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 (Dst > −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.
This study presents a suggestion for improvement of the ion temperature (Ti) model in the International Reference Ionosphere (IRI). We have re-examined ion temperature data (primarily available from NASA’s Space Physics Data Facility (SPDF)from older satellites and combined them with newly available data from the Defense Meteorological Satellite Program (DMSP), the Communication Navigation Outage Forecasting System (C/NOFS), and from the recently launched Ionospheric Connection Explorer (ICON). We have compiled these data into a unified database comprising in total Ti data from 18 satellites. By comparisons with long term records of ion temperature from the three incoherent scatter radars (ISRs) (Jicamarca, Arecibo, and Millstone Hill), it was found that an intercalibration is needed to achieve consistency with the ISR data and among individual satellite data sets. This database with thus corrected data has been used for the development of a new global empirical model of Ti with inclusion of solar activity variation. This solar activity dependence is represented by an additive correction term to the Ti global pattern. Due to the limited data coverage at altitudes above 1000 km, the altitude range described by the model ranges from 350 km to 850 km covering only the region where generally Ti is higher than the neutral temperature (Tn) and lower than the electron temperature (Te). This approach is consistent with the current description of Ti in the IRI model. However, instead of one anchor point at 430 km altitude as in the current IRI, our approach includes anchor points at 350, 430, 600, and 850 km. At altitudes above 850 km Ti is merged using a gradient derived from the model at 600 and 850 km, with the electron temperature described by the IRI-2016/TBT-2012 option. Comparisons with the ISR data (Jicamarca, Arecibo, Millstone Hill, and Kharkiv) for high and low solar activity and equinox show that the proposed Ti model captures local time variation of Ti at different altitudes and latitudes better than the current IRI-2016 Ti model.
A comprehensive study of the response of the ionosphere-plasmasphere system at mid-latitudes to weak (Dst min > −50 nT) magnetic storms is presented. For the first time, it is shown that weak magnetic disturbances can lead to significant modulation of ionosphere-plasmasphere H + ion fluxes. It is found that this modulation is caused by the enhancements/reductions of the topside O + ion density, which is induced by F2-layer peak height rise and fall during the storms. The F2-layer motion is caused by thermospheric wind changes and by a penetration electric field. Both drivers are closely related to the changes in the B z component of interplanetary magnetic field. The most prominent manifestation of the H + ion flux modulation is strong changes in H + ion fraction in the topside ionosphere. This study also indicates that the NRLMSISE-00 model provides the correct relative changes of neutral H density during weak magnetic storms and also that there is a compelling need to include geomagnetic activity indices, in addition to solar activity (F 10.7 ), as input parameters to empirical topside ionosphere models.
We present ionospheric observational results obtained over Ukrainian Antarctic Akademik Vernadsky station. Ionospheric parameters (peak electron density and height, electron density and electron and ion temperatures in the topside) during the period near the local winter solstice in the Southern Hemisphere (June 28-29, 2019) are considered. The main objective is to show distinctive features of variations in ionospheric parameters during a prolonged period with very low solar and magnetic activities, and minimal daily insolation. Methods. F2 layer peak electron density and height were calculated from ionograms obtained with ionosonde installed at the station with subsequent profile inversion. Defense Meteorological Satellite Program (DMSP) and Swarm data acquired over the station are used as well. Diurnal variations of electron density, and electron and ion temperatures at the altitude of the satellites' orbits were calculated using a set of sub-models of the International Reference Ionosphere-2016 (IRI-2016) model. Results. We found a very good agreement between the observed and model variations of F2 layer peak electron density. Significant (by ~2 times) nighttime enhancement of electron density was observed on June 29. Electron density models show the similar increase of the density at the same time interval but this enhancement is much more smoothed comparing with the observations. Peak height values obtained using ionosonde are very close to ones calculated with the IRI-2016 sub-models. Satellite data are in a good consistency with the IRI model predictions, especially for electron density obtained by Swarm satellite. Conclusions. Multi-instrumental observations revealed a number of unique features of the ionosphere over Antarctic Peninsula under minima of solar and magnetic activities, and daily insolation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.