The effect of geomagnetic activity on the dynamics of the upper mesosphere-lower thermosphere and on parameters of the Es-layer

1999 ◽  
Vol 24 (11) ◽  
pp. 1499-1502 ◽  
Author(s):  
A.N. Fahrutdinova ◽  
O.N. Sherstyukov ◽  
S.V. Maksyutin
Keyword(s):  
Geomagnetic Activity ◽  
Lower Thermosphere

scholarly journals Dependence of neutral temperatures in the lower thermosphere on geomagnetic activity

2007 ◽  
Vol 112 (A6) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. Aksnes ◽  
R. Eastes ◽  
S. Budzien ◽  
K. Dymond
Keyword(s):  
Geomagnetic Activity ◽  
Lower Thermosphere

scholarly journals Production and transport mechanisms of NO in observations and models

2018 ◽  
Author(s):  
Koen Hendrickx ◽  
Linda Megner ◽  
Daniel R. Marsh ◽  
Christine Smith-Johnsen
Keyword(s):  
Geomagnetic Activity ◽  
Climate Models ◽  
Climate Model ◽  
Heat Budget ◽  
Lower Thermosphere ◽  
Polar Vortex ◽  
Detailed Comparison ◽  
No Production ◽  
The Impact ◽  
Mlt Region

Abstract. A reservoir of Nitric Oxide (NO) in the lower thermosphere efficiently cools the atmosphere after periods of enhanced geomagnetic activity. Transport from this reservoir to the stratosphere within the winter polar vortex allows NO to deplete ozone levels and thereby affect the middle atmospheric heat budget. As more climate models resolve the mesosphere and lower thermosphere (MLT) region, the need for an improved representation of NO related processes increases. This work presents a detailed comparison of NO in the Antarctic MLT region between observations made by the Solar Occultation for Ice Experiment (SOFIE) instrument onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite and simulations performed by the Whole Atmosphere Community Climate Model with Specified Dynamics (SD-WACCM). We investigate 7 years of SOFIE observations and focus on the Southern hemisphere, rather than on dynamical variability in the Northern hemisphere or a specific geomagnetic perturbed event. The morphology of the simulated NO is in agreement with observations though the long term mean is too high and the short term variability is too low. Number densities are more similar during winter, though the altitude of peak densities, which reaches between 102–106 km in WACCM and between 98–104 km in SOFIE, is most separated during winter. Using multiple linear regressions and superposed epoch analyses we investigate how well the NO production and transport are represented in the model. The impact of geomagnetic activity is shown to drive NO variations in the lower thermosphere similarly across both datasets. The dynamical transport from the lower thermosphere into the mesosphere during polar winter is found to agree very well, with a descent rate of about 2.2 km/day in the 80–110 km region in both datasets. The downward transported NO fluxes are however too low in WACCM, which is likely due to medium energy electrons and D-region chemistry that are not represented in the model.

scholarly journals Variability of NO<sub>x</sub> in the polar middle atmosphere from October 2003 to March 2004: vertical transport versus local production by energetic particles

2014 ◽  
Vol 14 (1) ◽  
pp. 1-29 ◽  
Author(s):  
M. Sinnhuber ◽  
B. Funke ◽  
T. von Clarmann ◽  
M. Lopez-Puertas ◽  
G. P. Stiller
Keyword(s):  
Geomagnetic Activity ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Solar Proton ◽  
Electron Precipitation ◽  
Proton Event ◽  
Local Production ◽  
Altitude Range ◽  
Order Of Magnitude ◽  
The Impact

Abstract. We use NO, NO2 and CO from MIPAS/ENVISAT to investigate the impact of energetic particle precipitation onto the NOx budget from the stratosphere to the lower mesosphere in the period from October 2003 to March 2004, a time of high solar and geomagnetic activity. We find that in the winter hemisphere the indirect effect of auroral electron precipitation due to downwelling of upper mesospheric/lower thermospheric air into the stratosphere prevails. Its effect exceeds even the direct impact of the very large solar proton event in October/November 2003 by nearly one order of magnitude. Correlations of NOx and CO show that the unprecedented high NOx values observed in the Northern Hemisphere lower mesosphere and upper stratosphere in late January and early February are fully consistent with transport from the upper mesosphere/lower thermosphere and subsequent mixing at lower altitudes; an additional source of NOx due to local production by precipitating electrons at altitudes below 70 km as discussed in previous publications appears unlikely. In the polar summer Southern Hemisphere, we observed an enhanced variability of NO and NO2 on days with enhanced geomagnetic activity but they seem to indicate enhanced instrument noise rather than a direct increase due to electron precipitation. A direct effect of electron precipitation onto NOx can not be ruled out, but if any, it is lower than 3 ppb in the altitude range 40–56 km and lower than 6 ppb in the altitude range 56–70 km.

scholarly journals Production and transport mechanisms of NO in the polar upper mesosphere and lower thermosphere in observations and models

2018 ◽  
Vol 18 (12) ◽  
pp. 9075-9089 ◽  
Author(s):  
Koen Hendrickx ◽  
Linda Megner ◽  
Daniel R. Marsh ◽  
Christine Smith-Johnsen
Keyword(s):  
Geomagnetic Activity ◽  
Climate Models ◽  
Climate Model ◽  
Heat Budget ◽  
Lower Thermosphere ◽  
No Production ◽  
Superposed Epoch Analysis ◽  
Mesosphere And Lower Thermosphere ◽  
The Impact ◽  
Mlt Region

Abstract. A reservoir of nitric oxide (NO) in the lower thermosphere efficiently cools the atmosphere after periods of enhanced geomagnetic activity. Transport from this reservoir to the stratosphere within the winter polar vortex allows NO to deplete ozone levels and thereby affect the middle atmospheric heat budget. As more climate models resolve the mesosphere and lower thermosphere (MLT) region, the need for an improved representation of NO-related processes increases. This work presents a detailed comparison of NO in the Antarctic MLT region between observations made by the Solar Occultation for Ice Experiment (SOFIE) instrument on-board the Aeronomy of Ice in the Mesosphere (AIM) satellite and simulations performed by the Whole Atmosphere Community Climate Model with Specified Dynamics (SD-WACCM). We investigate 8 years of SOFIE observations, covering the period 2007–2015, and focus on the Southern Hemisphere (SH), rather than on dynamical variability in the Northern Hemisphere (NH) or a specific geomagnetic perturbed event. The morphology of the simulated NO is in agreement with observations though the long-term mean is too high and the short-term variability is too low in the thermosphere. Number densities are more similar during winter, though the altitude of peak NO density, which reaches between 102 and 106 km in WACCM and between 98 and 104 km in SOFIE, is most separated during winter. Using multiple linear regression (MLR) and superposed epoch analysis (SEA) methods, we investigate how well the NO production and transport are represented in the model. The impact of geomagnetic activity is shown to drive NO variations in the lower thermosphere similarly across both datasets. The dynamical transport from the lower thermosphere into the mesosphere during polar winter is found to agree very well with a descent rate of about 2.2 km day−1 in the 80–110 km region in both datasets. The downward-transported NO fluxes are, however, too low in WACCM, which is likely due to medium energy electrons (MEE) and D-region ion chemistry that are not represented in the model.

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