15057212
Mode selection mechanism and magnetic diffusivity in a non-axisymmetric solar dynamo model
The generation of solar non-axisymmetric magnetic fields is studied based on a linear � 2 − dynamo model in a rotating spherical frame. The model consists of a solarlike differential rotation, a magnetic diffusivity varied with depth, and three types of �-effects with different locations, i.e. the tachocline, the whole convective zone and the sub-surface. Some comparisons of the critical �-values of axisymmetric (m = 0) and longitude-dependent modes (m = 1,2,3) are presented to show the roles of the magnetic diffusivity in the problem of modes selection. With the changing of diffusivity intensity for the given solar differential rotation system, the dominant mode possibly changes likewise and the stronger the diffusivity is, the easier the non-axisymmetric modes are excited. The influence of the diffusivity and differential rotation on the configurations of the dominant modes are also presented.
17485528
Periodicities in Solar Coronal Mass Ejections
ABSTRACT Mid-term quasi-periodicities in solar coronal mass ejections (CMEs) during the mostrecent solar maximum cycle 23 are reported here for the ﬁrst time using the four-year data (February 5, 1999 to February 10, 2003) of the Large Angle SpectrometricCoronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). Inparallel, mid-term quasi-periodicities in solar X-ray ﬂares (class >M5.0) from theGeosynchronous Operational Environment Satellites (GOES) and in daily averages ofAp index for geomagnetic disturbances from the World Data Center (WDC) at theInternationalAssociation for Geomagnetism andAeronomy (IAGA)are alsoexaminedfor the same four-year time span. By Fourier power spectral analyses, the CME dataappears to contain signiﬁcant power peaks at periods of ∼ 358 ± 38, ∼ 272 ± 26,∼ 196±13 days and so forth, while except for the ∼ 259±24-day period, X-ray solarﬂares of class >∼ M5.0 show the familiar Rieger-type quasi-periods at ∼ 157 ± 11,∼ 122± 5, ∼ 98±3 days and shorter ones until ∼ 34±0.5 days. In the data of dailyaverages of Ap index, the two signiﬁcant peaks at periods ∼ 273±26 and ∼ 187±12days (the latter is most prominent) could imply that CMEs (periods at ∼ 272±26and∼ 196 ± 13 days) may be proportionally correlated with quasi-periodic geomagneticstorm disturbances; at the speculative level, the ∼ 138 ± 6-day period might implythat X-ray ﬂares of class >∼ M5.0 (period at ∼ 157±11 days) may drive certain typesof geomagnetic disturbances; and the ∼ 28±0.2-day periodicity is most likely causedby recurrent high-speed solar winds at the Earth’s magnetosphere. For the same threedata sets, we further perform Morlet wavelet analysis to derive period-time contoursand identify wavelet power peaks and timescales at the 99 percent conﬁdence level forcomparisons. Several conceptual aspects of possible equatorially trapped Rossby-typewaves at and beneath the solar photosphere are discussed.Key words: oscillations — space weather — Sun: activities — corona — coronalmass ejections — magnetic ﬁelds
119110634
Solar Intranetwork Magnetic Elements: Bipolar Flux Appearance
This study aims to quantify characteristic features of the bipolar flux appearance of solar intranetwork (IN) magnetic elements. To attack this problem, we use the Narrowband Filter Imager (NFI) magnetograms from the Solar Optical Telescope (SOT) on board Hinode; these data are from quiet and enhanced network areas. Cluster emergence of mixed polarities and IN ephemeral regions (ERs) are the most conspicuous forms of bipolar flux appearance within the network. Each of the clusters is characterized by a few well-developed ERs that are partially or fully coaligned in magnetic axis orientation. On average, the sampled IN ERs have a total maximum unsigned flux of several 1017 Mx, a separation of 3 – 4 arcsec, and a lifetime of 10 – 15 minutes. The smallest IN ERs have a maximum unsigned flux of several 1016 Mx, separations of less than 1 arcsec, and lifetimes as short as 5 minutes. Most IN ERs exhibit a rotation of their magnetic axis of more than 10 degrees during flux emergence. Peculiar flux appearance, e.g., bipole shrinkage followed by growth or the reverse, is not unusual. A few examples show repeated shrinkage–growth or growth–shrinkage, like magnetic floats in the dynamic photosphere. The observed bipolar behavior seems to carry rich information on magnetoconvection in the subphotospheric layer.
16400877
VECTOR MAGNETIC FIELDS OF SOLAR GRANULATION
Observations of the quiet Sun from the Solar Optical Telescope/Spectro-Polarimeter aboard the Hinode spacecraft reveal the magnetic characteristics of the solar photosphere. By making use of the deep-mode observations of three quiet regions, we have statistically studied the vector magnetic fields of solar granulation. More than 2000 normal granules are manually selected to form a sample. It is recognized that some granules are even darker than the mean photosphere in intensity, and there is a linear correlation between intensity and Doppler velocity in the granules. The distributions of longitudinal and transverse apparent magnetic flux densities, Doppler velocity, and continuum intensity of granules are obtained, and their unsigned magnetic flux measured. Two approaches are used in this study. First, we obtained the magnetic properties of granulation by averaging the measurements for all the sampling granules. Second, we reconstructed an average granular cell based on a subsample, and obtained the detailed distribution of apparent magnetic flux density within the model granular cell. All the results have been compared with those for intergranular lanes and a few typical abnormal granules. Our statistical analysis reveals the following results. (1) The unsigned magnetic flux of individual granules spans the range from 1.1 × 1015 Mx to 3.3 × 1018 Mx with a peak distribution at 1.6 × 1016 Mx. (2) The unsigned longitudinal apparent flux density of granules ranges from almost 0 to 212 Mx cm–2 with a mean longitudinal apparent flux density of 12 Mx cm–2, while the transverse apparent flux density of granules ranges from 4 to 218 Mx cm–2 with a mean transverse apparent flux density of 79 Mx cm–2. The longitudinal and transverse apparent magnetic flux densities of granules are positively correlated, and the longitudinal apparent flux density of granules is weaker than the corresponding transverse apparent flux density. (3) The magnetic inclination of granules with respect to the surface that is perpendicular to the line of sight falls in the range of 4.8-76.7 degrees with a peak distribution at 25 degrees. On average, the magnetic vectors in granules are more vertical than those in the intergranular lanes. (4) There is a strong preference that both the vertical and horizontal fields on the quiet Sun reside in the intergranular lanes. (5) The detailed distributions of apparent flux density, Doppler velocity, and continuum intensity within an average granular cell are presented. These distributions can be empirically formulated well.
108659847
Relativistic klystron research for linear colliders
Relativistic klystrons are being developed as a power source for high gradient accelerator applications which include large linear electron-positron colliders, compact accelerators, and FEL sources. We have attained 200 MW peak power at 11.4 GHz from a relativistic klystron, and 140 MV/m longitudinal gradient in a short 11.4 GHz accelerator section. We report here on the design of our relativistic klystrons, the results of our experiments so far, and some of our plans for the near future. 5 refs., 9 figs., 1 tab.
14129862
Extended Multiwavelength Fuzz around Red Quasars: The Observational Appearance of Radiative Feedback in Action
Red quasars are a population characterized by significant extinction in UV, which could be explained by absorption of dusty gas on a scale of a few kpc. We show that the enhanced radiation pressure drives the dusty gas to supersonically expand and produces shocks. The shocks energize electrons to be relativistic via the first Fermi acceleration. As a balance of shock acceleration and synchrotron emission and inverse Compton scattering, the maximum Lorentz factor of the electrons reaches ~106. The shocked interstellar medium appears as extended multiwavelength fuzz, in which synchrotron emission from the electrons peaks at near-infrared or UV bands and inverse Compton scattering around 1.0 GeV-0.1 TeV. Future multiwavelength images of the fuzz would provide new clues to study the details of radiative feedback if red quasars are a certain phase in the evolutionary chains of galaxies.
16215815
Design of 2x2 DLDS RF Components for JLC
We have studied a multi-mode Delay Line Distribution System (DLDS)[1][2] as the RF power distribution system from klystrons to RF structures for linear colliders. In particular, a 2×2 DLDS has been proposed and studied at KEK for Japan Linear Collider(JLC). It has been proved that the 2×2 DLDS is simple, bus has good transmission efficiency. We have designed RF components of a basic unit of a DLDS using the High Frequency Structure Simulator (HFSS) code[3]. They include the TE01 extractor, the TE11 to TE01 converter, and the TE11 to TE12 converter for TE12 mode. HFSS calculation of the system, which consists of TE01 extractor and TE11 to TE01 converter, shows that the transmission efficiency of each mode is better than 95%. A low power test model for the mode stability experiment in 55m long wave guide in DLDS is also being developed. Further study is underway.
7591156
Observation of Cabibbo suppressed B --> D(*)K- decays at Belle.
We report observations of the Cabibbo suppressed decays B-->D((*))K- using a 10.4 fb(-1) data sample accumulated at the Upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) storage ring. We find that the ratios of Cabibbo suppressed to Cabibbo favored branching fractions are B(B--->D0K-)/B(B--->D0pi(-)) = 0.079+/-0.009+/-0.006, B(B(0)-->D+K-)/B(B(0)-->D+pi(-)) = 0.068+/-0.015+/-0.007, B(B--->D(*0)K-)/B(B--->D(*0)pi(-)) = 0.078+/-0.019+/-0.009, and B(B(0)-->D(*+)K-)/B(B(0)-->D(*+)pi(-)) = 0.074+/-0.015+/-0.006. These are the first observations of the B-->D+K-, D(*0)K-, and D(*+)K- decay processes.
18821053
Comparisons Of Equivalent Circuit Predictions With Measurements For Short Stacks Of RDDS1 Discs, And Their Potential Application To Improved Wakefield Prediction
In fabricating the first X-Band RDDS (Rounded Damped Detuned Structure) accelerator structure, microwave measurements are made on short groups of discs prior to bonding the discs of the entire structure. The design dispersion curves are compared with the frequency measurements. The theory utilized is based on a circuit model adapted to a short stack of slowly varying non-uniform discs. The model reveals the nature of the modes in the structure and may also be used to refit the experimental data to the parameters in a model of the wakefield given earlier [1]. This method allows a more faithful determination of the wakefield that a beam will experience as it traverses the structure. Results obtained on the frequencies are compared to the original design.