Response of the thermosphere and ionosphere to geomagnetic storms

Fuller‐Rowell, T. J.; Codrescu, M.; Moffett, R. J.; Quegan, S.

doi:10.1029/93ja02015

Cited by 800 publications

(876 citation statements)

References 38 publications

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“…However, this is contrary to the predictions obtained in some recent storm modelling studies using major thermospheric general circulation models (Rishbeth et al, 1987;Crowley et al, 1989;Fuller-Rowell et al, 1991, 1994. This con¯icting result is also discussed by Burns et al.…”

Section: Thermospheric Compositioncontrasting

confidence: 64%

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Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

Namgaladze

Förster²,

Yurik³

2000

Ann. Geophys.

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Abstract. Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere±iono-sphere±plasmasphere±magnetosphere system including electrodynamical coupling e ects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exempli®es the complex storm phenomena. The study focuses on positive ionospheric storm e ects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical e ects of both neutral meridional winds and electric ®elds caused by the disturbance dynamo e ect. The penetration of short-time electric ®elds of magnetospheric origin during storm intensi®cation phases is shown for the ®rst time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N 2 ] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at ®xed altitudes) above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F 2 -region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic ®eld lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs). The calculated zonal electric ®eld disturbances also help to create the positive ionospheric disturbances both at middle and low latitudes. Minor contributions arise from the general density enhancement of all constituents during geomagnetic storms, which favours ion production processes above ion losses at ®xed height under daylight conditions.

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Section: Thermospheric Compositioncontrasting

confidence: 64%

“…More recent work of Fuller-Rowell et al (1994) and Burns et al (1995a, b) provoked the present investigations. Their results led them to conclude that there is a signi®cant enhancement of the [O]/[N 2 ] ratio in the evening sector of the mid-latitude winter hemisphere, providing an essential contribution to the positive storm e ect there.…”

Section: Introductionmentioning

confidence: 69%

Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

Namgaladze

Förster²,

Yurik³

2000

Ann. Geophys.

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“…The negative storm effects occurred often during the main and recovery phases of storms (Abdu, 1997;Cander and Mihajlovic, 2005). Negative storm effects at high and middle latitudes are caused primarily by neutral composition changes due to the upwelling of molecular-rich air to higher altitudes driven by storm-time enhanced Joule heating (Mayr, Harris, and Spencer, 1978;Burns et al, 1995;Fuller-Rowell et al, 1994). The negative storm effects around the geomagnetic Equator are more closely related to changes in transportation caused by penetration electric fields (Lei et al, 2008c;Wang et al, 2010), as well as changes in neutral composition at later times during strong storms (Prölss, 1995;Buonsanto, 1999).…”

Section: Discussionmentioning

confidence: 99%

Ionospheric Day-to-Day Variability Around the Whole Heliosphere Interval in 2008

et al. 2011

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Ionospheric F2 peak electron densities (NmF2) measured at ten ionosonde stations have been analyzed to investigate ionospheric day-to-day variability around the Whole Heliosphere Interval (WHI) in 2008 (Day of Year (DOY) 50 -140). The ionosonde data showed that there was significant global day-to-day variability in NmF2. This variability had 5-, 7-, 9-, 11-, 13.5-, and 16 -21-day periodicities. At middle latitudes, the ionosphere appeared to respond directly to the solar-wind and interplanetary-magnetic-field (IMF) induced geomagnetic-activity forcing, with the day-to-day variability having the same periods as those in the solar-wind/IMF and geomagnetic activity. At the geomagnetic Equator, the ionosphere had a strong 7-day periodicity, corresponding to the same periodicity in the IMF B z component. In the equatorial anomaly region, the ionosphere showed more complicated day-to-day variability, dominated by the 9-day periodicity. In addition, there were also peri- odicities of 11 days and 16 -21 days in the ionosonde data at some stations. The ionosonde data were compared with the Coupled Magnetosphere Ionosphere Thermosphere (CMIT) simulations that were driven by the observed solar-wind and IMF data during the WHI. The CMIT simulations showed similar ionospheric daily variability seen in the data. They captured the positive and negative responses of the ionosphere at middle latitudes during the first corotating interaction region (CIR) event in the WHI. The response of the model to the second CIR event, however, was relatively weak.

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“…The equatorward divergent¯ow from high latitudes causes upwelling through the pressure surfaces and increases of mean molecular mass ProÈ lss, 1987;Burns et al, 1991). The region of increased mean molecular mass has been termed a composition``bulge,'' and it has been recently shown that the bulge can be transported by the background and storm-time wind ®elds (Fuller-Rowell et al, 1994.…”

Section: Introductionmentioning

confidence: 99%

“…It should be noted that individual storms show large deviations from the average behavior. The dependence of the storm-time ionosphere to both local time and season can be explained as a response to neutral composition changes and their movement by the global wind ®eld (Fuller-Rowell et al, 1994.…”

Section: Introductionmentioning

confidence: 99%

Quantitative modeling of the ionospheric response to geomagnetic activity

Fuller‐Rowell

Codrescu

Wilkinson³

2000

Ann. Geophys.

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Abstract. A physical model of the coupled thermosphere and ionosphere has been used to determine the accuracy of model predictions of the ionospheric response to geomagnetic activity, and assess our understanding of the physical processes. The physical model is driven by empirical descriptions of the high-latitude electric ®eld and auroral precipitation, as measures of the strength of the magnetospheric sources of energy and momentum to the upper atmosphere. Both sources are keyed to the time-dependent TIROS/NOAA auroral power index. The output of the model is the departure of the ionospheric F region from the normal climatological mean. A 50-day interval towards the end of 1997 has been simulated with the model for two cases. The ®rst simulation uses only the electric ®elds and auroral forcing from the empirical models, and the second has an additional source of random electric ®eld variability. In both cases, output from the physical model is compared with F-region data from ionosonde stations. Quantitative model/data comparisons have been performed to move beyond the conventional``visual'' scienti®c assessment, in order to determine the value of the predictions for operational use. For this study, the ionosphere at two ionosonde stations has been studied in depth, one each from the northern and southern midlatitudes. The model clearly captures the seasonal dependence in the ionospheric response to geomagnetic activity at mid-latitude, reproducing the tendency for decreased ion density in the summer hemisphere and increased densities in winter. In contrast to the``visual'' success of the model, the detailed quantitative comparisons, which are necessary for space weather applications, are less impressive. The accuracy, or value, of the model has been quanti®ed by evaluating the daily standard deviation, the root-mean-square error, and the correlation coecient between the data and model predictions. The modeled quiet-time variability, or standard deviation, and the increases during geomagnetic activity, agree well with the data in winter, but is low in summer. The RMS error of the physical model is about the same as the IRI empirical model during quiet times. During the storm events the RMS error of the model improves on IRI, but there are occasionally falsealarms. Using unsmoothed data over the full interval, the correlation coecients between the model and data are low, between 0.3 and 0.4. Isolating the storm intervals increases the correlation to between 0.43 and 0.56, and by smoothing the data the values increases up to 0.65. The study illustrates the substantial dierence between scienti®c success and a demonstration of value for space weather applications.

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Response of the thermosphere and ionosphere to geomagnetic storms

Cited by 800 publications

References 38 publications

Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

Ionospheric Day-to-Day Variability Around the Whole Heliosphere Interval in 2008

Quantitative modeling of the ionospheric response to geomagnetic activity

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