Bulletin of the American Physical Society
Joint Spring 2014 Meeting of the Texas Sections of the APS, AAPT, and Zone 13 of the SPS
Volume 59, Number 2
Thursday–Saturday, March 20–22, 2014; Abilene, Texas
Session F4: Astrophysics I |
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Room: Hunter Welcome Center AT&T |
Friday, March 21, 2014 2:30PM - 2:42PM |
F4.00001: Thermospheric winds around the cusp region Cheng Sheng Due to the change of advection, the horizontal winds can be strongly influenced by the large vertical wind in the cusp. Indeed, the sunward wind has been observed by the balloon-borne Fabry-Perot interferometer (FPI) at the equatorward of the cusp on the dayside [Wu et al., 2012], which is caused by the heating added in the cusp and the corresponding changes of the horizontal pressure gradient. However, this phenomenon has not been reproduced by the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) under low resolution (5x5 degrees). The Global Ionosphere Thermosphere Model (GITM) has been run in different cases and different resolutions. First, we compared the simulations with and without the cusp energy inputs to identify the influence on the horizontal dynamics. Both runs were done under high resolution in order to better resolve the cusp region. Then we also compared the simulations with the same cusp energy inputs but different horizontal resolutions to identify the influence of the simulation resolution on the results. This work will significantly advance our understanding of the neutral dynamics and the relationship between winds and upper atmosphere storm time response. [Preview Abstract] |
Friday, March 21, 2014 2:42PM - 2:54PM |
F4.00002: Numerical experiments to investigate Alfv\'{e}nic fluctuations using a global MHD simulation Kevin Pham, Ramon Lopez The ambient solar wind flowing out from the Sun is typically magnetically calm and slow in speed. The solar wind flowing out at the edges of coronal holes is faster and will pile up the slower solar wind in front of it. This compression region can cause moderate magnetic storms in Earth's magnetosphere. The large amplitude magnetic fluctuations in the z component of the interplanetary magnetic field, contained in the compression regions and corresponding to faster solar wind, is thought to increase the strength of geomagnetic storms. The fluctuations are from Alfven waves that travel transverse to the propagation of the solar wind. The waves will cause oscillations in the velocity and magnitude of the magnetic field in the transverse direction. We will present an investigation of the Alfv\'{e}nic fluctuations using the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) simulation. The LFM simulation was driven using quiet standard conditions for the solar wind and idealized random fluctuations in the magnetic field and velocity were added in incremental steps with only one modification made per simulated event. Their total energy output and geoeffective length will be presented. [Preview Abstract] |
Friday, March 21, 2014 2:54PM - 3:06PM |
F4.00003: Statistical analysis of corotating interaction regions and high speed streams Kyle Van Zuiden, Soha Aslam, Derric Edwards, Kevin Pham, Ramon Lopez Many people believe the solar wind to be a constant, steady flow of charged particles from the Sun; however, this is generally not the case. Coronal holes on the Sun produce very fast solar wind, known as a high-speed stream (HSS), which can greatly affect the Earth's magnetosphere. When a HSS compresses the slower-moving solar wind ahead of it, a corotating interaction region (CIR) is created. Due to the compression, CIRs have a density spike, intense magnetic fields, and they are followed by a HSS which is faster than the preceding solar wind. The interaction of CIRs/HSSs with Earth's magnetic field may cause geomagnetic storms and affect space weather, so understanding HSSs is important. Since the Sun is currently in a solar minimum, HSSs occur very frequently. We have collected a number of HSSs that follow CIRs, and we will present an analysis of the mean and standard deviation of varying parameters for this collection of HSSs. [Preview Abstract] |
Friday, March 21, 2014 3:06PM - 3:18PM |
F4.00004: Studying how magnetopause erosion is affected by ionospheric conductivity, using GOES satellite data Spencer Durrenberger, Robert Bruntz, Ramon Lopez The solar wind confines Earth's magnetic field into a ``bubble,'' called the magnetosphere. The boundary between the solar wind and Earth's magnetosphere is called the magnetopause. At this surface, the pressures from the solar wind and Earth's magnetosphere balance out. When the interplanetary magnetic field (IMF) turns southward, the magnetopause moves earthward, an effect known as magnetopause erosion. The phenomenon of erosion can also be detected by observing a weakening of the magnetic field on the dayside magnetosphere. We will use data from the geosynchronous GOES satellites when they are at local noon, which should be able to detect the weakening of the field, to study erosion. By examining GOES data for two years classified as ``solar maximum'' and ``solar minimum,'' we expect higher and lower ionospheric conductivities (respectively), and so we hope to identify a pattern that lends evidence towards an effect of solar cycle variation on magnetopause erosion. [Preview Abstract] |
Friday, March 21, 2014 3:18PM - 3:30PM |
F4.00005: Investigating the effects of a purely y-component IMF on the ionosphere, using new linear superposition techniques Robert Bruntz, Shree Bhattarai, Ramon Lopez One of the major means by which the Sun transfers energy to the Earth is through the solar wind. The efficiency of that transfer is controlled by the orientation of the interplanetary magnetic field (IMF). Recent work has shown that the Lyon-Fedder-Mobarry (LFM) magnetohydrodynamic (MHD) simulation can simulate effects of the y and z components of the IMF (By and Bz) separately, as well as the viscous interaction (which is mostly independent of the IMF orientation), then linearly combine the three to produce the equivalent of a run with the full IMF. We are now reversing that process, to subtract out the effects of the viscous interaction from simulation runs with a purely-By IMF. With this technique, we are investigating ionospheric circulation patterns and potentials due only to the y component of the IMF, which has been difficult to deduce from observations. We will present our latest results and their implications for magnetospheric research. [Preview Abstract] |
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