulation results to satellite and radar data of ion and electron density, velocity, and temperature. The data and model agree reasonably well, and demonstrates that photoelectrons play an important role in explaining the differences between sunlit and dark results, ion composition, as well as ion and electron temperatures.