Climate Change in the Upper Atmosphere

Cnossen, Ingrid

doi:10.5772/32565

Cited by 18 publications

(18 citation statements)

References 64 publications

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“…Roble and Dickinson (1989) simulated the effect of increasing greenhouse gases on the globally averaged upper atmosphere, and their study stimulated a search for corresponding longterm trends in upper atmospheric data sets. Recent reviews of long-term upper atmospheric change results are given by Laštovička (2013), Cnossen (2012) and Qian et al (2011a).…”

Section: Other Climatological Variationsmentioning

confidence: 99%

Thermospheric mass density: A review

Emmert

2015

Advances in Space Research

210

217

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Section: Other Climatological Variationsmentioning

confidence: 99%

Thermospheric mass density: A review

Emmert

2015

Advances in Space Research

210

217

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“…[37] Since the thermosphere has been observed to have cooled over the past decades [Donaldson et al, 2010;Zhang et al, 2011], we must conclude that the decreasing dipole moment actually acts against the main mechanism(s) responsible for this cooling trend, which has still not been fully explained [Cnossen, 2012]. However, the influence of the decreasing dipole moment is very small compared to the magnitude of typical observed trends (À30 to À50 K/decade).…”

Section: Implications For Long-term Trend Studiesmentioning

confidence: 99%

The dependence of the coupled magnetosphere‐ionosphere‐thermosphere system on the Earth's magnetic dipole moment

2012

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The strength of the Earth's magnetic field changes over time. We use simulations with the Coupled Magnetosphere‐Ionosphere‐Thermosphere model to investigate how the magnetosphere, upper atmosphere, and solar quiet (Sq) geomagnetic variation respond as the geomagnetic dipole moment M varies between 2⋅1022 and 10⋅1022 Am2. We find that the magnetopause stand‐off distance and the cross‐polar cap potential increase, while the polar cap size decreases, with increasing M. Their dependence on M is stronger than predicted by previous studies. We also show for the first time that the shape of the magnetosphere starts to change for M ≤ 4⋅1022 Am2. This may be due to enhanced magnetopause erosion and/or to strong changes in the ionospheric conductance, which affect the field‐aligned currents and the magnetic fields they create in the magnetosphere, thus modifying the magnetic pressure inside the magnetosphere. E × B drift velocities, Joule heating power, the global mean thermospheric temperature and the global mean height of the peak of the ionospheric F2 layer, hmF2, all increase with increasing M for low dipole moments, but all decrease with increasing M for larger dipole moments. The peak electron density of the F2 layer, NmF2, shows the opposite behavior. The Sq amplitude decreases with increasing M and this dependence can be roughly described by a power law scaling. Most scaling relations show a weak dependence on the solar activity level, which is likely associated with a change in the relative contributions to the Pedersen conductance from the upper and lower ionosphere, which scale differently with M.

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“…Numerous studies have observed long‐term trends in the thermosphere and ionosphere over the past ~50–100 years [for reviews see, e.g., Qian et al ., and Cnossen ]. In general, the temperature in the thermosphere has been decreasing, leading to lower densities at fixed heights due to thermal contraction.…”

Section: Introductionmentioning

confidence: 99%

Changes in the Earth's magnetic field over the past century: Effects on the ionosphere‐thermosphere system and solar quiet (Sq) magnetic variation

Cnossen

Richmond

2013

JGR Space Physics

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[1] We investigated the contribution of changes in the Earth's magnetic field to long-term trends in the ionosphere, thermosphere, and solar quiet (Sq) magnetic variation using the Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model. Simulations with the magnetic fields of 1908, 1958, and 2008 were done. The strongest differences occurred between~40 S-40 N and~100 W-50 E, which we refer to as the Atlantic region. The height and critical frequency of the F 2 layer peak, h m F 2 and f o F 2 , changed due to changes in the vertical E Â B drift and the vertical components of diffusion and transport by neutral winds along the magnetic field. Changes in electron density resulted in changes in electron temperature of the opposite sign, which in turn produced small corresponding changes in ion temperature. Changes in neutral temperature were not statistically significant. Strong changes in the daily amplitude of the Sq variation occurred at low magnetic latitudes due to the northward movement of the magnetic equator and the westward drift of the magnetic field. The simulated changes in h m F 2 , f o F 2 , and Sq amplitude translate into typical trends of AE1 km/decade (night) to AE3 km/decade (day), À0.1 to +0.05 MHz/decade, and AE5 to AE10 nT/century, respectively. These are mostly comparable in magnitude to observed trends in the Atlantic region. The simulated Atlantic region trends in h m F 2 and f o F 2 are~2.5 times larger than the estimated effect of enhanced greenhouse gases on h m F 2 and f o F 2 . The secular variation of the Earth's magnetic field may therefore be the dominant cause of trends in the Atlantic region ionosphere.Citation: Cnossen I., and A. D. Richmond (2013), Changes in the Earth's magnetic field over the past century: Effects on the ionosphere-thermosphere system and solar quiet (Sq) magnetic variation,

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Climate Change in the Upper Atmosphere

Cited by 18 publications

References 64 publications

Thermospheric mass density: A review

Thermospheric mass density: A review

The dependence of the coupled magnetosphere‐ionosphere‐thermosphere system on the Earth's magnetic dipole moment

Changes in the Earth's magnetic field over the past century: Effects on the ionosphere‐thermosphere system and solar quiet (Sq) magnetic variation

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