August 19, 2011, 12:00 pm - 1:00 pm
Director's Seminar
Dr. Elizabeth Mitchell (NASA GSFC/NPP), Effects of Magnetic
Flux Circulation on the Ring Current
Abstract: The orientation of the interplanetary magnetic field (IMF) determines the location of the dayside merging line and the magnetic flux circulation patterns. Magnetic flux circulation determines the amount of energy which enters the magnetosphere and ionosphere. We use the Lyon-Fedder-Mobarry Global Magneto-Hydrodynamic (MHD) code to simulate both idealized and real solar wind cases. We examine the magnetic flux circulation under differing IMF orientations. We also use the Comprehensive Ring Current Model (CRCM) to examine the inner magnetospheric response to the orientation of the IMF. We will present the different magnetic flux circulation patterns and the resulting effects on the ring current.
Dr. Sabrina Savage (NASA GSFC/NPP), Low-Altitude
Reconnection Inflow-Outflow Observations During a
2010 November 3 Eruption
Abstract: For a flare occurring on 2010 November 3, we present observations using several AIA EUV passbands of an erupting filament followed by inflows sweeping into a current sheet region. The inflows are soon followed by outflows appearing to originate from newar the termination point of the inflowing motion--an observation in line with standard magnetic reconnection models. We measure average inflow plane-of-sky speeds to range from ~170 -690 km/s with the initial, high-temperature inflows being the fastest. We provide inflow and outflow timings with respect to RHESSI count rates and find that these fast, high-temperature inflows occur simultaneously with a peak in the RHESSI thermal lightcurve.
Dr. Torbjorn Sundberg, (NASA Goddard Space Flight Center/NPP),
Kelvin-Helmholtz boundary waves observed during MESSENGER's
first Mercury year in orbit.
Abstract: We present a survey oh Kelvin-Helmholtz (KH) waves at Mercury's magnetopause during MESSENGER's first Mercury year in orbit. The waves were identified on the basis of the well-established saw-tooth wave signatures that are associated with non-linear KH vortices at the magnetopause. Remarkably, the results show that MESSENGER frequently observed such KH waves in the dayside region of the magnetosphere where the magnetosheath flow velocity is still sub-sonic, which implies that instability growth rates at Mercury's magnetopause are much larger than at Earth. The wave amplitude was often on the order of 100 nT or more, and the wave periods were ~ 10-20s. A clear dawn-dusk asymmetry is also present in the data, with all of the observed events taking place in the post-noon and the dusk-side sectors of the magnetopause. This asymmetry is likely related to finite Larmor radius effects and is in agreement with the results from particle-in-cell simulations of the instability. Similar to most terrestrial events, the wave observations were made almost exclusively during periods when the north-south component of the magnetosheath magnetic field was northward. Accompanying plasma measurements show that the waves are associated with a substantial transport of magnetosheath plasma into the magnetosphere.