Ionospheric signatures of acoustic waves generated by transient tropospheric forcing

Zettergren, M. D.; Snively, J. B.

doi:10.1002/2013gl058018

Cited by 43 publications

(64 citation statements)

References 23 publications

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“…The order of the amplitude of the typical magnetic fluctuations, main magnetic field, and the latitudinal spatial scale estimated from the CHAMP observation are 1 nT, 10,000 nT, and 100 km, respectively. Then, the order of density at the CHAMP altitude is 0.01 μ Am −2 , which is consistent with that predicted by Zettergren and Snively (2013).…”

Section: Resultssupporting

confidence: 89%

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Global and frequent appearance of small spatial scale field-aligned currents possibly driven by the lower atmospheric phenomena as observed by the CHAMP satellite in middle and low latitudes

et al. 2014

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Using magnetic field data obtained by the Challenging Minisatellite Payload (CHAMP), we show global and frequent appearance of small-amplitude (1 to 5 nT on the dayside) magnetic fluctuations with period around a few tens of seconds along the satellite orbit in middle and low latitudes. They are different from known phenomena, such as the Pc3 pulsations. The following characteristics are presented and discussed in this paper: (1) The magnetic fluctuations are perpendicular to the geomagnetic main field, and the amplitude of the zonal (east-west) component is larger than that of the meridional component in general. (2) As latitude becomes lower around the dip equator, the period tends to become longer. (3) The amplitudes have clear local time dependence, which is highly correlated to the ionospheric conductivities in local time (LT) 06-18. (4) The amplitude of the fluctuations shows magnetic conjugacy to a certain extent. (5) The amplitude shows no dependence on solar wind parameters nor geomagnetic activity. (6) A seasonal dependence is seen clearly. The amplitudes in the northern summer and winter are larger than those in the equinoxes. In the northern summer, the amplitudes above the Eurasian and South American continents and their conjugate areas are larger. In the northern winter, those above the eastern Pacific Ocean are larger. We suggest that the above characteristics, (1) to (6), can be attributed to the small spatial scale field-aligned currents having a lower atmospheric origin through the ionospheric dynamo process.

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Section: Resultssupporting

confidence: 89%

“…With the possibility of a tropospheric origin shown by computer simulation (Zettergren and Snively 2013), the field-aligned currents are caused by the propagation of acoustic gravity waves generated by tropospheric sources through the E-layer dynamo. The period of the acoustic wave is around 3.5 min, i.e., near the vertical resonance period.…”

Section: Resultsmentioning

confidence: 99%

Global and frequent appearance of small spatial scale field-aligned currents possibly driven by the lower atmospheric phenomena as observed by the CHAMP satellite in middle and low latitudes

et al. 2014

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“…It has been proposed that this feature of the TEC perturbations is related to the local magnetic field geometry [Heki and Ping, 2005;Shinagawa et al, 2007]. Recent detailed simulations by Zettergren and Snively [2013] have confirmed that the geomagnetic field does induce significant anisotropy in TEC perturbations produced by a weather-related source of low-frequency acoustic waves which agree remarkably well with signatures reported by Nishioka et al [2013].…”

Section: Introductionsupporting

confidence: 66%

Ionospheric response to infrasonic‐acoustic waves generated by natural hazard events

2015

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Recent measurements of GPS‐derived total electron content (TEC) reveal acoustic wave periods of ∼1–4 min in the F region ionosphere following natural hazard events, such as earthquakes, severe weather, and volcanoes. Here we simulate the ionospheric responses to infrasonic‐acoustic waves, generated by vertical accelerations at the Earth's surface or within the lower atmosphere, using a compressible atmospheric dynamics model to perturb a multifluid ionospheric model. Response dependencies on wave source geometry and spectrum are investigated at middle, low, and equatorial latitudes. Results suggest constraints on wave amplitudes that are consistent with observations and that provide insight on the geographical variability of TEC signatures and their dependence on the geometry of wave velocity field perturbations relative to the ambient geomagnetic field. Asymmetries of responses poleward and equatorward from the wave sources indicate that electron perturbations are enhanced on the equatorward side while field aligned currents are driven principally on the poleward side, due to alignments of acoustic wave velocities parallel and perpendicular to field lines, respectively. Acoustic‐wave‐driven TEC perturbations are shown to have periods of ∼3–4 min, which are consistent with the fraction of the spectrum that remains following strong dissipation throughout the thermosphere. Furthermore, thermospheric acoustic waves couple with ion sound waves throughout the F region and topside ionosphere, driving plasma disturbances with similar periods and faster phase speeds. The associated magnetic perturbations of the simulated waves are calculated to be observable and may provide new observational insight in addition to that provided by GPS TEC measurements.

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“…After great earthquakes, short-period magnetic and atmospheric pressure oscillations (e.g., Iyemori et al 2005Iyemori et al , 2013 or TEC variations (e.g., Otsuka et al 2006;Saito et al 2011) were observed. As to the theoretical study, TEC oscillations observed after the 2011 off the Pacific coast of Tohoku Earthquake and FACs in the ionosphere generated by acoustic mode waves were well reproduced with numerical simulations by Matsumura et al (2011) and by Zettergren and Snively (2013), respectively. Zettergren and Snively (2015) performed the computer simulations showing that TEC and ground-level magnetic field perturbations and dynamo FACs can be caused by natural hazard events including volcanic eruptions.…”

Section: Introductionsupporting

confidence: 65%

Localized field-aligned currents and 4-min TEC and ground magnetic oscillations during the 2015 eruption of Chile’s Calbuco volcano

et al. 2016

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The Calbuco volcano in southern Chile erupted on April 22, 2015. About 2 h after the first eruption, a Swarm satellite passed above the volcano and observed enhancement of small-amplitude (~0.5 nT) magnetic fluctuations with wave-packet structure which extends 15° in latitude. Similar wave packet is seen at the geomagnetic conjugate point of the volcano. Just after the eruption, geomagnetic fluctuations with the spectral peaks around the vertical acoustic resonance periods, 215 and 260 s, were also observed at Huancayo Geomagnetic Observatory located on the magnetic equator. Besides these observations, around 4-min, i.e., 175, 205 and 260 s, oscillations of total electron content (TEC) were observed at global positioning system stations near the volcano. The horizontal propagation velocity and the spatial scale of the TEC oscillation are estimated to be 720 m/s and 1600 km, respectively. These observations strongly suggest that the atmospheric waves induced by explosive volcanic eruption generate TEC variation and electric currents. The Swarm observation may be explained as a manifestation of their magnetic effects observed in the topside ionosphere.

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Ionospheric signatures of acoustic waves generated by transient tropospheric forcing

Cited by 43 publications

References 23 publications

Global and frequent appearance of small spatial scale field-aligned currents possibly driven by the lower atmospheric phenomena as observed by the CHAMP satellite in middle and low latitudes

Global and frequent appearance of small spatial scale field-aligned currents possibly driven by the lower atmospheric phenomena as observed by the CHAMP satellite in middle and low latitudes

Ionospheric response to infrasonic‐acoustic waves generated by natural hazard events

Localized field-aligned currents and 4-min TEC and ground magnetic oscillations during the 2015 eruption of Chile’s Calbuco volcano

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