Simultaneous observations of Polar Mesosphere Summer Echoes at two different latitudes in Antarctica

Nilsson, Hans; Kirkwood, S.; Morris, R. J.; Latteck, R.; Klekociuk, Andrew; Murphy, D. J.; Zecha, M.; Belova, Evgenia

doi:10.5194/angeo-26-3783-2008

Cited by 7 publications

(8 citation statements)

References 23 publications

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“…This seemed to be consistent with the (limited) information then available, suggesting that summer mesopause temperatures at about 70 • latitude were about the same in both hemispheres (Lübken et al, 1999). Nilsson et al (2008) compared PMSE between Wasa and Davis, Antarctica (69 • S, 78 • E), and found about half the occurrence rates at Davis compared to Wasa, which was consistent with satellite indications of temperature differences at the time of those measurements between 69 • S and 73 • S. Latteck et al (2008) , and found occurrence rates of 18 %, 83 % and 38 %, respectively, with mean and maximum reflectivities also varying in the same order. For the same time interval, and the same detection threshold, Smirnova et al (2010) found about a 75 % occurrence rate at Kiruna, which gives a consistent difference between Andenes/Kiruna/Wasa (all about the same) and Davis.…”

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confidence: 70%

Response of polar mesosphere summer echoes to geomagnetic disturbances in the Southern and Northern Hemispheres: the importance of nitric oxide

et al. 2013

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The relationship between polar mesosphere summer echoes (PMSE) and geomagnetic disturbances (represented by magnetic <I>K</I> indices) is examined. Calibrated PMSE reflectivities for the period May 2006–February 2012 are used from two 52.0/54.5 MHz radars located in Arctic Sweden (68° N, geomagnetic latitude 65°) and at two different sites in Queen Maud Land, Antarctica (73°/72° S, geomagnetic latitudes 62°/63°). In both the Northern Hemisphere (NH) and the Southern Hemisphere (SH) there is a strong increase in mean PMSE reflectivity between quiet and disturbed geomagnetic conditions. Mean volume reflectivities are slightly lower at the SH locations compared to the NH, but the position of the peak in the lognormal distribution of PMSE reflectivities is close to the same at both NH and SH locations, and varies only slightly with magnetic disturbance level. Differences between the sites, and between geomagnetic disturbance levels, are primarily due to differences in the high-reflectivity tail of the distribution. PMSE occurrence rates are essentially the same at both NH and SH locations during most of the PMSE season when a sufficiently low detection threshold is used so that the peak in the lognormal distribution is included. When the local-time dependence of the PMSE response to geomagnetic disturbance level is considered, the response in the NH is found to be immediate at most local times, but delayed by several hours in the afternoon sector and absent in the early evening. At the SH sites, at lower magnetic latitude, there is a delayed response (by several hours) at almost all local times. At the NH (auroral zone) site, the dependence on magnetic disturbance is highest during evening-to-morning hours. At the SH (sub-auroral) sites the response to magnetic disturbance is weaker but persists throughout the day. While the immediate response to magnetic activity can be qualitatively explained by changes in electron density resulting from energetic particle precipitation, the delayed response can largely be explained by changes in nitric oxide concentrations. Observations of nitric oxide concentration at PMSE heights by the Odin satellite support this hypothesis. Sensitivity to geomagnetic disturbances, including nitric oxide produced during these disturbances, can explain previously reported differences between sites in the auroral zone and those at higher or lower magnetic latitudes. The several-day lifetime of nitric oxide can also explain earlier reported discrepancies between high correlations for average conditions (year-by-year PMSE reflectivities and <I>K</I> indices) and low correlations for minute-to-day timescales

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confidence: 70%

Response of polar mesosphere summer echoes to geomagnetic disturbances in the Southern and Northern Hemispheres: the importance of nitric oxide

et al. 2013

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“…In particular, when considering effects from different contributors to PMSE variability, it is important to separate strong ionization effects due to energetic particle precipitation from others players. In particular, PMSE and NLC have different daily variations: the former are observed to be strongest around noon and weakest in the evening hours, whereas the latter have a maximum in the morning hours and a minimum around noon (Nilsson et al, 2008;Smirnova et al, 2010;Fiedler et al, 2005). Thus, it is likely that PMSE have a strong variation component due to a highly variable ionization constituent.…”

Section: Introductionmentioning

confidence: 99%

Wave influence on polar mesosphere summer echoes above Wasa: experimental and model studies

et al. 2012

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Abstract. Comprehensive analysis of the wave activity in the Antarctic summer mesopause is performed using polar mesospheric summer echoes (PMSE) measurements for December 2010-January 2011. The 2-day planetary wave is a statistically significant periodic oscillation in the power spectrum density of PMSE power. The strongest periodic oscillation in the power spectrum belongs to the diurnal solar tide; the semi-diurnal solar tide is found to be a highly significant harmonic oscillation as well. The inertial-gravity waves are extensively studied by means of PMSE power and wind components. The strongest gravity waves are observed at periods of about 1, 1.4, 2.5 and 4 h, with characteristic horizontal wavelengths of 28, 36, 157 and 252 km, respectively. The gravity waves propagate approximately in the west-east direction over Wasa (Antarctica). A detailed comparison between theoretical and experimental volume reflectivity of PMSE, measured at Wasa, is made. It is demonstrated that a new expression for PMSE reflectivity derived by Varney et al. (2011) is able to adequately describe PMSE profiles both in the magnitude and in height variations. The best agreement, within 30 %, is achieved when mean values of neutral atmospheric parameters are utilized. The largest contribution to the formation and variability of the PMSE layer is explained by the ice number density and its height gradient, followed by waveinduced perturbations in buoyancy period and the turbulent energy dissipation rate.

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“…PMSE have a distinctly different daily variation from noctilucent clouds, being strongest around noon and weakest in the evening, in both hemispheres (e.g. Nilsson et al, 2008;Smirnova et al, 2010). If PMSE are caused by the same (or similar, but smaller) ice particles as noctilucent clouds we might expect a better correlation.…”

Section: Introductionmentioning

confidence: 99%

“…In this case, for averages over the whole season, during any particular hour of LT, median volume reflectivities are lower than means by about a factor 20. Previous estimates of the daily variation of PMSE reflectivity at Wasa/Aboa published in Nilsson et al (2008) are mean values, and are therofore much higher in numerical value. The diurnal variation in the present data, which represents 2 months of observations during the main PMSE season, is also slightly different from that found in Nilsson et al (2008), which represented only 16 days of observations, at the end of the previous season.…”

Section: Diurnal Variation Ice Mass Density Derived From Pmsementioning

confidence: 99%

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Quantitative relation between PMSE and ice mass density

et al. 2010

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Abstract. Radar reflectivities associated with Polar Mesosphere Summer Echoes (PMSE) are compared with measurements of ice mass density in the mesopause region. The 54.5 MHz radar Moveable Atmospheric Radar for Antarctica (MARA), located at the Wasa/Aboa station in Antarctica (73 • S, 13 • W) provided PMSE measurements in December 2007 and January 2008. Ice mass density was measured by the Solar Occultation for Ice Experiment (SOFIE). The radar operated continuously during this period but only measurements close to local midnight are used for comparison, to coincide with the local time of the measurements of ice mass density. The radar location is at high geographic latitude but low geomagnetic latitude (61 • ) and the measurements were made during a period of very low solar activity. As a result, background electron densities can be modelled based on solar illumination alone. We find a close correlation between the time and height variations of radar reflectivity and ice mass density, at all PMSE heights, from 80 km up to 95 km. A quantitative expression relating radar reflectivities to ice mass density is found, including an empirical dependence on background electron density. Using this relation, we can use PMSE reflectivities as a proxy for ice mass density, and estimate the daily variation of ice mass density from the daily variation of PMSE reflectivities. According to this proxy, ice mass density is maximum around 05:00-07:00 LT, with lower values around local noon, in the afternoon and in the evening. This is consistent with the small number of previously published measurements and model predictions of the daily variation of noctilucent (mesospheric) clouds and in contrast to the daily variation of PMSE, which has a broad daytime maximum, extending from 05:00 LT to 15:00 LT, and an evening-midnight minimum.

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Simultaneous observations of Polar Mesosphere Summer Echoes at two different latitudes in Antarctica

Cited by 7 publications

References 23 publications

Response of polar mesosphere summer echoes to geomagnetic disturbances in the Southern and Northern Hemispheres: the importance of nitric oxide

Response of polar mesosphere summer echoes to geomagnetic disturbances in the Southern and Northern Hemispheres: the importance of nitric oxide

Wave influence on polar mesosphere summer echoes above Wasa: experimental and model studies

Quantitative relation between PMSE and ice mass density

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