MF radar interferometer measurements of meteor trail motions

Abstract. The spring of 1997 has represented a stable period of operation for the joint University of Tromsø / University of Saskatchewan MF radar, being between refurbishment and upgrades. We examine the horizontal winds from the February to June inclusive and also include estimates of energy dissipation rates derived from signal fading times and presented as upper limits on the turbulent energy dissipation rate, ε. Here we address the periodicity in the dynamics of the upper mesosphere for time scales from hours to one month. Thus, we are able to examine the changes in the spectral signature of the mesospheric dynamics during the transition from winter to summer states.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides).

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Day to night variation in meteor trail measurements: Evidence for a new theory of plasma trail evolution

Geophysical Research Letters ◽

10.1029/2007gl032347 ◽

2008 ◽

Vol 35 (3) ◽

Cited By ~ 13

Author(s):

Meers M. Oppenheim ◽

Glenn Sugar ◽

Elizabeth Bass ◽

Yakov S. Dimant ◽

Jorge Chau

Keyword(s):

Meteor Trail

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NLC and the background atmosphere above ALOMAR

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-5701-2011 ◽

2011 ◽

Vol 11 (12) ◽

pp. 5701-5717 ◽

Cited By ~ 41

Author(s):

J. Fiedler ◽

G. Baumgarten ◽

U. Berger ◽

P. Hoffmann ◽

N. Kaifler ◽

...

Keyword(s):

Diurnal Cycle ◽

Middle Atmosphere ◽

Thermal State ◽

Atmospheric Tides ◽

Data Set ◽

Ice Particles ◽

Cloud Water Content ◽

Radar Measurements ◽

Mf Radar

Abstract. Noctilucent clouds (NLC) have been measured by the Rayleigh/Mie/Raman-lidar at the ALOMAR research facility in Northern Norway (69° N, 16° E). From 1997 to 2010 NLC were detected during more than 1850 h on 440 different days. Colocated MF-radar measurements and calculations with the Leibniz-Institute Middle Atmosphere (LIMA-) model are used to characterize the background atmosphere. Temperatures as well as horizontal winds at 83 km altitude show distinct differences during NLC observations compared to when NLC are absent. The seasonally averaged temperature is lower and the winds are stronger westward when NLC are detected. The wind separation is a robust feature as it shows up in measurements as well as in model results and it is consistent with the current understanding that lower temperatures support the existence of ice particles. For the whole 14-year data set there is no statistically significant relation between NLC occurrence and solar Lyman-α radiation. On the other hand NLC occurrence and temperatures at 83 km show a significant anti-correlation, which suggests that the thermal state plays a major role for the existence of ice particles and dominates the pure Lyman-α influence on water vapor during certain years. We find the seasonal mean NLC altitudes to be correlated to both Lyman-α radiation and temperature. NLC above ALOMAR are strongly influenced by atmospheric tides. The cloud water content varies by a factor of 2.8 over the diurnal cycle. Diurnal and semidiurnal amplitudes and phases show some pronounced year-to-year variations. In general, amplitudes as well as phases vary in a different manner. Amplitudes change by a factor of more than 3 and phases vary by up to 7 h. Such variability could impact long-term NLC observations which do not cover the full diurnal cycle.

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Meteor trail footprint statistics

10.1109/milcom.1990.117542 ◽

2002 ◽

Cited By ~ 4

Author(s):

S.Y. Mui ◽

R.C. Ellicott

Keyword(s):

Meteor Trail

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Probabilistic analysis of ambiguities in radar echo direction of arrival from meteors

10.5194/amt-2020-157 ◽

2020 ◽

Author(s):

Daniel Kastinen ◽

Johan Kero

Keyword(s):

Bayesian Method ◽

Direction Of Arrival ◽

Radar System ◽

Stable Region ◽

Radar Signal ◽

Ambient Atmosphere ◽

Radar Systems ◽

Mu Radar ◽

Meteor Trail ◽

The Antarctic

Abstract. Meteors and hard targets produce coherent radar echoes. If measured with an interferometric radar system, these echoes can be used to determine the position of the target through finding the Direction Of Arrival (DOA) of the incoming echo onto the radar. If the DOA of meteor trail plasma drifting with the ambient atmosphere is determined, the neutral wind at the observation altitude can be calculated. Specular meteor trail radars have become widespread scientific instruments to study atmospheric dynamics. Meteor head echo measurements also contribute to studies of the atmosphere as the meteoroid input of extraterrestrial material is relevant for a plethora of atmospheric phenomena. Depending on the spatial configuration of radar receiving antennas and their individual gain patterns, there may be an ambiguity problem when determining the DOA of an echo. Radars that are theoretically ambiguity free are known to still have ambiguities that depend on the total radar Signal to Noise Ratio (SNR). In this study we investigate robust methods which are easy to implement to determine the effect of ambiguities on any hard target DOA determination by interferometric radar systems. We apply these methods specifically to simulate four different radar systems measuring meteor head and trail echoes using the multiple signal classification (MUSIC) DOA determination algorithm. The four radar systems are the middle and upper atmosphere (MU) radar in Japan, a generic Jones 2.5λ specular meteor trail radar configuration, the Middle Atmosphere Alomar Radar System (MAARSY) radar in Norway and the The Program of the Antarctic Syowa Mesosphere Stratosphere Troposphere Incoherent Scatter (PANSY) radar in the Antarctic. We also examined a slightly perturbed Jones 2.5λ configuration used as a meteor trail echo receiver for the PANSY radar. All the results are derived from simulations and their purpose is to grant understanding of the behaviour of DOA determination. General results are: there may be a region of SNRs where ambiguities are relevant; Monte Carlo simulation determines this region and if it exists; the MUSIC function peak value is directly correlated with the ambiguous region; a Bayesian method is presented that may be able to analyse echoes from this region; the DOA of echoes with SNRs larger then this region are perfectly determined; the DOA of echoes with SNRs smaller then this region completely fail to be determined; the location of this region is shifted based on the total SNR versus the channel SNR in the direction of the target; asymmetric subgroups can cause ambiguities even for ambiguity free radars. For a DOA located at the zenith, the end of the ambiguous region is located at 17 dB SNR for the MU radar and 3 dB SNR for the PANSY radar. The Jones radars are usually used to measure specular trail echoes far from zenith. The ambiguous region for a DOA at 75.5° elevation and 0° azimuth ends at 12 dB SNR. Using the Bayesian method it may be possible to analyse echoes down to 4 dB SNR for the Jones configuration, given enough data points from the same target. The PANSY meteor trail echo receiver did not deviate significantly from the generic Jones configuration. The MAARSY radar could not resolve arbitrary DOAs sufficiently well to determine a stable region. However, if the DOA search is restricted to 70° elevation or above by assumption, stable DOA determination occurs above 15 dB SNR.

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VARIATION OF METEOR ECHO RATES WITH RADAR SYSTEM PARAMETERS

Canadian Journal of Physics ◽

10.1139/p51-044 ◽

1951 ◽

Vol 29 (5) ◽

pp. 403-426 ◽

Cited By ~ 14

Author(s):

D. W. R. McKinley

Keyword(s):

Radio Wave ◽

Wave Length ◽

Radar System ◽

Antenna Gain ◽

Scattering Pattern ◽

Magnitude Distribution ◽

System Parameters ◽

Transmitter Power ◽

Meteor Trail ◽

Strong Filter

Observations made with crossed-polarization radar system systems do not support the suggestion that the ionized meteor trail may act as a strong filter–polarizer of the incident radio wave. Experiments have been carried out to determine the variation of normal meteor echo rates with transmitter power, antenna gain, and radio wave length, and all confirm Lovell's scattering formula, provided that account is taken of the effective broadening of the scattering pattern of the meteor trail with increasing wave length. The limiting sensitivity of the 9.22 m. 200 kw. radar is determined to be about 9th magnitude. During a strong visual shower the observed increase in visual rates and low-power radar rates, compared to high-power radar rates, is explained by assuming that the magnitude distribution of the shower meteors differs from the normal nonshower distribution.

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Change in turbopause altitude at 52 and 70° N

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-2299-2016 ◽

2016 ◽

Vol 16 (4) ◽

pp. 2299-2308 ◽

Cited By ~ 7

Author(s):

Chris M. Hall ◽

Silje E. Holmen ◽

Chris E. Meek ◽

Alan H. Manson ◽

Satonori Nozawa

Keyword(s):

Time Series ◽

Atomic Oxygen ◽

Molecular Diffusion ◽

Temporal Evolution ◽

Molecular Mixing ◽

Trace Species ◽

Term Change ◽

Meteor Trail ◽

Altitude Estimation

Abstract. The turbopause is the demarcation between atmospheric mixing by turbulence (below) and molecular diffusion (above). When studying concentrations of trace species in the atmosphere, and particularly long-term change, it may be important to understand processes present, together with their temporal evolution that may be responsible for redistribution of atmospheric constituents. The general region of transition between turbulent and molecular mixing coincides with the base of the ionosphere, the lower region in which molecular oxygen is dissociated, and, at high latitude in summer, the coldest part of the whole atmosphere. This study updates previous reports of turbopause altitude, extending the time series by half a decade, and thus shedding new light on the nature of change over solar-cycle timescales. Assuming there is no trend in temperature, at 70° N there is evidence for a summer trend of ∼  1.6 km decade−1, but for winter and at 52° N there is no significant evidence for change at all. If the temperature at 90 km is estimated using meteor trail data, it is possible to estimate a cooling rate, which, if applied to the turbopause altitude estimation, fails to alter the trend significantly irrespective of season. The observed increase in turbopause height supports a hypothesis of corresponding negative trends in atomic oxygen density, [O]. This supports independent studies of atomic oxygen density, [O], using mid-latitude time series dating from 1975, which show negative trends since 2002.

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The Influence of the Atmosphere on Radar Meteor Rates

Symposium - International Astronomical Union ◽

10.1017/s0074180900066547 ◽

1980 ◽

Vol 90 ◽

pp. 101-104

Author(s):

W.G. Elford.

Keyword(s):

Initial Diameter ◽

Meteor Trail ◽

Radio Studies ◽

The Difference ◽

Sporadic Meteors ◽

Radar Meteor ◽

Sharp Cutoff ◽

Selection Of

The majority of radio studies of meteors have been carried out at frequencies higher than 17MHz and most of the rate observation at frequencies above 30MHz. At these frequencies a severe height selection of meteors occurs. In Figure 1(a) are shown the normalized height distributions of sporadic meteors observed at Adelaide on frequencies of 27MHz and 2MHz (Brown, 1976). The sharp cutoff of the latter distribution below 87 km is instrumental. The difference in the height distributions is due to the effect of the finite diameter of a meteor trail on its radar detectability. If the trail diameter is ≪ λ signals from the near and far edges reinforce but as the trail expands due to diffusion and the diameter becomes ≃ λ/4, interference reduces the amplitude. A meteor trail, produced by a particle with a velocity of 30 km s−1, has an initial diameter of 0.4m at 80 km, 2.0m at 104 km and 4.0m at 116 km.

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