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Journal Cover Journal of Atmospheric and Solar-Terrestrial Physics
  [SJR: 0.934]   [H-I: 70]   [142 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1364-6826
   Published by Elsevier Homepage  [3043 journals]
  • 3D electron density specification to support LEO and MEO satellite
    • Authors: Anna Belehaki; Ivan Kutiev; Pencho Marinov; Ioanna Tsagouri; Kostas Koutroumbas; Panagiotis Elias
      Pages: 1041 - 1056
      Abstract: Publication date: Available online 9 October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Pencho Marinov, Ivan Kutiev, Anna Belehaki, Ioanna Tsagouri
      The TaD three-dimensional (3D) electron density (Ne) specification model is compared with in situ measured Ne by the Instrument Sonde Langmuir (ISL) onboard DEMETER satellite. For this purpose, over 2000 parts of satellite orbits over the European region in the years 2009–2011 were selected. For each measured Ne value, a corresponding value was calculated with the TaD 3D model, using maps of foF2 and hmF2 from ionosondes and maps of TEC values from CODE software. To compare modelled and measured Ne, the relative to the model deviation between the two quantities was calculated. The comparisons exceeded the total number of 180,000. The main result shows that the modelled Ne extracted by the TaD profiles that have been calculated through adjustment with the TEC CODE parameters, exhibit significant deviations from the measured Ne at the satellite orbit height. Histograms of the relative deviations relNe show an average offset of 50–60%, while the standard deviation is around 30%. Separate analysis was performed to compare the modelled Ne over 11 ionosonde stations with the measured Ne by the satellite over the ionosonde locations and thus to eliminate the error inferred from the mapping procedure. Here the TaD profiles were adjusted with both the TEC CODE parameters and with TEC values extracted with the single GNSS station solution software with data from GNSS receivers co-located with the ionosondes. In the latter case, the lower TEC values compared to those of TEC CODE yield lower modelled Ne which resulted to smaller deviations with the satellite data. The present study reveals the low consistency between different measurements involved in modeled reconstruction. The comparison presented here shows the importance of assessing the inconsistency between different measurements being assimilated or ingested in the 3D Ne models. Probable inconsistency of different data can create a wrong base for further geophysical studies.

      PubDate: 2017-10-11T21:25:04Z
      DOI: 10.1016/j.asr.2016.11.031
      Issue No: Vol. 59, No. 4 (2017)
  • Experimental investigation of turbulent transport of momentum and heat in
           the atmospheric surface layer
    • Authors: Guowen Han; X.J. Zheng; Tianli Bo
      Pages: 18 - 28
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): Guowen Han, X.J. Zheng, Tianli Bo
      In our study, turbulent transport of momentum and heat is investigated in the neutral and unstable atmospheric surface layer (ASL) over the edge of a desert. Our results reveal that with the increase of wind speed the transport efficiencies for momentum and heat increased, furthermore, transport efficiency of momentum increases faster than that of heat. In addition, the method of quadrant analysis and turbulent events were used to analyze the moment flux and heat flux. Experimental results show that the influence of wind speed on moment flux and heat flux can be quite different, which maybe has a great impact on the turbulent transport of momentum and heat in ASL.

      PubDate: 2017-08-03T07:02:04Z
      DOI: 10.1016/j.jastp.2017.07.017
      Issue No: Vol. 164 (2017)
  • Stationary depletions in thermospheric atomic oxygen concentration and
           mass density observed with WINDII, GUVI, GOCE and simulated by NRLMSISE-00
    • Authors: Gordon G. Shepherd; Young-Min Cho
      Pages: 29 - 38
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): Gordon G. Shepherd, Young-Min Cho
      Observations of thermospheric atomic oxygen concentrations [O] by the Wind Imaging Interferometer (WINDII) and the Global Ultra Violet Imager (GUVI) derived from daytime airglow observations clearly show a persistent depletion in [O], for WINDII by about 63% below background, in the southern mid-latitudes, near 40° S latitude and 100° longitude. It appears less strongly in the northern hemisphere at about 250° longitude and is not evident in local winter for either hemisphere. The same feature appears strongly in the NRLMSISE-00 empirical model. Mass density observations by the Gravity field and steady-state Ocean Circulation Explorer (GOCE) available at dawn and dusk local times at times show similar depletions with a smaller reduction of about 20% but do not consistently agree with those of [O]. It has been shown elsewhere that Total Electron Content (TEC) observations are strongly related to the column ratio ΣO/N2. These observations clearly show the Weddell Sea Anomaly (WSA) enhancement as well as the [O] depletion at a similar latitude; these are oppositely phased and 180° apart in longitude, suggesting a common source.

      PubDate: 2017-08-03T07:02:04Z
      DOI: 10.1016/j.jastp.2017.07.016
      Issue No: Vol. 164 (2017)
  • Characteristics of longwave radiation through the statistical analysis of
           downward and upward longwave radiation and inter-comparison of two sites
           in Cyprus
    • Authors: S. Pashiardis; S.A. Kalogirou; A. Pelengaris
      Pages: 60 - 80
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): S. Pashiardis, S.A. Kalogirou, A. Pelengaris
      In this study, three years of hourly longwave downward and upward irradiance measurements for two sites in Cyprus representing two different climate regimes (inland vs coastal locations) are used to analyse and compare them. The quality control process was based on physically possible, extremely rare and climatological limits. Furthermore, comparison tests between the two longwave components as well as with air and ground surface temperatures were used to evaluate the hourly values of longwave irradiances. The annual mean daily downward longwave irradiation at Athalassa is 29.1 MJ m−2 and at Larnaca it is slightly higher (31.3 MJ m−2). On the other hand, the annual mean daily upward longwave irradiation at Athalassa is 38.2 MJ m−2, while at Larnaca it is slightly lower (37.4 MJ m−2). The performance of various models in estimating the daylight downward and upward longwave irradiances under clear-sky and all-sky conditions was evaluated. Root-mean-square errors, mean bias errors, and linear regression correlations have been used to compare measured and estimated values. The results of this comparison for the station of Athalassa, showed that Idso's model perform well and it can be used to estimate downward longwave irradiance under clear-sky conditions. Furthermore, Idso's model was extended to estimate the daylight downward longwave irradiance under all-sky conditions by taking into account the ratio of global to the clear-sky global solar irradiance. The RMSE of the local calibrated coefficients scheme of Idso's model was 17.70 W m−2. For the estimation of the daylight upward longwave irradiance under all-sky conditions, the calibrated Dognieux and Lemoine model was used which performed well. The RMSE in this case was 12.75 W m−2.

      PubDate: 2017-09-02T09:49:12Z
      DOI: 10.1016/j.jastp.2017.08.007
      Issue No: Vol. 164 (2017)
  • Three dimensional ray tracing technique for tropospheric water vapor
           tomography using GPS measurements
    • Authors: Saeid Haji Aghajany; Yazdan Amerian
      Pages: 81 - 88
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): Saeid Haji Aghajany, Yazdan Amerian
      Tropospheric water vapor has a key role in tropospheric processes and it is an important parameter in meteorology studies. Because of its non-uniform spatiotemporal distribution, modeling the spatiotemporal variations of water vapor is a challenging subject in meteorology. The GNSS tomography of the troposphere is a promising method to assess the spatiotemporal distribution of water vapor parameter in this layer. The tomography method efficiency is dependent on the ray tracing technique and GPS derived tropospheric slant wet delays. Implementing constraints and regularization methods are necessary in order to achieve the regularized solution in troposphere tomography. In this paper, the three dimensional (3D) ray tracing technique based on Eikonal equations and ERA-I data are used to perform the reconstruction the signal path, Iranian Permanent GPS Network (IPGN) measurements are used to calculate slant wet delays and the LSQR regularization technique is used to obtain a regularized tomographic solution for tropospheric water vapor. The modeled water vapor profiles are validated using radiosonde observations.

      PubDate: 2017-09-02T09:49:12Z
      DOI: 10.1016/j.jastp.2017.08.003
      Issue No: Vol. 164 (2017)
  • Is the “Earth-ionosphere capacitor” a valid component in the
           atmospheric global electric circuit'
    • Authors: Christos Haldoupis; Michael Rycroft; Earle Williams; Colin Price
      Pages: 127 - 131
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): Christos Haldoupis, Michael Rycroft, Earle Williams, Colin Price
      This paper examines whether the Earth-ionosphere capacitor (EIC) model is correct, by comparing observed atmospheric electrical properties with those expected for a spherical capacitor, as defined in electrostatics. The comparisons suggest that the EIC concept cannot be reconciled with, and hence cannot account for, the observations, particularly the rapid reduction of the atmospheric electric field with height that is measured. This means that the spherical EIC concept is incorrect by being too simplistic; it is thus misleading. The reason for this flawed concept is simple: the model disregards the non-uniform conductivity of the atmosphere which requires the presence of a net positive charge in the lower atmosphere that equals in magnitude the Earth's negative charge. This positive charge shields the action of the Earth's negative charge from polarizing the ionosphere positively. Thus, the lower D region ionosphere remains electrically neutral, which makes the EIC concept inappropriate.

      PubDate: 2017-09-02T09:49:12Z
      DOI: 10.1016/j.jastp.2017.08.012
      Issue No: Vol. 164 (2017)
  • Climatology of GW-TIDs in the magnetic equatorial upper thermosphere over
    • Authors: G. Manju; R.P. Aswathy
      Pages: 142 - 148
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): G. Manju, R.P. Aswathy
      An analysis of Gravity wave induced travelling ionospheric disturbances (GW-TIDs) in the thermosphere during high and low solar epochs is undertaken using ionosonde data at Trivandrum (8.50N, 770E). Wavelet analysis is performed on the temporal variations of foF2 and the amplitudes of waves present in two period bands of (0.5–1.5) h and (2–4) h are extracted. The real height profiles are generated at 15 min internal for the whole day (for sample days) during high and low solar activity years. The study reveals that the GW-TID activity is significantly greater for solar minimum compared to solar maximum for the period 8.5–17.5 h. Diurnally the GW-TID activity in the (2–4) h period band peaks in the post sunset hours for both high and low solar epochs. For the 0.5–1.5 h period band, the diurnal maximum in GW-TID is occurring in the post sunset hours for high solar epoch while it occurs in the morning hours around 10 h LT for low solar epoch. Seasonally the day time GW-TID activity maximizes (minimizes) for winter (vernal equinox). The post sunset time GW-TID maximizes (minimizes) either for summer/winter (vernal equinox). The other interesting observation is the anti correlation of GW-TID in upper thermosphere with solar activity for day time and the correlation of the same with solar activity in the post sunset hours. The present results for daytime are in agreement with the equatorial daytime GW-TID behaviour reported from CHAMP satellite observations. The GW-TID activity during post sunset time for equatorial region upper thermosphere has not been reported so far.

      PubDate: 2017-09-02T09:49:12Z
      DOI: 10.1016/j.jastp.2017.08.015
      Issue No: Vol. 164 (2017)
  • The evolution of geomagnetotail magnetic flux in isolated substorms
    • Authors: Y.Y. Yang; C. Shen; Z.J. Rong; M. Dunlop; X.H. Shen; J.P. Huang; Z.Q. Chen
      Pages: 163 - 171
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): Y.Y. Yang, C. Shen, Z.J. Rong, M. Dunlop, X.H. Shen, J.P. Huang, Z.Q. Chen
      The magnetic field energy stored in geomagnetotail released during a substorm period, cause significant magnetic disturbance of the space environment. The quantitative relationship between the magnetic field energy and the level of substorm activity, however, is still unclear, although many studies have qualitatively revealed the correlation between them. Here, using data from four selected isolated substorm cases, the evolution of the magnetic flux (MF) in the magnetotail observed by Cluster is quantitatively surveyed. The results from the four cases demonstrate that the evolution of magnetotail MF is closely related to the phases of substorm development. For quiet time, the magnetotail is in the ground state with MF being about 0.6 GWb. During the growth phase, however, as the substorm develop the MF keeps increasing, the substorm onset is triggered when the MF has increased up to some threshold. The comparison between the four cases shows that the accumulation of more magnetic field energy corresponds to more released energy, and consistently, the more intense a substorm can be powered. The study also finds that there is an imbalance between the increased and decreased MF amplitude, indicating that the substorm may not be the only way to release the stored magnetotail energy.

      PubDate: 2017-09-02T09:49:12Z
      DOI: 10.1016/j.jastp.2017.08.016
      Issue No: Vol. 164 (2017)
  • Unusual lightning electric field waveforms observed in Kathmandu, Nepal,
           and Uppsala, Sweden
    • Authors: Pitri Bhakta Adhikari; Shriram Sharma; Kedarnath Baral; Vladimir A. Rakov
      Pages: 172 - 184
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): Pitri Bhakta Adhikari, Shriram Sharma, Kedarnath Baral, Vladimir A. Rakov
      Unusual lightning events have been observed in Uppsala, Sweden, and Kathmandu, Nepal, using essentially the same electric field measuring system developed at Uppsala University. They occurred in the storms that also generated “normal” lightning events. The unusual events recorded in Uppsala occurred on one thunderstorm day. Similar events were observed in Kathmandu on multiple thunderstorm days. The unusual events were analyzed in this study assuming them to be positive ground flashes (+CGs), although we cannot rule out the possibility that some or most of them were actually cloud discharges (ICs). The unusual events were each characterized by a relatively slow, negative (atmospheric electricity sign convention) electric field waveform preceded by a pronounced opposite-polarity pulse whose duration was some tens of microseconds. To the best of our knowledge, such unusual events have not been reported in the literature. The average amplitudes of the opposite-polarity pulses with respect to those of the following main waveform were found to be about 33% in Uppsala (N = 31) and about 38% in Kathmandu (N = 327). The average durations of the main waveform and the preceding opposite-polarity pulse in Uppsala were 8.24 ms and 57.1 μs, respectively, and their counterparts in Kathmandu were 421 μs and 39.7 μs. Electric field waveforms characteristic of negative ground flashes (-CGs) were also observed, and none of them exhibited an opposite-polarity pulse prior to the main waveform. Possible origins of the unusual field waveforms are discussed.

      PubDate: 2017-09-02T09:49:12Z
      DOI: 10.1016/j.jastp.2017.08.028
      Issue No: Vol. 164 (2017)
  • Longitudinal expansion of field line dipolarization
    • Authors: O. Saka; K. Hayashi
      Pages: 235 - 242
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): O. Saka, K. Hayashi
      We examine the substorm expansions that started at 1155 UT 10 August 1994 in the midnight sector focusing on the longitudinal (eastward) expansion of field line dipolarization in the auroral zone. Eastward expansion of the dipolarization region was observed in all of the H, D, and Z components. The dipolarization that started at 1155 UT (0027 MLT) from 260° of geomagnetic longitude (CMO) expanded to 351°(PBQ) in about 48 min. The expansion velocity was 0.03–0.04°/s, or 1.9 km/s at 62°N of geomagnetic latitude. The dipolarization region expanding to the east was accompanied by a bipolar event at the leading edge of the expansion in latitudes equatorward of the westward electrojet (WEJ). In the midnight sector at the onset meridian, the Magnetospheric Plasma Analyzer (MAP) on board geosynchronous satellite L9 measured electrons and ions between 10 eV and 40 keV. We conclude from the satellite observations that this dipolarization was characterized by the evolution of temperature anisotropies, an increase of the electron and ion temperatures, and a rapid change in the symmetry axis of the temperature tensor. The field line dipolarization and its longitudinal expansion were interpreted in terms of the slow MHD mode triggered by the current disruption. We propose a new magnetosphere-ionosphere coupling (MI-coupling) mechanism based on the scenario that transmitted westward electric fields from the magnetosphere in association with expanding dipolarization produced electrostatic potential (negative) in the ionosphere through differences in the mobility of collisional ions and collisionless electrons. The field-aligned currents that emerged from the negative potential region are arranged in a concentric pattern around the negative potential region, upward toward the center and downward on the peripheral.

      PubDate: 2017-09-14T10:17:30Z
      DOI: 10.1016/j.jastp.2017.09.009
      Issue No: Vol. 164 (2017)
  • Exploring noctilucent cloud variability using the nudged and extended
           version of the Canadian Middle Atmosphere Model
    • Authors: Maartje Kuilman; Bodil Karlsson; Susanne Benze; Linda Megner
      Pages: 276 - 288
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): Maartje Kuilman, Bodil Karlsson, Susanne Benze, Linda Megner
      Ice particles in the summer mesosphere – such as those connected to noctilucent clouds and polar mesospheric summer echoes - have since their discovery contributed to the uncovering of atmospheric processes on various scales ranging from interactions on molecular levels to global scale circulation patterns. While there are numerous model studies on mesospheric ice microphysics and how the clouds relate to the background atmosphere, there are at this point few studies using comprehensive global climate models to investigate observed variability and climatology of noctilucent clouds. In this study it is explored to what extent the large-scale inter-annual characteristics of noctilucent clouds are captured in a 30-year run - extending from 1979 to 2009 - of the nudged and extended version of the Canadian Middle Atmosphere Model (CMAM30). To construct and investigate zonal mean inter-seasonal variability in noctilucent cloud occurrence frequency and ice mass density in both hemispheres, a simple cloud model is applied in which it is assumed that the ice content is solely controlled by the local temperature and water vapor volume mixing ratio. The model results are compared to satellite observations, each having an instrument-specific sensitivity when it comes to detecting noctilucent clouds. It is found that the model is able to capture the onset dates of the NLC seasons in both hemispheres as well as the hemispheric differences in NLCs, such as weaker NLCs in the SH than in the NH and differences in cloud height. We conclude that the observed cloud climatology and zonal mean variability are well captured by the model.

      PubDate: 2017-09-25T11:18:52Z
      DOI: 10.1016/j.jastp.2017.08.019
      Issue No: Vol. 164 (2017)
  • κ distribution of carbon II doublet in the solar transition region
    • Authors: Jian He; Qingguo Zhang
      Pages: 289 - 293
      Abstract: Publication date: Available online 22 September 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jian He, Qingguo Zhang
      For accurate spectral diagnostics of the solar plasma in the transition region, the averaged collision strength of the κ distribution of electron energies is discussed for non-Maxwellian distribution, and the Maxwellian averaged collision strengths and the non-Maxwellian averaged collision strengths for κ  = 2, 3 and 5 from 104.4 to 106.0 K are calculated for Carbon II doublet in the transition region. Results are in agreement with those from the CHIANTI database, and the main error comes from the approximation of the collision strength. This calculation will be significant for spectral diagnostics of the solar plasma for non-Maxwellian distribution of the electron energies.

      PubDate: 2017-09-25T11:18:52Z
      DOI: 10.1016/j.jastp.2017.09.017
      Issue No: Vol. 164 (2017)
  • Mesospheric temperature trends derived from standard phase-height
    • Authors: Dieter H.W. Peters; Günter Entzian; Philippe Keckhut
      Pages: 23 - 30
      Abstract: Publication date: October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 163
      Author(s): Dieter H.W. Peters, Günter Entzian, Philippe Keckhut
      New homogeneous time series of daily standard phase-height (SPH) and daily plasma scale-height (PSH) have been derived from a 50-year long-radio-wave measurement of the broadcasting station Allouis (France, 162kHz). The signal was received at Kühlungsborn (54°N, 12°E, Mecklenburg, Germany) and the present series is a third release. The daily time series of SPH shows in its spectrum dominant modes which are typical for the solar cycle (SC), for El Niño-Southern Oscillation (ENSO) and for quasi-biannual oscillation (QBO), indicating solar and lower atmospheric influences. Surprisingly, the time series of daily PSH shows a band of dominant cycles larger than 16 years. In order to exclude the influence of the winter anomaly in the determination of column-integrated mesospheric temperature trends the phase-height-temperature procedure is confined to summer months. The derived thickness temperature of the mesosphere decreased statistically significant over the period 1959–2008 after pre-whitening with summer mean of solar sun spot numbers. The trend value is in the order of about −1.05K/decade if the stratopause trend is excluded. The linear regression is more pronounced, −1.35K/decade for the period of 1963–1985 (2 SCs), but weaker, −0.51K/decade during 1986-2008 (last 2 SCs). The linear regression is in very good agreement with a mean column-integrated mesospheric trend derived from OHP-Lidar temperatures on a monthly mean basis for the last two SCs. This clearly shows that the thickness temperature of the mesosphere derived from phase-height measurement is a useful proxy for the long-term summer temperature change in the mesosphere from 1959 until 2008.

      PubDate: 2017-10-11T21:25:04Z
      DOI: 10.1016/j.jastp.2017.04.007
      Issue No: Vol. 163 (2017)
  • Variability of virtual layered phenomena in the mesosphere observed with
           medium frequency radars at 69°N
    • Authors: Toralf Renkwitz; Ralph Latteck
      Pages: 38 - 45
      Abstract: Publication date: October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 163
      Author(s): Toralf Renkwitz, Ralph Latteck
      The MF-Saura radar positioned at polar latitudes is very sensitive to enhanced ionization caused by solar and geomagnetic activity. Differing from the intensities normally detected by partial reflections from the ionospheric D region during quiet conditions, distinct layers can be seen due to intense increase of electron number density at as low as 50 km altitude caused by particle precipitation. Effects of energetic particle precipitation on observations by medium frequency (MF) radars have been rarely reported so far, generally associated with solar proton events, which are rather scarce especially during solar minimum conditions. Here, we focus on events associated with precipitation of particles with lower energy (<10 MeV), which are seen by the MF radar with occurrence rates of as much as 40% at times. Such situations are studied for a period of continuous observations for one solar cycle and statistical results like diurnal and annual distributions are presented.

      PubDate: 2017-10-11T21:25:04Z
      DOI: 10.1016/j.jastp.2017.05.009
      Issue No: Vol. 163 (2017)
  • Long term variabilities and tendencies of mesospheric lunar semidiurnal
           tide over Tirunelveli (8.7°N, 77.8°E)
    • Authors: S. Sathishkumar; S. Sridharan; P.V. Muhammed Kutty; S. Gurubaran
      Pages: 46 - 53
      Abstract: Publication date: October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 163
      Author(s): S. Sathishkumar, S. Sridharan, P.V. Muhammed Kutty, S. Gurubaran
      The medium frequency radar deployed at Tirunelveli (8.7°N, 77.8°E), which is located near the southmost tip of peninsular India, have been providing continuous data from the year 1993 to the year 2012 that helped to study the long term tendencies in the lunar tidal variabilities over this geographic location. In the present paper we present the results of seasonal, interannual and long-term variabilities of lunar semi-diurnal tides in the upper mesosphere over Tirunelveli. The present study also includes comparison with model values. The study shows that the tidal amplitudes are larger in the meridional components of the mesospheric winds than the zonal winds. The seasonal variations of the tides are similar in both the components. The tides show maximum amplitudes of about ∼5 m/s in February/March, secondary maximum amplitudes of about ∼3 m/s in September and minimum amplitudes during summer months (May–August). The observed seasonal variation of the lunar tides do not compare well with Vial and Forbes (1994) model values, though it is consistent with earlier observations. The lunar tidal phase in meridional winds leads that in zonal winds from January to June and from September to November, while the latter leads the former during July/August. The lunar tides show large interannual variability. There are unusual amplitude enhancements in the lunar tide in meridional winds during the winters of 2006 and 2009, when major sudden stratospheric warmings (SSW) occurred at high latitude northern hemisphere, whereas zonal lunar tide does not show any clear association with the SSW. Vertical wavelengths of lunar tides in zonal and meridional wind are in the range of 20–90 km. The vertical wavelengths of lunar tides in both zonal and meridional component are smaller in June and larger in November and December. The monthly mean zonal and meridional winds are subjected to regression analysis to study the tidal response to long-period oscillations, namely, quasi-biennial oscillation (QBO), solar cycle variation and El-nino southern oscillation (ENSO). It is found the lunar tide in both zonal and meridional winds show significant QBO response, whereas zonal tide only shows significant negative response to solar cycle and positive response to ENSO. Besides, zonal tide only shows significant long-term increasing trend.

      PubDate: 2017-10-11T21:25:04Z
      DOI: 10.1016/j.jastp.2017.05.015
      Issue No: Vol. 163 (2017)
  • Radar observations of the quarterdiurnal tide at midlatitudes: Seasonal
           and long-term variations
    • Authors: Christoph Jacobi; Amelie Krug; Eugeny Merzlyakov
      Pages: 70 - 77
      Abstract: Publication date: October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 163
      Author(s): Christoph Jacobi, Amelie Krug, Eugeny Merzlyakov
      The seasonal and interannual variability of the quarterdiurnal tide is analysed using meteor radar wind observations at the two midlatitude sites Collm and Obninsk. Generally tidal amplitudes increase with height. Maximum tidal amplitudes are found in winter. Meridional amplitudes are smaller than zonal ones on an average. Phases mainly differ between summer and winter. Zonal and meridional phases differ by slightly less than 90°. The vertical wavelengths are very long in winter, but shorter and on the order of 20 km in summer. Collm and Obninsk amplitudes and phases agree well, indicating that the migrating quarterdiurnal tide may be responsible for a major part of the observed waves. Observations since 1980 show that the tidal amplitudes have increased on a whole, although the increase is not linear but mainly happening during the late 1990s and the early 2000s.

      PubDate: 2017-10-11T21:25:04Z
      DOI: 10.1016/j.jastp.2017.05.014
      Issue No: Vol. 163 (2017)
  • Long-term trends in the D- and E-region based on rocket-borne measurements
    • Authors: M. Friedrich; C. Pock; K. Torkar
      Pages: 78 - 84
      Abstract: Publication date: October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 163
      Author(s): M. Friedrich, C. Pock, K. Torkar
      Electron densities obtained from rocket borne measurements are compared to an empirical, steady state model built from these data. The ratios between each measured value and its corresponding model value vs. time yield trends which significantly vary with altitude. Notably above 120–130km the electron densities generally increase, whereas between 95 and 120km the ionosphere appears stable. Somewhere below 80–90km - depending on the investigated data subset - there is again a positive trend down to below 70km. Tentative explanations such as cooling of the mesosphere are suggested and may be confirmed by comprehensive theoretical models of the upper atmosphere.

      PubDate: 2017-10-11T21:25:04Z
      DOI: 10.1016/j.jastp.2017.04.009
      Issue No: Vol. 163 (2017)
  • Long-term variations and trends in the polar E-region
    • Authors: L.M. Bjoland; Y. Ogawa; C. Hall; M. Rietveld; U.P. Løvhaug; C. La Hoz; H. Miyaoka
      Pages: 85 - 90
      Abstract: Publication date: October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 163
      Author(s): L.M. Bjoland, Y. Ogawa, C. Hall, M. Rietveld, U.P. Løvhaug, C. La Hoz, H. Miyaoka
      As the EISCAT UHF radar system in Northern Scandinavia started its operations in the early 1980s, the collected data cover about three solar cycles. These long time-series provide us the opportunity to study long-term variations and trends of ionospheric parameters in the high latitude region. In the present study we have used the EISCAT Tromsø UHF data to investigate variations of the Hall conductivity and ion temperatures in the E-region around noon. Both the ion temperature and the peak altitude of the Hall conductivity are confirmed to depend strongly on solar zenith angle. However, the dependence on solar activity seems to be weak. In order to search for trends in these parameters, the ion temperature and peak altitude of the Hall conductivity data were adjusted for their seasonal and solar cycle dependence. A very weak descent (∼0.2km/ decade) was seen in the peak altitude of the Hall conductivity. The ion temperature at 110km shows a cooling trend (∼10K/ decade). However, other parameters than solar zenith angle and solar activity seem to affect the ion temperature at this altitude, and a better understanding of these parameters is necessary to derive a conclusive trend. In this paper, we discuss what may cause the characteristics of the variations in the electric conductivities and ion temperatures in the high latitude region.

      PubDate: 2017-10-11T21:25:04Z
      DOI: 10.1016/j.jastp.2017.02.007
      Issue No: Vol. 163 (2017)
  • Equivalent slab thickness of the ionosphere over Europe as an indicator of
           long-term temperature changes in the thermosphere
    • Authors: Norbert Jakowski; Mohammed Mainul Hoque; Jens Mielich; Chris Hall
      Pages: 91 - 102
      Abstract: Publication date: October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 163
      Author(s): Norbert Jakowski, Mohammed Mainul Hoque, Jens Mielich, Chris Hall
      Simultaneous measurements of the total electron content (TEC) and the peak electron density NmF2 at vertical sounding stations enable the estimation of the equivalent slab thickness of the ionosphere. This shape parameter, defined as the ratio of the observables TEC and NmF2 of the vertical electron density profile, is closely related to the neutral gas scale height under steady-state conditions at daytime. In this paper we present for the first time a long term trend (LTT) analysis of the equivalent slab thickness for estimating long term trends of thermospheric temperature changes. The analysis is made for 5 vertical sounding stations located in the latitude range 40–70°N in Europe and covers the entire solar cycle 23 during the years 1995–2009. The observations indicate a long term decrease of the equivalent slab thickness at all ionosonde stations considered here from 11 to 62km/decade with increasing tendency towards higher latitudes. Since the seasonal dynamics of the slab thickness clearly overestimates expected temperature changes, it has been found that composition changes, in particular the atomic oxygen/molecular nitrogen density ratio, contribute essentially to the high dynamics of the equivalent slab thickness closely associated with the occurrence of the well-known daytime winter anomaly in Northern mid-latitudes. In analogy, to explain remaining temperature overestimates in the long term trends of the equivalent slab thickness, it is assumed that a long term increase of the atomic oxygen/molecular nitrogen density ratio exist. So the contraction (decrease of scale height and equivalent slab thickness) and the lowering (decrease of the peak density height hmF2) of the electron density profile can be understood in a consistent manner. It is demonstrated that a permanent monitoring of the equivalent slab thickness can contribute to explore long term changes of the thermosphere. To get quantitative estimates of thermospheric temperature changes based on this new LTT monitoring technique, more detailed studies including first principles models are needed.

      PubDate: 2017-10-11T21:25:04Z
      DOI: 10.1016/j.jastp.2017.04.008
      Issue No: Vol. 163 (2017)
  • Performance analysis of 60-min to 1-min integration time rain rate
           conversion models in Malaysia
    • Authors: Yun-Yann Ng; Mandeep Singh Jit Singh; Vinesh Thiruchelvam
      Abstract: Publication date: Available online 12 October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Yun-Yann Ng, Mandeep Singh Jit Singh, Vinesh Thiruchelvam
      Utilizing the frequency band above 10 GHz is in focus nowadays as a result of the fast expansion of radio communication systems in Malaysia. However, rain fade is the critical factor in attenuation of signal propagation for frequencies above 10 GHz. Malaysia is located in a tropical and equatorial region with high rain intensity throughout the year, and this study will review rain distribution and evaluate the performance of 60-min to 1-min integration time rain rate conversion methods for Malaysia. Several conversion methods such as Segal, Chebil & Rahman, Burgeono, Emiliani, Lavergnat and Gole (LG), Simplified Moupfouma, Joo et al., fourth order polynomial fit and logarithmic model have been chosen to evaluate the performance to predict 1-min rain rate for 10 sites in Malaysia. After the completion of this research, the results show that Chebil & Rahman model, Lavergnat & Gole model, Fourth order polynomial fit and Logarithmic model have shown the best performances in 60-min to 1-min rain rate conversion over 10 sites. In conclusion, it is proven that there is no single model which can claim to perform the best across 10 sites. By averaging RMSE and SC-RMSE over 10 sites, Chebil and Rahman model is the best method.

      PubDate: 2017-10-13T21:34:38Z
      DOI: 10.1016/j.jastp.2017.10.004
  • Comment on the paper by Popova et al. “On a role of quadruple component
           of magnetic field in defining solar activity in grand cycles”
    • Authors: V. Zharkova; E. Popova; S. Shepherd; S. Zharkov
      Abstract: Publication date: Available online 7 October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Ilya G. Usoskin
      The paper by Popova et al. presents an oversimplified mathematical model of solar activity with a claim of predicting/postdicting it for several millennia ahead/backwards. The work contains several flaws devaluating the results: (1) the method is unreliable from the point of view of signal processing (it is impossible to make harmonic predictions for thousands of years based on only 35 years of data) and lacks quality control; (2) the result of post-diction apparently contradicts the observational data. (3) theoretical speculations make little sense. To summarize, a multi-harmonic mathematical model, hardly related to full solar dynamo theory, is presented, which is not applicable to realistic solar conditions because of the significant chaotic/stochastic intrinsic component and strong non-stationarity of solar activity. The obtained result is apparently inconsistent with the data in the past and thus cannot be trusted for the future predictions.

      PubDate: 2017-10-11T21:25:04Z
      DOI: 10.1016/j.jastp.2017.09.019
  • Preface to Long-term trends in the upper atmosphere and ionosphere
    • Authors: F.-J.
      Abstract: Publication date: October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 163
      Author(s): J. Laštovička, F.-J. Lübken

      PubDate: 2017-10-11T21:25:04Z
  • A review of recent progress in trends in the upper atmosphere
    • Authors: Jan
      Abstract: Publication date: October 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 163
      Author(s): Jan Laštovička
      The anthropogenic emissions of greenhouse gases affect not only the weather and climate in the troposphere; they affect also long-term trends in the mesosphere-thermosphere-ionosphere system, where the amplitudes of anthropogenic changes are substantially larger than in the troposphere. The last four years have seen significant progress in investigating these trends but also some new puzzles have been created. Observations of the CO2 trend in the lower thermosphere appeared but their interpretation is a matter of debate. The role of ozone in mesospheric temperatures and E-region ionosphere has been confirmed and quantified. Agreement between observational and simulated trends in the thermospheric density, supported by satellite observations of radiative cooling was reached but the most recent result re-opened the problem. Much new partial information about trends in the ionospheric F region was reported. Also new information on other experimental trends helped to improve our understanding of long-term trends in the upper atmosphere. Significant progress has been reached in modelling the long-term trends; in a few parameters the agreement with observed trends is now not only quantitative but also qualitative. Several attempts to explain ionospheric trends without CO2 appeared but they are shown not to be correct; CO2 remains to be the primary (although not the only) trend driver. On the other hand, many open questions or puzzles, listed in Concluding remarks, remain to be investigated.

      PubDate: 2017-10-11T21:25:04Z
  • DMSP observations of high latitude Poynting flux during magnetic storms
    • Authors: Cheryl Y. Huang; Yanshi Huang; Yi-Jiun Su; Marc R. Hairston; Thomas Sotirelis
      Abstract: Publication date: Available online 21 September 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Cheryl Y. Huang, Yanshi Huang, Yi-Jiun Su, Marc R. Hairston, Thomas Sotirelis
      Previous studies have demonstrated that energy can enter the high-latitude regions of the Ionosphere-Thermosphere (IT) system on open field lines. To assess the extent of high-latitude energy input, we have carried out a study of Poynting flux measured by the Defense Meteorological Satellite Program (DMSP) satellites during magnetic storms. We report sporadic intense Poynting fluxes measured by four DMSP satellites at polar latitudes during two moderate magnetic storms which occurred in August and September 2011. Comparisons with a widely used empirical model for energy input to the IT system show that the model does not adequately capture electromagnetic (EM) energy at very high latitudes during storms. We have extended this study to include more than 30 storm events and find that intense EM energy is frequently detected poleward of 75° magnetic latitude.

      PubDate: 2017-09-25T11:18:52Z
      DOI: 10.1016/j.jastp.2017.09.005
  • Impacts of spectral nudging on the simulated surface air temperature in
           summer compared with the selection of shortwave radiation and land surface
           model physics parameterization in a high-resolution regional atmospheric
    • Authors: Jun Park; Seung-On Hwang
      Abstract: Publication date: Available online 6 September 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jun Park, Seung-On Hwang
      The impact of a spectral nudging technique for the dynamical downscaling of the summer surface air temperature in a high-resolution regional atmospheric model is assessed. The performance of this technique is measured by comparing 16 analysis-driven simulation sets of physical parameterization combinations of two shortwave radiation and four land surface model schemes of the model, which are known to be crucial for the simulation of the surface air temperature. It is found that the application of spectral nudging to the outermost domain has a greater impact on the regional climate than any combination of shortwave radiation and land surface model physics schemes. The optimal choice of two model physics parameterizations is helpful for obtaining more realistic spatiotemporal distributions of land surface variables such as the surface air temperature, precipitation, and surface fluxes. However, employing spectral nudging adds more value to the results; the improvement is greater than using sophisticated shortwave radiation and land surface model physical parameterizations. This result indicates that spectral nudging applied to the outermost domain provides a more accurate lateral boundary condition to the innermost domain when forced by analysis data by securing the consistency with large-scale forcing over a regional domain. This consequently indirectly helps two physical parameterizations to produce small-scale features closer to the observed values, leading to a better representation of the surface air temperature in a high-resolution downscaled climate.

      PubDate: 2017-09-08T10:00:34Z
      DOI: 10.1016/j.jastp.2017.09.001
  • Effects of atmospheric oscillations at different time scales on persistent
           autumn rainstorms in Hainan, China
    • Authors: Jiangnan Li; Qingwen Ye; Fangzhou Li; Chenghui Ding; Youlong Chen; Yanbin Huang
      Abstract: Publication date: Available online 6 September 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jiangnan Li, Qingwen Ye, Fangzhou Li, Chenghui Ding, Youlong Chen, Yanbin Huang
      In the autumn of 2008, 2010, and 2011, Hainan experienced anomalously persistent rainstorms. The objective of this study was to examine the roles of atmospheric oscillations at different time scales on these three rainstorm events. A wavelet analysis of daily rainfall data revealed that the 3–10-day synoptic-scale oscillations were the dominant mode in 2008 and 2011 and the 8–15-day quasi-biweekly oscillations were dominant in 2010. These three autumn rainstorm events can be divided into two major periods. Both the synoptic-scale and quasi-biweekly mode influenced the rainstorms, but their oscillation centers and propagation directions were completely different. There is a good corresponding relationship between the two heavy rain periods and the synoptic-scale oscillation cyclones and convection during the autumn of 2008 and 2011. During the first period, moisture mainly came from vapor convergence in the South China Sea (SCS), but during the second period, moisture came from the equatorial Indian Ocean. The major source of the synoptic-scale oscillation was the western North Pacific. The synoptic-scale oscillation cyclones and convection moved northwest to Hainan, resulting in heavy rainfall. Moisture during the first period mainly came from water vapor convergence in the SCS during the autumn of 2010, but moisture in the second period came from western North Pacific. The quasi-biweekly oscillation convection was generated and developed mainly over the equatorial Indian Ocean. Strong convection accompanying oscillation cyclones spread toward the northeast, triggering heavy precipitation in the Hainan region.

      PubDate: 2017-09-08T10:00:34Z
      DOI: 10.1016/j.jastp.2017.09.002
  • Considering the potential of IAR emissions for ionospheric sounding
    • Authors: A.S. Potapov; T.N. Polyushkina; B. Tsegmed; A.V. Oinats; A. Yu. Pashinin; I.K. Edemskiy; A.A. Mylnikova; K.G. Ratovsky
      Abstract: Publication date: Available online 4 September 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.S. Potapov, T.N. Polyushkina, B. Tsegmed, A.V. Oinats, A. Yu. Pashinin, I.K. Edemskiy, A.A. Mylnikova, K.G. Ratovsky
      Knowledge of the ionospheric state allows us to adjust the forecasts of radio wave propagation, specify the environment models, and follow the changes of space weather. At present, probing of the ionosphere is produced by radio sounding with ground ionosondes, as well as by raying signals from satellites. We want to draw attention to the possibility of the diagnosis of the ionospheric parameters by detecting ultra-low frequency (ULF) electromagnetic emission generated in the so-called ionospheric Alfvén resonator (IAR). To do this, we present observations of the IAR emission made simultaneously for the first time at three stations using identical induction magnetometers. The stations are within one-hour difference of local time, two of them are mid-latitudinal; the third one is situated in the auroral zone. We compare frequency and frequency difference between adjacent harmonics of the observed multi-band emission with ionospheric parameters measured at the stations using ionosondes and GPS-observations. Diurnal variations of the ionospheric and ULF emission characteristics are also compared. The results show that there is quite a stable correlation between the resonant frequencies of the resonator bands and the critical frequency of the F2 layer of the ionosphere, namely, the frequency of the IAR emission varies inversely as the critical frequency of the ionosphere. This is due to the fact that the frequency of oscillation captured in the resonator is primarily determined by the Alfvén velocity (which depends on the plasma density) in the ionospheric F2 layer. The correlation is high; it varies at different stations, but is observed distinctly along the whole meridian. However, coefficients of a regression equation that connects the ionosphere critical frequency with DSB frequency vary significantly from day to day at all stations. The reason for such a big spread of the regression parameters is not clear and needs further investigation before we are able to develop a method for evaluating the ionosphere critical frequency using the IAR emission observations. Such a method may prove to be useful as an additional alternative to the basic method for probing the ionosphere using digisondes. This is especially important for auroral regions, where the presence of strong absorption, shielding by a lower layer, stratification, the presence of echoes, etc. make the sounding difficult.

      PubDate: 2017-09-08T10:00:34Z
      DOI: 10.1016/j.jastp.2017.08.026
  • Investigation of Kelvin wave periods during Hai-Tang typhoon using
           Empirical Mode Decomposition
    • Authors: P. Kishore; J. Jayalakshmi; Pay Liam-Lin; Isabella Velicogna; Tyler C. Sutterley; Enrico Ciracì; Yara Mohajerani; S. Balaji Kumar
      Abstract: Publication date: Available online 1 September 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): P. Kishore, J. Jayalakshmi, Pay Liam-Lin, Isabella Velicogna, Tyler C. Sutterley, Enrico Ciracì, Yara Mohajerani, S. Balaji Kumar
      Equatorial Kelvin waves (KWs) are fundamental components of the tropical climate system. In this study, we investigate Kelvin waves (KWs) during the Hai-Tang typhoon of 2005 using Empirical Mode Decomposition (EMD) of regional precipitation, zonal and meridional winds. For the analysis, we use daily precipitation datasets from the Global Precipitation Climatology Project (GPCP) and wind datasets from the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-analysis (ERA-Interim). As an additional measurement, we use in-situ precipitation datasets from rain-gauges over the Taiwan region. The maximum accumulated precipitation was approximately 2400 mm during the period July 17–21, 2005 over the southwestern region of Taiwan. The spectral analysis using the wind speed at 950 hPa found in the 2nd, 3rd, and 4th intrinsic mode functions (IMFs) reveals prevailing Kelvin wave periods of ∼3 days, ∼4–6 days, and ∼6–10 days, respectively. From our analysis of precipitation datasets, we found the Kelvin waves oscillated with periods between ∼8 and 20 days.

      PubDate: 2017-09-02T09:49:12Z
      DOI: 10.1016/j.jastp.2017.07.025
  • GPS amplitude and phase scintillation associated with polar cap auroral
    • Authors: P.T. Jayachandran; A.M. Hamza; K. Hosokawa; H. Mezoui; K. Shiokawa
      Abstract: Publication date: Available online 1 September 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): P.T. Jayachandran, A.M. Hamza, K. Hosokawa, H. Mezoui, K. Shiokawa
      Global Positioning System (GPS) signal amplitude and phase scintillation occurrence were observed in close association with polar cap auroral forms. Scintillation were present on most GPS ray paths irrespective of the ray path's location and orientation relative to arc alignment, motion and the direction of E × B drift. Spectra of amplitude and phase scintillation show similar power law behaviour with close to identical power law coefficients. The distribution of power law coefficients shows an average power law coefficient of ∼−2.3, which is different from the spectral characteristics of equatorial and low latitude scintillation.

      PubDate: 2017-09-02T09:49:12Z
      DOI: 10.1016/j.jastp.2017.08.030
  • Numerical study of heating the upper atmosphere by acoustic-gravity waves
           from a local source on the Earth's surface and influence of this heating
           on the wave propagation conditions
    • Authors: I.V. Karpov; S.P. Kshevetskii
      Abstract: Publication date: Available online 31 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): I.V. Karpov, S.P. Kshevetskii
      The propagation of acoustic-gravity waves (AGW) from a source on the Earth's surface to the upper atmosphere is investigated with methods of mathematical modeling. The applied non-linear model of wave propagation in the atmosphere is based on numerical integration of a complete set of two-dimensional hydrodynamic equations. The source on the Earth's surface generates waves with frequencies near to the Brunt-Vaisala frequency. The results of simulation have revealed that some region of heating the atmosphere by propagated upward and dissipated AGWs arises above the source at altitudes nearby of 200 km. The horizontal scale of this heated region is about 1000 km in the case of the source that radiates AGWs during approximately 1 h. The appearing of the heated region has changed the conditions of AGW propagation in the atmosphere. When the heated region in the upper atmosphere has been formed, further a waveguide regime of propagation of waves with the periods shorter the Brunt-Vaisala period is realized. The upper boundary of the wave-guide coincides with the arisen heated region in the upper atmosphere. The considered mechanism of formation of large-scale disturbances in the upper atmosphere may be useful for explanation of connections of processes in the upper and lower atmospheric layers.

      PubDate: 2017-08-03T07:02:04Z
      DOI: 10.1016/j.jastp.2017.07.019
  • Characteristics of convective structures of sodium layer in lower
           thermosphere (105–120 km) at Haikou (19.99°N, 110.34°E), China
    • Authors: Jing Jiao; Guotao Yang; Jihong Wang; Tiemin Zhang; Hongyan Peng; Yuchang Xun; Zhengkuan Liu; Chi Wang
      Abstract: Publication date: Available online 29 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jing Jiao, Guotao Yang, Jihong Wang, Tiemin Zhang, Hongyan Peng, Yuchang Xun, Zhengkuan Liu, Chi Wang
      The atmospheric sodium layer normally occurs in the mesopause (80–105 km) region, but rarely in the lower thermosphere region (>105 km) at low latitude. We observed a kind of peculiar sodium layer in lower thermosphere at Haikou (19.99.00°N, 110.34°E)—the thermospheric convective sodium layer (TCSL) in a lidargram. The TCSL's sodium density unstably developed over time and appeared as several discontinuous convective shapes vertically. It is the first time convective sodium layer observed in the lower thermosphere region (105–120 km). Based on Haikou lidar data, we obtained 14 TCSL events during 180 nights from March 2010 to August 2012. Most of the apogees of the TCSL events are higher than 108 km. A TCSL event lasts several hours and is composed of several convective structures, with each veitical shape lasting ∼5–30 min. All TCSL events occurred during spring and summer, and generally appear near midnight (22:00–00:00 LT). The TCSL has potential regional feature and appears to be related to the thermospheric sporadic E (Es) layers, winds, and field-aligned ionospheric irregularities (FAI).

      PubDate: 2017-08-03T07:02:04Z
      DOI: 10.1016/j.jastp.2017.07.020
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Heriot-Watt University
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