Browsing by Author "Maruyama, N."
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Item Coincident Observations by the Kharkiv IS Radar and Ionosonde, DMSP and Arase (ERG) Satellites, and FLIP Model Simulations: Implications for the NRLMSISE-00 Hydrogen Density, Plasmasphere, and Ionosphere(Blackwell Publishing Ltd) Kotov, D. V.; Richards, P. G.; Truhlík, V.; Bogomaz, O. V.; Shulha, M. O.; Maruyama, N.; Hairston, Marc R.; Miyoshi, Y.; Kasahara, Y.; Kumamoto, A.; Tsuchiya, F.; Matsuoka, A.; Shinohara, I.; Hernández-Pajares, M.; Domnin, I. F.; Zhivolup, T. G.; Emelyanov, L. Y.; Chepurnyy, Y. M.; 0000-0003-4524-4837 (Hairston, MR); Hairston, Marc R.This paper reports the results of ionosphere and plasmasphere observations with the Kharkiv incoherent scatter radar and ionosonde, Defense Meteorological Satellite Program, and Arase (ERG) satellites and simulations with field line interhemispheric plasma model during the equinoxes and solstices of solar minimum 24. The results reveal the need to increase NRLMSISE-00 thermospheric hydrogen density by a factor of ~2. For the first time, it is shown that the measured plasmaspheric density can be reproduced with doubled NRLMSISE-00 hydrogen density only. A factor of ~2 decrease of plasmaspheric density in deep inner magnetosphere (L ≈ 2.1) caused by very weak magnetic disturbance (D_{st} > -22 nT) of 24 December 2017 was observed in the morning of 25 December 2017. During the next night, prominent effects of partially depleted flux tube were observed in the topside ionosphere (~50% reduced H⁺ ion density) and at the F2-layer peak (~50% decreased electron density). The likely physical mechanisms are discussed.Item Storm-Time Meridional Flows: A Comparison of CINDI Observations and Model Results(Copernicus Gmbh, 2014-06-17) Hairston, Marc R.; Maruyama, N.; Coley, William R.; Stoneback, Russell A.During a large geomagnetic storm, the electric field from the polar ionosphere can expand far enough to affect the mid-latitude and equatorial electric fields. These changes in the equatorial zonal electric field, called the penetration field, will cause changes in the meridional ion flows that can be observed by radars and spacecraft. In general this E x B ion flow near the equator caused by the penetration field during undershielding conditions will be upward on the dayside and downward on the nightside of the Earth. Previous analysis of the equatorial meridional flows observed by CINDI instrument on the C/NOFS spacecraft during the 26 September 2011 storm showed that all of the response flows on the dayside were excess downward flows instead of the expected upward flows. These observed storm-time responses are compared to a prediction from a physics-based coupled model of thermosphere-ionosphere- inner-magnetosphere in an effort to explain these observations. The model results suggest that the equatorial downward flow could be attributed to a combined effect of the overshielding and disturbance dynamo processes. However, some discrepancy between the model and observation indicates a need for improving our understanding of how sensitive the equatorial electric field is to various model input parameters that describe the magnetosphere-ionosphere coupling processes.