1,509 research outputs found
Quaternion Analysis for Generalized Electromagnetic Fields of Dyons in Isotropic Medium
Quaternion analysis of time dependent Maxwell's equations in presence of
electric and magnetic charges has been developed and the solutions for the
classical problem of moving charges (electric and magnetic) are obtained in
unique, simple and consistent manner
Observations of Multiple Surges Associated with Magnetic Activities in AR10484 on 25 October 2003
We present a multiwavelength study of recurrent surges observed in H{\alpha},
UV (SOHO/EIT) and Radio (Learmonth, Australia) from the super-active region
NOAA 10484 on 25 October, 2003. Several bright structures visible in H{\alpha}
and UV corresponding to subflares are also observed at the base of each surge.
Type III bursts are triggered and RHESSI X-ray sources are evident with surge
activity. The major surge consists of the bunches of ejective paths forming a
fan-shape region with an angular size of (\approx 65\degree) during its maximum
phase. The ejection speed reaches upto \sim200 km/s. The SOHO/MDI magnetograms
reveal that a large dipole emerges east side of the active region on 18-20
October 2003, a few days before the surges. On October 25, 2003, the major
sunspots were surrounded by "moat regions" with moving magnetic features
(MMFs). Parasitic fragmented positive polarities were pushed by the ambient
dispersion motion of the MMFs and annihilated with negative polarities at the
borders of the moat region of the following spot to produce flares and surges.
A topology analysis of the global Sun using PFSS shows that the fan structures
visible in the EIT 171 A images follow magnetic field lines connecting the
present AR to a preceding AR in the South East. Radio observations of type III
bursts indicate that they are coincident with the surges, suggesting that
magnetic reconnection is the driver mechanism. The magnetic energy released by
reconnection is transformed into plasma heating and provides the kinetic energy
for the ejections. A lack of a radio signature in the high corona suggests that
the surges are confined to follow the closed field lines in the fans. We
conclude that these cool surges may have some local heating effects in the
closed loops, but probably play a minor role in global coronal heating and the
surge material does not escape to the solar wind.Comment: Accepted for the Publication in ApJ; 25 pages, 10 Figures, and 1
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Far-infrared observations of Circinus and NGC 4945 galaxies
Circinus and NGC 4945 are two galaxies luminous in the infrared and are characterized by compact non thermal radio nuclei, deep silicate absorption features and unusually strong water vapor maser luminosities. Moorwood and Glass (1984) have observed these galaxies extensively in the 1 to 20 micron range. In the far-infrared, observations up to 100 microns are available from the Infrared Astronomy Satellite (IRAS). In order to study the cool dust component of these galaxies, researchers observed them at 150 microns using the Tata Institute of Fundamental Research (TIFR) 100 cm balloon-borne telescope. Here, they report observations along with deconvolved maps at 50 and 100 microns obtained from the Chopped Photometric Channel (CPC) on board IRAS
Quaternion Octonion Reformulation of Quantum Chromodynamics
We have made an attempt to develop the quaternionic formulation of Yang -
Mill's field equations and octonion reformulation of quantum chromo dynamics
(QCD). Starting with the Lagrangian density, we have discussed the field
equations of SU(2) and SU(3) gauge fields for both cases of global and local
gauge symmetries. It has been shown that the three quaternion units explain the
structure of Yang- Mill's field while the seven octonion units provide the
consistent structure of SU(3)_{C} gauge symmetry of quantum chromo dynamics
Mass function and dynamical study of the open clusters Berkeley 24 and Czernik 27
We present a photometric study of the open clusters Berkeley 24 (Be
24) and Czernik 27 (Cz 27). The radii of the clusters are determined as
2\farcm7 and 2\farcm3 for Be 24 and Cz 27, respectively. We use the Gaia Data
Release 2 (GDR2) catalogue to estimate the mean proper motions for the
clusters. We found the mean proper motion of Be 24 as mas
yr and mas yr in right ascension and declination
for Be 24 and mas yr and mas yr for
Cz 27. We used probable cluster members selected from proper motion data for
the estimation of fundamental parameters. We infer reddenings =
mag and mag for the two clusters. Analysis of
extinction curves towards the two clusters show that both have normal
interstellar extinction laws in the optical as well as in the near-IR band.
From the ultraviolet excess measurement, we derive metallicities of [Fe/H]=
dex and dex for the clusters Be 24 and Cz 27,
respectively. The distances, as determined from main sequence fitting, are
kpc and kpc. The comparison of observed CMDs with
isochrones, leads to an age of Gyr and Gyr for
Be 24 and Cz 27, respectively.
In addition to this, we have also studied the mass function and dynamical
state of these two clusters for the first time using probable cluster members.
The mass function is derived after including the corrections for data
incompleteness and field star contamination. Our analysis shows that both
clusters are now dynamically relaxedComment: 16 pages including 8 tables. 22 figures. Accepted by MNRA
Generalized Gravi-Electromagnetism
A self consistant and manifestly covariant theory for the dynamics of four
charges (masses) (namely electric, magnetic, gravitational, Heavisidian) has
been developed in simple, compact and consistent manner. Starting with an
invariant Lagrangian density and its quaternionic representation, we have
obtained the consistent field equation for the dynamics of four charges. It has
been shown that the present reformulation reproduces the dynamics of individual
charges (masses) in the absence of other charge (masses) as well as the
generalized theory of dyons (gravito - dyons) in the absence gravito - dyons
(dyons). key words: dyons, gravito - dyons, quaternion PACS NO: 14.80H
A new species of Plectocarpon (Roccellaceae, lichenised ascomycetes) from India
A new gall-inducing and lirellate lichenicolous fungus, Plectocarpon diedertzianum Y. Joshi, Upadhyay et Chandra, is described from Kumaun Himalayan regions of India colonising thallus of various parmelioid lichens (Flavoparmelia caperata, Myelochroa aurulenta, Parmotrema crinitum, P. melanothrix, P. reticulatum, Punctelia subrudecta). The new species is characterised by black, epruinose rounded to lirellate ascomata with a carbonised surface and a ±thalline pseudomargin, as well as a carbonised, sterile stromatic tissue, 4-spored asci and 3-septate hyaline ascospores
Efficient absolute aspect determination of a balloon borne far infrared telescope using a solid state optical photometer
The observational and operational efficiency of the TIFR 1 meter balloon
borne far infrared telescope has been improved by incorporating a multielement
solid state optical photometer (SSOP) at the Cassegrain focus of the telescope.
The SSOP is based on a 1-D linear photo diode array (PDA). The online and
offline processing schemes of the PDA signals which have been developed, lead
to improvement in the determination of absolute telescope aspect (
0\farcm8), which is very crucial for carrying out the observations as well as
offline analysis. The SSOP and its performance during a recent balloon flight
are presented here.Comment: To appear in the February 2000 issue of the PAS
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