A dominant acoustic-gravity mode in the polar thermosphere

Fedorenko, A.K.; Bespalova, Alla; Cheremnykh, O. K.; Kryuchkov, E. I.

doi:10.5194/angeo-33-101-2015

Cited by 35 publications

(11 citation statements)

References 24 publications

(33 reference statements)

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“…It is generally thought that auroral generated AGWs/TIDs propagate away from the disturbance source latitudes, moving equatorward into lower latitudes and poleward into higher latitudes. In the polar region, there have indeed been reports of trans–polar cap propagation of TIDs/AGWs from the nightside into the dayside (Balthazor & Moffett, ; Cai et al, ; Fedorenko et al, ; Johnson et al, ). In this study, however, we demonstrate an event characterized by predominant trans‐polar propagation from the dayside into the nightside, opposite to the expected propagation direction for a disturbance source located in the nightside aurora.…”

Section: Introductionmentioning

confidence: 99%

“…In the polar region, there have indeed been reports of trans-polar cap propagation of TIDs/AGWs from the nightside into the dayside (Balthazor & Moffett, 1999;Cai et al, 2011;Fedorenko et al, 2015;Johnson et al, 1995). It is generally thought that auroral generated AGWs/TIDs propagate away from the disturbance source latitudes, moving equatorward into lower latitudes and poleward into higher latitudes.…”

Section: Introductionmentioning

confidence: 99%

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Subauroral and Polar Traveling Ionospheric Disturbances During the 7–9 September 2017 Storms

et al. 2019

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This study provides new scenarios for storm time traveling ionospheric disturbance excitation and subsequent propagation at subauroral and polar latitudes. We used ground-based total electron content observations from Global Navigation Satellite System receivers combined with wide field, subauroral ionospheric plasma parameters measured with the Millstone Hill Incoherent Scatter Radar during strong September 2017 geospace storms. Observations provide the first evidence of significant influences on traveling ionospheric disturbance (TID) propagation and excitation caused by the presence of large subauroral polarization stream flow channels. Simultaneous large-and medium-scale TIDs evolved during the event in a broad subauroral and midlatitude area near dusk. Similar concurrent TIDs occurred near dawn sectors as well during a period of sustained southward Bz. Medium-scale TIDs at subauroral and midlatitudes had wave fronts aligned northwest-southeast near dusk, and northeast-southwest near dawn. These wave fronts were highly correlated with the direction of storm time large zonal plasma drift enhancements at these latitudes. At high latitudes, unexpected, predominant, and persistent storm time TIDs were identified with 2000+ km zonal wave fronts and 15% total electron content perturbation amplitudes, moving in transpolar propagation pathways from the dayside into the nightside. This propagation direction in the polar region was opposite to the normal assumption that TIDs originated in the nightside auroral region. Results suggest that significant dayside sources, such as cusp regions, can be efficient in generating transpolar TIDs during geospace storm intervals.Plain Language Summary This paper reports several new findings on the traveling ionospheric disturbances (TIDs) excited during geospace storms in 7-8 September 2017. Storm time TIDs provide pathway for momentum and energy dispersion from the solar wind-magnetosphere system to various components of the global ionosphere and thermosphere. Storm time large-scale TIDs (LSTIDs) have been identified by many studies as being initiated generally in the auroral zone where significant heating is injected, with subsequent propagation away from the source: equatorward into lower latitudes and poleward into high latitudes. Our study indicates that, during equatorward propagation, LSTIDs can encounter strong dynamic forcing at subauroral latitudes in the zonal direction. This westward velocity forcing is provided by a SAPS (subauroral polarization stream) channel and furthermore appears to be associated with the developing of medium-scale TIDs (MSTIDs). Thus, this paper provides the first causal link between these TIDs and SAPS flow channels. Concurrent LSTIDs and MSTIDs existed during the September storm in not only near dusk but also dawn sectors. In the polar cap region, conventionally anticipated poleward propagation away from the auroral zone was unexpectedly weak. In contrast, an opposite sense of transpolar propagation from the dayside into the nightside (i.e., eq...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Subauroral and Polar Traveling Ionospheric Disturbances During the 7–9 September 2017 Storms

et al. 2019

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“…Likewise, some previous papers addressed fluctuations of thermospheric quantities at F region altitudes using in situ neutral component observations but showed no decisive evidence of accompanying fluctuations in F region plasma density [e.g., Johnson et al , ; Forbes et al , ; Liu et al , ; Fedorenko , ; Fedorenko and Kryuchkov , ; Park et al , ; Fedorenko et al , ]. A comparison between F region ionospheric fluctuations and E region atmospheric gravity waves (AGWs) at high latitudes has been conducted by Nygrén et al [].…”

Section: Introductionmentioning

confidence: 99%

Plasma density undulations correlated with thermospheric neutral mass density in the daytime low‐latitude to midlatitude topside ionosphere

et al. 2015

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Plasma density undulations in the dayside low‐latitude/midlatitude ionospheric F region were often attributed to thermospheric gravity waves (TGWs). However, the relationship between the former and the latter has been at best indirectly evidenced. In this study we investigate daytime fluctuations in neutral mass density (ρ) and plasma density (ne) measured onboard CHAMP from 2001 to 2010. A significant amount of daytime fluctuations in ne is strongly correlated with in situ fluctuations of ρ, which we term “TGW‐related ne fluctuations.” The TGW‐related ne fluctuations are (1) stronger in the winter hemisphere than in the summer hemisphere and (2) strongest in the South American sector during June solstice months. These climatological features are in general agreement with those of TGWs reported previously, especially at midlatitudes. On the other hand, the relative amplitude of TGW‐related ne fluctuations does not depend strongly on solar activity.

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“…Satellite observations of AGWs in the Earth's polar thermosphere indicate a prevailing presence of waves with oscillation periods concentrated around the Brunt-Väisälä period and of horizontal scale of about 500 -700 km (Johnson et al, 1995;Innis and Conde, 2002;Fedorenko et al, 2015). Azimuths of the propagation of these AGW demonstrate the close connection with the directions of background winds in the thermosphere.…”

Section: Introductionmentioning

confidence: 88%

Evanescent acoustic-gravity modes in the isothermal atmosphere: systematization, applications to the earth's and solar atmospheres

Cheremnykh¹,

Fedorenko²,

Kryuchkov³

et al. 2019

Preprint

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Abstract. The objects of research in this work are evanescent wave modes in a gravitationally stratified atmosphere and their associated pseudo-modes. Whereas the former, according to the dispersion relation, rapidly decrease with distance from a certain surface, the latter, having the same dispersion law, differ from the first by the form of polarization and the character of its decreasing away from the surface. Within a linear hydrodynamic model, the propagation features of evanescent wave modes in an isothermal atmosphere are studied. Research carried out for different assumptions about the properties of the medium. On this way, a new wave mode – anelastic evanescent wave mode – was discovered. Also, the possibility of the existence of a pseudo-mode related to it is indicated. The case of two isothermal media differing in temperature at the interface is studied in detail. It is shown that a non-divergent pseudo-mode with the dispersion of solar f-mode type can be realized on the interface for the specified horizontal scale. The newly discovered dispersion relation, at the interface of two media, is satisfied by the wave mode, which has different types of amplitude versus height dependencies at different horizontal scales. The applicability of the obtained results to clarify the properties of f-mode observed on the Sun is analyzed.

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A dominant acoustic-gravity mode in the polar thermosphere

Cited by 35 publications

References 24 publications

Subauroral and Polar Traveling Ionospheric Disturbances During the 7–9 September 2017 Storms

Subauroral and Polar Traveling Ionospheric Disturbances During the 7–9 September 2017 Storms

Plasma density undulations correlated with thermospheric neutral mass density in the daytime low‐latitude to midlatitude topside ionosphere

Evanescent acoustic-gravity modes in the isothermal atmosphere: systematization, applications to the earth's and solar atmospheres

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