A Great Space Weather Event in February 1730

Aims. Historical records provide evidence of extreme magnetic storms with equatorward auroral extensions before the epoch of systematic magnetic observations. One significant magnetic storm occurred on February 15, 1730. We scale this magnetic storm with auroral extension and contextualise it based on contemporary solar activity. Methods. We examined historical records in East Asia and computed the magnetic latitude (MLAT) of observational sites to scale magnetic storms. We also compared them with auroral records in Southern Europe. We examined contemporary sunspot observations to reconstruct detailed solar activity between 1729 and 1731. Results. We show 29 auroral records in East Asian historical documents and 37 sunspot observations. Conclusions. These records show that the auroral displays were visible at least down to 25.8{\deg} MLAT throughout East Asia. In comparison with contemporary European records, we show that the boundary of the auroral display closest to the equator surpassed 45.1{\deg} MLAT and possibly came down to 31.5{\deg} MLAT in its maximum phase, with considerable brightness. Contemporary sunspot records show an active phase in the first half of 1730 during the declining phase of the solar cycle. This magnetic storm was at least as intense as the magnetic storm in 1989, but less intense than the Carrington event.Comment: 30 pages, 5 figures, and 2 tables, accepted for publication in Astronomy & Astrophysics on 25 April 2018. The figures and transcriptions/translations of historical documents are partially omitted in this manuscript due to the condition of reproduction. They are available in the publisher versio

Results of the search for inspiraling compact star binaries from TAMA300's observation in 2000-2004

We analyze the data of TAMA300 detector to search for gravitational waves from inspiraling compact star binaries with masses of the component stars in the range 1-3Msolar. In this analysis, 2705 hours of data, taken during the years 2000-2004, are used for the event search. We combine the results of different observation runs, and obtained a single upper limit on the rate of the coalescence of compact binaries in our Galaxy of 20 per year at a 90% confidence level. In this upper limit, the effect of various systematic errors such like the uncertainty of the background estimation and the calibration of the detector's sensitivity are included.Comment: 8 pages, 4 Postscript figures, uses revtex4.sty The author list was correcte

Observation results by the TAMA300 detector on gravitational wave bursts from stellar-core collapses

We present data-analysis schemes and results of observations with the TAMA300 gravitational-wave detector, targeting burst signals from stellar-core collapse events. In analyses for burst gravitational waves, the detection and fake-reduction schemes are different from well-investigated ones for a chirp-wave analysis, because precise waveform templates are not available. We used an excess-power filter for the extraction of gravitational-wave candidates, and developed two methods for the reduction of fake events caused by non-stationary noises of the detector. These analysis schemes were applied to real data from the TAMA300 interferometric gravitational wave detector. As a result, fake events were reduced by a factor of about 1000 in the best cases. The resultant event candidates were interpreted from an astronomical viewpoint. We set an upper limit of 2.2x10^3 events/sec on the burst gravitational-wave event rate in our Galaxy with a confidence level of 90%. This work sets a milestone and prospects on the search for burst gravitational waves, by establishing an analysis scheme for the observation data from an interferometric gravitational wave detector

Stability Analysis of Multi-Fingered Grasp under Destabilizing Gravity Effect

In this paper, we deal with the stability analysis of an object grasped by fingers with linear stiffness in the case where the gravity effect is considered. The stability of the grasp is defined based on the potential energy of the grasp. The analysis problem is formulated as finding a condition of the stiffness parameters and contact points for the position of the center of gravity (COG) to exist such that the grasp is stable. A necessary and sufficient condition is derived on assumptions with respect to the stiffness and contact points. Furthermore, on the derived condition, the position of the COG is characterized with respect to the stiffness and contact points. It is especially indicated that the grasp can be stable with any position of the COG. Numerical examples are shown to prove the effectiveness of the analysis.the 18th World Congress The International Federation of Automatic Control, Milano (Italy), August 28 - September 2, 201

Floquet Transformations for Discrete-time Systems: Equivalence between periodic systems and time-invariant ones

This paper considers discrete-time periodic linear systems and their Floquet transformations, by which the periodic systems can be equivalently transformed to time-invariant ones. When the system matrix is nonsingular, it is very easy to derive the discrete-time Floquet transformation, however, when the system matrix is singular, the derivation is essentially different from the continuous-time case. A necessary and sufficient condition for Floquet transformation to exist has been already known and this paper aims to give a simpler proof, by which all the similarity classes of Floquet transformations could be made clear. And also an extension of Floquet transformations to non-autonomous systems is shown