CICR colloquium

25th ISEE/CICR colloquium

Speaker: Associate prof. Jeonghoon Lee, Korea University of Technology and Education
Date and Time: Jul 14 (Fri), 2017, 15:30-17:00
Place: Research Institutes Building I (ISEE), 5th floor meeting space (517)
Title: Photothermal Interferometry : An alternative tool for measuring light absorbing carbon

Abstract: Aerosol light absorption is a difficult quantity to measure without interference from the light scattering which dominates the light extinction of atmospheric aerosol. Photothermal interferometric technique is one of the photothermal spectroscopic techniques utilized to directly measure the light absorption from lab-generated aerosols as well as ambient aerosols.Photothermal interferometric technique usually detects the signal of shift in the interference pattern brought about when the optical pathlength of the probe beam is altered due to the heating of aerosol surrounding the probe beam. Two different type of photothermal interferometers will be introduced. One is an image based interferometer and the other is a polarization based interferometer. The interferometer used in this study is comprised of mirrors, beam splitters and He-Ne laser. Specifically, a diode laser having 532 nm wavelength is substituted for the large sized Ar-ion laser and is employed to heat up the aerosol sample. This study is believed to help us to elucidate the mechanism occurring inside the interferometer for aerosol absorption measurement in real time.

24th ISEE/CICR colloquium

Speaker: Prof. Surendra Kumar Dhaka, Department of Physics, Rajdhani College, University of Delhi, India
Date and Time: Jul 6 (Thu), 2017, 13:00-15:00
Place: Research Institutes Building I (ISEE), 5th floor meeting space (517)
Title: An overview of convective sources and dynamical processes in shaping the troposphere and stratosphere

Abstract: Almost over the past two decades, we have made measurements from radars during different convection seasons over Indonesia and India to demonstrate the influence of convection in connecting the lower troposphere to upper troposphere, in general these observations show fine time scale (minutes to hours) features. However, these observations were limited to a particular location. In addition, we have also used COSMIC satellite radio occultations temperature data over the globe covering almost a decade (2006 onwards, still continuing), mainly over tropical latitudes presenting a broad overview of dynamical features, such as influence of ENSO in the lower troposphere and dominance of QBO in the lower stratosphere and interaction at upper troposphere and lower stratosphere (UTLS) region. Temperature analyses for association of lower and upper troposphere are shown over different regions of the globe having contrast topography namely over Pacific sector, Indian sector, and African sector. Correlation coefficient, taken as a measurement of association, show specific longitudinal differences between lower troposphere (from 1 km to 5 km height) and cold point tropopause (CPT), which is located nearly 16 km height. The Northern and Southern hemispheres show contrast coupling between lower tropospheric region and the CPT. Land and ocean surfaces are found to contribute in a different way to the correlation coefficient (r) between lower troposphere and CPT. Analyses show symmetrical structure of ‘r’ on both side of the equator over the African region, as data included over land region on both side of equator. Data represent positive correlation (r ~ 0.5) over 15-20 degree latitudes on either side of the equator over African region, suggesting the strong hold of variation of seasonal solar diabatic heating influence over the tropic of cancer and tropic of Capricorn. On the other hand, there is a contrast behavior over the Indian region, ‘r’ is nearly negative (~ -1.0) each year in the southern hemisphere (SH) and positive (~0.4) in the northern hemisphere (NH) with a maxima near tropic of cancer. Analyses suggest that variability in CPT over different regions of globe show significant seasonal association with the lower troposphere. Thus CPT variability, not only governed by QBO, ENSO, gravity waves and Kelvin wave system as reported in earlier studies rather it also considerably affected by seasonal changes taking place in the lower troposphere.

23rd ISEE/CICR colloquium

Speaker: Prof. Bernhard Kliem Visiting Professor at ISEE / Professor at Institute of Physics and Astronomy, University of Potsdam, Germany
Date and Time: May 15 (Mon), 2017, 16:30-17:30
Place: Research Institutes Building I (ISEE), 3rd floor meeting space (301)
Title: Decay index profile and coronal mass ejection speed

Abstract: The properties of the torus instability suggest that the decay index of the coronal field has a strong influence on the acceleration of erupting flux ropes. For high decay index, the acceleration is concentrated at relatively small heights and reaches a high peak value. For small decay index, only slightly above the critical value, the acceleration extends over a large height range with relatively little variation. Correspondingly, if only the evolution in the corona is considered, one expects fast CMEs for high decay index and slow CMEs for small (but still supercritical) decay index. The former situation is typically found in compact, complex active regions, while the latter is more relevant for the quiet Sun. A statistical study of 15 fast CMEs (v > 1500 km/s) and 38 slower halo CMEs (v < 1500 km/s) supports this concept. It yields a relatively high correlation between CME speed and the decay index profile of the coronal field estimated by a PFSS extrapolation, provided some outliers -- slow CMEs from compact and complex active regions -- can be excluded. The consideration of the latter cases led us to suggest that part of the flux in their source regions should be considered as "exterior" flux. Such flux has little or no influence on the equilibrium in the region's core field but influences the propagation of flux ropes erupting from the core field. A parametric simulation study based on the Titov-Demoulin equilibrium of a force-free flux rope in a quadrupolar external field demonstrates that exterior flux can slow down and even halt a flux rope erupting from the core field. This yields a model for confined eruptions solely in terms of the torus instability (i.e., without invoking the helical kink). Strong exterior flux leaves a characteristic signature in the height profile of the magnetic field's decay index. Thus, the decay index profile may provide a useful indication whether a fast CME can potentially be formed by a given active region.

22nd ISEE/CICR colloquium

Speaker: Dr. K. D. Leka Designated Professor at ISEE / Senior Research Scientist at NorthWest Research Associates, USA
Date and Time: April 24 (Mon), 2017, 16:30-17:30
Place: Research Institutes Building I (ISEE), 3rd floor meeting space (301)
Title: Solar Flares and Space Weather Forecasting

Abstract: Heliospheric Space Weather is a very complicated system, and Solar Flares play an important role. Flares can be Earth-Impacting by themselves, but they also serve as indicators for other phenomena such as Coronal Mass Ejections and Solar Energetic Particle Events. In this seminar, I will discuss Space Weather Forecasting with a focus on Solar Flares, and the need for true forecasting (as compared to "now-casting") methods for these statistically rare events. I will ask "How well are flare forecasts doing?", discuss how success is measured, and finally ask "what is needed next?" in order to improve future Solar Flare forecasts.

21st ISEE/CICR colloquium

Speaker: Prof Cesar La Hoz Emeritus professor of UiT The Arctic University of Norway
Date and Time: March 27 (Mon), 2017, 13:00-14:30
Place: Research Institutes Building I (ISEE), 5th floor meeting space (517)
Title: Tutorial on PMSE and PMSE modification by RF heating -including recent results-

Abstract: This presentation is a tutorial on Polar Mesospheric Summer Echoes (PMSE), on multi- scale observations of PMSE and on the modification of PMSE by powerful Radio Frequency Heating. Both experiments and theory will be described. The experimental observations were obtained mostly with the EISCAT radars in Tromso, Norway and the modification of PMSE was done using the EISCAT Heater also in Tromso. I will describe the generally accepted mechanism of PMSE based on enhancement of the Schmidt number. The physics of this mechanism is somewhat involved and more often than not, not well understood. Thus, I will put special emphasis in making the physics of the Schmidt number accessible and understandable. I will describe how PMSE responds to RF heating, both in terms of observations and the proposed theoretical models that have been largely successful in explaining the observations. However, and finally, I will present recent new results that the same models fail to reproduce.

20th ISEE/CICR colloquium

Speaker: Joseph B.H. Baker Designated Associate Professor at ISEE / Associate Professor at Virginia Tech, USA
Date and Time: February 17 (Fri), 2017, 13:00-14:30
Place: Research Institutes Building I (ISEE), 7th floor meeting space (717)
Title: Large-Scale Structure and Dynamics of the Sub-Auroral Polarization Stream (SAPS)

Abstract: The Sub-Auroral Polarization Stream (SAPS) is a narrow channel of enhanced westward ionospheric convection which tends to form just equatorward of the dusk-side auroral oval during geomagnetic storms. Influences thought to drive SAPS formation include ionospheric closure of the region-2 field- aligned currents across the mid-latitude trough, pronounced separation between the electron and ion auroral precipitation boundaries, and active thermospheric feedback to magnetosphere-ionosphere coupling. The earliest observations of SAPS were obtained by low-altitude satellites and incoherent scatter radars which were only able to provide longitudinally limited views of the phenomenon. Recent expansion of the Super Dual Auroral Radar Network (SuperDARN) into middle latitudes has opened up new possibilities to examine the large-scale structure of SAPS and the coherence of its dynamics over extended regions of magnetic local time. In this presentation, several case study events will be presented for which SuperDARN data has provided new insights into the physics of SAPS. Statistical results will also be presented which show that SAPS-like events can also occur during non-storm periods, though their physics may be different. Finally, I will discuss recent initiatives within the US scientific community to better understand SAPS through coordinated data-model comparisons.

19th ISEE/CICR colloquium

Speaker: Dr. Martin Connors Foreign Designated Professor at ISEE / Professor of Athabasca University, Canada
Date and Time: February 10 (Fri), 2017, 13:00-14:30
Place: Research Institutes Building I (ISEE), 7th floor meeting space (717)
Title: Inversion and Interpretation of Ground Magnetic Data, Including Impulsive Events

Abstract: The sparse distribution of ground magnetometers has traditionally hampered interpretation of data they provide. While there are practical limitations on how many magnetometers can be installed in the world, another limitation on interpretation is data reduction methods. In the case of substorms, the substorm current wedge likely carries the most information about the underlying physics. It is particularly important to be able to determine its parameters, which can in turn be related to physical changes in the magnetosphere. The simple method known as Automated Forward Modelling (AFM) allows this, and has recently been shown to robustly determine field-aligned currents as determined by the near-global measurements of the AMPERE constellation based on the Iridium satellites. AFM can also be used to determine currents across a meridian. To fill a large gap in magnetometer distribution, ten new instruments forming the AUTUMNX array were installed in the eastern Canadian province of Québec, forming a dense chain along the east coast of Hudson Bay (near 77º west geodetic longitude), and a more widely spaced one near 68º. Some subauroral stations are also in place near major hydroelectric power corridors. AFM can determine current in this meridian, and the stations also detect impulsive magnetic field changes, not necessarily associated with substorms. In a few cases, we have related these to geomagnetic induced currents (GIC), as measured through harmonic distortion measurements for larger events, by the electric grid operator Hydro Québec. Preliminary indications are that GIC is most closely connected to changes in the magnetic Z (downward) component, which elementary consideration of Faraday’s Law might lead one to expect. However, verifying this needs a yet denser network, so we are working on low-cost magnetometers to implement it. Some examples of substorm and GIC data will be discussed.

18th ISEE/CICR colloquium

Speaker: Pasha Ponomarenko Designated Associate Professor at ISEE / Professional Research Associate Institute of Space and Atmospheric Studies University of Saskatchewan, Canada
Date and Time: February 3 (Fri), 2017, 13:00-14:30
Place: Research Institutes Building I (ISEE), 7th floor meeting space (717)
Title: Effects of refractive index of the ionosphere on characteristics of SuperDARN echoes

Abstract: Super Dual Auroral Radar Network (SuperDARN) consists of more than 30
high-frequency (HF, 10-15 MHz) radars which monitor high-latitude ionospheric plasma circulation in both Northern and Southern hemispheres. Each of these radars scans an extensive area of the ionosphere (~55 deg in azimuth and up to 3000-4000 km in range) and provides estimates of Doppler shift, range and direction of arrival for signals scattered by irregularities of the ionospheric plasma with high spatial and temporal resolution. These data are then used for deriving spatial distribution of the ionospheric electric field at high latitudes which carries important information about Space Weather. The extensive range coverage of SuperDARN radars is achieved through bending the ray trajectories back to the Earth due to decrease of the ionospheric refractive index with altitude. The signals then are reflected from the ground back to the ionosphere, and the whole process is repeated again leading to so-called multi-hop over-the-horizon propagation. While ionospheric refraction of HF radio waves plays a major role in the multi-hop scenario, by no means this is the only way the refractive index affects operations of such systems. Another important effect is distortion of the Doppler velocity estimate which leads to underestimation of the ionospheric electric field. This problem became apparent while comparing SuperDARN velocities with those measured by other instruments. In order to correct the velocity data, it was necessary to know the refractive index value along the radio wave path, which could be estimated in several ways. The optimal solution occurred to be using SuperDARN own data on the arrival direction of the signal (elevation). In a process of implementing this approach several other physical and technical problems have been identified and resolved. This activity led to significant improvement of radar data quality and expanded SuperDARN diagnostic capability to measuring main parameters of the regular ionospheric layers over areas inaccessible to the conventional instruments like ionosondes.

17th ISEE/CICR colloquium

Speaker: Keun-Ok Lee LATMOS/IPSL, UPMC Univ. Paris 06, Sorbonne Universit´es, UVSQ, CNRS, Paris, France Taiwan)
Date and Time: November 30 (Wed), 2016, 15:00-17:00
Place: Research Institutes Building I (ISEE), 3rd floor meeting room (301)
Title: Heavy precipitation events around Mediterranean Sea and field campaign

Abstract: During Intensive Observation Period 13 (15−16 October 2012) of the first Special Observing Period of the Hydrological cycle in the Mediterranean Experiment (HyMeX), Southern Italy (SI) was affected by two consecutive heavy precipitation events (HPEs). Both HPEs were associated with multi-cell V-shaped retrograde regeneration mesoscale convective systems (MCSs). The life cycle of two MCSs in connection with their dynamic and thermodynamic environments were analysed using a combination of ground-based, airborne and spaceborne observations and numerical simulations. Rain gauges revealed that heavy precipitation occurred in two phases: the first one from 1300 to 1700 UTC (35 mm h–1) was caused by a V-shaped system initiating over the Tyrrhenian Sea in the early morning of 15 October. Convection was triggered by the low-level convergence between the south-westerlies ahead of an upper-level trough positioned over south-eastern France and very moist southerlies from the Strait of Sicily. The convection was favoured by high convective available potential energy (1500 J kg–1) resulting from warm and moist conditions at low levels associated with high sea surface temperatures in the Sicily Channel. In addition, humidity at mid-level was enriched by the presence of an elevated moisture plume from tropical Africa, favouring the efficiency of the convection to produce more precipitation. The second phase of heavy precipitation (2300 UTC on 15 October to 0200 UTC on 16 October, 34 mm h–1) was caused by a MCS initiating over Algeria around 1300 UTC, which subsequently traveled over the Strait of Sicily toward Sicily and SI. Convection was maintained by the combination of large low-level moisture contents and a marked convergence ahead of the cold front. Unlike other MCSs forming in the same region earlier on that day, this huge V-shaped system did affect SI because the strong upper-level flow progressively veered from southwesterly to south-southwesterly.

16th ISEE/CICR colloquium

Speaker: C. Z. (Frank) Cheng (National Cheng Kung University, Taiwan)
Date and Time: November 11 (Fri), 2016, 13:00-14:00
Place : Research Institutes Building I (ISEE), 4th floor meeting room
Title: Driven magnetic reconnection processes

Abstract: In this talk I will discuss the basic idea of driven magnetic reconnection and the development of magnetic reconnection theories. I will then explain the physics of driven magnetic reconnection processes based on the full kinetic model. Finally, I will discuss the applications in solar flares and coronal mass ejections phenomena and in laboratory magnetic confinement plasmas.

15th ISEE/CICR colloquium

Speaker:Jeongwoo Lee (Foreign Designated Associate Professor of ISEE,Nagoya University)
Date and time: November 1 (Tue), 2016, 16:30-17:30
Place: ISEE Research Institutes Building I, Room 301
Title: Study of solar flares inside a large magnetic fan structure with NoRH observations

Abstract: Understanding how solar eruption proceeds is an important step toward the ultimate goal of solar physics and space weather forecast. Although the exact mechanisms for solar eruptions are still under debate, it is generally believed that the key information lies in the characteristic magnetic configuration of source active regions. In this talk I will present an on-going study of two successive solar flares from NOAA AR 12371 that occurred on 2015 June 21. The photospheric magnetograms and coronal EUV images from the Solar Dynamic Observatory (SDO) imply that the active region consists of two sunspots embedded within a strikingly large magnetic fan structure. It is therefore of new interest how the compact sunspot fields were interacting with the extended overlying magnetic structure to produce the such successive flares, one associated with a sigmoid structure and the other, with a halo CME. We analyze the unique dataset from the Nobeyama Radioheliograph (NoRH) operated by Nagoya University to derive information on the primary energy release and high energy particles accelerated during the two flares. While the solar EUV images show a continuous change of the coronal features, the NoRH detected two well separated (>25 min) radio bursts with distinct properties of both spectral and spatial morphologies. We relate the former radio bursts to an impulsive energy release within a confined magnetic structure and the latter to the aftermath of the CME. Our ultimate goal is to figure out the magnetic connectivity change that is responsible for the transition from the confined flare to the eruptive flare within 40 min time interval.

14th ISEE/CICR colloquium

Speaker:Prof. Syun-Ichi Akasofu (International Arctic Research Center (IARC), University of Alaska Fairbanks (UAF))
Date and time: October 18 (Tue), 2016, 13:00-14:30
Place: ISEE Research Institutes Building I, 6th floor Meeting Room
Title: The forthcoming Big Ice Age

Abstract: The so-called “interglacial periods (IGP)” are defined on the basis of the global average temperature (15°C) in 1950, which has no meaning in terms of climate change physics (why 1950 ? and many glaciers still exist). Thus, instead, a new physically meaningful baseline for a long-term climate change is considered. It is the minimum temperature which the earth has experience during last 2 million years or perhaps longer, about 8°-12° C lower than the 1950 baseline (15° C), not too far from the freezing temperature; in fact, it is possible to take 0°C as the physically meaningful baseline. In this view, the earth has experienced successive heat inputs, rather than successive Big Ice Ages during at least 2 million years.
From this point of view, water at the distance of the earth from the sun must be near freezing. It is very fortunate that the present time is near the peak of the successive and impulsive heat inputs, not at the baseline level. Thus, the terms ‘Recovery from the Big Ice Age’ and IGP do not describe climate change adequately and are even misleading.
What is causing the successive impulsive heat inputs ? It is unlikely that CO2 is the initiating cause of the impulsive heat input because the temperature increase precedes CO2 increase during each of the early epoch of the impulsive increase and also is not the main cause of the impulsive increase and the present temperature (more than 90% of the present warming is due to water vapor).
In predicting future climate change, it is more important to study the nature of the impulsive heat input process than the CO2 effects.

13th ISEE/CICR colloquium

Speaker: Dr. Antti E. Kero Visiting Associate Professor of ISEE, Nagoya University  Sodankyla Geophysical Observatory, University of Oulu, Finland
Date and time: October 14 (Fri), 2016, 13:00-14:30
Place: ISEE Research Institutes Building I, 7th floor Meeting Room
Title: D-region ionization characteristics inverted from ground based electron density measurements

Abstract: Three case studies related to ground based estimation of D-region ionization characteristics are shown: 1) Photoionization during the ESR IPY 1-year run, 2) Electron precipitation inversion from EISCAT VHF data during a pulsating aurora event and 3) Spectral riometer observation of a solar proton event.

12th ISEE/CICR colloquium

Speaker:Jozsef Kota(The University of Arizona, LPl,Tucson, Arizona, USA)
Date and time: October 12(Wed), 2016, 15:00-
Place: ISEE Research Institutes Building I, Room 301
Title: Voyager 1 Observations in the Interstellar Space

Abstract: There is a broad consensus that, in August 2012, the Voyager-1 spacecraft crossed the Heliopause (HP) and entered into the interstellar space. In the talk I shall briefly describe the Voyager mission,and overview the particle and field measurements of Voyager-1 during and after the HP crossing. Small variations in the galactic cosmic-ray flux will be discussed. The global structure ofour Heliosphere is still debated, there are two alternative views on the Heliotail. I shall discuss how energetic neutral atom (ENAs) of the IBEX spacecraft and the anisotropies of TeV cosmic rays detected in ground based air-shower experiments can contribute to the remote exploration of the heliosphere and help to decide between competing theoretical models.

11th ISEE/CICR colloquium

Speaker: Prof. Balan Nanan Visiting Professor of ISEE, Nagoya University University of Sheffield, UK
Date and time: October 7 (Fri), 2016, 13:00-14:30
Place:ISEE Research Institutes Building I, 7th floor Meeting Room
Title: Severe space weather and its relevance to the High-Tech society

Abstract: Like Earth’s weather space weather sometimes become severe. When it becomes severe it can cause extensive social and economic disturbances in the high-tech society by damaging satellite systems and ground systems. For example, an event such as the Carrington event of 1859 at present times can cause damages costing up to 1 to 2 trillion US Dollars. The seminar will introduce space weather, address what determines the severity of space weather as experienced by satellite systems and electric power grids, suggest indices for forecasting (early warning) severe space weather (SvSW), and discus the mechanisms of SvSW through modeling the geomagnetic storms associated with SvSW and simulating geomagnetically induced current.

10th ISEE/CICR colloquium

Speaker: Prof. Hisao Takahashi Visiting Professor of ISEE, Nagoya University Instituto Nacional de Pesquisas Espaciais (INPE), Brasil
Date and time: September 27 (Tue), 2016, 13:00-14:30
Place: ISEE Research Institutes Building I, 7th floor Meeting Room
Title: Ionospheric Plasma Bubble Study in Brazil: Today´s Aspect

Abstract:The ionospheric plasma irregularities (bubbles) in the low to middle latitudes have been subject of research issues in the last 40 years. Different observation techniques (ionosonde, VHF radar, optical imagers, GNSS receivers, satellite beacon etc.) have been used to study different physical parameters of the bubbles. Simulation models of plasma bubbles have also been significantly progressed in the last 10 years. Today, we know general characteristics of plasma bubbles, frequency of occurrence and statistically when and where to happen. Implication of such ionospheric disturbances to our social infrastructures (GPS positioning systems, for example) is also well recognized. However, an important matter is still not known yet, it is “plasma bubble seeding mechanism”, how, where and when it starts. Some historical survey of the plasma bubble observation (mainly in Brazil) and today´s interest in its subject will be presented and discussed.

9th ISEE/CICR colloquium

Speaker: Prof. Rene A. Ong (University of California, Los Angeles)
Date and time: September 15 (Thu), 2016, 16:00-17:00
Place: KMI Science Symposia (ES635) <= ES building
Title: The Future of Very High Energy Astrophysics

Abstract:The field of very high energy (VHE) astrophysics had been revolutionized by the results from ground-based gamma-ray telescopes, including the current imaging atmospheric Cherenkov telescope (IACT) arrays: HESS, MAGIC and VERITAS. A worldwide consortium of scientists from 32 countries has formed to develop the Cherenkov Telescope Array (CTA) that will capitalize on the power of this technique to greatly expand the scientific reach of ground-based gamma-ray telescopes. CTA science topics will include the origin of cosmic rays and cosmic particle acceleration, understanding extreme environments in regions close to neutron stars and black holes, and exploring physics frontiers through, e.g., the search for WIMP dark matter, axion-like particles and Lorentz invariance violation.
CTA is envisioned to consist of two large arrays of Cherenkov telescopes, one in the southern hemisphere and one in the north. Each array will contain telescopes of different sizes to provide a balance between cost and array performance over an energy range from 20 GeV to above 100 TeV. Compared to the existing IACT arrays, CTA will have substantially better angular resolution and energy resolution, will cover a much wider energy range, and will have up to an order of magnitude better sensitivity. CTA will also be operated as an open observatory and high-level CTA data will be placed into the public domain; these aspects will enable broad participation in CTA science from the worldwide scientific community.
This talk will review the scientific motivation and capabilities of CTA, provide an overview of the technical design and the status of prototype development, and summarize the current status of the project in terms of its proposed organization and timeline.

8th ISEE/CICR colloquium

Speaker: Prof. Jorge L. Chau Head of the Radar Department, Leibniz Institute of Atmospheric Physics (IAP), Germany
Date and time: September 12 (Mon), 2016, 10:30-12:00
Place: ISEE Research Institutes Building I, 3rd floor Meeting Room
Title: Unusual 5-m E region field-aligned irregularities observed from Northern Germany during the magnetic storm of March 17, 2015

Abstract:Coherent E region echoes were observed during the March 17-2015 storm at mid-latitudes by multi-static wide-field of view radars operating in northern Germany. Two of the stations operated in a monostatic configuration while one link was set in bistatic mode. Interferometry made it feasible to locate the targets. While the radars were built to measure mesospheric winds from specular meteor echoes, the storm was so intense that it allowed them to observe auroral E region echoes for more than four hours. All stations detected numerous examples of narrow spectra with slow (~180 m/s) and fast (up to 1600 m/s) Doppler velocities. The target speeds were much faster than the Doppler velocities for the slow narrow echoes (more than 800 m/s vs 180 m/s) but comparable to the observed Doppler shift for the 1500 m/s narrow fast types. The narrow types came from localized horizontal structures 50 to 80 km wide in range. The fast narrow types came from the upper part of the altitudes associated with Farley-Buneman waves. The slow-narrow structures were typically from altitudes lower than 100 km. Unexpectedly, the great majority of the echoes associated with more ordinary ion-acoustic turbulence had a positive Doppler shift and came from the east. A companion paper uses these new observations to re-evaluate the origin of the narrow echoes and of the asymmetry in the counts. Irrespective of the generation mechanisms, our observations indicate that a combination of unusually large electric field and strong precipitation is needed to produce the unusual echoes.

7th ISEE/CICR colloquium

Speaker: Dr. Michael M. Bell (Assistant Professor at University of Hawai`i at Manoa,Associate Professor at Colorado State University (since Fall 2016))
Date and time: August 3 (Wed), 14:00-15:15
Place: ISEE Research Institutes Building I, 3rd floor Letcure Room (301)
Title: Aircraft Observations of Tropical Cyclones: Past, Present, and Future

Abstract:Tropical cyclones (TCs) are a yearly threat to coastal populations around the world with heavy rainfall, strong winds, and powerful storm surge. While our ability to forecast TCs continues to improve on average, individual typhoons or hurricanes can present significant forecast challenges. Rapid formation and intensification prove especially difficult for numerical weather prediction models, producing large errors in track and intensity at longer lead times of three to five days. This talk will review recent advances in our scientific understanding of TCs, with a focus on the insights obtained from aircraft observations. Though satellites provide the most frequent observations of TCs and their environment around the globe, direct aircraft measurements are still a primary tool for revealing and understanding the structure, intensity, and track of these storms. A review of the history of operational aircraft reconnaissance and results from field experiments using research aircraft from 2005 - 2015 will be highlighted. Challenges to further improvements in forecast skill will be discussed, along with future directions for observations and research that will benefit Japan, Hawaii, and other coastal areas affected by typhoons and hurricanes.

6th ISEE/CICR colloquium

Speaker: Takanobu Yamaguchi (Research Scientist II, CIRES UC Boulder/NOAA ESRL, USA)
Date and time: June 15 (Wed), 15:00-
Place: Research Institutes Building I, Rm. 617 (6F Meeting Room)
Title: Stratocumulus to cumulus transition in the presence of elevated smoke layers

Abstract:The transition from stratocumulus to cumulus clouds in the presence of elevated light-absorbing smoke layers is investigated with idealized large-eddy simulations. A smoke layer is placed 1 km above stratocumulus top and evolves with the cloud fields over the course of a 3 day simulation. The simulations presented vary the smoke-generated heating and the moisture content of the smoke layer. A control case without smoke is simulated for comparison. On day 2 of the transition, when still above cloud, smoke generates a more broken cloud field than the control case, depending weakly on the strength of the aerosol heating but strongly on the water vapor content in the smoke layer. Following nighttime recovery and contact with the stratocumulus, smoke hinders the transition by strengthening the inversion, limiting boundary layer deepening and reducing precipitation-related breakup. This modulation delays the transition, which may extend the stratocumulus deck westward, with con comitant implications for climate forcing.

5th ISEE/CICR colloquium

Speaker: Dr. J. Michael Ruohoniemi (Virginia Tech, USA)
Date and time: March 18 (Fri) 13:30-15:00
Place: Room 301 of the Institute for Space-Earth Environmental Research
Title: The SuperDARN HF radar technique and new perspectives on geospace research from mid-latitudes to the polar cap

Abstract: The ionosphere is the region of Earth’s near-space environment that is most accessible to observation by ground-based instrumentation. The SuperDARN HF radar technique utilizes coherent scattering by small-scale density irregularities to observe the irregularities themselves and to measure the motion of ionospheric plasma. Since the early 1990s chains of SuperDARN radars have been assembled at mid-, high, and polar cap latitudes by an international team of collaborators to take advantage of the sensitivity of the HF measurement technique to a variety of space weather effects. In this talk I will review recent developments in the expansion of SuperDARN and discuss research carried out at Virginia Tech that relates to views of geospace processes that have been made possible by synthesizing over distributed measurements or by integrating across different measurement techniques.

4th ISEE/CICR colloquium

Speaker: Dr. Andrew W. Yau (University of Calgary, Canada)
Date and time: December 7 (Mon) 13:30-
Place: Room 301 of the Institute for Space-Earth Environmental Research
Title: Heavy Ion Energization and Outflow

Abstract: The discovery of precipitating energetic oxygen ions from the magnetosphere in the 1970’s [Shelley et al., 1972] prompted a fundamental paradigm shift in our perception of the compositional origin of the Earth’s magnetosphere. The discovery also heralded an extensive body of studies of heavy ion energization and outflows based on satellite, rocket and radar observations over the past four decades. We discuss our contemporary view on the variety of heavy ion outflows and their source origins and energization, as well as the consequence of their transport in the context of magnetosphere-ionosphere coupling and planetary atmospheric escape.

3nd ISEE/CICR colloquium

Speaker: Dr. Barry Gardiner (INRA-ISPA, Villenave d'Ornon, France)
Date and time: December 4 (Fri) 15:00-
Place: Room 606 of the Institute for Space-Earth Environmental Research
Title: Prediction of wind speeds and wind damage risk in forested complex terrain

Abstract: Wind is a major disturbance agent in many forest. It is also the cause of economically important damage in many boreal forests, and in temperate and tropical forests affected by storms, hurricanes, or typhoons. Predicting the risk of wind damage is important for advising forest managers and planners and for mitigating the impact of storms. A key component of any risk model is the ability to predict the wind speeds over and within forests. This is relatively straightforward in homogeneous forests on flat terrain. However, in most parts of the world the terrain is not flat and in addition forests are rarely homogenous. Predicting wind speeds in complex forested terrain is a major current challenge for meteorologists and forest scientists. In this talk we will present recent measurements of airflow and turbulence over a forested ridge in the west of Scotland, and over model forests with different levels of fragmentation in a wind tunnel. We will discuss the results in comparison to the predictions of airflow models and show how this new data can help to improve the accuracy of existing forest wind risk models.

2nd ISEE/CICR colloquium

Speaker: Prof. Hung-Chi Kuo (Department of Atmospheric Sciences, National Taiwan University)
Date and time: November 24 (Tue) 10:30-12:00
Place: Room 617 of the Institute for Space-Earth Environmental Research
Title: Wavenumber-2 Deep Convection in Tropical Cyclones

Abstract: Many radar observations, such as in the Second Miyakojima typhoon (1966), Typhoon Herb (1999), Typhoon Haitang (2005) and Typhoon Dujuan (2015), are with cyclonically rotating elliptical eyewall. Interestingly, there were often the deep convection occurred on the tips of the major axis in the elliptical eyewall. This paper investigates the structure of boundary layer pumping and convection in tropical cyclones that have elliptical eyewalls or polygonal eyewalls. We use the simple approach of a nondivergent barotropic model for the inviscid flow above the boundary layer (BL), and then use the associated pressure field (derived from the nonlinear balance condition) to drive a slab boundary layer model. The BL flow driven by this pressure field is divergent so that the spatial distribution of BL pumping (updraft on top of BL) can be calculated. The interaction is one-way in the sense that the overlying flow drives the BL, but the BL pumping does not feed back onto the overlying flow. The model calculations are in the Cartesian geometry with double Fourier pseudospectral method. The model results of maximum BL pumping on the tips of the major axis of the elliptical eyewall is in general agreement with the observations. The model also indicates the existence of jet-like high speed tangential winds upstream the major axis tips in the BL. The formation of BL pumping (and convergence) in the tip of the major axis is caused by local super- gradient winds, in a way similar to the dynamics of super-geostrophic winds in the midlatitude jet exit region. The results highlight the wavenumber-two feature of the BL radial wind in shock-like structures, which lead to large BL pumping. Our experiments also indicate that the similar radial profiles and BL pumping may occur in the tips of the polygonal eyewalls.

1st ISEE/CICR colloquium

Speaker: Syun-Ichi Akasofu (Professor of Physics Emeritus, University of Alaska, Fairbanks)
Date and time: October 27 (Tue) 15:00-16:30
Place: Room 301 of the Institute for Space-Earth Environmental Research
Title: Auroral substorms and solar flares

Abstract: Both auroral substorms and solar flares have many close morphological similarities, as well as magnetic energy as their source of energy. A study of auroral substorms has an advantage of studying them in terms of the input-output relationship on the basis of ground- and satellite-based observations. It is shown that the epsilon function is the power (in watts) of the solar wind-magnetosphere interaction; auroral substorms are a manifestation of dissipation processes of the power. Solar flares are examined in a similar way, namely the input-output relationship on the basis of the epsilon function. In fact, the epsilon function may be applicable in astrophysical problems. A new idea of the formationof single (solitary) spots and pairs of spots is also discussed.