Generation of atmospheric gravity waves associated with auroral activity in the polar <i>F</i> region

Oyama, S.; Ishii, Mamoru; Murayama, Yasuhiro; Shinagawa, Hiroyuki; Buchert, S. C.; Fujii, Ryoichi; Kofman, W.

doi:10.1029/2001ja900032

Cited by 23 publications

(24 citation statements)

References 31 publications

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“…Our observations suggest that large vertical winds may occur at intervals of high-temporal variation in Joule heating. This was not explored in the modelling study of Oyama et al (2001). Our experiment appears to provide the first evidence that meso-scale variability must be taken into account when calculating Joule heating.…”

Section: The Tristatic Experimentsmentioning

confidence: 98%

“…As stated previously, Shinagawa et al (2003) carried out a modelling study of vertical winds generated by a moving auroral arc based on an EISCAT experiment by Oyama et al (2001). The study produced maximum vertical winds of 20 m/s, which were considerably less than the observations, and the authors acknowledge the need for a larger energy flux.…”

Section: The Tristatic Experimentsmentioning

confidence: 99%

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First direct evidence of meso-scale variability on ion-neutral dynamics using co-located tristatic FPIs and EISCAT radar in Northern Scandinavia

et al. 2005

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Abstract. This paper presents the first direct empirical evidence that mesoscale variations in ion velocities must be taken into consideration when calculating Joule heating and relating it to changes in ion temperatures and momentum transfer to the neutral gas. The data come from the first tristatic Fabry-Perot Interferometer (FPI) measurements of the neutral atmosphere co-located with tristatic measurements of the ionosphere made by the European Incoherent Scatter (EISCAT) radar which were carried out during the nights of 27-28 February 2003 and 28 February until 1 March 2003. Tristatic measurements mean that there are no assumptions of uniform wind fields and ion drifts, nor zero vertical winds. The independent, tristatic, thermospheric measurements presented here should provide unambiguous vector wind information, and hence reduce the need to supplement observations with information obtained from models of the neutral atmosphere, or with estimates of neutral parameters derived from ionospheric measurements. These new data can also test the assumptions used in models and in ion-neutral interactions. The FPIs are located close to the 3 radars of the EISCAT configuration in northern Scandinavia, which is a region well covered by a network of complementary instruments. These provide a larger scale context within which to interpret our observations of mesoscale variations on the scales of tens of kilometres spatially and minutes temporally. Initial studies indicate that the thermosphere is more dynamic and responsive to ionospheric forcing than expected. Calculations using the tristatic volume measurements show that the magnitude of the neutral wind dynamoCorrespondence to: A. L. Aruliah (a.aruliah@ucl.ac.uk) contribution was on average 29% of Joule heating during the first night of observation. At times it either enhanced or reduced the effective electric field by up to several tens of percent. The tristatic experiment also presents the first validation of absolute temperature measurements from a common volume observed by independently calibrated FPIs. Comparison of EISCAT ion temperatures at an altitude of 240 km with FPI neutral temperatures show that T i was around 200 K below T n for nearly 3 h on the first night during a period of strong geomagnetic activity. This is inconsistent with energy transfer. Comparison with FPI temperatures from surrounding regions indicate that it could not be accounted for by height variations. Indeed, these first results seem to indicate that the 630-nm emission did not stray too far from 240 km. There were also apparent drops in T e at the same time as the anomalous T i values which are energetically implausible. Incorrect assumptions of composition or nonMaxwellian spectra are likely to be the problem.

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Section: The Tristatic Experimentsmentioning

confidence: 98%

Section: The Tristatic Experimentsmentioning

confidence: 99%

First direct evidence of meso-scale variability on ion-neutral dynamics using co-located tristatic FPIs and EISCAT radar in Northern Scandinavia

et al. 2005

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“…At high latitudes, Samson et al (1990) suggested that the AGWs observed by SuperDARN originate near the ionospheric convection reversal boundary. Thus, it has been hypothesized that the IMF variations that lead to auroral electrojet fluctuations generate AGWs/TIDs, but the actual identification of the distant sources of the observed TIDs has posed difficulties in spite of the use of various observation techniques (Lewis et al, 1996;MacDougall et al, 1997;Hall et al, 1999, Oyama et al, 2001. One of the advantages of SuperDARN for the study of gravity waves is that it allows simultaneous observations of TIDs and of their high-latitude source activity.…”

Section: Introductionmentioning

confidence: 99%

“…Both the auroral activity (e.g. Hunsucker, 1982, Lewis et al, 1996Oyama et al, 2001) and tropospheric weather disturbances (e.g. Bertin et al, 1975;Waldock and Jones, 1987;Oliver et al, 1997) can generate medium-scale AGWs, particularly for TIDs that are observed at middle latitudes.…”

Section: Introductionmentioning

confidence: 99%

Solar wind Alfvén waves: a source of pulsed ionospheric convection and atmospheric gravity waves

et al. 2005

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Abstract.A case study of medium-scale travelling ionospheric disturbances (TIDs) that are correlated with solar wind Alfvén waves is presented. The HF radar groundscatter signatures of TIDs caused by atmospheric gravity waves with periods of 20-40 min are traced to a source at high latitudes, namely pulsed ionospheric flows (PIFs) due to bursts in the convection electric field and/or the associated ionospheric current fluctuations inferred from ground magnetic field perturbations. The significance of PIFs and TIDs in the context of solar-terrestrial interaction is that Alfvénic fluctuations of the interplanetary magnetic field (IMF) observed in the solar wind plasma streaming from a coronal hole correlate with PIFs and TIDs. The link between the solar wind Alfvén waves and TIDs is corroborated by the ground magnetic field signatures of ionospheric current fluctuations that are associated with the IMF-B y oscillations and TIDs. The observed PIFs and the associated negative-topositive deflections of the ground magnetic field X component are interpreted as ionospheric signatures of magnetic reconnection pulsed by solar wind Alfvén waves at the dayside magnetopause. Although the clarity of the radar lineof-sight velocity data may have been affected by anomalous HF propagation due to intervening TIDs, the application of a pure state filtering technique to analyze the radar data time series reveals a one-to-one correspondence between PIFs, TIDs and solar wind Alfvén waves. The spectra of solar wind and ground magnetic field perturbations are similar to those of PIFs and TIDs. The ground-scatter signatures indicate TID wavelengths, phase velocities and travel times that are consistent with ray tracing, which shows a subset of possible gravity wave group paths that reach the F region from a source in the E region after the wave energy first travel downward to the upper mesosphere where the waves are reflected upward. The observed one-to-one correspondence between the convection electric field bursts and TIDs is consistent with the modeling results for large-scale TIDs by Millward et al. (1993a,b). The correlation with solar wind Alfvén wavesCorrespondence to: P. Prikryl (paul.prikryl@crc.ca) points to very direct coupling of energy in the solar wind into the subauroral atmosphere.

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“…There is strong evidence that highlatitude AGW sources are localized in or near the auroral oval (e.g. Sakanoi and Fukunishi, 1999;Oyama et al, 2001). Pervious statistical investigations also revealed that polar cap gravity waves frequently originate from sources in or near the midnight-dawn auroral oval (Innis and Conde, 2002) and that the horizontal phase progression is from the nightside to the dayside (Johnson et al, 1995).…”

Section: Properties Of the Polar Cap Agw/tidmentioning

confidence: 99%

Observations of AGW/TID propagation across the polar cap: a case study

Cai

Yin

et al. 2011

Ann. Geophys.

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Abstract. In this paper, we present observational evidence for the trans-polar propagation of large-scale Traveling Ionospheric Disturbances (TIDs) from their nightside source region to the dayside. On 13 February 2001, the 32 m dish of EISCAT Svalbard Radar (ESR) was directing toward the geomagnetic pole at low elevation (30 • ) during the interval 06:00-12:00 UT (MLT ≈ UT + 3 h), providing an excellent opportunity to monitor the ionosphere F-region over the polar cap. The TIDs were first detected by the ESR over the dayside north polar cap, propagating equatorward, and were subsequently seen by the mainland UHF radar at auroral latitudes around geomagnetic local noon. The propagation properties of the observed ionization waves suggest the presence of a moderately large-scale TIDs, propagating across the northern polar cap from the night-time auroral source during substorm conditions. Our results agree with the theoretical simulations by Balthazor and Moffett (1999) in which poleward-propagating large-scale traveling atmospheric disturbances were found to be self-consistently driven by enhancements in auroral heating.

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Generation of atmospheric gravity waves associated with auroral activity in the polar F region

Cited by 23 publications

References 31 publications

First direct evidence of meso-scale variability on ion-neutral dynamics using co-located tristatic FPIs and EISCAT radar in Northern Scandinavia

First direct evidence of meso-scale variability on ion-neutral dynamics using co-located tristatic FPIs and EISCAT radar in Northern Scandinavia

Solar wind Alfvén waves: a source of pulsed ionospheric convection and atmospheric gravity waves

Observations of AGW/TID propagation across the polar cap: a case study

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