Arctic and Antarctic polar mesosphere summer echoes observed with oblique incidence HF radars: analysis using simultaneous MF and VHF radar data

Abstract. Polar mesosphere summer echoes (PMSEs) have been well studied using vertical incidence VHF radars at northern high-latitudes. In this paper, two PMSE events detected with the oblique incidence SuperDARN HF radars at Hankasalmi, Finland (62.3° N) and Syowa Station, Antarctica (69.0° S), are analyzed, together with simultaneous VHF and medium-frequency (MF) radar data. Altitude resolutions of the HF radars in the mesosphere and the lower thermosphere are too poor to know exact PMSE altitudes. However, a comparison of Doppler velocity from the HF radar and neutral wind velocity from the MF radar shows that PMSEs at the HF band appeared at altitudes within 80-90km, which are consistent with those from previous vertical incidence HF-VHF radar results. The HF-VHF PMSE occurrences exhibit a semidiurnal behavior, as observed by other researchers. It is found that in one event, PMSEs occurred when westward semidiurnal winds with large amplitude at 85-88km altitudes attained a maximum. When the HF-VHF PMSEs were observed at distances beyond 180km from MF radar sites, the MF radars detected no appreciable signatures of echo enhancement. Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides)

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Frequency domain interferometry mode observations of PMSE using the EISCAT VHF radar

Annales Geophysicae ◽

10.1007/s00585-001-1599-8 ◽

2000 ◽

Vol 18 (12) ◽

pp. 1599-1612 ◽

Cited By ~ 6

Author(s):

P. B. Chilson ◽

S. Kirkwood ◽

I. Häggström

Keyword(s):

Frequency Domain ◽

Middle Atmosphere ◽

Lower Boundary ◽

Doppler Velocity ◽

Vhf Radar ◽

Radio Science ◽

First Results ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes ◽

Frequency Coherence

Abstract. During the summer of 1997 investigations into the nature of polar mesosphere summer echoes (PMSE) were conducted using the European incoherent scatter (EISCAT) VHF radar in Norway. The radar was operated in a frequency domain interferometry (FDI) mode over a period of two weeks to study the frequency coherence of the returned radar signals. The operating frequencies of the radar were 224.0 and 224.6 MHz. We present the first results from the experiment by discussing two 4-h intervals of data collected over two consecutive nights. During the first of the two days an enhancement of the FDI coherence, which indicates the presence of distinct scattering layers, was found to follow the lower boundary of the PMSE. Indeed, it is not unusual to observe that the coherence values are peaked around the heights corresponding to both the lower- and upper-most boundaries of the PMSE layer and sublayers. A Kelvin-Helmholtz mechanism is offered as one possible explanation for the layering structure. Additionally, our analysis using range-time-pseudocolor plots of signal-to-noise ratios, spectrograms of Doppler velocity, and estimates of the positions of individual scattering layers is shown to be consistent with the proposition that upwardly propagating gravity waves can become steepened near the mesopause.Key words: Ionosphere (polar ionosphere) · Meteorology and Atmospheric Dynamics (middle atmosphere dynamics) · Radio Science (Interferometry)

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Finland HF and Esrange MST radar observations of polar mesosphere summer echoes

Annales Geophysicae ◽

10.5194/angeo-21-1047-2003 ◽

2003 ◽

Vol 21 (4) ◽

pp. 1047-1055 ◽

Cited By ~ 16

Author(s):

T. Ogawa ◽

N. F. Arnold ◽

S. Kirkwood ◽

N. Nishitani ◽

M. Lester

Keyword(s):

Middle Atmosphere ◽

Spectral Width ◽

Hf Radar ◽

Doppler Velocity ◽

Short Period ◽

Mst Radar ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes ◽

Thermospheric Dynamics ◽

Atmospheric Gravity

Abstract. Peculiar near range echoes observed in summer with the SuperDARN HF radar in Finland are presented. The echoes were detected at four frequencies of 9, 11, 13 and 15 MHz at slant ranges of 105–250 km for about 100 min. Interferometer measurements indicate that the echoes are returned from 80–100 km altitudes with elevation angles of 20°–60°. Echo power (< 16 dB), Doppler velocity (between –30 and + 30 ms-1) and spectral width (< 60 ms-1) fluctuate with periods of several to 20 min, perhaps due to short–period atmospheric gravity waves. When the HF radar detected the echoes, a vertical incidence MST radar, located at Esrange in Sweden (650 km north of the HF radar site), observed polar mesosphere summer echoes (PMSE) at altitudes of 80–90 km. This fact suggests that the near range HF echoes are PMSE at HF band, although both radars did not probe a common volume. With increasing radar frequency, HF echo ranges are closer to the radar site and echo power becomes weaker. Possible mechanisms to explain these features are discussed.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides; instruments and techniques)

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PMSE observations at three different frequencies in northern Europe during summer 1994

Annales Geophysicae ◽

10.1007/s00585-996-1317-7 ◽

1996 ◽

Vol 14 (12) ◽

pp. 1317-1327 ◽

Cited By ~ 27

Author(s):

J. Bremer ◽

P. Hoffmann ◽

A. H. Manson ◽

C. E. Meek ◽

R. Rüster ◽

...

Keyword(s):

Wind Field ◽

Vhf Radar ◽

Half Wavelength ◽

Measuring Period ◽

Spatial Differences ◽

Strongly Connected ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes ◽

The Common ◽

Mf Radar

Abstract. Simultaneous observations of polar mesosphere summer echoes (PMSE) have been carried out during summer 1994 in northern Norway using three radars on different frequencies: the ALOMAR SOUSY radar at Andenes on 53.5 MHz, the EISCAT VHF radar at Tromsø on 224 MHz and the MF radar at Tromsø on 2.78 MHz. During the common measuring period in July/August 1994, PMSE could be detected at 224 and 53.5 MHz, and there are strong hints that PMSE also occur at 2.78 MHz. Reliable correlations between hourly backscattered power values indicate that the PMSE structures have zonal extensions of more than 130 km and can be detected at very different scales (half wavelength) between 0.67 (EISCAT VHF radar) and 54 m (MF radar). Using the wind values derived by the MF radar it can be shown that the mesospheric wind field influences the structure of PMSE. The diurnal variation of PMSE is strongly connected with tidal-wind components, whereas spatial differences of PMSE can partly be explained by the mean wind field.

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Occurrence frequencies of polar mesosphere summer echoes observed at 69° N during a full solar cycle

Advances in Radio Science ◽

10.5194/ars-11-327-2013 ◽

2013 ◽

Vol 11 ◽

pp. 327-332 ◽

Cited By ~ 2

Author(s):

R. Latteck ◽

J. Bremer

Keyword(s):

Middle Atmosphere ◽

Wave Radiation ◽

Signal Power ◽

Water Vapour Content ◽

Vhf Radar ◽

The North ◽

Initial Stage ◽

Significance Levels ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes

Abstract. Polar mesosphere summer echoes (PMSE) are strong enhancements of received signal power at very high radar frequencies occurring at altitudes between about 80 and 95 km at polar latitudes during summer. PMSE are caused by inhomogeneities in the electron density of the radar Bragg scale within the plasma of the cold summer mesopause region in the presence of negatively charged ice particles. Thus the occurrence of PMSE contains information about mesospheric temperature and water vapour content but also depends on the ionisation due to solar wave radiation and precipitating high energetic particles. Continuous and homogeneous observations of PMSE have been done on the North-Norwegian island Andøya (69.3° N, 16.0° E) from 1999 until 2008 using the ALWIN VHF radar at 53.5 MHz. In 2009 the Leibniz-Institute of Atmospheric Physics in Kühlungsborn, Germany (IAP) started the installation of the Middle Atmosphere Alomar Radar System (MAARSY) at the same location. The observation of mesospheric echoes could be continued in spring 2010 starting with an initial stage of expansion of MAARSY and is carried out with the completed installation of the radar since May 2011. Since both the ALWIN radar and MAARSY are calibrated, the received echo strength of PMSE from 14 yr of mesospheric observations could be converted to absolute signal power. Occurrence frequencies based on different common thresholds of PMSE echo strength were used for investigations of the solar and geomagnetic control of the PMSE as well as of possible long-term changes. The PMSE are positively correlated with the solar Lyman α radiation and the geomagnetic activity. The occurrence frequencies of the PMSE show slightly positive trends but with marginal significance levels.

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Aspect sensitivity measurements of polar mesosphere summer echoes using coherent radar imaging

Annales Geophysicae ◽

10.5194/angeo-20-213-2002 ◽

2002 ◽

Vol 20 (2) ◽

pp. 213-223 ◽

Cited By ~ 22

Author(s):

P. B. Chilson ◽

T.-Y. Yu ◽

R. D. Palmer ◽

S. Kirkwood

Keyword(s):

Middle Atmosphere ◽

Radar Imaging ◽

Brightness Distribution ◽

High Signal ◽

Vhf Radar ◽

Radio Science ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes ◽

Coherent Radar ◽

Aspect Sensitivity

Abstract. The Esrange VHF radar (ESRAD), located in northern Sweden (67.88° N, 21.10° E), has been used to investigate polar mesosphere summer echoes (PMSE). During July and August of 1998, coherent radar imaging (CRI) was used to study the dynamic evolution of PMSE with high temporal and spatial resolution. A CRI analysis provides an estimate of the angular brightness distribution within the radar’s probing volume. The brightness distribution is directly related to the radar reflectivity. Consequently, these data are used to investigate the aspect sensitivity of PMSE. In addition to the CRI analysis, the full correlation analysis (FCA) is used to derive estimates of the prevailing three-dimensional wind associated with the observed PMSE. It is shown that regions within the PMSE with enhanced aspect sensitivity have a correspondingly high signal-to-noise ratio (SNR). Although this relationship has been investigated in the past, the present study allows for an estimation of the aspect sensitivity independent of the assumed scattering models and avoids the complications of comparing echo strengths from vertical and off-vertical beams over large horizontal separations, as in the Doppler Beam Swinging (DBS) method. Regions of enhanced aspect sensitivity were additionally shown to correlate with the wave-perturbation induced downward motions of air parcels embedded in the PMSE.Key words. Ionosphere (polar ionosphere) Meteorology and Atmospheric Dynamics (middle atmosphere dynamics) Radio Science (Interferometry)

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Studies of polar mesosphere summer echoes by VHF radar and rocket probes

Advances in Space Research ◽

10.1016/0273-1177(94)90126-0 ◽

1994 ◽

Vol 14 (9) ◽

pp. 139-148 ◽

Cited By ~ 25

Author(s):

U.-P. Hoppe ◽

T.A. Blix ◽

E.V. Thrane ◽

F.-J. Lübken ◽

J.Y.N. Cho ◽

...

Keyword(s):

Vhf Radar ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes

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Horizontally resolved structures of radar backscatter from polar mesospheric layers

Advances in Radio Science ◽

10.5194/ars-10-285-2012 ◽

2012 ◽

Vol 10 ◽

pp. 285-290 ◽

Cited By ~ 5

Author(s):

R. Latteck ◽

W. Singer ◽

M. Rapp ◽

T. Renkwitz ◽

G. Stober

Keyword(s):

Middle Atmosphere ◽

Beam Steering ◽

Lower Thermosphere ◽

The Arctic ◽

Phased Array Antenna ◽

Vhf Radar ◽

The North ◽

Expansion Stage ◽

Arctic Atmosphere ◽

High Flexibility

Abstract. The Leibniz-Institute of Atmospheric Physics in Kühlungsborn, Germany (IAP) installed a new powerful VHF radar on the North-Norwegian island Andøya (69.30° N, 16.04° E) from 2009 to 2011. The new Middle Atmosphere Alomar Radar System (MAARSY) replaces the existing ALWIN radar which has been in continuous operation on Andøya for more than 10 yr. MAARSY is a monostatic radar operated at 53.5 MHz with an active phased array antenna consisting of 433 Yagi antennas each connected to its own transceiver with independent control of frequency, phase and power of the transmitted signal. This arrangement provides a very high flexibility of beam forming and beam steering. It allows classical beam swinging operation as well as experiments with simultaneous multiple beams and the use of modern interferometric applications for improved studies of the Arctic atmosphere from the troposphere up to the lower thermosphere with high spatial-temporal resolution. The installation of the antenna was completed in August 2009. An initial expansion stage of 196 transceiver modules was installed in spring 2010, upgraded to 343 transceiver modules in December 2010 and the installation of the radar was completed in spring 2011. Beside standard observations of tropospheric winds and Polar Mesosphere Summer Echoes, multi-beam experiments using up to 91 beams quasi-simultaneously in the mesosphere have been carried out using the different expansion stages of the system during campaigns in 2010 and 2011. These results provided a first insight into the horizontal variability of Polar Mesosphere Summer and Winter Echoes in an area of about 80 km by 80 km with time resolutions between 3 and 9 min.

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ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes

Annales Geophysicae ◽

10.1007/s00585-000-1009-7 ◽

2000 ◽

Vol 18 (9) ◽

pp. 1009-1026 ◽

Cited By ~ 22

Author(s):

I. W. McCrea ◽

M. Lockwood ◽

J. Moen ◽

F. Pitout ◽

P. Eglitis ◽

...

Keyword(s):

Large Scale ◽

Initial Conditions ◽

Plasma Temperature ◽

Radar Data ◽

Auroral Oval ◽

Hf Radar ◽

High Electron ◽

Vhf Radar ◽

Ionosphere Plasma ◽

Main Cusp

Abstract. We report observations of the cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) VHF radar at Tromsø and the EISCAT Svalbard radar (ESR). We compare them with observations of the dayside auroral luminosity, as seen by meridian scanning photometers at Ny Ålesund and of HF radar backscatter, as observed by the CUTLASS radar. We study the response to an interval of about one hour when the interplanetary magnetic field (IMF), monitored by the WIND and ACE spacecraft, was southward. The cusp/cleft aurora is shown to correspond to a spatially extended region of elevated electron temperatures in the VHF radar data. Initial conditions were characterised by a northward-directed IMF and cusp/cleft aurora poleward of the ESR. A strong southward turning then occurred, causing an equatorward motion of the cusp/cleft aurora. Within the equatorward expanding, southward-IMF cusp/cleft, the ESR observed structured and elevated plasma densities and ion and electron temperatures. Cleft ion fountain upflows were seen in association with elevated ion temperatures and rapid eastward convection, consistent with the magnetic curvature force on newly opened field lines for the observed negative IMF By. Subsequently, the ESR beam remained immediately poleward of the main cusp/cleft and a sequence of poleward-moving auroral transients passed over it. After the last of these, the ESR was in the polar cap and the radar observations were characterised by extremely low ionospheric densities and downward field-aligned flows. The IMF then turned northward again and the auroral oval contracted such that the ESR moved back into the cusp/cleft region. For the poleward-retreating, northward-IMF cusp/cleft, the convection flows were slower, upflows were weaker and the electron density and temperature enhancements were less structured. Following the northward turning, the bands of high electron temperature and cusp/cleft aurora bifurcated, consistent with both subsolar and lobe reconnection taking place simultaneously. The present paper describes the large-scale behaviour of the ionosphere during this interval, as observed by a powerful combination of instruments. Two companion papers, by Lockwood et al. (2000) and Thorolfsson et al. (2000), both in this issue, describe the detailed behaviour of the poleward-moving transients observed during the interval of southward Bz, and explain their morphology in the context of previous theoretical work.Key words: Ionosphere (ionosphere - magnetosphere interactions; auroral ionosphere; plasma temperature and density)

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Polar mesosphere summer echoes: a comparison of simultaneous observations at three wavelengths

Annales Geophysicae ◽

10.5194/angeo-25-2487-2007 ◽

2007 ◽

Vol 25 (12) ◽

pp. 2487-2496 ◽

Cited By ~ 10

Author(s):

E. Belova ◽

P. Dalin ◽

S. Kirkwood

Keyword(s):

Short Interval ◽

Beam Width ◽

Turbulent Energy ◽

Energy Dissipation Rate ◽

Theory Model ◽

Turbulence Theory ◽

Vhf Radar ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes ◽

Uhf Radar

Abstract. On 5 July 2005, simultaneous observations of Polar Mesosphere Summer Echoes (PMSE) were made using the EISCAT VHF (224 MHz) and UHF (933 MHz) radars located near Tromsø, Norway and the ALWIN VHF radar (53.5 MHz) situated on Andøya, 120 km SW of the EISCAT site. During the short interval from 12:20 UT until 12:26 UT strong echoes at about 84 km altitude were detected with all three radars. The radar volume reflectivities were found to be 4×10−13 m−1, 1.5×10−14 m−1 and 1.5×10−18 m−1 for the ALWIN, EISCAT-VHF and UHF radars, respectively. We have calculated the reflectivity ratios for each pair of radars and have compared them to ratios obtained from the turbulence-theory model proposed by Hill (1978a). We have tested different values of the turbulent energy dissipation rate ε and Schmidt number Sc, which are free parameters in the model, to try to fit theoretical reflectivity ratios to the experimental ones. No single combination of the parameters ε and Sc could be found to give a good fit. Spectral widths for the EISCAT radars were estimated from the spectra computed from the autocorrelation functions obtained in the experiment. After correction for beam-width broadening, the spectral widths are about 4 m/s for the EISCAT-VHF and 1.5–2 m/s for the UHF radar. However, according to the turbulence theory, the spectral widths in m/s should be the same for both radars. We also tested an incoherent scatter (IS) model developed by Cho et al. (1998), which takes into account the presence of charged aerosols/dust at the summer mesopause. It required very different sizes of particles for the EISCAT-VHF and UHF cases, to be able to fit the experimental spectra with model spectra. This implies that the IS model cannot explain PMSE spectra, at least not for monodisperse distributions of particles.

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