NNSS satellite observations of medium-scale traveling ionospheric disturbances at southern high-latitudes.

Ogawa, T.; Igarashi, K.; Aikyo, K.; Maeno, Hideo

doi:10.5636/jgg.39.709

Cited by 51 publications

(63 citation statements)

References 14 publications

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“…Although the numbers of active nights are low so the results are inconclusive, it appears that changes in solar output has little effect on the gravity waves produced. This would be in agreement with, for example, Ogawa et al (1987), who proposed that gravity waves are relatively easily formed in the thermosphere and large amounts of precipitation or energy input are not required to produce the gravity waves. This was, however, from ionospheric data from a range of lower thermospheric altitudes, so may not be applicable to the FPI data.…”

Section: Solar Cycle Variationssupporting

confidence: 79%

“…The only year with more than two active nights available was the 2000-2001 season, which was at solar maximum. Figure 8 shows, particularly with the intensities, that the moderate and active nights have a similar distribution of periods to that of the quiet nights, with a peak between approximately 1 and 4 h. This is in agreement with the individual seasons' histograms and for example results from Ogawa et al (1987) to indicate that the distribution of gravity wave periods is independent of geomagnetic activity. As the Sodankylä FPI was not installed until 2002, past the solar maximum, and there were roughly half the total number of nights available compared to KEOPS, there were only two active nights for the total of the Sodankylä data, shown in Fig.…”

Section: Geomagnetic Activity Dependencessupporting

confidence: 76%

“…However, summer/winter effects can not be detectable with optical data as is used here. Ogawa et al (1987) also found that the majority of the waves propagate equatorward, and that the number of waves detected did not increase with geomagnetic activity.…”

Section: Data and Analysismentioning

confidence: 87%

“…This effect, however, was observed at lower altitudes where the source of the gravity waves was likely to be tropospheric. Ogawa et al (1987) also found that there was a maximum in gravity wave activity in winter and a minimum in summer in medium scale TIDs from satellite data. However, summer/winter effects can not be detectable with optical data as is used here.…”

Section: Data and Analysismentioning

confidence: 91%

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Statistical analysis of thermospheric gravity waves from Fabry-Perot Interferometer measurements of atomic oxygen

et al. 2008

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Abstract. Data from the Fabry-Perot Interferometers at KEOPS (Sweden), Sodankylä (Finland), and Svalbard (Norway), have been analysed for gravity wave activity on all the clear nights from 2000 to 2006. A total of 249 nights were available from KEOPS, 133 from Sodankylä and 185 from the Svalbard FPI. A Lomb-Scargle analysis was performed on each of these nights to identify the periods of any wave activity during the night. Comparisons between many nights of data allow the general characteristics of the waves that are present in the high latitude upper thermosphere to be determined. Comparisons were made between the different parameters: the atomic oxygen intensities, the thermospheric winds and temperatures, and for each parameter the distribution of frequencies of the waves was determined. No dependence on the number of waves on geomagnetic activity levels, or position in the solar cycle, was found. All the FPIs have had different detectors at various times, producing different time resolutions of the data, so comparisons between the different years, and between data from different sites, showed how the time resolution determines which waves are observed. In addition to the cutoff due to the Nyquist frequency, poor resolution observations significantly reduce the number of short-period waves (<1 h period) that may be detected with confidence. The length of the dataset, which is usually determined by the length of the night, was the main factor influencing the number of long period waves (>5 h) detected. Comparisons between the number of gravity waves detected at KEOPS and Sodankylä over all the seasons showed a similar proportion of waves to the number of nights used for both sites, as expected since the two sites are at similar latitudes and therefore locations with respect to the auroral oval, confirming this as a likely source region. Svalbard showed fewer waves with short periods than KEOPS data for a season when both had the same time resolution data. This Correspondence to: E. A. K. Ford (eakf@bas.ac.uk) gives a clear indication of the direction of flow of the gravity waves, and corroborates that the source is the auroral oval. This is because the energy is dissipated through heating in each cycle of a wave, therefore, over a given distance, short period waves lose more energy than long and dissipate before they reach their target.

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Section: Solar Cycle Variationssupporting

confidence: 79%

Section: Geomagnetic Activity Dependencessupporting

confidence: 76%

Section: Data and Analysismentioning

confidence: 87%

Section: Data and Analysismentioning

confidence: 91%

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Statistical analysis of thermospheric gravity waves from Fabry-Perot Interferometer measurements of atomic oxygen

et al. 2008

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“…Medium-scale traveling ionospheric disturbances (MSTIDs) are quasiperiodic density perturbations of the F region ionosphere with periods between 15 and 60 min, wavelengths of several hundred kilometers, and velocities between 100 and 250 m s −1 [e.g., Ogawa et al, 1987]. MSTIDs have been demonstrated to be associated with both electrodynamic processes and atmospheric gravity waves (AGWs).…”

Section: Introductionmentioning

confidence: 99%

Climatology of medium‐scale traveling ionospheric disturbances observed by the midlatitude Blackstone SuperDARN radar

et al. 2014

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Horizontal velocities ranged from 50 to 250 m s −1 with a distribution maximum between 100 and 150 m s −1 . Horizontal wavelengths ranged from 100 to 500 km with a distribution peak at 250 km, and periods between 23 and 60 min, suggesting that the MSTIDs may be consistent with thermospheric gravity waves. A local time (LT) dependence was observed such that the dominant (southeastward) population decreased in number as the day progressed until a late afternoon increase. The secondary (northwestward) population appeared only in the afternoon, possibly indicative of neutral wind effects or variability of sources. LT dependence was not observed in other parameters. Possible solar-geomagnetic and tropospheric MSTID sources were considered. The auroral electrojet (AE) index showed a correlation with MSTID statistics. Reverse ray tracing with the HINDGRATS model indicates that the dominant population has source regions over the Great Lakes and near the geomagnetic cusp, while the secondary population source region is 100 km above the Atlantic Ocean east of the Carolinas. This suggests that the dominant population may come from a region favorable to either tropospheric or geomagnetic sources, while the secondary population originates from a region favorable to secondary waves generated via lower atmospheric convection.

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Sources and characteristics of medium‐scale traveling ionospheric disturbances observed by high‐frequency radars in the North American sector

et al. 2016

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Medium‐scale traveling ionospheric disturbances (MSTIDs) are wave‐like ionospheric perturbations routinely observed by high‐frequency radars. We focus on a class of MSTIDs observed during the winter daytime at high latitudes and midlatitudes. The source of these MSTIDs remains uncertain, with the two primary candidates being space weather and lower atmospheric processes. We surveyed observations from four high‐latitude and six midlatitude Super Dual Auroral Radar Network radars in the North American sector from November to May 2012 to 2015. The MSTIDs observed have horizontal wavelengths between ∼150 and 650 km and horizontal velocities between ∼75 and 325 m s−1. In local fall and winter seasons the majority of MSTIDs propagated equatorward, with bearings ranging from ∼125° to 225° geographic azimuth. No clear correlation with space weather activity as parameterized by AE and SYM‐H could be identified. Rather, MSTID observations were found to have a strong correlation with polar vortex dynamics on two timescales. First, a seasonal timescale follows the annual development and decay of the polar vortex. Second, a shorter 2–4 week timescale again corresponds to synoptic polar vortex variability, including stratospheric warmings. Additionally, statistical analysis shows that MSTIDs are more likely during periods of strong polar vortex. Direct comparison of the MSTID observations with stratospheric zonal winds suggests that a wind filtering mechanism may be responsible for the strong correlation. Collectively, these observations suggest that polar atmospheric processes, rather than space weather activity, are primarily responsible for controlling the occurrence of high‐latitude and midlatitude winter daytime MSTIDs.

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NNSS satellite observations of medium-scale traveling ionospheric disturbances at southern high-latitudes.

Cited by 51 publications

References 14 publications

Statistical analysis of thermospheric gravity waves from Fabry-Perot Interferometer measurements of atomic oxygen

Statistical analysis of thermospheric gravity waves from Fabry-Perot Interferometer measurements of atomic oxygen

Climatology of medium‐scale traveling ionospheric disturbances observed by the midlatitude Blackstone SuperDARN radar

Sources and characteristics of medium‐scale traveling ionospheric disturbances observed by high‐frequency radars in the North American sector

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