Browsing by Author "Hairston, Marc R."
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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.Item Study of the Equatorial and Low-Latitude Electrodynamic and Ionospheric Disturbances during the 22–23 June 2015 Geomagnetic Storm Using Ground-Based and Spaceborne Techniques(Blackwell Publishing Ltd) Astafyeva, E.; Zakharenkova, I.; Hozumi, K.; Alken, P.; Coïsson, P.; Hairston, Marc R.; Coley, William R.; 0000-0003-4524-4837 (Hairston, MR); Hairston, Marc R.; Coley, William R.We use a set of ground-based instruments (Global Positioning System receivers, ionosondes, magnetometers) along with data of multiple satellite missions (Swarm, C/NOFS, DMSP, GUVI) to analyze the equatorial and low-latitude electrodynamic and ionospheric disturbances caused by the geomagnetic storm of 22-23 June 2015, which is the second largest storm in the current solar cycle. Our results show that at the beginning of the storm, the equatorial electrojet (EEJ) and the equatorial zonal electric fields were largely impacted by the prompt penetration electric fields (PPEF). The PPEF were first directed eastward and caused significant ionospheric uplift and positive ionospheric storm on the dayside, and downward drift on the nightside. Furthermore, about 45 min after the storm commencement, the interplanetary magnetic field (IMF) Bz component turned northward, leading to the EEJ changing sign to westward, and to overall decrease of the vertical total electron content (VTEC) and electron density on the dayside. At the end of the main phase of the storm, and with the second long-term IMF Bz southward turn, we observed several oscillations of the EEJ, which led us to conclude that at this stage of the storm, the disturbance dynamo effect was already in effect, competing with the PPEF and reducing it. Our analysis showed no significant upward or downward plasma motion during this period of time; however, the electron density and the VTEC drastically increased on the dayside (over the Asian region). We show that this second positive storm was largely influenced by the disturbed thermospheric conditions. ©2018. The Authors.Item Testing Nowcasts of the Ionospheric Convection from the Expanding and Contracting Polar Cap Model(Amer Geophysical Union, 2017-04-20) Walach, M. -T; Milan, S. E.; Yeoman, T. K.; Hubert, B. A.; Hairston, Marc R.; Hairston, Marc R.The expanding/contracting polar cap (ECPC) model, or the time-dependent Dungey cycle, provides a theoretical framework for understanding solar wind-magnetosphere-ionosphere coupling. The ECPC describes the relationship between magnetopause reconnection and substorm growth phase, magnetotail reconnection and substorm expansion phase, associated changes in auroral morphology, and ionospheric convective motions. Despite the many successes of the model, there has yet to be a rigorous test of the predictions or nowcasts made regarding ionospheric convection, which remains a final hurdle for the validation of the ECPC. In this study we undertake a comparison of ionospheric convection, as measured in situ by ion drift meters on board DMSP (Defense Meteorological Satellite Program) satellites and from the ground by SuperDARN (Super Dual Auroral Radar Network), with motions nowcasted by a theoretical model. The model is coupled to measurements of changes in the size of the polar cap made using global auroral imagery from the IMAGE FUV (Imager for Magnetopause to Aurora Global Exploration Far Ultraviolet) instrument, as well as the dayside reconnection rate, estimated using the OMNI data set. The results show that we can largely nowcast the magnitudes of ionospheric convection flows using the context of our understanding of magnetic reconnection at the magnetopause and in the magnetotail. Plain Language Summary We test a physics-based model which describes flows in the ionosphere near the magnetic poles due to solar wind driving of the activity within the Earth's magnetic environment using spacecraft and radar measurements of the flows. The results of this comparison show that our knowledge of the interactions of the solar wind, the Earth's magnetic environment, and ionosphere encompasses the general pattern of flows well, as well as the flow strengths. Further work is required to expand our understanding of asymmetric flows and to be able to model them better.