Global Change in the Upper Atmosphere

Laštovička, Jan; Akmaev, R. A.; Beig, G.; Bremer, J.; Emmert, J. T.

doi:10.1126/science.1135134

Cited by 114 publications

(111 citation statements)

References 11 publications

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“…[19] The increase in greenhouse gas concentrations also produces long-term variation in the E-region temperature [Aikin et al, 1991;Akmaev and Fomichev, 1998;Beig et al, 2003;Lastovicka et al, 2006a] and diurnal tidal amplitude [Bremer et al, 1997;Baumgaertner et al, 2005]. Temperature trends may affect Sq through the collision frequency and tidal amplitude trends through the V × B term in J.…”

Section: Discussionmentioning

confidence: 99%

Trends in the solar quiet geomagnetic field variation linked to the Earth's magnetic field secular variation and increasing concentrations of greenhouse gases

2010

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Long‐term trends in solar quiet geomagnetic field variation (Sq) are studied in connection to the Earth's magnetic field secular variations and increasing greenhouse gas concentrations. Sq is mainly caused by ionospheric current systems that flow in the E region and depends, among other variables, on the ionospheric conductivities. These conductivities in turn depend on the Earth's main magnetic field (B) and the electron concentration in the E region, for which foE is a measure of its peak value. Since B shows secular variation, induced long‐term changes in Sq might be expected. Another possible mechanism that would be able to induce Sq trends is the increasing concentrations of greenhouse gases that produce a cooling effect in the upper atmosphere and, according to model predictions and experimental results, an increasing trend in foE. To detect if both mechanisms mentioned are able to induce trends in Sq, the Sq variation of the horizontal intensity (H) of three magnetic observatories (Apia, Fredericksburg, and Hermanus), for which B is decreasing, is analyzed for the period 1960–2001. We find significant increasing trends (6.6%, 5.4%, and 9.9%, respectively) which may be partially accounted for by B secular variations in the respective sites. The Sq trend expected from the theoretically predicted foE increase is low (∼0.5%), although positive, as is the observed trend.

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Section: Discussionmentioning

confidence: 99%

Trends in the solar quiet geomagnetic field variation linked to the Earth's magnetic field secular variation and increasing concentrations of greenhouse gases

2010

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“…The solar minimum between solar cycles 23 and 24 was significantly longer than it has been expected. Lastovicka et al (2006) pointed out that besides other aspects, the significance of understanding of the solar minimum lies in revealing the nature of solar variability, its effects on geospace, and assessing the predictability of current models. Within the minimum of cycle 23/24 measurements from instruments placed on SOHO (the Solar and Heliospheric Observatory) and TIMED (the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics) satellites indicated that solar EUV irradiance levels were lower comparing with previous solar minimum, which led to lower thermospheric density and temperature.…”

Section: Latitude-dependent Response Of Tec To Solar Euv Changesmentioning

confidence: 99%

Solar activity impact on the Earth’s upper atmosphere

Kutiev

Tsagouri

Perrone

et al. 2013

J. Space Weather Space Clim.

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The paper describes results of the studies devoted to the solar activity impact on the Earth's upper atmosphere and ionosphere, conducted within the frame of COST ES0803 Action. Aim: The aim of the paper is to represent results coming from different research groups in a unified form, aligning their specific topics into the general context of the subject. Methods: The methods used in the paper are based on data-driven analysis. Specific databases are used for spectrum analysis, empirical modeling, electron density profile reconstruction, and forecasting techniques. Results: Results are grouped in three sections: Medium-and long-term ionospheric response to the changes in solar and geomagnetic activity, storm-time ionospheric response to the solar and geomagnetic forcing, and modeling and forecasting techniques. Section 1 contains five subsections with results on 27-day response of low-latitude ionosphere to solar extreme-ultraviolet (EUV) radiation, response to the recurrent geomagnetic storms, long-term trends in the upper atmosphere, latitudinal dependence of total electron content on EUV changes, and statistical analysis of ionospheric behavior during prolonged period of solar activity. Section 2 contains a study of ionospheric variations induced by recurrent CIR-driven storm, a case-study of polar cap absorption due to an intense CME, and a statistical study of geographic distribution of so-called E-layer dominated ionosphere. Section 3 comprises empirical models for describing and forecasting TEC, the F-layer critical frequency foF2, and the height of maximum plasma density. A study evaluates the usefulness of effective sunspot number in specifying the ionosphere state. An original method is presented, which retrieves the basic thermospheric parameters from ionospheric sounding data.

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“…The ionosphere contains a high concentration of electrons and ions because of the ionization of gases in that region by short wavelength radiation from the Sun. Therefore, these species play an important role in atmospheric electricity, influencing radio propagation to different regions on the Earth's surface and space-based navigational systems (1). The D layer is the innermost layer of the ionosphere, ranging from 60 to 90 km in altitude, where Lyman series-α hydrogen radiation from the Sun gives rise to abundant nitrosonium ions (NO + ).…”

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Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations

Zhong

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Solar emission produces copious nitrosonium ions (NO + ) in the D layer of the ionosphere, 60 to 90 km above the Earth's surface. NO + is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200-220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates-tetrahydrate NO + (H 2 O) 4 and pentahydrate NO + (H 2 O) 5 -are identified and shown to be responsible for HONO formation in the ionosphere. The critical tetrahydrate NO + (H 2 O) 4 exhibits a chainlike structure through which all of the lowest-energy isomers must go. However, most lowest-energy isomers of pentahydrate NO + (H 2 O) 5 can be converted to the HONO-containing product, encountering very low barriers, via a chain-like or a three-armed, star-like structure. Although these structures are not the global minima, at 220 K, most lowest-energy NO + (H 2 O) 4 and NO + (H 2 O) 5 isomers tend to channel through these highly populated isomers toward HONO formation.ionosphere | HONO | mechanism | water | clusters T he ionosphere is the largest layer in the Earth's atmosphere, ranging in altitude from ∼60 to 1,000 km and includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere contains a high concentration of electrons and ions because of the ionization of gases in that region by short wavelength radiation from the Sun. Therefore, these species play an important role in atmospheric electricity, influencing radio propagation to different regions on the Earth's surface and space-based navigational systems (1). The D layer is the innermost layer of the ionosphere, ranging from 60 to 90 km in altitude, where Lyman series-α hydrogen radiation from the Sun gives rise to abundant nitrosonium ions (NO + ). In addition to the ionospheric reaction between NO + and water, explorations of the chemical reactivity of NO + and water clusters (2-4) have implications for understanding the mechanisms of atmospherically relevant reactions in water clusters (5-9).Over the past two decades, several experimental and theoretical studies (10-13) have focused on understanding the chemical and physical properties of the small-sized hydrated nitrosonium ion NO + (H 2 O) n , where n = 1-5. Two key processes have been proposed for HONO formation: NO + ðH 2 OÞ n + H 2 O → fðHONOÞH + ðH 2 OÞ n É → H + ðH 2 OÞ n + HONO .[1]Lee and coworkers (14) used vibrational spectroscopy to obtain clear evidence of the rearrangement of the NO + (H 2 O) n cluster by observing the appearance of new hydrogen (H)-bonded OH stretching lines. Using quantum molecular dynamics, Ye and Cheng (15) suggested possible structures and corresponding IR spectra for NO + (H 2 O) n (n = 1-3) clusters. In a major experimental breakthrough, Relph et al. (16) showed that the extent to which reaction 1 produces HONO ...

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Global Change in the Upper Atmosphere

Cited by 114 publications

References 11 publications

Trends in the solar quiet geomagnetic field variation linked to the Earth's magnetic field secular variation and increasing concentrations of greenhouse gases

Trends in the solar quiet geomagnetic field variation linked to the Earth's magnetic field secular variation and increasing concentrations of greenhouse gases

Solar activity impact on the Earth’s upper atmosphere

Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations

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