Impact of the semidiurnal lunar tide on the midlatitude thermospheric wind and ionosphere during sudden stratosphere warmings

Pedatella, N. M.; Maute, Astrid

doi:10.1002/2015ja021986

Cited by 60 publications

(96 citation statements)

References 72 publications

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“…Both the observations and simulation show a strong decrease following the peak of the SSW, and a small increase prior to the warming, though the increase only occurs in the northern hemisphere in the simulations. We note that the N m F 2 reduction in the TIE‐GCM is stronger than seen in the observations, and this may be due to the dynamical changes associated with the 2013 SSW having a greater impact on the upper atmosphere compared to the 2009 SSW [e.g., Goncharenko et al , ; Pedatella and Maute , ]. In addition to the decrease at low to midlatitudes, there is a minor short‐term relative increase at high latitudes in the southern hemisphere around days 10–20, and this is most evident in the [O]/[N 2 ] around 70°S.…”

Section: Resultsmentioning

confidence: 99%

Impact of semidiurnal tidal variability during SSWs on the mean state of the ionosphere and thermosphere

et al. 2016

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Observations from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites reveal a global reduction in the zonal and diurnal mean F region peak electron density (NmF2) during sudden stratosphere warmings (SSWs). The present study investigates the source of the global NmF2 decrease by performing numerical experiments with the National Center for Atmospheric Research (NCAR) thermosphere‐ionosphere‐electrodynamics general circulation model. The simulations reveal that the NmF2 reduction coincides with a depletion of thermospheric [O]/[N2], indicating that the NmF2 depletion is related to changes in thermospheric composition during SSWs. Numerical experiments further illustrate that the short‐term (∼10 day) enhancement of the migrating semidiurnal solar tide (SW2) during SSWs is the source of the variability in thermospheric composition. In particular, the enhancement of the SW2 during SSWs alters the lower thermosphere zonal mean circulation, leading to a reduction in atomic oxygen in the lower thermosphere. The atomic oxygen reduction propagates into the upper thermosphere through molecular diffusion, leading to a decrease in [O]/[N2] throughout the low‐ to middle‐latitude thermosphere. It is anticipated that the effects of the SW2 on the ionosphere and thermosphere investigated herein will be modulated by SSW related enhancements of the migrating semidiurnal lunar tide (M2). The magnitude of the combined impact of the SW2 and M2 on the ionosphere‐thermosphere mean state will depend on the relative phasing of the solar and lunar tides. The results demonstrate that in addition to modulating the low‐latitude electrodynamics, tidal variability during SSWs can significantly impact the mean state of the ionosphere and thermosphere.

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Section: Resultsmentioning

confidence: 99%

Impact of semidiurnal tidal variability during SSWs on the mean state of the ionosphere and thermosphere

et al. 2016

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“…The tides influence the equatorial and low‐latitude ionosphere primarily by modulating the E region dynamo generation of electric fields. The middle‐ and high‐latitude ionosphere variability during SSWs is thought to be related to the direct propagation of tides into the upper thermosphere [ Pedatella and Maute , ] along with possible changes in thermosphere neutral composition [ Korenkov et al , ; Shpynev et al , ]. Changes in the high‐latitude zonal mean temperature during SSWs may also alter the electric fields at midlatitudes [e.g., Pancheva and Mukhtarov , ]; however, electric field changes are thought to have a relatively minor role in the midlatitude ionosphere variability during SSWs compared to other mechanisms [ Korenkov et al , ].…”

Section: Introductionmentioning

confidence: 99%

Multimodel comparison of the ionosphere variability during the 2009 sudden stratosphere warming

et al. 2016

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A comparison of different model simulations of the ionosphere variability during the 2009 sudden stratosphere warming (SSW) is presented. The focus is on the equatorial and low‐latitude ionosphere simulated by the Ground‐to‐topside model of the Atmosphere and Ionosphere for Aeronomy (GAIA), Whole Atmosphere Model plus Global Ionosphere Plasmasphere (WAM+GIP), and Whole Atmosphere Community Climate Model eXtended version plus Thermosphere‐Ionosphere‐Mesosphere‐Electrodynamics General Circulation Model (WACCMX+TIMEGCM). The simulations are compared with observations of the equatorial vertical plasma drift in the American and Indian longitude sectors, zonal mean F region peak density (NmF2) from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites, and ground‐based Global Positioning System (GPS) total electron content (TEC) at 75°W. The model simulations all reproduce the observed morning enhancement and afternoon decrease in the vertical plasma drift, as well as the progression of the anomalies toward later local times over the course of several days. However, notable discrepancies among the simulations are seen in terms of the magnitude of the drift perturbations, and rate of the local time shift. Comparison of the electron densities further reveals that although many of the broad features of the ionosphere variability are captured by the simulations, there are significant differences among the different model simulations, as well as between the simulations and observations. Additional simulations are performed where the neutral atmospheres from four different whole atmosphere models (GAIA, HAMMONIA (Hamburg Model of the Neutral and Ionized Atmosphere), WAM, and WACCMX) provide the lower atmospheric forcing in the TIME‐GCM. These simulations demonstrate that different neutral atmospheres, in particular, differences in the solar migrating semidiurnal tide, are partly responsible for the differences in the simulated ionosphere variability in GAIA, WAM+GIP, and WACCMX+TIMEGCM.

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“…The influence of SSWs on the middle-to high-latitude ionosphere is generally small (∼20%) [Oyama et al, 2015;Pedatella and Maute, 2015], and therefore, the impact of lower atmosphere forcing on the geomagnetic storm response is considered to be less important at these latitudes. Since SSWs have their greatest influence on the low-latitude ionosphere, it is anticipated that this is where lower atmosphere forcing will have the most influence on the response to a geomagnetic disturbance.…”

Section: Resultsmentioning

confidence: 99%

Impact of the lower atmosphere on the ionosphere response to a geomagnetic superstorm

Pedatella

2016

Geophysical Research Letters

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Numerical simulations in the National Center for Atmospheric Research (NCAR) thermosphere‐ionosphere‐electrodynamics general circulation model (TIE‐GCM) are performed to elucidate the impacts of lower atmosphere forcing on the ionosphere response to a geomagnetic superstorm. In particular, how the ionosphere variability due to the October 2003 Halloween storm would be different if it occurred in January coincident with a major sudden stratosphere warming (SSW) event is investigated. The TIE‐GCM simulations reveal that the E× B vertical drift velocity and total electron content (TEC) respond differently to the geomagnetic forcing when the lower atmosphere forcing is representative of SSW conditions compared to climatological lower atmosphere forcing conditions. Notably, the storm time variations in the E× B vertical drift velocity differ when the SSW‐induced zonal mean and tidal variability in the lower thermosphere are considered, and this is in part due to effects of the SSW on the equatorial ionosphere being potentially misinterpreted as being of geomagnetic origin. Differences in the TEC response to the geomagnetic storm can be up to 100% (∼30 TEC unit (TECU: 1 TECU = 1016 el m−2)) of the storm‐induced TEC change, and the temporal variability of the TEC during the storm recovery phase is considerably different if SSW effects are considered. The results demonstrate that even during periods of extreme geomagnetic forcing, it is important to consider the effects of lower atmosphere forcing on the ionosphere variability.

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Impact of the semidiurnal lunar tide on the midlatitude thermospheric wind and ionosphere during sudden stratosphere warmings

Cited by 60 publications

References 72 publications

Impact of semidiurnal tidal variability during SSWs on the mean state of the ionosphere and thermosphere

Impact of semidiurnal tidal variability during SSWs on the mean state of the ionosphere and thermosphere

Multimodel comparison of the ionosphere variability during the 2009 sudden stratosphere warming

Impact of the lower atmosphere on the ionosphere response to a geomagnetic superstorm

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