令和３年度　総合解析セミナー

日時：　金曜 13:30 – 15:00
場所：　ZOOM （参加ご希望の方は　 nakamura.satoko[at]isee.nagoya-u.ac.jp　まで事前にご連絡ください。
[at]は@に置き換えてください。）

セミナースケジュール

date Speaker title
2/25 Keitaro Matsumoto Study of electron acceleration/propagation process in a solar flare using Nobeyama Radioheliograph
Abstract : Particle acceleration takes place during a solar flare. Information about pitch angle distribution is important to understand particle acceleration/propagation process. Yokoyama et al. (2002) estimated the pitch angle of nonthermal electrons from the propagation speed of a microwave emitting region along a loop. After that, there is no significant progress in observational studies. Thus, I investigated all the flares between 2000 and 2017 observed in the event mode (time-resolution = 0.1s) with Nobeyama Radioheliograph and found that an M8.7 flare on 22 October 2014, clearly showed a high-speed propagation. Following the method of Yokoyama et al.(2002), it was found that the pitch angle of the accelerated electrons was about 65 degrees. In this study, we have the information of the magnetic field strength at the starting point of the propagation in the corona and that of the footpoint region. From this information, the size of loss cone is estimated to be about 36 degrees. Considering the pitch angle derived above, most of accelerated electrons are reflected to the corona at the footpoint region. Actually, we found a faint microwave feature which might correspond to a bounce motion of the accelerated electrons. In this presentation we will mainly report the results of microwave data analysis. For a further understanding of this phenomenon, we need analyses of hard X-rays and so on.
2/9 Akari Nagatani Time variations of molecular ions in the inner magnetosphere observed by Arase
Abstract : In the Earth’s magnetosphere, there are several kind of ions originated from both the solar wind and the ionosphere and molecular ions in the magnetosphere are originated in the Earth’s ionosphere. Observations about molecular ions are not enough compared with other ion observations, and the mechanism of the outflow from the ionosphere as well as the long term variations are not well known. The Arase satellite has observed various kinds of ions since 2017 and two ion analyzers LEPi and MEPi cover energy range from 10 eV/q to 180 keV/q. Using the data from the MEPi instrument, variations of molecular ions to the magnetic storms and solar wind conditions are investigated [Seki+, 2019], and molecular ions are often observed in the inner magnetosphere even small magnetic storms. In this study, we analyzed the time-of-flight (TOF) data from the LEPi [Asaramura+, 2018] to investigate variations of molecular ions in the inner magnetosphere and their dependence about magnetic storms and solar wind conditions. LEPi covers the energy range from 10 eV/q to 25 keV/q and counts as function of energy and TOF are obtained every 16 seconds. The TOF measurements of LEPi have been operated in the outbound pass every 4 revolutions around the Earth. In the analysis, we estimate counts of molecular ions by fitting the empirical functions for TOF profile using the non-linear least square method. The estimated counts were calibrated by the time variations of efficiency of the LEPi instrument. Using the data set, we investigated time variations of molecular ions in the inner magnetosphere and found that enhancement of molecular ions takes place associated with magnetic storms, which is consistent with the previous studies. The molecular ions are found in not only severe magnetic storms but small storm activities of ~ 30 nT, which suggests that molecular ions frequently escape from the Earth ionosphere event in geomagnetically weak conditions.
2/9 Tomonori Arita Calculation of solar rotation using multi-point satellite observation
Abstract : Prediction of solar activity is important in predicting the space environment. Recently, it is concidered that there is a correlation between the polar magnetic field in the Solar minimum and the next solar cycle activity. The surface flux transport models(SFT)are often used to predict polar magnetic field. However, various parameters that required by SFT models like surface flows and diffusion are not completely understood. In this study, we focused on differential rotation(DR) which is one of solar surface flow. To calculate solar surface flow, tracking of surface features like magnetic elements is often used. However, feature tracking has "center-limb effect" that makes calculated velocities differ between center and limb. In order to understand "center-limb effect", we tracked coronal bright point by used two instruments, SDO/AIA and SolO/EUI. These satellites have different orbits and observe different area of the sun. As a result of tracking and caluculate DR by SDO/AIA and SolO/EUI, we found possibility that we can estimate "center-limb effect" by using SDO and Solar Orbiter.
2/9 Harune Sekido 高階微分項を用いた陽的時間領域差分法の高精度化
Abstract : FDTD(Finite-Difference Time-Domain)法は、Yee(1966)によって開発された、電磁界の時間発展を解 く数値計算手法であり、空間と時間ともに2次精度の差分でMaxwell方程式を近似することで求められる。不連 続波形で数値振動が発生するほか、連続波形でも傾きが大きいと数値振動や振幅の減衰が起こるといった欠点 が存在する。これらの欠点を改善するため、Petropoulos(1994)は空間微分項の差分精度を4次精度とした FDTD(2,4)法を提案したが、数値不安定が生じないクーラン数Cの上限値が小さくなるという問題を抱えてい る。本研究では電界および磁界のそれぞれの時間発展方程式に高階空間微分項を付加することにより、新たな 陽的時間発展式を導出した。その結果、従来の手法では数値不安定が生じ、計算することができなかった範囲 においても計算が可能となることを確認した。また、従来の手法で計算が可能であった範囲においては、位相速度の誤差を抑えることができた。
2/9 Yudai Morii Characteristics of precipitating electrons of the omega band based on two wavelength optical measurement
Abstract : The auroral omega band is found from midnight to dawn side during substorms and is characterized by a curved “Omega” structure that drifts to the east. The omega bands have a latitudinal structure, with discrete auroras on the polar side, while diffuse and pulsating auroras occur on the low-latitude side. It has been discussed that the omega-bands are related to fast plasma flow and shear motion in the magnetosphere, and the spatial structure and temporal variation of the omega-bands are important to understand the coupling between the magnetosphere and ionosphere. In this study, we investigate the two-dimensional spatial distribution of the characteristic energy and downward energy flux of the precipitating electrons in the omega-band using data from a multi-wavelength EMCCD camera in Tromsø, Norway. In this study, we estimate the characteristic energies of the omega-band events in the substorm recovery phase observed on February 3, 2017 from 1:30-2:30 UT, based on the ratio of emission intensities at two wavelengths, 427.8 nm and 844.6 nm. The east-west structure of the diffuse aurora on the low-latitude side of the omega band is found and the downward energy flux is approximately 2 times larger on the west side, although there is no difference in the downward electron characteristic energy. Discrete and diffuse auroras were observed from the polar to the low latitudes of the omega band, and black auroras were also observed inside the diffuse auroras. In the presentation, we will discuss the characteristics and temporal variations of the precipitating electron energy in each region of the omega band.
2/4 Masaya Yakura Time of Flight analysis of accelerated electrons in solar flares by using Fermi Gamma-ray Space Telescope
Abstract : It is known that particle acceleration occurs during a solar flares. However, the detail of this process is not known well. In 1990’s, Aschwanden and his colleagues performed so-called Time-of-Flight (ToF) analysis for many solar flares observed with CGRO and concluded that the electron acceleration site is located slightly above the corresponding soft X-ray flare loop. Although the time evolution of the acceleration site is one of the important information to understand the acceleration process, there are no studies about it. Therefore, we are trying to investigate it during a solar flare based on ToF analysis, using the solar flare data taken by Fermi Gamma-ray Space Telescope. In this seminar, we will report the progress of our research.
1/28 Kazuteru Takahashi The effect of quasi-steady scattering on the pulsating aurora
Abstract : We have studied non-linear wave-particle interactions caused by chorus waves and electrons using the test particle simulation, GEMSIS-RBW (Saito+, 2012). Using the GEMSIS-RBW, we have been studied numerical experiments about various wave-particle interaction process such as relativistic electron acceleration, microbursts, and pulsating aurora.　 A quasi-steady precipitations caused by weak-amplitude waves also occurs in the magnetosphere. The quasi-linear approach using the Fokker-Planck equation has been used as a model in previous research. In order to include such quasi-steady precipitations in GEMSIS-RBW, we develop the new code to implement quasi-linear wave-particle interactions by adopting stochastic differential equations that are equivalent to the Fokker-Planck equation. In this presentation, we present the effect of quasi-steady precipitation on the pulsating aurora electron scattering.
1/21 Hotaka Tsujimura Probabilistic prediction of solar wind speed change with solar cycle activity
Abstract : As the solar wind continues to blow towards the Earth, there are concerns about communication problems and the impact on power transmission facilities. To avoid these risks, prediction of solar wind is important. It is empirically known that the speed of the solar wind is determined by the ratio of the magnetic field of the solar surface to the magnetic field of the solar wind. (The Wang-Sheeley-Arge model (WSA model) is an empirical expression of this relationship.) Therefore, if we can predict the magnetic fields at these two locations, we can predict the speed of the solar wind. There are two ways to calculate these two magnetic fields: the Surface Flux Transport model (SFT model) and the Potential-Field Source-Surface model (PFSS model). The SFT model consists of an advection term, a magnetic diffusion term, and a magnetic flux emergence term. The magnetic flux appearance term requires information on the number, latitude, area, and inclination angle of the appearing sunspots. However, these parameters characterizing sunspots are generally statistically indeterminate, and it is not yet well understood how this statistical variability affects the solar surface magnetic field and solar wind speed. In this study, these three models were used to predict the solar wind. Among them, the variation of solar wind speed was predicted by probabilistically varying the input parameters of the SFT model: sunspot number, tilt angle, latitude of emergence, and longitude of emergence. In this time, we will compare the solar surface magnetic field and magnetic field lines based on the results.
1/14 Ryota Ikeba Computer simulation on the structure of double layer in the auroral acceleration region
Abstract : The existence of electric fields in the auroral region was predicted by Alfven (1957). Rocket observations of aurora in 1960's showed the precipitation of high energy electrons, possible due to electric fields in the acceleration region (McIlwain 1960). Evans (1974) reproduced the result of rocket observation by a model calculation, which demonstrated the existence of the auroral acceleration region. Electric fields due to the electric double layers in the auroral acceleration region were first observed by spacecrafts in 1970's (Mozer et al. 1977). The FAST observation showed detailed multi dimensional structures of the auroral double layer (Ergun et al. 20 01). The previous one dimensional Vlasov Poisson simulation of a current carrying plasma showed that a double layer was generated by a strong density depression (Newman et al. 2001). However, multi dimensional kinetic simulations have not been performed yet due to both computational resources and computational techniques. In the present study, we first perform a two dimensional particle in cell simulation of a current carrying plasma with a density depression. It is demonstrated that a double layer is driven generated in the two dimensional system with a weak ambient magnetic field. An electrostatic wave is excited inside the double layer at the frequency around the ion plasma frequency and at the phase velocity around the ion acoustic speed, which propagates in the direction oblique to the ambient magneto field.
12/17 Sandeep Kumar Contribution of ions and electron Pressure to Ring Current and Ground Magnetic Depression during CIR and CME originating geomagnetic storms using Arase observations and RAM-SCB simulations
Abstract : There is increased interest recently in understanding Sun-Earth interactions and space weather events due to the increasing reliability on space-based technological systems. Geomagnetic storms are the main component of space weather and are driven by coronal mass ejections (CMEs) or corotating interaction regions (CIRs). During the main phase of geomagnetic storms, the ring current enhances and a global decrease in the H component of geomagnetic field is observed. The storm time distribution of ring current ions and electrons in the inner magnetosphere depend strongly on their transport in evolutions of electric and magnetic fields along with acceleration and loss. Recently, we showed that the electron pressure contributes to the depression of ground magnetic field during the storm time by comparing Ring current Atmosphere interactions Model with Self Consistent magnetic field (RAM-SCB) simulation, Arase in-situ plasma/particle data, and ground-based magnetometer data [Kumar et al., 2021]. The previous results show that the ions are the major contributor (~ 90 %) to the total ring current and the electron contribute ~10 % to the ring current pressure in the post-midnight to dawn sector where electrons flux is higher compared to ions flux. However, the comparative contribution of each ion and electron pressure to the total ring current during CIR and CME events is not explored much. In this talk, I will discuss the contribution of ions and electron pressure to the total ring current during selected CIR and CME storms.
12/10 Masafumi Shoji Repetitive emissions of electromagnetic ion cyclotron rising tone waves by recycling scattered protons
Abstract : Electromagnetic ion cyclotron (EMIC) rising tone emissions which are similar to the whistler mode chorus emissions are generated through the nonlinear interactions with anisotropic protons in the inner magnetosphere. Theoretical studies suggest that whistler waves cause the anomalous trapping of low pitch angle electrons. By test particle simulations, we find that EMIC rising tone emissions also scatter the significant number of low pitch angle protons to the higher pitch angle. Hybrid simulations on the EMIC rising tone emissions, however, have been performed with subtracted Maxwell distribution function for the energetic protons which exclude low pitch angle protons. We perform a self-consistent hybrid simulation with bi-Maxwellian protons to investigate the effect of the anomalous trapping on the generation of the rising tone emissions. We find several EMIC rising tone emissions are generated while only one pair of forward and backward propagating rising tone emissions is generated in the subtracted Maxwellian case. The low pitch angle protons are also scattered to the higher pitch angle obtaining kinetic energy from the EMIC wave in the simulation. The higher pitch angle proton flux formed by the anomalous trapping becomes a part of the energy source of another EMIC emission. The new EMIC wave repeats the process, and then the multiple rising tone emission occurs.
12/3 Chae-Woo Jun The influence of electromagnetic ion cyclotron (EMIC) wave-particle interactions on energetic proton distributions in the magnetosphere during the Arase era
Abstract : Electromagnetic ion cyclotron (EMIC) waves have been considerin to play the important role in controlling magnetospheric plasma dynamics. Especially, EMIC wave-particle interaction can cause loss of energetic protons and subrelativistic electrons in the Earth’s magnetosphere and the scattered particles precipitate into the ionosphere, creating the isolated proton auroras at the sub-auroral latitudes (55-65 geomagnetic latitudes). To understand the influence of EMIC waves on energetic protons in the magnetosphere, we perform a comprehensive study of proton distributions associated with EMIC waves using a 4-year in-situ observation obtained by the Arase satellite. In this talk, we present energetic proton distributions depending on geomagnetic conditions and EMIC wave activity at different magnetic local time regions. We also introduce the proton minimum resonance energy calculation from the cold plasma approximation and compare the computed results with the Arase observations. Finally, we discuss possible generation processes of EMIC waves in the magnetosphere. We believe that this study will provide new insights into the dynamics of EMIC waves in the magnetosphere.
11/26 Masahiro Kitahara The exact analytic solutions of non-relativistic particles in the cyclotron resonance condition
Abstract : Wave-particle interactions play a crucial role in the dynamics of charged particles such as particle acceleration, pitch angle scattering, wave growth in space plasmas. For quantitative evaluation of wave-particle interactions, it is most important to estimate the size of a trapping region of charged particles encountering plasma waves in the velocity space (phase space). The trapping region in wave-particle interaction is expressed as a set of closed trajectories in the velocity space with the conserved quantities. In this study, we solve the equation of motion for a non-relativistic charged particle in electromagnetic waves propagating along the uniform ambient magnetic field, and we derived two conserved quantities, which correspond to the diffusion curve in the velocity space and the rescaled Hamiltonian introduced by Albert et al. (2021). Classifying particle trajectories by using the conserved quantities, we derived the exact trapping region in the velocity space. Because the exact trapping region includes trajectories of ”transversal phase bunching” mentioned by Matsumoto et al. (1974), the size of the exact trapping region is larger than that of the trapping region of ”longitudinal phase bunching”. This fact should indicate that the trapping efficiency estimated from the exact trapping region should be higher than that from the longitudinal trapping region. We also found that the parallel velocities of some trapped particles do not always meet the cyclotron resonance condition. These particles can be classified as non-resonance trapping in the sense that the particle velocities do not match the cyclotron resonance velocity, while the particles can also be classified as the resonance trapping in a broad sense that the resonance condition is defined as the temporal-stationary points of the relative phase angles. Our derived exact solution can be applied to the particle data analysis of the high-time-resolution observations and contribute to more quantitative interpretations of wave-particle interactions through the cyclotron resonance.
11/19 Sung-Hong Park Hemispheric sign preference of helicity in the Sun: its relation to long-term flaring activity
Abstract : Over the past decades, extensive observations of various solar features revealed that the Sun preferentially exhibits left-handed helical features in its northern hemisphere and their opposite counterparts in the southern hemisphere, independent of the solar cycle. This is called the hemispheric sign preference (HSP) of helicity in the Sun. Uncovering the underlying physical mechanism(s) of the HSP is essential for a better understanding of magnetic dynamo action achieved by turbulent convection in the solar envelope. In this talk, I will present a statistical study of magnetic helicity flux across the photospheric surfaces of solar active regions, in the context of the HSP and its relation to long-term flaring activity over the solar cycle 23. In addition, I'd like to briefly summarize what I have done over the last 4.5 years at ISEE with nice colleagues here, and also suggest what future research collaborations can be made between Stanford and ISEE.
11/12 Takayuki Umeda Generation of uniform and normal distributions revisited
Abstract : Uniformly and normally distributed random numbers are commonly used in scientific computing in various fields. It is important to use a set of random numbers as uniform/normal as possible for reducing initial fluctuations, which affects final results. A numerical procedure for generating samples with a uniform distribution in two and three dimensions is proposed in the present study. Then, the conversion of a uniform distribution to a normal distribution with three types of inverse transform sampling methods is discussed by using a new approximation of inverse cumulative distribution functions.
11/5 Tomoaki Hori In-flight evaluation and calibration of the high-energy electron experiments (HEP) instrument aboard the Arase satellite
Abstract : The high-energy electron experiments (HEP) instrument onboard the Exploration of energization and Radiation in Geospace (ERG, also known as Arase) satellite have been collecting 3-D velocity distribution data of energetic electrons with energies from several tens of keV up to a few MeV. Although the instrument has been in good shape and continued its measurement, raw electron count data have various nonuniformity and inhomogeneity over energy and directional channels, which is not expected from the design of the instrument. In this talk, we show how raw electron counts yielded by the instrument are analyzed, evaluated, and finally converted all the way to electron flux data of science quality. In particular, the talk addresses the in-flight analysis and empirical correction for inter-directional-channel nonuniformity in detection sensitivity, as well as the error evaluation of electron fluxes if time permits.
10/29 KENTO MICHIWAKI Prediction of number and latitude/ tilt angle / area distribution of sunspot using machine learning
Abstract : In space weather forecasting, it is important to estimate the solar activity in near future. Recent studies have shown that there is a correlation between the value of the polar magnetic field during the solar minimum and the next solar activity level. This means that the value of the polar magnetic field is one of the most important indicators for predicting the activity level. For this reason, many studies have tried to predict the polar magnetic field. The value of the polar field can be calculated using the surface flux transport model (SFT model). The SFT model consists of advection term due to differential rotation and meridional circulation, magnetic diffusion term, and flux emergence term. The advection and the diffusion coefficients are estimated by modern observations. On the other hand, estimation of future flux emergence is still very difficult without reliable information about these coefficients. Therefore, it is crucial problem about the solar cycle prediction to estimate when and where the sunspots will emerge. In this study, we constructed a prediction frame for solar activity by combining the calculation of the polar magnetic field by the SFT model and the prediction of sunspot information by machine learning. In the sunspot information prediction, we used RNN (Recurrent Neural Network) to predict the shape of the cycle. We also used CNN (Convolutional Neural Network) to predict the probability distribution of latitude, area, and tilt angle. As a result of creating butterfly diagrams based on the predicted probability distribution of latitude of appearance, we were able to reproduce the transition and periodicity of sunspot appearance from mid-latitudes to low latitudes. In addition, the tilt angle prediction was able to predict the difference in latitude dependence for each cycle. However, it can be said that further improvement of accuracy is necessary for both sunspot number, latitude, tilt angle, and area. In addition, we inserted the sunspot data from NOAA and KODAIKANAL into the SFT model to calculate the polar field, and confirmed whether the SFT model can reproduce the value of the polar field from the actual magnetic field observation.
10/22 KANG YEONGMIN Data-driven MHD Simulation of Solar Active Region NOAA 11283
Abstract : Solar eruptive events such as flares are caused by release of magnetic energy accumulated in the solar atmosphere. They occur in the solar active regions (ARs) where the strong magnetic fields are present. The ARs can be classified by the distribution of magnetic fields. For example, the ARs which have a simple bipolar magnetic field are classified as beta-type. The ARs which have opposite polarities close to each other in a single penumbra are classified as delta-type. It is empirically known that huge flares are more likely to occur in the delta-type ARs than in beta-type ARs. The formation mechanism of delta-type ARs and their energy build-up process required for huge flares have not been understood completely. The objective of this study is to reveal the mechanism of energy build-up during the evolution of the AR. The target of this study is AR11283 which caused multiple M and X class flares. The AR11283 evolved from beta-type to delta-type one day before the first flare. We conducted a MHD simulation of AR11283 to investigate the evolution of magnetic energy. We applied a newly developed data-driven simulation method in which time series observational data of the photospheric magnetic field (SDO/HMI) are introduced as the bottom boundary condition. We successfully reproduced the flux emergence responsible for the energy build-up during the pre-flare phase.
10/15 Kengo Matoba Calculation of solar surface flow using a magnetic element tracking module
Abstract : Building the next cycle prediction scheme is the key to long-term space weather research. Recently, it has been suggested that the polar magnetic field during the minimum period is one of the good indicators for the next solar cycle activity. The surface flux transport (SFT) models are often used to estimate polar magnetic fields. On the other hand, the SFT models require several parameters, such as meridional circulation, rotational difference, and turbulent diffusion. These parameters are not fully understood, and especially their temporal variation and polar region are still unclear. In this study, we focused on two typical solar surface flows, differential rotation and meridional circulation, which are parameters of the SFT model. We apply a magnetic element tracking (MET) module to SDO/HMI magnetic field data to obtain solar surface velocities. The surface velocities in the polar regions, which are difficult to observe with the HMI, were obtained using high resolution, high frame rate Hinode/SOT magnetic field data. The location information of the SOT data was obtained by comparing it with the HMI data. Because HMI has been available since 2010, we calculated solar surface flow using eleven years data. We studied the solar surface flow. We find that the differential rotation/meridional flow speed is faster/slower at the latitude where the sunspots frequently emerge, respectively. From Hinode/SOT magnetic field data, we calculated solar surface flow of the polar region. We were able to obtain results from higher resolution and higher frame rate data than before.
10/8 Minami Mori Simulation study on the deformation of magnetic field in interplanetary CMEs
Abstract : Coronal mass ejections (CMEs) are large-scale phenomena in which plasma and magnetic fields are ejected from the solar corona into interplanetary space, and are a major cause of disturbances in space weather. In particular, since the southward component of the interplanetary magnetic field due to CMEs is an important factor in causing disturbances such as magnetic storms, predicting the magnetic field due to CMEs is one of the most important tasks in space weather forecasting. To do this, it is important to understand how the magnetic field of a CME changes after it leaves the solar corona. In this study, we will focus on the deformation caused by the interaction between the interplanetary magnetic field and the CME, although it has been thought that the CME magnetic field changes mainly due to the non-uniformity of the solar wind and the interplanetary magnetic field. In this study, we focus on the deformation caused by the interaction between the interplanetary magnetic field and the CME. We aim to clarify whether such a phenomenon can occur, and if so, how much and by what mechanism. For this purpose, we performed a 3D MHD simulation using the SUSANOO-CME model (Shiota & Kataoka, 2016). In this study, the following two assumptions were made in order to explore the fundamental processes of the interaction between the CME and the solar wind. First, the velocity and magnetic field of the background solar wind were assumed to be isotropic, avoiding the effect of the complex anisotropy of the solar wind. In addition, the main axis of the spheromak magnetic field inside the CME incident from the inner boundary of the computational domain was assumed to be along the solar equator and facing west. Using this result as a reference, we investigated the dependence of three parameters: the background magnetic field strength, the initial magnetic field structure of the CME, and the initial velocity of the CME. The results show that during the evolution of the CME in interplanetary space, there is a north-south deflection and a rotation of the magnetic flux on the solar equatorial plane. These trends were found to be due to the orientation of the toroidal and poloidal components of the spheromak. These results imply that not only the fluid interaction with the solar wind but also the magnetohydrodynamic interaction has a significant effect on the magnetic field deformation of ICME, and these effects should be well understood and taken into account for accurate prediction of B_z.
10/4 Satoshi Fukuoka Development of a new flare prediction method based on the 𝜅-scheme
Abstract : The relativistic/sub-relativistic electron flux variations often cause serious damage on the satellite operations through the dielectric charging. In order to forecast flux variations of these electron flux variations, various forecast methods based on the physical based simulations and empirical models have been developed. For the physics-based simulation, the SUSANOO that operates a code-coupling simulation of heliosphere and radiation belt provides MeV electron flux variations for the next couple of days. For the empirical modeling, the linear prediction filter(LPF) and the auto-regressive moving average(ARMA) have been commonly used for the forecast of MeV electrons at geosynchronous Earth orbit (GEO). Recently, the machine learning techniques have widely been used for the space weather forecast, for example, ionospheric variations, the flare prediction, etc. In this study, we have developed the forecast system of relativistic/sub-relativistic electron flux variations based on long short-term memory recurrent neural network (LSTM-RNN). As the training data, we use the solar wind data and energetic electron flux data observed by Arase/HEP and XEP instruments at different L-shells of the outer belt. The developed network provides time variations of the energetic electron flux at L=4, 5 and 6 using the solar wind data as an input parameter. In this presentation, we evaluate how the solar wind parameters affect the temporal variation of the high-energy electron flux. We also report the results of another network developed using Arase space weather data for the real time space weather forecast.
9/24 Kaho Kondo Development of a new flare prediction method based on the 𝜅-scheme
Abstract : Solar flares suddenly emit electromagnetic waves, plasma and energetic particles into the interplanetary space, and cause the space weather disturbances. Therefore, the prediction of solar flares is important to mitigate the space weather impact. For predicting solar flares, various types of empirical methods have been developed so far, and very recently the physics-based method for predicting large solar flares, called the kappa-scheme, has been developed by Kusano et al. (2020). The 𝜅-scheme indicates that the magnetic twist flux, which is the numerator of the parameter κ, is important to determine the onset of flares. However, the 𝜅-scheme needs heavy computation to evaluate the magnetic twist flux because the nonlinear force-free field (NLFFF) extrapolation was used. The objective of our study is to develop an more efficient prediction method for solar flares through the comparison between the 𝜅-schemethe and empirical predictions, such as Schrijver’s R-parameter (Schrijver 2007). To this end, we conducted the following two studies to approximate 𝜅 directly from magnetic field data. First, we analyzed the relationship between the local magnetic flux 𝜙 near the polarity inversion line (PIL) and the occurrence of flares. The local magnetic flux is the unsigned magnetic flux within a circle of radius 2 Mm centered at each point on the PILs. As a result, we found that although the local magnetic flux at the flaring point was high the points of high local flux were not only at the flaring point. Second, we developed a method to evaluate the mean magnetic twist near the PIL directly from the observed magnetic field data on the solar surface (photosphere). Two methods have been investigated. In the the method one, we approximated the magnetic twist by 𝛼l where 𝛼 is the force free field parameter and l is the distance between the conjugated foot points in the linear force-free field. In the method two, we approximated the magnetic twist using the relationship of the linear force-free field between the magnetic shear angle 𝜃 and the magnetic twist. We analyzed the two methods for 198 active regions which produced large flares or had large sunspots by comparing the magnetic twist derived by the NLFFF. The results show that the magnetic twist calculated by the latter method better correlates with the results of the NLFFF. We plan to apply these results for developing a new method predicting solar flares more efficiently.
9/17 Kohei Toyama Precipitating electron energy of pulsating aurora estimated from multi-wavelength observations
Abstract : Pulsating aurora (PsA) is characterized by quasi-periodic intensity modulations with a period of a few to tens of seconds which is known as the main modulation. Electrostatic Cyclotron Harmonic waves and whistler-mode waves are known to cause the pitch angle scattering of energetic electrons in the magnetosphere. In particular, whistler-mode chorus waves play a crucial role in the pitch angle scattering of electrons. The lower-band chorus causes precipitation of electrons whose energy is greater than several keV [Miyoshi et al., 2015]. The energy of precipitating electrons causing PsA may be estimated from ground-based optical observations. Ono [1993] observed the emission intensities of PsAs at wavelengths of 427.8 and 844.6 nm using a photometer in Antarctica, and estimated the energy of precipitating electrons by combining the ratio of the emission intensities at the two wavelengths and the model calculation. However, Ono [1993] conducted observations using the instrument with a narrow field-of-view, and the energy estimation using all-sky imagers has not yet been performed. In Tromsoe, Norway, several highly-sensitive EMCCD cameras have been operated, which have simultaneously observed all-sky images of the emission intensity at the two wavelengths (427.8 and 844.6 nm) with a sampling frequency of 10 Hz. In this study, we investigate the spatio-temporal variations of precipitating electron energy using these EMCCD camera data. We estimated the precipitating electron energy of PsA by comparing the emission intensity ratio of the two emission lines using the all-sky image and the emission intensity calculation results obtained by the GLobal airglOW (GLOW) model [Solomon, 2017]. We have also developed a code coupling simulation using both the test particle simulation GEMSIS-RBW that calculates wave-particle interactions and the GLOW model, and we compared the ratios at different wavelength between the model and the observations. The analysis showed that the spatial distribution of precipitating electron energies are not uniform, and a few keV differences are found inside the patch.
7/16 Park Inchun Energetic electron flux variations of the outer radiation belt during magnetic storms observed by Arase/HEP
Abstract : The Arase satellite has been regularly observing high-energy electrons of the outer radiation-belt since March 2017 with the HEP (High-energy electron experiments) instrument that measures electrons with energies from 70 keV to 2 MeV. Since the beginning of the HEP observations, the Arase has observed more than 17 magnetic storms with Dst values under −30 nT which are driven by CIR. For these storm events, we have investigated variations of energetic electron flux, primarily focusing on the changing of the pitch angle distribution (PAD) where occurred at the outer radiation belt during the storm main phases. Using the superposed epoch analysis, we derived average variations of the PAD and tried several parameters to simplify the variation of PAD. The result indicates before and after the magnetic storm, enhancement of PAD 90-degree direction showed depending on the energy and L*. This result could provide the clue for the seed of acceleration of the relativistic electrons.
7/9 Kawai Toshiki (河合 敏輝) What determines the power-law index of solar flares?
Abstract : It is known that the occurrence frequency of solar/stellar flares is distributed as a power-law. The slope of the distribution, so-called power-law index, is one of the most important indicators to understand the mechanism of the coronal heating. Many studies tried to derive the power-law index using various methods and instruments for a few decades and obtained results ranging from 1.4 to 2.9. However, the cause of this large dispersion in the estimated indices is unclear. Therefore, we investigated the dependences of the power-law index on the solar activity, coronal features, released energy, and magnetic properties using SDO/AIA and SHARP dataset. Our results are as follows: 1) The power-law index derived from Sun-as-a-star observation has a negative correlation with sunspot number. 2) The quiet Sun tends to have larger power-law index (~2.2) than those of active regions (~1.8). 3) The power-law index is approximately independent of released energy in the range from 10^{23} to 10^{30} erg. 4) The power-law index has negative correlations with thermal input from impulsive heating and with some SHARP parameters such as magnetic free energy density in the active region. We also discuss a relationship between the heating flux and magnetic properties to evaluate the contribution of flares to the active region heating.
7/2 Matsushita Toshinori (松下敏法) Design of a 2-Dimensional Phased Array Antenna for IPS Observations
Abstract : Interplanetary scintillation (IPS) have been discovered as the scattering phenomena of the radio sources caused by density variations of the solar wind [Hewish, Scott, and Wills, 1964]. IPS data is an important tool for observing the solar wind. We have a radio telescope system operated at 327 MHz for IPS observations which consists of the three observatories which are located at Toyokawa, Kiso and Fuji. A higher sensitivity receiver system and a simultaneous multi-observation system for two or more radio sources is required to obtain a more accurate synoptic map of solar wind parameters. For the requirement, we have been developing a 2-dimensional phased array antenna system. This detailed design of the phased antenna must account for some mutual effects in order to obtain enough accuracy for a gain and directivity. The mutual effects are neglected by the classical design method such as the array factor method. We have applied a Network theory model including mutual effects and been designing a 2-dimensional phased antenna. We will present an interim report about the designing of a 2-dimensional phased array antenna and the progress.
6/25 Bamba Yumi (伴場 由美) Introduction of the HINODE satellite and its scientific operations
Abstract : HINODE was launched from Uchinoura Space Center on September 23, 2006. It was developed through international collaboration among primarily Japan, the United States, and the United Kingdom. HINODE has three telescopes to observe the Sun: the Solar Optical Telescope (SOT), the X-Ray Telescope (XRT), and the Extreme-ultraviolet Imaging Spectrometer (EIS). These innovative telescopes can capture complex solar magnetic field and three-dimensional solar plasma dynamics in real time. The main purpose of this talk is to let students know the HINODE satellite and its scientific operations. I will review the HINODE satellite, especially the SOT. Then I introduce HINODE scientific operations
, specifically, what "chief observers", "chief planner", and "flare watchdog" do. Further, I will review HINODE operation for AR NOAA 12673 observation in September, 2017, as an example of successful operation. I hope that the talk will help to get students (and researchers who have never used HINODE data) interested in HINODE data analysis.
6/18 Iijima Haruhisa (飯島 陽久) Comprehensive MHD simulation of coronal hole from upper convection zone to 30 Rsun
Abstract : The coronal hole is considered as one of the most important source regions of solar wind. Large number of studies has been devoted to understand the coronal plasma heating and solar wind acceleration. However, the complexity of the near-Sun magnetic field structure and the high nonlinearity of coronal waves have prevented a more quantitative understanding of coronal heating and solar wind acceleration processes. To overcome this difficulty, we performed the first comprehensive magnetohydrodynamic simulation of a coronal hole. Since the numerical domain extends from the convection zone to the solar wind region, the generation of the complex magnetic field structure through the local dynamo action, the excitation/propagation/dissipation of various MHD wave modes are realized self-consistently. In this talk, I will present a preliminary analysis of the simulation.
6/11 Nakamura Satoko (中村 紗都子) The role of EMIC waves in the inner magnetosphere
Abstract : Plasma waves are readily recorded throughout the Earth’s magnetosphere and on the ground. Generated by a variety of instabilities, waves transport and couple energy throughout the system, and may play important roles in the energization and loss of radiation belt particles. I review the role of electromagnetic ion cyclotron (EMIC) waves in the inner magnetosphere. EMIC waves excited in the equatorial magnetosphere propagate along the field line to the ionosphere and are observed as Pc 1 geomagnetic pulsations on the ground. EMIC waves have been identified as a potential driver of the precipitation of not only energetic ions with energy of tens of kiloelectron volts but also relativistic electrons with energy of sub–megaelectron volts or greater than 1 MeV
5/28 Masuda Satoshi (増田 智) Electron acceleration region in a small solar flare observed with NoRH.0 and MUSER
Abstract : We analyzed a small solar flare simultaneously observed with Nobeyama Radioheliograph (NoRH) and Mingantu Spectral Radioheliograph (MUSER) on 22 November 2015. A group of weak type-III radio bursts were observed in the 0.4-2 GHz range. Its appearance radio frequency changed from low/high to high/low before/after the peaktime of the 17 GHz flux. In addition, there was a blank (= no emission) frequency range. In the frequency range higher/lower than this blank, the most of type-III bursts showed a positive/negative frequency drift. This blank might correspond to the acceleration. In addition, the frequency of the blank continuously moved to the higher frequency range at least until the peaktime. This indicates that the electron acceleration region gradually moved to a higher altitude during the flare. We discuss what kind of acceleration region is plausible.
5/21 Kaneko Takafumi (金子 岳史) Impact of convection on sunspot formation and evolution
Abstract : Huge solar flares occur in sunspots where strong magnetic fields emerge from the convection zone (interior of the sun) to the photosphere (solar surface). In observations, the features of flare-productive sunspots. e.g., area and distribution of magnetic fields, are empirically known. However, the mechanism of formation and evolution of the flare-productive sunspots has not been revealed. The aim of our study is to reveal the impact of convection on formation and evolution of the sunspot. We cannot directly observe the interior of the sun where the magnetic fields of the sunspots are born and transported. We simulated the transport of magnetic fields in the convection zone and the formation of the sunspot in the photosphere using radiative magnetohydrodynamic (MHD) simulations. At first, solar convection was reproduced without magnetic field. After the convection reached steady state, we set a magnetic flux rope inside the convection zone. We conducted parameter survey by changing the initial positions of the magnetic flux ropes relative to the convection cells. We fixed the magnetic parameters of the initial flux rope. As a result, various kinds of the sunspots were reproduced only by the difference of the convective velocity fields. In several cases, flare-productive sunspots consistent with observations were reproduced. Our result suggests that convection has great impact on formation and evolution of the sunspots, and the features of the flare-productive sunspots were not always determined by the initial magnetic fields of the flux ropes. We also introduce a future plan to reproduce huge solar flare using the simulated sunspot magnetic fields and a data-driven MHD method.
5/14 Ieda Akimasa (家田 章正) Preliminary Analyses of the Solar-Terrestrial Environment during the Dalton Minimum
Abstract : Collision between ions and neutral particles is an essential characteristic of Earth’s ionosphere. This ion-neutral collision is usually caused by the polarization of neutral particles. This collision can also be caused by charge exchange, if the particle pair is parental, such as atomic oxygen and its ion. The total collision frequency is not the sum of the polarization and charge-exchange components, but is essentially equal to the dominant component. The total is enhanced only around the classic transition temperature, which is near the ionospheric temperature range (approximately 200-2000 K). However, the magnitude of this enhancement has been unclear; the maximum enhancement has been reported as 41% and 11% in separate previous studies. In the present study, the contribution of the polarization force to the charge-exchange collision is expressed as a simple curved particle trajectory effect. As a result, the maximum enhancement was 22%. It is discussed that the enhancement has been neglected in classic models partly due to confusion with the glancing particle contribution, which is 10.5% to the polarization component. This neglect has been partly inevitable because there has been no functional form to express the enhancement. Such an expression is derived in this study.
4/30 Hayakawa Hisashi (早川 尚志) Preliminary Analyses of the Solar-Terrestrial Environment during the Dalton Minimum
Abstract : The Dalton Minimum (1797-1827) is considered one of the two extended solar activity minima during the last 4 centuries. During this interval, the solar activity was probably weakened than the modern solar cycles, while its actual amplitude was not fully understood. In this presentation, the historical observations are analysed to visualise the sunspot group number, sunspot positions, solar coronal structure, and the auroral activity at that time. Their results are contrasted with the Maunder Minimum (1645-1715).
4/23 Shinsuke Imada(今田 晋亮) Solar-C_EUVST Mission
Abstract : I will briefly introduce the solar physics and discuss what is the big issue which should be solve in the category of solar physics. Later, I will talk about the next generation solar satellite mission. Now in the solar community are preparing to launch the new satellite. Solar-C(EUVST) (EUV High-Throughput Spectroscopic Telescope) is designed to answer how stellar plasma are created and evolve, and how the Sun influences the Earth and other planets in our solar system. The proposed mission is designed to comprehensively understand the energy and mass transfer from the solar surface to the solar corona and interplanetary space, and to investigate the elementary processes that take place universally in cosmic plasmas. The two primary science objectives for Solar-C_EUVST are : I) Understand how fundamental processes lead to the formation of the solar atmosphere and the solar wind, II) Understand how the solar atmosphere becomes unstable, releasing the energy that drives solar flares and eruptions. Solar-C_EUVST will, A) seamlessly observe all the temperature regimes of the solar atmosphere from the chromosphere to the corona at the same time, B) resolve elemental structures of the solar atmosphere with high spatial resolution and cadence to track their evolution, and C) obtain spectroscopic information on the dynamics of elementary processes taking place in the solar atmosphere. In this talk, we will first introduce the science targets of the Solar-C_EUVST, and then discuss in detail the topics related to the magnetic reconnection such as hot plasmas in magnetic reconnection region.
4/16 Kanya Kusano (草野完也) ntroduction to Integrated Studies Seminar and the Challenge to the Integrated Model of Solar and Heliospheric System. 総合解析セミナーへのお誘い＆太陽太陽圏統合モデルへの挑戦
Abstract : The solar-terrestrial environment is a complex system that consists of nonlinear, non-equilibrium, and multi-scale interacting processes. The Integrated Studies Division aims to improve our understanding of the dynamics of various phenomena in the solar-terrestrial environment through data analyses, numerical simulations, and modelings. Integrated Studies Seminar plays a vital role in discussing different research topics of the solar-terrestrial environment with all members of the division. In the first part of this seminar, I will give a brief introduction to the integrated studies seminar and explain how important is the holistic aspect to understand and predict the dynamics of the solar-terrestrial environment. In the second part, I will talk about our new research project for the solar and heliospheric integrated model. Solar explosions, such as solar flares and coronal mass ejections (CMEs), occur as the consequence of the destabilization of the coronal magnetic field generated by the dynamo process inside the sun (convection zone). The solar explosion may cause space weather disturbance, and thus it is a potential risk for the infrastructure that supports modern society. However, research on the inside and outside of the Sun has been separated so far, and the physics that interconnects the convection zone, the solar atmosphere, and the interplanetary space has not been well elucidated. Therefore, the ability to predict solar explosions and changes in the space environment is still insufficient. To overcome this difficulty, we recently launched a new research project for the integrated model of the solar and heliospheric system. In this project, we challenge to develop the integrated model including from the solar convection zone to interplanetary space. Through this project, we aim at (1) realizing advanced prediction of solar explosions, elucidating the cause of the power-law of scale and frequency of solar flares, and clarifying the physics that determine the maximum limit of solar explosions. Finally, we discuss the prospective role of our project as an interdisciplinary study.
　太陽地球環境は、非線形、非平衡、およびマルチスケール相互作用プロセスが支配する複雑なシステムです。総合解析研究部では、データ分析や数値シミュレーション、モデリングを通じて、太陽地球環境におけるこうした様々な現象のダイナミクスの理解を深めることを目的としています。総合解析セミナーは、太陽地球環境のさまざまな研究トピックについて研究部のすべてのメンバーが議論する重要な役割を果たす場です。この講演ではまず、総合解析セミナーの役割を簡単に説明し、太陽地球環境のダイナミクスを理解し予測するための統合研究がいかに重要であるかを議論します。 　後半では、太陽と太陽圏の統合モデルに関する新しい研究プロジェクトについてお話します。太陽フレアやコロナ質量放出（CME）などの太陽面爆発は、太陽内部（対流層）のダイナモプロセスによって生成された磁場が太陽表面とコロナで不安定化する結果として発生します。太陽面爆発はしばしば大規模な宇宙天気擾乱を引き起こす可能性があり、現代社会を支えるインフラストラクチャーにとっても潜在的なリスクです。しかし、これまで、太陽の内部と外部の研究は分断されており、太陽対流層、太陽大気、惑星間空間を相互に結合する物理は十分に理解できていません。そのため、太陽面爆発の発生や宇宙環境の変化を予測する能力はまだ不十分です。この困難を克服するために、私たちは太陽・太陽圏システムの統合モデルに関する新しい研究プロジェクトを立ち上げました。このプロジェクトでは、太陽対流層から惑星間空間までを含むモデルの開発に挑戦します。このプロジェクトを通じて、①これまで不可能であった太陽面爆発の早期予測を実現すると共に、②太陽恒星フレアの基本性質である規模と頻度のべき乗則の原因を解明し、③太陽フレアの最大限界を決定する物理を明らかにすることを目指しています。さらに、学際研究としての私たちのプロジェクトの役割についても議論します。