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Found 4 entries in the Bibliography.
Showing entries from 1 through 4
| 2022 |
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A Simulation Study on the Variation of Thermospheric O/N2 With Solar Activity The ratio of number density of atomic oxygen (O) to that of molecular nitrogen (N2) in the thermosphere (O/N2) on the constant pressure surface, which has complex temporal and spatial characteristics, is widely regarded as an important parameter connecting the terrestrial thermosphere and daytime ionosphere. Previous studies demonstrated that the thermospheric O/N2 increases with increasing solar activity, and the changes in O/N2 with solar activity show significant difference between winter and summer hemispheres. However, the root causes, which are responsible for the solar activity variation of O/N2, are not fully understood. In this study, the contributions of various physical and chemical processes on the response of O/N2 to the solar radiation change were quantitatively investigated through a series of controlled simulations from the Thermosphere Ionosphere Electrodynamics General Circulation Model. The simulation results suggested that the chemical processes lead to the increase of thermospheric O/N2 over the globe with increasing solar activity. The increase of O/N2 with solar activity is dominated by the enrichment of O abundance and the loss of N2 abundance in the lower and upper thermosphere, respectively. Moreover, the simulation results suggested that the stronger hemispheric asymmetry is attributed to the stronger thermospheric circulation, which changes the vertical advection of O/N2 through both direct and indirect effects. Li, Zhongli; Luan, Xiaoli; Lei, Jiuhou; Ren, Dexin; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2022 DOI: 10.1029/2022JA030305 circulation; O/N2; photochemistry; solar cycle; thermosphere |
| 2015 |
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Explaining solar cycle effects on composition as it relates to the winter anomaly The solar cycle variation of\ F2\ region winter anomaly is related to solar cycle changes in the latitudinal winter-to-summer difference of O/N2. Here we use the National Center for Atmospheric Research\textendashGlobal Mean Model to develop a concept of why the latitudinal winter-to-summer difference of O/N2\ varies with solar cycle. The main driver for these seasonal changes in composition is vertical advection, which is expressed most simply in pressure coordinates. Meridional winds do not change over the solar cycle, so the vertical winds should also not change. The other component of vertical advection is the vertical gradient of composition. Is there any reason that this should change? At solar maximum vertical temperature gradients between 100 and 200 km altitude are strong, whereas they are weak at solar minimum. To maintain the same pressure, the weak vertical temperature gradients at solar minimum must be balanced by weak density gradients and the strong temperature gradients at solar maximum must be balanced by strong density gradients to obtain the same pressure profile. Changes in the vertical density gradients are species dependent: heavy species change more and light species change less than the average density change. Hence, vertical winds act on stronger O/N2\ gradients at solar maximum than they do at solar minimum, and a stronger winter-to-summer difference of O/N2\ occurs at solar maximum compared with solar minimum. Burns, A.; Solomon, S.; Wang, W.; Qian, L.; Zhang, Y.; Paxton, L.; Yue, X.; Thayer, J.; Liu, H.; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2015 YEAR: 2015 DOI: 10.1002/2015JA021220 |
| 2013 |
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Solar cycle dependence of the seasonal variation of auroral hemispheric power Although much has been done on the hemispheric asymmetry (or seasonal variations) of auroral hemispheric power (HP), the dependence of HP hemispheric asymmetry on solar cycle has not yet been studied. We have analyzed data during 1979\textendash2010 and investigated the dependence of HP hemispheric asymmetry/seasonal variation for the whole solar cycle. Here we show that (1) the hemispheric asymmetry of HP is positively correlated to the value of solar F10.7 with some time delay; (2) it is closely related to the coupling function between the solar wind and magnetosphere; and (3) the winter hemisphere receives more auroral power than the summer hemisphere for K p\~0 to 6. The statistic results can be partly understood in the framework of the ionospheric conductivity feedback model. The similarity and differences between our results and previous results are discussed in the paper. Zheng, Ling; Fu, SuiYan; Zong, QuiGang; Parks, George; Wang, Chi; Chen, Xi; Published by: Chinese Science Bulletin Published on: 02/2013 YEAR: 2013 DOI: 10.1007/s11434-012-5378-6 auroral power; coupling function; hemispheric asymmetry; precipitation; solar cycle |
| 2012 |
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Recent Progresses on Ionospheric Climatology Investigations The ionosphere varies over multiple time scales, which are classified into two categories: the climatology and weather variations. In this national report, we give a brief summary of recent progresses in ionospheric climatology with focus on (1) the seasonal variations, (2) solar cycle effects, and (3) empirical modeling of the ionosphere. The seasonal variations of the ionosphere have been explored in many works to give a more detailed picture with regional and global features at various altitudes by analyzing the observation data from various sources and models. Moreover, a series of studies reported the response of the ionosphere to solar cycle variations, which revealed some novel and detailed features of solar activity dependence of ionospheric parameters at different altitudes. These investigations have improved our understanding on the states of the ionosphere and underlying fundamental processes, provided clues to future studies on ionospheric weather, and guided ionospheric modeling, forecasting and related applications.
Published by: Chin. J. Space Sci. Published on: Climatological variation; Ionosphere; Ionospheric modeling; Seasonal variations; solar cycle |
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