Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Bibliography : leaves 57-58. / by Bonnie J. Buratti. / M.S.

Yes / A web-based prototype system for predicting solar energetic particle (SEP) events and solar flares for use by space launch operators is presented. The system has been developed as a result of the European Space Agency (ESA) project SEPsFLAREs (Solar Events Prediction system For space LAunch Risk Estimation). The system consists of several modules covering the prediction of solar flares and early SEP Warnings (labeled Warning tool), the prediction of SEP event occurrence and onset, and the prediction of SEP event peak and duration. In addition, the system acquires data for solar flare nowcasting from Global Navigation Satellite Systems (GNSS)-based techniques (GNSS Solar Flare Detector, GSFLAD and the Sunlit Ionosphere Sudden Total Electron Content Enhancement Detector, SISTED) as additional independent products that may also prove useful for space launch operators. / This work has been developed in the frame of 34 SEPsFLAREs project (ESA Contract Number 4000109626/13/NL/ 35 AK), which is an activity funded by ESA/ESTEC Space Environ- 36 ment (TEC-EES) section. The authors of this work are grateful to 37 ESA’s MONITOR project (Contract Number 4000100988/2010/F/ 38 WE) for allowing the use of GSFLAD and SISTED products. 39 We also thank AGAUR (Generalitat de Catalunya) for the financial 40 support from Grant PDJ 2014 00074.

The objective of this thesis is to use radio emissions from lightning, known as `radio atmospherics' or `sferics', to study the temporal and spatial variation of the lower ionosphere, a layer of ionized atmosphere beginning at $\sim$70 km altitude (D-region). Very Low Frequency (VLF, 3$-$30kHz) radio waves are a useful diagnostic for lower ionospheric monitoring due to their reflection from this region and global propagation. Traditionally, the lower ionosphere has been sensed using single-frequency VLF transmitters allowing for analysis of a single propagation path, as there are only a small number of transmitters. A lightning stroke, however, releases an intense amount of impulsive broadband VLF radio energy in the form of a sferic, which propagates through the Earth-ionosphere waveguide. Lightning is globally distributed and very frequent, so a sferic is therefore also a useful diagnostic of the D-region. This is true both for ambient or quiet conditions, and for ionospheric perturbations such as solar flare x-ray bursts. Lightning strokes effectively act as separate VLF transmitting sources. As such, they uniquely provide the ability to add a spatial component to ionospheric remote sensing, in addition to their broadband signature which cannot be achieved with man-made transmitters. We describe the methods of processing in detail. As an example, we analyze a solar flare during which time there is a significant change in magnitude and frequency content of sferics. This disturbance varies with distance from the source, as well as time. We describe the methods of processing in detail, and show results at Palmer Station, Antarctica for both a quiet and active solar day.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (p. 101-105).

This thesis studies the acceleration of particles to super-thermal energies in explosive solar events as well as the magnetic changes in connectivity that may be responsible for changes in the morphology of quiescent filaments. Firstly a review of some of the observations of solar flare dynamics is given, as well as an introduction to the competing theories attempting to explain both particle acceleration and filament formation. An explanation of the numerical FORTRAN code that is used to calculate the trajectories of particle distribution functions in prescribed electromagnetic fields is given. Examples of known fields are used to test the accuracy of the code and the simple example of the well-known Litvinenko current sheet field is investigated. The results of charged particle orbit calculations in prescribed electric and magnetic fields motivated by magnetic reconnection models are then presented. The electromagnetic fields are chosen to resemble a current sheet with a localised reconnection region. The dependence of the model on the important physical parameters is considered. An introduction to the mathematical formulation of a collapsing magnetic trap is given. The same numerical code is used to calculate single electron orbits in this more complicated time dependent electromagnetic field. Consideration of important previous work is given before describing the best attempts to model the movement of flare loops in a realistic fashion. Finally the process of flux cancellation and filament formation is studied using a range of data including ground-based Hα and SoHO MDI magnetograms. It is found that the cancellation occurs at the ends of Hα sections of the filament and is accompanied by a noticeable increase in the Hα intensity and linkage of the sections. Measurements of the amount of flux cancelled at each site show it is in agreement with an estimate of the axial flux contained in the filament.

Le soleil est une étoile active, et les éruptions solaires sont une des manifestations de cette activité. Il est admis que l'énergie disponible pour les éruptions solaires a une origine magnétique, et est transmise au milieu lors de phénomènes de reconnexion magnétique dans la couronne. Une partie de cette énergie permet d'accélérer les particules du milieu (électrons et ions). Cependant, les détails concernant les conditions dans lesquelles les particules sont accélérées et se propagent des régions d'accélération aux sites d'interaction lors des éruptions solaires ne sont pas encore tous compris.Plusieurs modèles d'accélération de particules ont été développés dans le cadre de l'étude des éruptions solaires. Dans certains modèles, les particules sont accélérées par un champ électrique généré au niveau de couches de courants électriques, qui peuvent être fragmentées, et qui sont préférentiellement localisées au niveau de surfaces quasi-séparatrices. Afin d'étudier le lien entre l'accélération de particules et le champ électrique direct produit au niveau de couches de courants, nous avons recherché s'il y avait des corrélations entre les sites d'émission des particules énergétiques et les courants électriques mesurés au niveau de la photosphère. Les observations X (dur) représentent les diagnostics les plus directs des électrons énergétiques produits pendant les éruptions solaires (rayonnement de freinage des électrons dans l'atmosphère solaire) et nous avons donc utilisé les observations X du satellite RHESSI (Reuven Ramaty High Energy Solar Spectrometric Imager) afin de produire des images et des spectres du rayonnement X dur des électrons énergétiques. Afin de caractériser les courants électriques dans la région éruptive, nous avons utilisé les données spectropolarimétriques de l'instrument HMI (Helioseismic and Magnetic Imager) du satellite SDO (Solar Dynamic Observatory) et nous avons calculé les densités de courants verticales photosphériques à partir du champ magnétique vectoriel reconstruit. Une corrélation entre les émissions X coronales (dues aux particules énergétiques proches du site d'accélération) et les rubans de forte densité de courants photosphériques (traces des couches de courants coronales) a été mise en évidence pour les cinq éruptions de classe X étudiées. De plus, grâce à la cadenc / The Sun is an active star and one manifestation of its activity is the production of solar flares. It is currently admitted that solar flares are caused by the release of magnetic energy during the process of magnetic reconnection in the solar upper atmosphere, the solar corona. During these flares, a large fraction of the magnetic energy is transferred to the acceleration of particles (electrons and ions). However, the details of particle acceleration during flares are still not completely understood.Several scenarios and models have been developed to explain particle acceleration. In some of them, electric fields, produced at the location of current sheets, which can be fragmented or collapsing, and which are preferentially located on quasi-separatrix layers (QSLs), are accelerating particles. To investigate a possible link between energetic particles and direct electric fields produced at current sheet locations, we looked for a correlation between X-ray emission from energetic electrons and electric currents which can be measured at the photospheric level. We used the Reuven Ramaty High Energy Solar Spectrometric Imager (RHESSI) data to produce spectra and images of the X-ray emissions during GOES X-class flares, and spectropolarimetric data from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) to calculate the vertical current densities from the reconstructed 3D vector magnetic field. A correlation between the coronal X-ray emissions (tracing the energetic electrons near the acceleration site) and the strong current ribbons at the photospheric level (tracing the coronal current sheet) was found in the five studied X-class flares. Moreover, thanks to the 12-minute time cadence of SDO/HMI, we could study for the first time the time evolution of electric currents: in several flares, a change in the current intensity, occurring during the flare peak, was found to be spatially correlated with X-ray emission sites. These observations enlighten a common evolution of both electric currents and X-ray emissions during the

We present a unique design of a post-focal instrument suitable to detect fast changes of flux in waveband 350 - 440 nm. As it is not possible to measure the Sun as a star because of a strong background radiation in this waveband and using a thin slit makes it impossible to measure the whole flaring area we made a set of circular diaphragms of different sizes able to collect light only from a limited part of the Sun's atmosphere. For our data we also evolved new software technique based on statistical methods that even more increases a sensitivity on any changes in spectra. First results of observations of three X-class solar flares obtained in June 2014 proved significant increase of flux in Balmer continuum. One of these flares was measured from 20 minutes before a peak in SXR (GOES) so we were able to compare a whole impulsive phase with a state with no signs of a flare before it. Data suggest a radiation at Balmer limit (364,5 nm) of up to 5,5 stronger from flaring kernels compared to the quiet Sun. Powered by TCPDF (www.tcpdf.org)

Solar Orbiter is a mission launched in 2020 that will take images closer than ever of the Sun. It has ten instruments on board, including The Spectrometer/Telescope for Imaging X-rays (STIX) and The Extreme Ultraviolet Imager (EUI). STIX is a hard X-ray imaging spectrometer which observes bremsstrahlung from the non-thermal accelerated electrons in the footpoints of solar flares and from thermal hot plasma in flare loops. EUI consists of three telescopes, including a Full Sun Imager which is a one-mirror telescope that observes the solar corona and chromosphere in extreme ultraviolet (EUV) wavelengths 174Å and 304Å, respectively.   The purpose of the project was to determine the alignment between STIX and EUI to better understand and improve the pointing of STIX. It is important to know the accuracy of the pointing before using the instruments for science. The alignment was studied by looking at the flare location of the two instruments for about 30 flares. The flare location was approximated to be the brightest pixel in the image. The aspect solution of STIX was applied and this was also compared to the flare seen by EUI. For some of the flares, also imaging data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) was used to get a more detailed comparison. One flare was studied in more detail, using thermal and non-thermal emission seen by STIX, EUV emission seen by EUI 174Å and AIA 171Å as well as UV emission seen by AIA 1600Å. For four flares, the flare location was determined from the visible ribbons and loops instead of the brightest pixel. The methods of finding the flare location by brightest pixel and by looking at flare features were compared.   The average difference between the EUI and STIX flare location was within 12 arcseconds with a standard deviation between 18 and 42 arcseconds for the brightest pixel method. This difference has two main contributions: the accuracy of the STIX aspect solutions and the accuracy of identifying the common source features in EUV and X-rays. To increase the accuracy of finding common sources, four flares with well defined ribbons and loops were analyzed in detail. For these events, the accuracy of the STIX aspect system was determined to be better than 10.5 arcseconds. This is still significantly higher than the design requirements of being better than 4 arcsecs. Detailed analysis clearly showed that the method of determining the flare location by brightest pixel was not accurate enough to evaluate the STIX pointing. Further studies need to be done to improve the aspect solution.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20181号 / 理博第4266号 / 新制||理||1613(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 柴田 一成, 教授 一本 潔, 准教授 浅井 歩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Yes / In this work, machine learning algorithms are applied to explore the relation between significant flares and their associated CMEs. The NGDC flares catalogue and the SOHO/LASCO CMEs catalogue are processed to associate X and M-class flares with CMEs based on timing information. Automated systems are created to process and associate years of flares and CMEs data, which are later arranged in numerical training vectors and fed to machine learning algorithms to extract the embedded knowledge and provide learning rules that can be used for the automated prediction of CMEs. Different properties are extracted from all the associated (A) and not-associated (NA) flares representing the intensity, flare duration, duration of decline and duration of growth. Cascade Correlation Neural Networks (CCNN) are used in our work. The flare properties are converted to numerical formats that are suitable for CCNN. The CCNN will predict if a certain flare is likely to initiate a CME after input of its properties. Intensive experiments using the Jack-knife techniques are carried out and it is concluded that our system provides an accurate prediction rate of 65.3%. The prediction performance is analysed and recommendation for enhancing the performance are provided.