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Journal articles on the topic 'MLT radars'

Author: Grafiati

Published: 6 September 2023

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1

Hasebe, F., T. Tsuda, T. Nakamura, and M. D. Burrage. "Validation of HRDI MLT winds with meteor radars." Annales Geophysicae 15, no. 9 (1997): 1142–57. http://dx.doi.org/10.1007/s00585-997-1142-7.

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Abstract. A validation study of the mesospheric and lower-thermospheric (MLT) wind velocities measured by the High-Resolution Doppler Imager (HRDI) on board the Upper-Atmosphere Research Satellite (UARS) has been carried out, comparing with observations by meteor radars located at Shigaraki, Japan and Jakarta, Indonesia. The accuracy of the HRDI winds relative to the meteor radars is obtained by a series of simultaneous wind measurements at the time of UARS overpasses. Statistical tests on the difference in the wind vectors observed by HRDI and the meteor radars are applied to determine whethe

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Portnyagin, Y. I., T. V. Solovjova, N. A. Makarov, et al. "Monthly mean climatology of the prevailing winds and tides in the Arctic mesosphere/lower thermosphere." Annales Geophysicae 22, no. 10 (2004): 3395–410. http://dx.doi.org/10.5194/angeo-22-3395-2004.

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Abstract. The Arctic MLT wind regime parameters measured at the ground-based network of MF and meteor radar stations (Andenes 69° N, Tromsø 70° N, Esrange 68° N, Dixon 73.5° N, Poker Flat 65° N and Resolute Bay 75° N) are discussed and compared with those observed in the mid-latitudes. The network of the ground-based MF and meteor radars for measuring winds in the Arctic upper mesosphere and lower thermosphere provides an excellent opportunity for study of the main global dynamical structures in this height region and their dependence from longitude. Preliminary estimates of the differences be

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Stober, Gunter, Alan Liu, Alexander Kozlovsky, et al. "Identifying gravity waves launched by the Hunga Tonga–Hunga Ha′apai volcanic eruption in mesosphere/lower-thermosphere winds derived from CONDOR and the Nordic Meteor Radar Cluster." Annales Geophysicae 41, no. 1 (2023): 197–208. http://dx.doi.org/10.5194/angeo-41-197-2023.

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Abstract. The Hunga Tonga–Hunga Ha′apai volcano eruption was a unique event that caused many atmospheric phenomena around the globe. In this study, we investigate the atmospheric gravity waves in the mesosphere/lower-thermosphere (MLT) launched by the volcanic explosion in the Pacific, leveraging multistatic meteor radar observations from the Chilean Observation Network De Meteor Radars (CONDOR) and the Nordic Meteor Radar Cluster in Fennoscandia. MLT winds are computed using a recently developed 3DVAR+DIV algorithm. We found eastward- and westward-traveling gravity waves in the CONDOR zonal a

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Singer, W., J. Bremer, P. Hoffmann, et al. "Geomagnetic influences upon tides—winds from MLT radars." Journal of Atmospheric and Terrestrial Physics 56, no. 10 (1994): 1301–11. http://dx.doi.org/10.1016/0021-9169(94)90068-x.

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Manson, A. H., C. E. Meek, C. M. Hall, et al. "Mesopause dynamics from the scandinavian triangle of radars within the PSMOS-DATAR Project." Annales Geophysicae 22, no. 2 (2004): 367–86. http://dx.doi.org/10.5194/angeo-22-367-2004.

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Abstract. The "Scandinavian Triangle" is a unique trio of radars within the DATAR Project (Dynamics and Temperatures from the Arctic MLT (60–97km) region): Andenes MF radar (69°N, 16°E); Tromsø MF radar (70°N, 19°E) and Esrange "Meteor" radar (68°N, 21°E). The radar-spacings range from 125-270km, making it unique for studies of wind variability associated with small-scale waves, comparisons of large-scale waves measured over small spacings, and for comparisons of winds from different radar systems. As such it complements results from arrays having spacings of 25km and 500km that have been loca

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van Caspel, Willem E., Patrick J. Espy, Robert E. Hibbins, and John P. McCormack. "Migrating tide climatologies measured by a high-latitude array of SuperDARN HF radars." Annales Geophysicae 38, no. 6 (2020): 1257–65. http://dx.doi.org/10.5194/angeo-38-1257-2020.

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Abstract. This study uses hourly meteor wind measurements from a longitudinal array of 10 high-latitude SuperDARN high-frequency (HF) radars to isolate the migrating diurnal, semidiurnal, and terdiurnal tides at mesosphere–lower-thermosphere (MLT) altitudes. The planetary-scale array of radars covers 180∘ of longitude, with 8 out of 10 radars being in near-continuous operation since the year 2000. Time series spanning 16 years of tidal amplitudes and phases in both zonal and meridional wind are presented, along with their respective annual climatologies. The method to isolate the migrating tid

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Zhong, Wei, Xianghui Xue, Wen Yi, Iain M. Reid, Tingdi Chen, and Xiankang Dou. "Error analyses of a multistatic meteor radar system to obtain a three-dimensional spatial-resolution distribution." Atmospheric Measurement Techniques 14, no. 5 (2021): 3973–88. http://dx.doi.org/10.5194/amt-14-3973-2021.

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Abstract. In recent years, the concept of multistatic meteor radar systems has attracted the attention of the atmospheric radar community, focusing on the mesosphere and lower thermosphere (MLT) region. Recently, there have been some notable experiments using such multistatic meteor radar systems. Good spatial resolution is vital for meteor radars because nearly all parameter inversion processes rely on the accurate location of the meteor trail specular point. It is timely then for a careful discussion focused on the error distribution of multistatic meteor radar systems. In this study, we dis

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Rokade, M. V., R. Kondala Rao, S. S. Nikte, et al. "Intraseasonal oscillation (ISO) in the MLT zonal wind over Kolhapur (16.8° N) and Tirunelveli (8.7° N)." Annales Geophysicae 30, no. 12 (2012): 1623–31. http://dx.doi.org/10.5194/angeo-30-1623-2012.

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Abstract. Simultaneous observations of the mean zonal winds at 88 km obtained by the medium-frequency (MF) radars at Kolhapur (16.8° N, 74.2° E) and Tirunelveli (8.7° N, 77.8° E) have been used to study the intraseasonal oscillation (ISO) in the MLT region. The influences of the intraseasonal variations in the lower tropospheric convective activity associated with the Madden-Julian oscillations on the latitudinal behavior of intraseasonal oscillations (ISO) of the zonal winds in the equatorial mesosphere and lower thermosphere (MLT) have been studied. The ISO activity in the lower tropospheric

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Makarevich, R. A., and P. L. Dyson. "Dual HF radar study of the subauroral polarization stream." Annales Geophysicae 25, no. 12 (2007): 2579–91. http://dx.doi.org/10.5194/angeo-25-2579-2007.

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Abstract. The dual HF radars comprising the Tasman International Geophysical Environment Radar (TIGER) system often observe localized high-velocity F-region plasma flows (≥1500 m/s) in the midnight sector (20:00–02:00 MLT) at magnetic latitudes as low as Λ=60° S. The flow channels exhibit large variability in the latitudinal extent and electric field strength, and are similar to the subauroral polarization stream or SAPS, a plasma convection feature thought to be related to the polarization electric field due to the charge separation during substorm and storm development. In this study, the 2-

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Chau, Jorge Luis, Juan Miguel Urco, Juha Pekka Vierinen, et al. "Novel specular meteor radar systems using coherent MIMO techniques to study the mesosphere and lower thermosphere." Atmospheric Measurement Techniques 12, no. 4 (2019): 2113–27. http://dx.doi.org/10.5194/amt-12-2113-2019.

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Abstract. Typical specular meteor radars (SMRs) use one transmitting antenna and at least a five-antenna interferometric configuration on reception to study the mesosphere and lower thermosphere (MLT) region. The interferometric configuration allows the measurement of the angle-of-arrival (AOA) of the detected meteor echoes, which in turn is needed to derive atmospheric parameters (e.g., mean winds, momentum fluxes, temperatures, and neutral densities). Recently, we have shown that coherent MIMO configurations in atmospheric radars, i.e., multiple input (transmitters) and multiple output (rece

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Kozlovsky, A., V. Safargaleev, N. Østgaard, et al. "On the motion of dayside auroras caused by a solar wind pressure pulse." Annales Geophysicae 23, no. 2 (2005): 509–21. http://dx.doi.org/10.5194/angeo-23-509-2005.

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Abstract. Global ultraviolet auroral images from the IMAGE satellite were used to investigate the dynamics of the dayside auroral oval responding to a sudden impulse (SI) in the solar wind pressure. At the same time, the TV all-sky camera and the EISCAT radar on Svalbard (in the pre-noon sector) allowed for detailed investigation of the auroral forms and the ionospheric plasma flow. After the SI, new discrete auroral forms appeared in the poleward part of the auroral oval so that the middle of the dayside oval moved poleward from about 70° to about 73° of the AACGM latitude. This poleward shif

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Jaen, Juliana, Toralf Renkwitz, Jorge L. Chau, et al. "Long-term studies of mesosphere and lower-thermosphere summer length definitions based on mean zonal wind features observed for more than one solar cycle at middle and high latitudes in the Northern Hemisphere." Annales Geophysicae 40, no. 1 (2022): 23–35. http://dx.doi.org/10.5194/angeo-40-23-2022.

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Abstract. Specular meteor radars (SMRs) and partial reflection radars (PRRs) have been observing mesospheric winds for more than a solar cycle over Germany (∼ 54∘ N) and northern Norway (∼ 69∘ N). This work investigates the mesospheric mean zonal wind and the zonal mean geostrophic zonal wind from the Microwave Limb Sounder (MLS) over these two regions between 2004 and 2020. Our study focuses on the summer when strong planetary waves are absent and the stratospheric and tropospheric conditions are relatively stable. We establish two definitions of the summer length according to the zonal wind

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Pitkänen, T., A. T. Aikio, A. Kozlovsky, and O. Amm. "Reconnection electric field estimates and dynamics of high-latitude boundaries during a substorm." Annales Geophysicae 27, no. 5 (2009): 2157–71. http://dx.doi.org/10.5194/angeo-27-2157-2009.

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Abstract. The dynamics of the polar cap and the auroral oval are examined in the evening sector during a substorm period on 25 November 2000 by using measurements of the EISCAT incoherent scatter radars, the north-south chain of the MIRACLE magnetometer network, and the Polar UV Imager. The location of the polar cap boundary (PCB) is estimated from electron temperature measurements by the mainland low-elevation EISCAT VHF radar and the 42 m antenna of the EISCAT Svalbard radar. A comparison to the poleward auroral emission (PAE) boundary by the Polar UV Imager shows that in this event the PAE

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Clark, R. R., M. D. Burrage, S. J. Franke, et al. "Observations of 7-d planetary waves with MLT radars and the UARS-HRDI instrument." Journal of Atmospheric and Solar-Terrestrial Physics 64, no. 8-11 (2002): 1217–28. http://dx.doi.org/10.1016/s1364-6826(02)00070-6.

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Shand, B. A., T. K. Yeoman, R. V. Lewis, R. A. Greenwald, and M. R. Hairston. "Interhemispheric contrasts in the ionospheric convection response to changes in the interplanetary magnetic field and substorm activity: a case-study." Annales Geophysicae 16, no. 7 (1998): 764–74. http://dx.doi.org/10.1007/s00585-998-0764-8.

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Abstract. Interhemispheric contrasts in the ionospheric convection response to variations of the interplanetary magnetic field (IMF) and substorm activity are examined, for an interval observed by the Polar Anglo-American Conjugate Experiment (PACE) radar system between ~1600 and ~2100 MLT on 4 March 1992. Representations of the ionospheric convection pattern associated with different orientations and magnitudes of the IMF and nightside driven enhancements of the auroral electrojet are employed to illustrate a possible explanation for the contrast in convection flow response observed in radar

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Parkinson, M. L. "Complexity in the scaling of velocity fluctuations in the high-latitude F-region ionosphere." Annales Geophysicae 26, no. 9 (2008): 2657–72. http://dx.doi.org/10.5194/angeo-26-2657-2008.

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Abstract. The temporal scaling properties of F-region velocity fluctuations, δvlos, were characterised over 17 octaves of temporal scale from τ=1 s to <1 day using a new data base of 1-s time resolution SuperDARN radar measurements. After quality control, 2.9 (1.9) million fluctuations were recorded during 31.5 (40.4) days of discretionary mode soundings using the Tasmanian (New Zealand) radars. If the fluctuations were statistically self-similar, the probability density functions (PDFs) of δvlos would collapse onto the same PDF using the scaling Ps (δvs, τ)=ταP (δvlos, τ) and δvs=δvlosτ−α

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Makarevitch, R. A., and F. Honary. "Correlation between cosmic noise absorption and VHF coherent echo intensity." Annales Geophysicae 23, no. 5 (2005): 1543–53. http://dx.doi.org/10.5194/angeo-23-1543-2005.

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Abstract. We present examples and statistical analysis of the events with statistically significant correlation between the cosmic noise absorption (CNA) and the signal-to-noise ratio (SNR) of the VHF coherent echo intensity in the area monitored simultaneously by an imaging riometer and two oblique-sounding coherent VHF radars in Northern Scandinavia. By only considering the observations from the narrow riometer beams comparable (in terms of the intersection with the ionosphere) with the VHF radar cells, we identify ~200 one-hour high correlation periods (HCPs) for 2 years near the solar cycl

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Goldberg, R. A., D. C. Fritts, F. J. Schmidlin, et al. "The MaCWAVE program to study gravity wave influences on the polar mesosphere." Annales Geophysicae 24, no. 4 (2006): 1159–73. http://dx.doi.org/10.5194/angeo-24-1159-2006.

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Abstract. MaCWAVE (Mountain and Convective Waves Ascending VErtically) was a highly coordinated rocket, ground-based, and satellite program designed to address gravity wave forcing of the mesosphere and lower thermosphere (MLT). The MaCWAVE program was conducted at the Norwegian Andøya Rocket Range (ARR, 69.3° N) in July 2002, and continued at the Swedish Rocket Range (Esrange, 67.9° N) during January 2003. Correlative instrumentation included the ALOMAR MF and MST radars and RMR and Na lidars, Esrange MST and meteor radars and RMR lidar, radiosondes, and TIMED (Thermosphere Ionosphere Mesosph

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Sharma, A. K., M. V. Rokade, R. Kondala Rao, S. Gurubaran, and P. T. Patil. "Comparative study of MLT mean winds using MF radars located at 16.8°N and 8.7°N." Journal of Earth System Science 119, no. 4 (2010): 461–70. http://dx.doi.org/10.1007/s12040-010-0031-8.

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Safargaleev, V., A. Kozlovsky, T. Sergienko, et al. "Optical, radar, and magnetic observations of magnetosheath plasma capture during a positive IMF <I>B<sub>z</sub></I> impulse." Annales Geophysicae 26, no. 3 (2008): 517–31. http://dx.doi.org/10.5194/angeo-26-517-2008.

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Abstract. We present a multi-instrument study of the ionospheric response to a northward turning of the IMF. The observations were made in the near-noon (11:00 MLT) sector on Svalbard (at 75° MLAT). The data set includes auroral observations, ionospheric flows obtained from the EISCAT and CUTLASS radars, the spectral width of the HF radar backscatter, particle precipitation and plasma flow data from the DMSP F13 satellite, and Pc1 frequency band pulsations observed by induction magnetometers. Careful collocation of all the observations has been made with the HF radar backscatter located by a r

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Stray, N. H., Y. J. Orsolini, P. J. Espy, V. Limpasuvan, and R. E. Hibbins. "Observations of PW activity in the MLT during SSW events using a chain of SuperDARN radars and SD-WACCM." Atmospheric Chemistry and Physics Discussions 15, no. 1 (2015): 393–413. http://dx.doi.org/10.5194/acpd-15-393-2015.

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Abstract. This study investigates the effect of Stratospheric Sudden Warmings (SSWs) on Planetary Wave (PW) activity in the Mesosphere-Lower Thermosphere (MLT). PW activity near 95 km is derived from meteor wind data using a chain of 8 SuperDARN radars at high northern latitudes that span longitudes from 150° W to 25° E and latitudes from 51 to 66° N. Zonal wave number 1 and 2 components were extracted from the meridional wind for the years 2000–2008. The observed wintertime PW activity shows common features associated with the stratospheric wind reversals and the accompanying stratospheric wa

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Wild, J. A., T. K. Yeoman, P. Eglitis, and H. J. Opgenoorth. "Multi-instrument observations of the electric and magnetic field structure of omega bands." Annales Geophysicae 18, no. 1 (2000): 99–110. http://dx.doi.org/10.1007/s00585-000-0099-6.

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Abstract. High time resolution data from the CUTLASS Finland radar during the interval 01:30-03:30 UT on 11 May, 1998, are employed to characterise the ionospheric electric field due to a series of omega bands extending ~5° in latitude at a resolution of 45 km in the meridional direction and 50 km in the azimuthal direction. E-region observations from the STARE Norway VHF radar operating at a resolution of 15 km over a comparable region are also incorporated. These data are combined with ground magnetometer observations from several stations. This allows the study of the ionospheric equivalent

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Milan, S. E., M. Lester, R. A. Greenwald, and G. Sofko. "The ionospheric signature of transient dayside reconnection and the associated pulsed convection return flow." Annales Geophysicae 17, no. 9 (1999): 1166–71. http://dx.doi.org/10.1007/s00585-999-1166-2.

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Abstract. Three SuperDARN coherent HF radars are employed to investigate the excitation of convection in the dayside high-latitude ionosphere in response to transient reconnection occurring in the cusp region. This study demonstrates the existence of transient antisunward-propagating backscatter features at the expected location of the ionospheric footprint of the cusp region, which have a repetition rate near 10 min. These are interpreted as the ionospheric signature of flux transfer events. Moreover, transient sunward-propagating regions of backscatter are observed in the convection return f

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Kishore Kumar, G., and W. K. Hocking. "Climatology of northern polar latitude MLT dynamics: mean winds and tides." Annales Geophysicae 28, no. 10 (2010): 1859–76. http://dx.doi.org/10.5194/angeo-28-1859-2010.

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Abstract. Mean winds and tides in the northern polar Mesosphere and Lower Thermosphere (MLT) have been studied using meteor radars located at Resolute Bay (75° N, 95° W) and Yellowknife (62.5° N, 114.3° W). The measurements for Resolute Bay span almost 12 years from July 1997 to February 2009 and the Yellowknife data cover 7 years from June 2002 to October 2008. The analysis reveals similar wind flow over both sites with a difference in magnitude. The summer zonal flow is westward at lower heights, eastward at upper heights and the winter zonal flow is eastward at all heights. The winter merid

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Senior, C., J. C. Cerisier, F. Rich, M. Lester, and G. K. Parks. "Strong sunward propagating flow bursts in the night sector during quiet solar wind conditions: SuperDARN and satellite observations." Annales Geophysicae 20, no. 6 (2002): 771–79. http://dx.doi.org/10.5194/angeo-20-771-2002.

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Abstract. High-time resolution data from the two Iceland SuperDARN HF radars show very strong nightside convection activity during a prolonged period of low geomagnetic activity and northward interplanetary magnetic field (IMF). Flows bursts with velocities ranging from 0.8 to 1.7 km/s are observed to propagate in the sunward direction with phase velocities up to 1.5 km/s. These bursts occur over several hours of MLT in the 20:00–01:00 MLT sector, in the evening-side sunward convection. Data from a simultaneous DMSP pass and POLAR UVI images show a very contracted polar cap and extended region

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Sandholt, P. E., J. Moen, C. J. Farrugia, et al. "Multi-site observations of the association between aurora and plasma convection in the cusp/polar cap during a southeastward(<i>B<sub>y</sub></i> <u>~</u> |<i>B<sub>z</sub></i>|) IMF orientation." Annales Geophysicae 21, no. 2 (2003): 539–58. http://dx.doi.org/10.5194/angeo-21-539-2003.

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Abstract. In a case study we demonstrate the spatiotemporal structure of aurora and plasma convection in the cusp/polar cap when the interplanetary magnetic field (IMF) Bz < 0 and By ~ | Bz | (clock angle in GSM Y - Z plane: ~ 135°). This IMF orientation elicited a response different from that corresponding to strongly northward and southward IMF. Our study of this "intermediate state" is based on a combination of ground observations of optical auroral emissions and ionospheric plasma convection. Utilizing all-sky cameras at NyAlesund, Svalbard and Heiss Island (Russian arctic), we are able

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Stober, G., and J. L. Chau. "A multistatic and multifrequency novel approach for specular meteor radars to improve wind measurements in the MLT region." Radio Science 50, no. 5 (2015): 431–42. http://dx.doi.org/10.1002/2014rs005591.

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McWilliams, K. A., T. K. Yeoman, J. B. Sigwarth, L. A. Frank, and M. Brittnacher. "The dayside ultraviolet aurora and convection responses to a southward turning of the interplanetary magnetic field." Annales Geophysicae 19, no. 7 (2001): 707–21. http://dx.doi.org/10.5194/angeo-19-707-2001.

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Abstract. We examine the large-scale ultraviolet aurora and convection responses to a series of flux transfer events that immediately followed a sharp and isolated southward turning of the IMF. During the interval of interest, SuperDARN was monitoring the plasma convection in the dayside northern ionosphere, while the VIS Earth Camera and the Far Ul-traviolet Imager (UVI) were monitoring the northern hemisphere’s ultraviolet aurora. Reconnection signatures were seen in the SuperDARN HF radar data in the postnoon sector following a sharp southward turning of the IMF. The presence of flux transf

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Wilhelm, Sven, Gunter Stober, and Jorge L. Chau. "A comparison of 11-year mesospheric and lower thermospheric winds determined by meteor and MF radar at 69 ° N." Annales Geophysicae 35, no. 4 (2017): 893–906. http://dx.doi.org/10.5194/angeo-35-893-2017.

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Abstract. The Andenes Meteor Radar (MR) and the Saura Medium Frequency (MF) Radar are located in northern Norway (69° N, 16° E) and operate continuously to provide wind measurements of the mesosphere and lower thermosphere (MLT) region. We compare the two systems to find potential biases between the radars and combine the data from both systems to enhance altitudinal coverage between 60 and 110 km. The systems have altitudinal overlap between 78 and 100 km at which we compare winds and tides on the basis of hourly winds with 2 km altitude bins. Our results indicate reasonable agreement for the

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Manson, A. H., C. Meek, M. Hagan, et al. "Seasonal variations of the semi-diurnal and diurnal tides in the MLT: multi-year MF radar observations from 2–70° N, modelled tides (GSWM, CMAM)." Annales Geophysicae 20, no. 5 (2002): 661–77. http://dx.doi.org/10.5194/angeo-20-661-2002.

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Abstract. In an earlier paper (Manson et al., 1999a) tidal data (1990–1997) from six Medium Frequency Radars (MFR) were compared with the Global Scale Wave Model (GSWM, original 1995 version). The radars are located between the equator and high northern latitudes: Christmas Island (2° N), Hawaii (22° N), Urbana (40° N), London (43° N), Saskatoon (52° N) and Tromsø (70° N). Common harmonic analysis was applied, to ensure consistency of amplitudes and phases in the 75–95 km height range. For the diurnal tide, seasonal agreements between observations and model were excellent while for the semi-di

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Lockwood, M., J. A. Davies, J. Moen, et al. "Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate." Annales Geophysicae 23, no. 11 (2005): 3513–32. http://dx.doi.org/10.5194/angeo-23-3513-2005.

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Abstract. Using data from the EISCAT (European Incoherent Scatter) VHF and CUTLASS (Co-operative UK Twin-Located Auroral Sounding System) HF radars, we study the formation of ionospheric polar cap patches and their relationship to the magnetopause reconnection pulses identified in the companion paper by Lockwood et al. (2005). It is shown that the poleward-moving, high-concentration plasma patches observed in the ionosphere by EISCAT on 23 November 1999, as reported by Davies et al. (2002), were often associated with corresponding reconnection rate pulses. However, not all such pulses generate

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Stray, N. H., Y. J. Orsolini, P. J. Espy, V. Limpasuvan, and R. E. Hibbins. "Observations of planetary waves in the mesosphere-lower thermosphere during stratospheric warming events." Atmospheric Chemistry and Physics 15, no. 9 (2015): 4997–5005. http://dx.doi.org/10.5194/acp-15-4997-2015.

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Abstract. This study investigates the effect of stratospheric sudden warmings (SSWs) on planetary wave (PW) activity in the mesosphere–lower thermosphere (MLT). PW activity near 95 km is derived from meteor wind data using a chain of eight SuperDARN radars at high northern latitudes that span longitudes from 150° W to 25° E and latitudes from 51 to 66° N. Zonal wave number 1 and 2 components were extracted from the meridional wind for the years 2000–2008. The observed wintertime PW activity shows common features associated with the stratospheric wind reversals and the accompanying stratospheri

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Koshin, Dai, Kaoru Sato, Masashi Kohma, and Shingo Watanabe. "An update on the 4D-LETKF data assimilation system for the whole neutral atmosphere." Geoscientific Model Development 15, no. 5 (2022): 2293–307. http://dx.doi.org/10.5194/gmd-15-2293-2022.

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Abstract. The four-dimensional local ensemble transform Kalman filter (4D-LETKF) data assimilation system for the whole neutral atmosphere is updated to better represent disturbances with wave periods shorter than 1 d in the mesosphere and lower thermosphere (MLT) region. First, incremental analysis update (IAU) filtering is introduced to reduce the generation of spurious waves arising from the insertion of the analysis updates. The IAU is better than other filtering methods, and also is commonly used for middle atmospheric data assimilation. Second, the order of horizontal diffusion in the fo

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Merzlyakov, E. G., D. J. Murphy, R. A. Vincent, and Yu I. Portnyagin. "Long-term tendencies in the MLT prevailing winds and tides over Antarctica as observed by radars at Molodezhnaya, Mawson and Davis." Journal of Atmospheric and Solar-Terrestrial Physics 71, no. 1 (2009): 21–32. http://dx.doi.org/10.1016/j.jastp.2008.09.024.

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Lockwood, M., H. Opgenoorth, A. P. van Eyken, et al. "Coordinated Cluster, ground-based instrumentation and low-altitude satellite observations of transient poleward-moving events in the ionosphere and in the tail lobe." Annales Geophysicae 19, no. 10/12 (2001): 1589–612. http://dx.doi.org/10.5194/angeo-19-1589-2001.

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Abstract. During the interval between 8:00–9:30 on 14 January 2001, the four Cluster spacecraft were moving from the central magnetospheric lobe, through the dusk sector mantle, on their way towards intersecting the magnetopause near 15:00 MLT and 15:00 UT. Throughout this interval, the EISCAT Svalbard Radar (ESR) at Longyearbyen observed a series of poleward-moving transient events of enhanced F-region plasma concentration ("polar cap patches"), with a repetition period of the order of 10 min. Allowing for the estimated solar wind propagation delay of 75 ( ± 5) min, the interplanetary magneti

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Ford, E. A. K., A. L. Aruliah, E. M. Griffin, and I. McWhirter. "Thermospheric gravity waves in Fabry-Perot Interferometer measurements of the 630.0nm OI line." Annales Geophysicae 24, no. 2 (2006): 555–66. http://dx.doi.org/10.5194/angeo-24-555-2006.

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Abstract. Gravity waves are an important feature of mesosphere - lower thermosphere (MLT) dynamics, observed using many techniques and providing an important mechanism for energy transfer between atmospheric regions. It is known that some gravity waves may propagate through the mesopause and reach greater altitudes before eventually "breaking" and depositing energy. The generation, propagation, and breaking of upper thermospheric gravity waves have not been studied directly often. However, their ionospheric counterparts, travelling ionospheric disturbances (TIDs), have been extensively studied

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Korotyshkin, Dmitriy, Eugeny Merzlyakov, Christoph Jacobi, Friederike Lilienthal, and Qian Wu. "Longitudinal MLT wind structure at higher mid-latitudes as seen by meteor radars at central and Eastern Europe (13°E/49°E)." Advances in Space Research 63, no. 10 (2019): 3154–66. http://dx.doi.org/10.1016/j.asr.2019.01.036.

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Kleinknecht, Nora H., Patrick J. Espy, and Robert E. Hibbins. "The climatology of zonal wave numbers 1 and 2 planetary wave structure in the MLT using a chain of Northern Hemisphere SuperDARN radars." Journal of Geophysical Research: Atmospheres 119, no. 3 (2014): 1292–307. http://dx.doi.org/10.1002/2013jd019850.

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Jacobi, Christoph, Friederike Lilienthal, Dmitry Korotyshkin, Evgeny Merzlyakov, and Gunter Stober. "Influence of geomagnetic disturbances on mean winds and tides in the mesosphere/lower thermosphere at midlatitudes." Advances in Radio Science 19 (December 17, 2021): 185–93. http://dx.doi.org/10.5194/ars-19-185-2021.

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Abstract. Observations of upper mesosphere/lower thermosphere (MLT) wind have been performed at Collm (51.3∘ N, 13.0∘ E) and Kazan (56∘ N, 49∘ E), using two SKiYMET all-sky meteor radars with similar configuration. Daily vertical profiles of mean winds and tidal amplitudes have been constructed from hourly horizontal winds. We analyse the response of mean winds and tidal amplitudes to geomagnetic disturbances. To this end, we compare winds and amplitudes for very quiet (Ap ≤ 5) and unsettled/disturbed (Ap ≥ 20) geomagnetic conditions. Zonal winds in both the mesosphere and lower thermosphere a

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Borälv, E., P. Eglitis, H. J. Opgenoorth, E. Donovan, G. Reeves, and P. Stauning. "The dawn and dusk electrojet response to substorm onset." Annales Geophysicae 18, no. 9 (2000): 1097–107. http://dx.doi.org/10.1007/s00585-000-1097-4.

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Abstract. We have investigated the time delay between substorm onset and related reactions in the dawn and dusk ionospheric electrojets, clearly separated from the nightside located substorm current wedge by several hours in MLT. We looked for substorm onsets occurring over Greenland, where the onset was identified by a LANL satellite and DMI magnetometers located on Greenland. With this setup the MARIA magnetometer network was located at dusk, monitoring the eastward electrojet, and the IMAGE chain at dawn, for the westward jet. In the first few minutes following substorm onset, sudden enhanc

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Merzlyakov, E., D. Pancheva, N. Mitchell, et al. "High- and mid-latitude quasi-2-day waves observed simultaneouslyby four meteor radars during summer 2000." Annales Geophysicae 22, no. 3 (2004): 773–88. http://dx.doi.org/10.5194/angeo-22-773-2004.

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Abstract. Results from the analysis of MLT wind measurements at Dixon (73.5°N, 80°E), Esrange (68°N, 21°E), Castle Eaton (UK) (53°N, 2°W), and Obninsk (55°N, 37°E) during summer 2000 are presented in this paper. Using S-transform or wavelet analysis, quasi-two-day waves (QTDWs) are shown to appear simultaneously at high- and mid-latitudes and reveal themselves as several bursts of wave activity. At first this activity is preceded by a 51–53h wave with S=3 observed mainly at mid-latitudes. After a short recess (or quiet time interval for about 10 days near day 205), we observe a regular sequenc

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Luo, Y., A. H. Manson, C. E. Meek, et al. "The 16-day planetary waves: multi-MF radar observations from the arctic to equator and comparisons with the HRDI measurements and the GSWM modelling results." Annales Geophysicae 20, no. 5 (2002): 691–709. http://dx.doi.org/10.5194/angeo-20-691-2002.

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Abstract. The mesospheric and lower thermospheric (MLT) winds (60–100 km) obtained by multiple MF radars, located from the arctic to equator at Tromsø (70° N, 19° E), Saskatoon (52° N, 107° W), London (43° N, 81° W), Hawaii (21° N, 157° W) and Christmas Island (2° N, 157° W), respectively, are used to study the planetary-scale 16-day waves. Based on the simultaneous observations (1993/1994), the variabilities of the wave amplitudes, periods and phases are derived. At mid- and high-latitude locations the 16-day waves are usually pervasive in the winter-centred seasons (October through March), w

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Woodfield, E. E., J. A. Davies, M. Lester, T. K. Yeoman, P. Eglitis, and M. Lockwood. "Nightside studies of coherent HF Radar spectral width behaviour." Annales Geophysicae 20, no. 9 (2002): 1399–413. http://dx.doi.org/10.5194/angeo-20-1399-2002.

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Abstract. A previous case study found a relationship between high spectral width measured by the CUTLASS Finland HF radar and elevated electron temperatures observed by the EISCAT and ESR incoherent scatter radars in the post-midnight sector of magnetic local time. This paper expands that work by briefly re-examining that interval and looking in depth at two further case studies. In all three cases a region of high HF spectral width (>200 ms-1) exists poleward of a region of low HF spectral width (<200 ms-1). Each case, however, occurs under quite different geomagnetic conditions. The or

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Matsui, H., P. A. Puhl-Quinn, V. K. Jordanova, Y. Khotyaintsev, P. A. Lindqvist, and R. B. Torbert. "Derivation of inner magnetospheric electric field (UNH-IMEF) model using Cluster data set." Annales Geophysicae 26, no. 9 (2008): 2887–98. http://dx.doi.org/10.5194/angeo-26-2887-2008.

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Abstract. We derive an inner magnetospheric electric field (UNH-IMEF) model at L=2–10 using primarily Cluster electric field data for more than 5 years between February 2001 and October 2006. This electric field data set is divided into several ranges of the interplanetary electric field (IEF) values measured by ACE. As ring current simulations which require electric field as an input parameter are often performed at L=2–6.6, we have included statistical results from ground radars and low altitude satellites inside the perigee of Cluster in our data set (L~4). Electric potential patterns are d

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Sandholt, P. E., and C. J. Farrugia. "Poleward moving auroral forms (PMAFs) revisited: responses of aurorae, plasma convection and Birkeland currents in the pre- and postnoon sectors under positive and negative IMF <I>B<sub>y</sub></I> conditions." Annales Geophysicae 25, no. 7 (2007): 1629–52. http://dx.doi.org/10.5194/angeo-25-1629-2007.

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Abstract. Using five case studies, we investigate the dynamical evolution of dayside auroral precipitation in relation to plasma convection, classifying it by the IMF By component and position with respect to noon. Auroral observations were made by meridian scanning photometers (MSPs) and an all-sky camera (ASC) in Ny Ålesund, Svalbard at 76° MLAT, while the spatial structure of the ionospheric plasma convection is inferred from SuperDARN radars and ion drift observations from spacecraft in polar orbit. The IMF configuration of major interest here is one pointing southward and with a dominant

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Sandholt, P. E., Y. Andalsvik, and C. J. Farrugia. "Polar cap convection/precipitation states during Earth passage of two ICMEs at solar minimum." Annales Geophysicae 28, no. 4 (2010): 1023–42. http://dx.doi.org/10.5194/angeo-28-1023-2010.

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Abstract. We report important new aspects of polar cap convection and precipitation (dawn-dusk and inter-hemisphere asymmetries) associated with the different levels of forcing of the magnetosphere by two interplanetary (IP) magnetic clouds on 20 November 2007 and 17 December 2008 during solar minimum. Focus is placed on two intervals of southward magnetic cloud field with large negative By components (Bx=−5 versus 0 nT) and with high and low plasma densities, respectively, as detected by spacecraft Wind. The convection/precipitation states are documented by DMSP spacecraft (Southern Hemispher

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Sandholt, P. E., Y. Andalsvik, and C. J. Farrugia. "Polar cap flow channel events: spontaneous and driven responses." Annales Geophysicae 28, no. 11 (2010): 2015–25. http://dx.doi.org/10.5194/angeo-28-2015-2010.

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Abstract. We present two case studies of specific flow channel events appearing at the dusk and/or dawn polar cap boundary during passage at Earth of interplanetary (IP) coronal mass ejections (ICMEs) on 10 January and 25 July 2004. The channels of enhanced (>1 km/s) antisunward convection are documented by SuperDARN radars and dawn-dusk crossings of the polar cap by the DMSP F13 satellite. The relationship with Birkeland currents (C1–C2) located poleward of the traditional R1–R2 currents is demonstrated. The convection events are manifest in ground magnetic deflections obtained from the IM

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Потехин, Александр, Aleksandr Potekhin, Артём Сетов, et al. "Prospective IS-MST radar. Potential and diagnostic capabilities." Solar-Terrestrial Physics 2, no. 3 (2016): 3–21. http://dx.doi.org/10.12737/22281.

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In the next few years, a new radar is planned to be built near Irkutsk. It should have capabilities of incoherent scatter (IS) radars and mesosphere-stratosphere-troposphere (MST) radars [Zherebtsov et al., 2011]. The IS-MST radar is a phased array of two separated antenna panels with a multichannel digital receiving system, which allows detailed space-time processing of backscattered signal. This paper describes characteristics, configuration, and capabilities of the antenna and transceiver systems of this radar. We estimate its potential in basic operating modes to study the ionosphere by th

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Medvedev, Andrey, Aleksandr Potekhin, Artem Setov, Dmitriy Kushnarev, and Valentin Lebedev. "All-atmosphere IS-MST Radar." Solar-Terrestrial Physics 6, no. 2 (2020): 41–48. http://dx.doi.org/10.12737/stp-62202004.

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The IS-MST radar, as the name implies, combines two different methods for studying the atmosphere using a backscatter signal. Turbulent fluctuations of the medium cause scattering in the mesosphere—stratosphere—troposphere (MST). In the upper atmosphere, incoherent scatter (IS) appears in ionospheric plasma. Special-purpose instruments have been built before such that measurements in one of these modes were the most effective. MST radars were utilized for studying wave activity in the lower and middle atmosphere; the IS radar, for ionospheric research. Nowadays, however, for a comprehensive in

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Friedt, Jean-Michel, Éric Bernard, and Madeleine Griselin. "Ground-Based Oblique-View Photogrammetry and Sentinel-1 Spaceborne RADAR Reflectivity Snow Melt Processes Assessment on an Arctic Glacier." Remote Sensing 15, no. 7 (2023): 1858. http://dx.doi.org/10.3390/rs15071858.

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The snowpack evolution during the melt season on an Arctic glacier is assessed using ground-based oblique-view cameras, spaceborne imaging and spaceborne RADAR. The repeated and systematic Synthetic Aperture RADAR (SAR) imaging by the European Space Agency’s Sentinel-1 spaceborne RADARs allows for all-weather, all-illumination condition monitoring of the snow-covered fraction of the glacier and hence assessing its water production potential. A comparison of the RADAR reflectivity with optical and multispectral imaging highlights the difference between the observed quantities—water content in t

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