Variations in the mass density in the magnetosphere can have significant effects on a number of important magnetospheric phenomena. Mass loading is expected to effect the rate of magnetic reconnection and it effects the processes related to Ultra-Low Frequency (ULF) waves. Mass loading effects the growth rate and frequency of Kelvin-Helmholtz (K-H) oscillations at the magnetopause and in the low latitude boundary layer (LLBL). Although the effects are important, it has been difficult to get a quantitative measure of the mass loading and the associated effects. This project will develop a database of events for two classes of solar wind inputs. In each case, the event will begin with a prolonged period of northward interplanetary magnetic field (IMF), which will establish a "ground-state" of the magnetosphere. The first class of events that will be examined is Corotating Interaction Regions (CIRs) and the second class is periods of prolonged southward IMF. The mass loading effect on dayside magnetic merging will be examined by statistically comparing the rate of magnetic flux crossing the polar cap boundary as a function of the magnetospheric density. The project will use data from the Geotail and THEMIS satellite missions in conjunction with ground-based magnetometers and incoherent scatter radar data.
The project will include research activities for a graduate student or advanced undergraduate student. The results will be of importance to the Geosapce Environment Modeling program as well as to our understanding and ability to forecast space weather events.
Publications that acknowledge NSF support 1. Nosé, M., K. Takahashi, R. R. Anderson, and H. J. Singer (2011), Oxygen torus in the deep inner magnetosphere and its contribution to recurrent process of O+-rich ring current formation, J. Geophys. Res., 116, A10224, doi:10.1029/2011JA016651. 2. Takahashi, K., K. Yumoto, S. G. Claudepierre, E. R. Sanchez, O. A. Troshichev, and A. S. Janzhura (2012), Dependence of the amplitude of Pc5-band magnetic field variations on the solar wind and solar activity, J. Geophys. Res., 117, A04207, doi:10.1029/2011JA017120. 3. Sánchez, E. R., J. Gjerloev, R. A. Doe, and K. Takahashi (2014, submitted), Direct measurement of reconnection rate attenuation by plasmasphere plumes, Geophys. Res. Lett. 4. Denton, R. E., K. Takahashi, M. F. Thomsen, H. J. Singer, Y. Wang, J. Goldstein, P. C. Brandt, and B. W. Reinisch (2013, in preparation), Mass density refilling and O+ concentration during NASA FST and GEM PMI events, J. Geophys. Res. 5. Takahashi, K., R. E. Denton, M. Hirahara, K. Min, E. Sánchez, S.-I. Ohtani, and H. Kojima (2013, in preparation), Frequency of toroidal Alfvén waves observed by Geotail and its relation to plasma mass density, J. Geophys. Res. Presentations Takahashi, K., and R. E. Denton, Plasma Mass Density in the Inner Magnetosphere Derived From the Frequency of Standing Alfven Waves Observed With Spacecraft (Invited), IUGG IAGA Symposia, Session A07.2, Melbourne, Australia, June 28- July 7, 2011. Takahashi, K., Dawn/dusk asymmetry of field line resonance (Invited), Plasma Seminar, Department of Physics and Astronomy, April 24, 2012. Takahashi, K., K. Yumoto, S. G. Claudepierre, E. R. Sánchez, O. A. Troshichev, and A. S. Janzhura, Solar activity dependence of the relationship between the solar wind and Pc5 ULF waves (Contributed), IAGA 2013 The XIIth Assembly, Merida, Mexico, August 26, 2013. Takahashi, K., M. Hirahara, R. E. Denton, K. Min, E. Sánchez, and S.-I. Ohtani, Frequency of toroidal Alfvén waves observed by Geotail and its relation to plasma mass density (Contributed), SGEPSS Meeting, Kochi, Japan, November 3, 2013. Sánchez, E. R., K. Takahashi, and J. Gjerloev, Direct measurements of reconnection rate attenuation by plasmasphere plumes, Abstract SM43B-2314 presented at 2013 Fall Meeting, AGU, San Francisco, Calif., 9-13 Dec. Summer student support Mr. Daniel L. Kang, a sophomore at College of William and Mary, was a summer student who participated in the NSF-supported research under the supervision of Dr. Kazue Takahashi. Mr. Kang was selected through the NASA/APL internship program for 2013 and worked at APL from June 4 to August 9. In this program, NASA provided logistic support to students and APL provided stipend to them. Mr. Kang was supported by the NSF/SRI funding for the " Measurements of mass loading effects." Mr. Kang's task was to edit a large volume of Geotail plasma and magnetic field data obtained from JAXA, identify times when the spacecraft was in the magnetosphere, and determine whether standing Alfven waves were present.
