Author name code: sivaraman
ADS astronomy entries on 2022-09-14
author:"Sivaraman, K."
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Title: Evidence for the return meridional flow in the convection
zone from latitude motions of sunspots
Authors: Sivaraman, K. R.; Sivaraman, H.; Gupta, S. S.; Howard, R. F.
Bibcode: 2011IAUS..273..434S
Altcode:
We have derived the latitude motions of sunspots classified into three
area categories using the measures of positions and areas of their
umbrae from the white - light images of the Sun for the period 1906 -
1987 from the Kodaikanal Observatory archives. The latitude motions
are directed equator - ward in all the three area classes. We interpret
that these equator - ward latitude motions reflect the meridional flows
at the three depths in the convection zone where the magnetic flux
loops of the spots of the three area classes are anchored. We obtain
estimates of the anchor depths through a comparison of the rotation
rates of the spots in each area class with the rotation rate profiles
from helioseismic inversions. The equator - ward flows measured by us
thus provide evidence of the return meridional flows in the convection
zone as required in the flux transport solar dynamo models. We have
done an identical analysis using a similar data set derived from the
photoheliogram collections of the Mt.Wilson Observatory for the period
1917 - 1985. There is good agreement between the results from the data
sets of the two observatories.
Title: Return Meridional Flow in the Convection Zone from Latitudinal
Motions of Umbrae of Sunspot Groups
Authors: Sivaraman, K. R.; Sivaraman, H.; Gupta, S. S.; Howard, R. F.
Bibcode: 2010SoPh..266..247S
Altcode: 2010SoPh..tmp..157S
We have derived the velocities of meridional flows by measuring the
latitudinal motions (or drifts) of umbrae of spot groups classified
into three categories of area: 0 - 5 μ, 5 - 10 μ, and >10 μ
(μ area in millionths of the solar hemisphere). The latitudinal
drifts (or the meridional flows) in all three categories are directed
equatorward in both the northern and southern hemispheres. By sorting
the spot groups into three area classes, we are able to relate the
respective latitudinal drifts with the three depths in the convection
zone where the footpoints of the flux loops of the spot groups of each
area class are anchored. We obtain estimates of the anchor depths
through a comparison of the rotation rates of the spot groups of
each area class with the rotation-rate profiles from helioseismic
inversions. The equatorward drifts obtained provide estimates of
the meridional flows at the three depths in the convection zone and
thereby suggest the presence of return meridional flows as envisaged
in the flux-transport dynamo models, which have remained undetected so
far. The data sources for this study are measurements of positions and
areas of umbrae of sunspots from the photographic white-light images
of the Sun of the Kodaikanal Observatory archives for the period 1906 -
1987 and a very similar, but independent, data set from the Mt. Wilson
Observatory archives for the period 1917 - 1985.
Title: Evidence for Return Meridional Flows in the Convection Zone
Authors: Sivaraman, K. R.; Sivaraman, H.; Gupta, S. S.; Howard, R. F.
Bibcode: 2010ASSP...19..357S
Altcode: 2010mcia.conf..357S
We report velocities of meridional motions derived from the latitude
drifts of spot groups measured on photographic images of the Sun
in the Kodaikanal observatory archives. They serve to measure
different meridional flows for spot groups anchored at different
depths. Comparison of spot-group rotation rates with the rotation
profile resulting from helioseismic inversions yields estimates of
the anchoring depths. The measured latitudinal drifts correspond
to meridional flows at these depths. They show evidence of return
meridional flows as required in a flux-transport dynamo.
Title: Are Polar Faculae Generated by a Local Dynamo?
Authors: Sivaraman, K. R.; Antia, H. M.; Chitre, S. M.
Bibcode: 2010ASSP...19..386S
Altcode: 2010mcia.conf..386S
Polar faculae (PF) are bright, small-scale structures measuring a few
seconds of arc, populating the polar zones at latitudes >50°. They
possess magnetic fields ranging from 150 to 1,700 Gauss and largely
constitute the polar magnetic fields. Where and how their fields
are generated in the solar interior remain open questions. Using
measurements of PF rotation rates, we show that their anchor depths
probably lie in subsurface layers at radius r/R ⊙ =
0:94-1.00. If so, the PF fields are possibly generated by a local dynamo
in a subsurface shear layer extending to r/R ⊙ > 0:94.
Title: Zonal Velocity Bands and the Solar Activity Cycle
Authors: Sivaraman, K. R.; Antia, H. M.; Chitre, S. M.; Makarova, V. V.
Bibcode: 2008SoPh..251..149S
Altcode: 2008arXiv0802.0907S; 2008SoPh..tmp...72S
We compare the zonal-flow pattern in subsurface layers of the Sun
with the distribution of surface magnetic features such as sunspots
and polar faculae. We demonstrate that, in the activity belt, the
butterfly pattern of sunspots coincides with the fast stream of zonal
flows, although part of the sunspot distribution does spill over to
the slow stream. At high latitudes, the polar faculae and zonal-flow
bands have similar distributions in the spatial and temporal domains.
Title: Measurement of Kodaikanal White-Light Images: Relaxation of
Tilts of Spot Groups as Indicator of Subsurface Dynamics of Parent
Flux Loops
Authors: Sivaraman, K. R.; Gokhale, M. H.; Sivaraman, Hari; Gupta,
S. S.; Howard, Robert F.
Bibcode: 2007ApJ...657..592S
Altcode:
We reexamine the evolution of the observed tilts θ of spot groups
with life spans 2-7 days in the two latitude belts <13° and
>13°. Using an iterative procedure, we refine the linear fit
between θ and the daily tilt angle changes δθ and obtain reliable
estimates of the fit coefficients. We interpret our results in light
of the scenario implied by the theoretical model of Longcope &
Choudhuri for the subsurface dynamics of parent flux loops of bipolar
magnetic regions and arrive at the following conclusions: (1) the
parent flux tubes of spot groups possess a nonzero tilt at the onset
of rise from the depths of their origin; these ``inborn tilts'' are
~4°-11° in latitudes <13° and ~3°-15° in latitudes >13° (2)
during the rise the tilt of the omega loops of spot groups living 2-7
days get reduced to ~2°-6° in both the latitude belts, and this calls
for reexamination of the role of Coriolis force as understood so far;
(3) after emergence of the top of the loop above the surface, magnetic
tension in the legs tends to restore the tilt to the inborn tilt on
timescales of ~5 to 14 days; and (4) these timescales correspond to
field strengths in the range ~14-40 kG for the parent flux loops and
are close to the limits set by Fan et al.
Title: Measurement of Solar Diameter
Authors: Sivaraman, K. R.; Gupta, S. S.; Ananth, A. V.
Bibcode: 2006ihy..workE..25S
Altcode:
We have used the photographic images of the Kodaikanal observatory
archives to measure the solar diameter. These images obtained with
a 6-inch refractor form part of an ongoing programme of synoptic
observations that commenced in 1914. The reduced diameter measures
(annual means) completed for 4 half solar cycles show that the solar
radius is anti correlated with the sunspot activity.
Title: Variability of CaII K Emission Flux Over the Solar Cycle
Authors: Kariyappa, R.; Sivaraman, K. R.
Bibcode: 2005BASI...33..365K
Altcode:
No abstract at ADS
Title: Anchor depths of flux elements and depths of flux sources in
relation to the two rotation profiles of the sun's surface magnetic
fields
Authors: Sivaraman, K. R.; Gokhale, M. H.
Bibcode: 2004SoPh..221..209S
Altcode:
It is known for over two decades now that the rotation of the
photospheric magnetic fields determined by two different methods of
correlation analysis leads to two vastly differing rotation laws -
one the differential and the other rigid rotation. Snodgrass and
Smith (2001) reexamining this puzzle show that the averaging of
the correlation amplitudes can tilt the final profile in favour of
rigid rotation whenever the contribution of the rigidly rotating
large-scale magnetic structures (the plumes) to the correlation
dominates over that of the differentially rotating small-scale and
mesoscale features. We present arguments to show that the large-scale
unipolar structures in latitudes >40 deg, which also show rigid
rotation (Stenflo, 1989), are formed mainly from the intranetwork
magnetic elements (abbreviated as IN elements). We then estimate the
anchor depths of the various surface magnetic elements as locations
of the Sun's internal plasma layers that rotate at the same rate as
the flux elements, using the rotation rates of the internal plasma
layers given by helioseismology. We infer that the anchor depths
of the flux broken off from the decay of sunspot active regions
(the small-scale and mesoscale features that constitute the plumes)
are located in the shallow layers close to the solar surface. From a
similar comparison with helioseismic rotation rates we infer that the
rigid rotation of the large-scale unipolar regions in high latitudes
could only be coming from plasma layers at a radial distance of about
0.66-0.68 R⊙ from the Sun's centre. Using Stenflo's (1991)
`balloon man' analogy, we interpret these layers as the source of the
magnetic flux of the IN elements. If so, the IN flux elements seem to
constitute a fundamental component of solar magnetism.
Title: Measurement of Kodaikanal white-light images - VI. Variation
of Rotation Rate with Age of Sunspot Groups
Authors: Sivaraman, K. R.; Sivaraman, Hari; Gupta, S. S.; Howard,
Robert F.
Bibcode: 2003SoPh..214...65S
Altcode:
We find from an analysis of the Kodaikanal sunspot group data that the
rotation rates of spot groups increase with their age when the rotation
rates are computed after sorting the spot groups life-span-wise. We
confirm these findings from an analysis of the Mt. Wilson sunspot data
set too. We show that this trend is in good agreement with the internal
rotation profiles from helioseismology (GONG) observations and is also
consistent with the concept that the footpoints of the magnetic loops
of spot groups are initially anchored in the deeper layers in the solar
interior and rise to shallower layers as the spots age, and that the
spots reflect the rotation rates at the respective depths at which their
footpoints are temporally located. We project the `first-day rotation
rates' and the `daily rotation rates' of spot groups on the rotation
profiles from the GONG observations and derive the initial anchoring
depths of the footpoints of the magnetic loops of the spot groups and
their rates of rise as the spot groups age. Our results of the rotation
rates are in antithesis to the results reported by investigators from
the Greenwich spot group data that show a deceleration in rotation
rates as the spot groups age which are also inconsistent with the
rotation profiles from helioseismology observations.
Title: Duration of Polar Activity Cycles and Their Relation to
Sunspot Activity
Authors: Makarov, V. I.; Tlatov, A. G.; Sivaraman, K. R.
Bibcode: 2003SoPh..214...41M
Altcode:
We have defined the duration of polar magnetic activity as the time
interval between two successive polar reversals. The epochs of the
polarity reversals of the magnetic field at the poles of the Sun
have been determined (1) by the time of the final disappearance
of the polar crown filaments and (2) by the time between the two
neighbouring reversals of the magnetic dipole configuration (l=1)
from the Hα synoptic charts covering the period 1870-2001. It is
shown that the reversals for the magnetic dipole configuration (l=1)
occur on an average 3.3±0.5 years after the sunspot minimum according
to the Hα synoptic charts (Table I) and the Stanford magnetograms
(Table III). If we set the time of the final disappearance of the polar
crown filaments (determined from the latitude migration of filaments)
as the criterion for deciding the epoch of the polarity reversal of the
polar fields, then the reversal occurs on an average 5.8±0.6 years
from sunspot minimum (last column of Table I). We consider this as
the most reliable diagnostic for fixing the epoch of reversals, as the
final disappearance of the polar crown filaments can be observed without
ambiguity. We show that shorter the duration of the polar activity cycle
(i.e., the shorter the duration between two neighbouring reversals),
the more intense is the next sunspot cycle. We also notice that the
duration of polar activity is always more in even solar cycles than
in odd cycles whereas the maximum Wolf numbers W\max is
always higher for odd solar cycles than for even cycles. Furthermore,
we assume there is a secular change in the duration of the polar
cycle. It has decreased by ∼ 1.2 times during the last 120 years.
Title: When does the polar activity cycle start?
Authors: Makarov, V. I.; Tlatov, A. G.; Sivaraman, K. R.
Bibcode: 2003AN....324..382M
Altcode:
No abstract at ADS
Title: Does the Poleward Migration Rate of the Magnetic Fields Depend
on the Strength of the Solar Cycle?
Authors: Makarov, V. I.; Tlatov, A. G.; Sivaraman, K. R.
Bibcode: 2001SoPh..202...11M
Altcode:
We present the pattern of the polar magnetic reversal for cycle 23
derived from Hα synoptic charts and have also included the reversals
of the earlier cycles 18-22 for comparison. At the beginning of a
new cycle (i.e., soon after the polar reversal) the zonal boundaries
of unipolar magnetic regions of opposite polarities (seen as filament
bands on the synoptic charts) appear close to and on either side of the
equator continuing through the years of minimum indicating the onset
of the cancellation of flux at these low latitudes. The cycle thus
starts with cancellation of flux close to the equator and ends with the
polar reversal or flux cancellation near the poles. The filament bands
just below the polemost ones migrate and reach latitudes 35°-45° by
the time of polar reversal and become the polemost, once the polar
reversal has taken place. During the years of minimum that follow,
these filament bands remain more or less stagnant at the latitudes
35°-45° except for occasional slow migration towards the equator. The
migration to the poles starts at a low speed of 3 m s−1
only when the spot activity has risen to a significant level and then it
accelerates to 30 m s−1 at the peak of the activity. It
takes 3-4 years for the polemost bands to reach the poles moving
at these high speeds. We quantify this possible cause and effect
phenomenon by introducing the concept of the `strength of the solar
cycle' and represent this by either of a set of three parameters. We
show that the velocity of poleward migration is a linear function of
the `strength of the solar cycle'.
Title: Poleward migration rate of the magnetic fields and the power
of the solar cycle
Authors: Makarov, V. I.; Tlatov, A. G.; Callebaut, D. K.; Sivaraman,
K. R.
Bibcode: 2001ESASP.464..115M
Altcode: 2001soho...10..115M
We show that the velocity of poleward migration of the magnetic fields
is a linear function of the "strength of the solar cycle". We introduce
a new index "the strength of the solar cycle" and represent this
quantitatively by the two parameters: Σminrev
Ssp - summation of all the annual means of sunspot areas
Ssp of the cycle for the N and S hemispheres separately
starting from the lowest value of the annual mean in Ssp in
the minimum phase all the way to the year of the polarity reversal and
Σminrev W - summation of the Wolf numbers as done
for Σminrev Ssp but over the entire
visible hemisphere. Each of these parameters according to us represents
the "strength of the solar cycle" although they are not independent
of each other. We also discuss some questions regarding the role of
the meridional circulation in transporting the fields towards the poles.
Title: Results from a revisit to the K2V bright points
Authors: Sivaraman, K. R.; Gupta, S. S.; Livingston, W. C.; Damé,
L.; Kalkofen, W.; Keller, C. U.; Smartt, R.; Hasan, S. S.
Bibcode: 2000A&A...363..279S
Altcode:
We have used pairs of temporally simultaneous CaII K-line
spectroheliograms and magnetic area scans to search for spatial
correlation between the CaII K2V bright points in the
interior of the network and corresponding magnetic elements. We find
that about 60% of the K2V bright points spatially coincide
with magnetic elements of flux density > 4 Mx cm-2. About
25% of the K2V bright points with equally enhanced emission
lie over bipole elements where the fields are > 4 Mx cm-2
for both polarity elements which merge and presumably cancel and
result in low fields. The rest, 15%, of the bright points coincide
with areas of fields < 4 Mx cm-2 which is the noise
level set by us for the magnetic scans. When magnetic elements of
opposite polarity merge and form bipoles, the associated K2V
bright points show excess emission. Although such excess emission is a
magnetic-field-driven phenomenon, the measured value of the field at the
site of the bipole is typically low, and these cases would therefore be
excluded in the count of coincidences of excess emission with excess
magnetic fields. In our opinion, these cases of excess emission at
the sites of the bipoles, as well as at the sites of fields >
4 Mx cm-2, are both instances of magnetic-field-related
emissions. If the former are not taken into account as coincidences,
the correlation will drop down and this might be interpreted as not an
obvious correlation. Our present results, taking into account the low
fields of merging bipoles, establish the association of K2V
bright points with magnetic elements.
Title: MEASUREMENT OF KODAIKANAL WHITE-LIGHT IMAGES - V. Tilt-Angle
and Size Variations of Sunspot Groups
Authors: Howard, Robert F.; Sivaraman, K. R.; Gupta, S. S.
Bibcode: 2000SoPh..196..333H
Altcode:
We examine here the variations of tilt angle and polarity separation
(as defined in this paper) of multi-spot sunspot groups from the
Kodaikanal and Mount Wilson data sets covering many decades. We confirm
the tilt-angle change vs tilt-angle result found earlier from the Mount
Wilson data alone. Sunspot groups tend on average to rotate their axes
toward the average tilt angle. We point out that if we separate groups
into those with tilt angles greater than and less than the average
value, they show tilt-angle variations that vary systematically with
the growth or decay rates of the groups. This result emphasizes again
the finding that growing (presumably younger) sunspot groups rotate
their magnetic axes more rapidly than do decaying (presumably older)
groups. The tilt-angle variation as a function of tilt angle differs for
those groups whose leading spots have greater area than their following
spots and vice versa. Tilt-angle changes and polarity separation changes
show a clear relationship, which has the correct direction and magnitude
predicted by the Coriolis force, and this strongly suggests that the
Coriolis force is largely responsible for the axial tilts observed in
sunspot groups. The distribution of polarity separations shows a double
peak. These peaks are perhaps related to super- and meso-granulation
dimensions. Groups with polarity separations less than 43 Mm expand
on average, while those groups with separations more than this value
contract on average. We present evidence that the rotation of the
magnetic axes of sunspot groups is about a location closer to the
following than to the leading sunspots.
Title: Results from Kodaikanal Synoptic Observations
Authors: Sivaraman, K. R.
Bibcode: 2000JApA...21..149S
Altcode:
No abstract at ADS
Title: Polar Activity and Magnetic Field Reversal in Current Solar
Cycle 23
Authors: Makarov, V. I.; Makarova, V. V.; Tlatov, A. G.; Callebaut,
D. K.; Sivaraman, K. R.
Bibcode: 2000ESASP.463..367M
Altcode: 2000sctc.proc..367M
No abstract at ADS
Title: Measurement of Kodaikanal white-light images - IV. Axial Tilt
Angles of Sunspot Groups
Authors: Sivaraman, K. R.; Gupta, S. S.; Howard, Robert F.
Bibcode: 1999SoPh..189...69S
Altcode:
The Kodaikanal sunspot data set, covering the interval 1906-1987, is
used in conjunction with the similar Mount Wilson sunspot data set,
covering the interval 1917-1985, to examine characteristics of sunspot
group axial tilt angles. Good agreement is demonstrated between various
results derived from the two independent data sets. In particular, the
tendency for sunspot groups near the average tilt angle to be larger
than those far from the average tilt angle is confirmed. Similarly the
faster residual rotation rate for groups near the average tilt angle
is also confirmed. Other confirmations are made for the relationships
between latitude drift of sunspot groups and tilt angle, polarity
separations, and axial expansion. Evidence is presented that tilt
angles averaged over these long time intervals differ between the
north and south hemispheres by about 1.4 deg. It is suggested that
residual tilt angles show a slight systematic variation with phase in
the activity cycle.
Title: Measurement of Kodaikanal White-Light Images - III. Rotation
Rates and Activity Cycle Variations
Authors: Gupta, S. S.; Sivaraman, K. R.; Howard, Robert F.
Bibcode: 1999SoPh..188..225G
Altcode:
The Kodaikanal sunspot data set covering the interval 1906-1987 is
analyzed for differential rotation of sunspots of different sizes. As
is known, smaller sunspots rotate faster than larger sunspots, and
this result is verified in the analysis of this data set. These results
agree well with the Mount Wilson sunspot results published earlier. The
activity cycle dependence of sunspot rotation is studied. An increase
in this rate at the minimum phase is seen, which has been reported
earlier. It is demonstrated that this cycle variation is seen for
sunspots in all size categories, which suggests that it is not a
relative increase in the number of the faster-rotating small sunspots
that causes the cycle dependence. These results are discussed as they
may relate to subsurface dynamic properties of the Sun.
Title: Measurement of Kodaikanal White-Light Images - II. Rotation
Comparison and Merging with Mount Wilson Data
Authors: Howard, Robert F.; Gupta, S. S.; Sivaraman, K. R.
Bibcode: 1999SoPh..186...25H
Altcode:
Sunspot umbral positions and areas were measured for 82 years
(1906-1987) of daily, full-disk photoheliogram observations at the
Kodaikanal station of the Indian Institute of Astrophysics. The
measurement technique and reduction procedures used were nearly
identical to those used earlier for the reduction of Mount Wilson
daily full-disk photoheliograms, covering an overlapping interval of
69 years. In this paper we compare the differential rotation of the
Sun from the analysis of the Kodaikanal data with the Mount Wilson
results. In addition, we analyze the data set formed by combining the
data from the two sites for differential rotation. While doing this,
it has become apparent to us that small, subtle optical effects at
both sites produce systematic errors that have an influence on rotation
(and other) results from these data. These optical effects are analyzed
here, and corrections are made to the positional data of the sunspots
from both sites. A data set containing the combined positional data
of sunspots from both sites, corrected for these optical aberrations,
has been constructed. Results for both sunspot groups and individual
sunspots are presented. It is pointed out that optical aberrations
similar to those found in the Kodaikanal data may also exist in the
Greenwich photoheliograph data, because these two sets of solar images
were made with similar telescopes.
Title: An Overview of the Results From Synoptic Observations at
Kodaikanal
Authors: Sivaraman, K. R.
Bibcode: 1998ASPC..140..205S
Altcode: 1998ssp..conf..205S
No abstract at ADS
Title: Measurement of solar rotation from Kodaikanal images
Authors: Gupta, S. S.; Sivaraman, K. R.; Howard, R.
Bibcode: 1996BASI...24..189G
Altcode:
No abstract at ADS
Title: CA II K Line Profile of the Truly Quiet Sun
Authors: Sivaraman, K. R.; Gupta, S. S.; Kariyappa, R.
Bibcode: 1996SoPh..163...93S
Altcode:
While evaluating the chromospheric variability (solar cycle related or
any other) using the Ca II K line (λ3933.684 Å) as an indicator, an
essential prerequisite is the knowledge of the profile of a truly quiet
Sun in the integrated light. Such a profile can serve as a bench mark
over which enhancements can be measured, particularly when modelling
variability. This paper describes how such a K-line profile has been
derived for the quiet Sun using disc-integrated light.
Title: Direct Observational Evidence for the Heating of the Solar
Chromosphere
Authors: Kariyappa, R.; Sivaraman, K. R.; Anandaram, M. N.
Bibcode: 1995JApAS..16..383K
Altcode:
No abstract at ADS
Title: Solar granulation: an overview of observations
Authors: Sivaraman, K. R.
Bibcode: 1995BASI...23..331S
Altcode:
No abstract at ADS
Title: Variability of the Solar Chromospheric Network Over the
Solar Cycle
Authors: Kariyappa, R.; Sivaraman, K. R.
Bibcode: 1994SoPh..152..139K
Altcode: 1994svs..coll..139K; 1994IAUCo.143..139K
From a large sample of the Kodaikanal spectroheliograms in the Call
K line we have studied the variations in the intensity of the network
elements over two solar cycles and have estimated their contribution to
the overall variability seen in the disc-averaged K line profiles. The
relative contribution of the network elements and the bright points to
the K-emission are of the order of 25% and 15% respectively. We have
shown that the area of the network elements is anti-correlated with
the solar activity, and it increases by about 24% during the solar
minimum compared to the maximum period.
Title: Heating of the Quiet Solar Chromosphere - Part One
Authors: Kariyappa, R.; Sivaraman, K. R.; Anadaram, M. N.
Bibcode: 1994SoPh..151..243K
Altcode:
We have analyzed a large number of CaII H line profiles at the sites of
the bright points in the interior of the network using a 35-min-long
time sequence of spectra obtained at the Vacuum Tower Telescope
(VTT) of the Sacramento Peak Observatory on a quiet regon of the
solar disc and studied the dynamical processes associated with these
structures. Our analysis shows that the profiles can be grouped into
three classes in terms of their evolutionary behaviour. It is surmized
that the differences in their behaviour are directly linked with the
inner network photospheric magnetic points to which they have been
observed to bear a spatial correspondence. The light curves of these
bright points give the impression that the `main pulse', which is
the upward propagating disturbance carrying energy, throws the medium
within the bright point into a resonant mode of oscillation that is
seen as the follower pulses. The main pulse as well as the follower
pulses have identical periods of intensity oscillations, with a mean
value around 190 ± 20 s. We show that the energy transported by these
main pulses at the sites of the bright points over the entire visible
solar surface can account for a substantial fraction of the radiative
loss from the quiet chromosphere, according to current models.
Title: What is a quiet sun CaII K line profile?
Authors: Sivaraman, K. R.; Gupta, S. S.; Kariyappa, R.
Bibcode: 1993BASI...21..659S
Altcode:
We have derived a mean disc averaged K line profile from observations
at the Kodaikanal Solar Tower Telescope on days when sun was relatively
very quiet during the years 1985-86. This mean profile would represent
the K-line profile of a truly quiet sun.
Title: Solar variability in the Ca II K line during solar cycles 21
and 22.
Authors: Sivaraman, K. R.; Gupta, S. S.; Kariyappa, R.; Aleem,
P. S. M.; Sundararaman, K.
Bibcode: 1993BASI...21..655S
Altcode:
The authors have monitored the Sun in the light of the Ca II K line and
obtained the disc integrated profiles for the year 1974 - 91. From these
profiles they have estimated the variability of the Sun as a star as
seen in the various K line parameters. The 1 Å index shows an increase
of about 35% in 1990 from its minimum value attained in 1986 - 87.
Title: Measurement of Kodiakanal White-Light Images - Part One
Authors: Sivaraman, K. R.; Gupta, S. S.; Howard, Robert F.
Bibcode: 1993SoPh..146...27S
Altcode:
A program of digitization of the daily white-light solar images from
the Kodaikanal station of the Indian Institute of Astrophysics is in
progress. A similar set of white-light data from the Mount Wilson
Observatory was digitized some years ago. In both cases, areas
and positions of individual sunspot umbrae are measured. In this
preliminary report, comparisons of these measurements from the two
sites are made. It is shown that both area and position measurements
are in quite good agreement. The agreement is sufficiently good that
it is possible to measure motions and area changes of sunspots from
one site to the next, involving time differences from about 12 hours to
about 36 hours. This enables us to trace the motions of many more small
sunspots than could be done from one site alone. Very small systematic
differences in rotation rate between the two sites of about 0.4% are
found. A portion of this discrepancy is apparently due to the difference
in plate scales between the two sites. Another contributing factor in
the difference is the latitude visibility of sunspots. In addition it is
suggested that a small, systematic difference in the measured radii at
the two sites may contribute a small amount to this discrepancy, but it
has not been possible to confirm this hypothesis. It is concluded that
in general, when dealing with high precision rotation results of this
sort, one must be extremely careful about subtle systematic effects.
Title: A double-pass spectrograph for solar research.
Authors: Kariyappa, R.; Jayarajan, A. P.; Raheem, K. C. A.; Sivaraman,
K. R.
Bibcode: 1993BASI...21..139K
Altcode:
The authors describe the double-pass spectrograph built at the Indian
Institute of Astrophysics. Measurements of the scattered light within
the spectrograph using the photoelectric scans of the Na I D-lines
show that this is a good near-scatter-free system. The instrument is
used to monitor the disk integrated Ca II K line profile of the sun
on a regular basis.
Title: Magnetic Shear in Flaring Regions - Part One
Authors: Sivaraman, K. R.; Rausaria, R. R.; Aleem, S. M.
Bibcode: 1992SoPh..138..353S
Altcode:
We have evaluated the shear angle of the neutral line of the
non-potential magnetic field for one or two days prior to and after
the flare event for 10 cases. We have used the Hα filament positions
to evaluate the shear in the neutral line. We find from the samples
we have studied that it is the change in the shear that occurs a day
prior to the flare that can lead to the event. This change can be in
either direction, i.e., it can be a large increase from a small value
or a decrease from a large initial value. Thus it is the change in the
shear angle that seems to be a deciding criterion for a flare to occur
and not a large value for the shear angle itself. We have one instance
where there was no significant change in the shear angle over a period
of a few days and this region, although similar to other active regions
studied, did not produce any flare activity.
Title: Variations of prominence heights in high latitude global
magnetic neutral lines.
Authors: Makarov, V. I.; Tavastsherna, K. S.; Davydova, E. I.;
Sivaraman, K. R.
Bibcode: 1992BSolD...3...90M
Altcode:
An analysis of the heights of prominences referring to the high latitude
global magnetic neutral line has been made. The analysis shows that
the mean height of the high-latitude ring of prominences decreases
by 12 per year (900 km/year) as they approach the pole with a single
reversal of the magnetic field. In the case of a 3-fold reversal the
mean heights of polar prominences do not practically change. It is
shown that the variations of height allow to judge on the inhomogeneity
in longitudinal distribution of magnetic fields. A dependence of the
variation of prominence height on the latitude of the polar filament
ring has been obtained.
Title: Green Coronal Emission and the Global Solar Cycle
Authors: Sivaraman, K. R.; Makarov, V. I.
Bibcode: 1992ASPC...27..415S
Altcode: 1992socy.work..415S
No abstract at ADS
Title: Observational evidence for mesogranular cells in the solar
photosphere.
Authors: Bagare, S. P.; Sivaraman, K. R.
Bibcode: 1991BASI...19..207B
Altcode:
No abstract at ADS
Title: Role of small scale dynamical processes in the heating of
the solar chromosphere.
Authors: Sivaraman, K. R.; Kariyappa, R.; Gupta, S. S.
Bibcode: 1991BASI...19..207S
Altcode:
No abstract at ADS
Title: Behaviour of even and odd l-modes of the solar magnetic
field with the phase of the global solar cycle on the basis of Hα
charts. Interval: 1915 - 1985.
Authors: Makarov, V. I.; Tavastsherna, K. S.; Gokhale, M. H.;
Sivaraman, K. R.
Bibcode: 1991BSolD...6...95M
Altcode:
The properties of the latitude-time distribution of the area of
predominant polarity of a large-scale magnetic field on the Sun have
been studied in 10° latitude zones on Hα charts for 1915 - 1985. The
power spectrum of the rotating symmetric harmonic, l-mode, when m =
0 has been calculated for the entire period in question and separated
for the epoch of maxima and minima of the cycle. It is shown that
alongside with the dipole component l = 1, the mode l = 3 (octapole)
is dominant at some intervals of the minimum activity. The mode l =
5 is dominant at the maximum of activity. The intensity of even modes
is 3 - 5 times smaller than that of odd modes. Two dominant periods
are detected: 22 year and 7 year; they have the maximum intensity of
the power spectrum at l = 3 and l = 5, respectively. The dependence
of the phase φ(l)/2π on l-mode is determined. The phase displacement
between the activity of the large-scale magnetic field at the latitude
larger 40° and the zone of sunspot activity is derived.
Title: Nova Herculis 1991
Authors: Iijima, T.; Gehrz, R. D.; Jones, T. J.; Lawrence, G.;
Sivaraman, K. R.; Prabhu, T. P.; Ghosh, K. K.; Anupama, G. C.;
Selvakumar, G.
Bibcode: 1991IAUC.5236....1I
Altcode:
T. Iijima, Osservatorio Astrofisico, Asiago, reports: "Optical
spectra of Nova Her 1991 were obtained on Mar. 31.2 and Apr. 1.1
UT with the Mt. Ekar 1.82-m telescope and CCD spectrograph (range
386- 715 nm, resolution 0.2 nm) at the Astronomical Observatory
of Padua. In addition to the features reported on IAUC 5223 and
5227, broad emissions are visible at 424.2 (N II), 465.0 (C III),
468.6 (He II), 505.6 (Si II), and probably at 580.2 and 581.2 nm
(C IV). The emissions of H I and He I show castellated profiles with
at least five peaks, while those of C III and He II show shapes that
are smoother." R. D. Gehrz, T. J. Jones and G. Lawrence, University of
Minnesota, provide further infrared magnitudes, obtained on Apr. 10.4 UT
with the bolometer on the 0.76-m telescope at the O'Brien Observatory,
using a 25" beam: J = 7.5, H = 5.8, K = 4.1, L = 2.8, M = 2.1, N =
1.0. They note that these measurements appear to conform to a 1200-K
blackbody, and that measurements in several silicate filters show no
evidence for silicate emission. They add that the Mar. 29 observations
(IAUC 5232) indicate that the nova was then in a free- free emission
phase. K. R. Sivaraman, Indian Institute of Astrophysics, Bangalore,
telexes: "Nova Her 1991 was observed by T. P. Prabhu, K. K. Ghosh,
G. C. Anupama, and G. Selvakumar using CCD spectrographs (range 425-
680 nm, resolution 0.2 nm) at the 1.02- and 2.34-m reflectors of Vainu
Bappu Observatory, Kavalur, on Apr. 2, 3, and 4. Identified emission
lines are H-alpha, H-beta, H-gamma, He I (447.1, 587.6, 667.8 nm), Na I
D, N II (566.7, 568.0 nm), Si II (634.7, 637.1 nm), and N II (464.0 nm),
with contributions from He II 468.6-nm and Fe II multiplet 42. All lines
are broad and show structure. The H- alpha line has FWZI = 5980 km/s,
FWHI = 4510 km/s. P-Cyg absorption features are exhibited by H-alpha
(-3280, -4010 km/s), H-beta and H- gamma (-3130 km/s), and Si II and
He I (-3090 km/s). All line profiles are similar. Prominent peaks in
H-alpha are at -1910, -940, -210, +730, and +1560 km/s; additional
peaks are present at -1740, -1510, -1220, -780, and +1880 km/s. The
blue peaks brightened significantly with respect to the red peaks
between Apr. 2 and 4. All the peaks narrowed down with time, revealing
fainter structure in between. Strong interstellar lines due to Na I
(589.0, 589.6 nm) are seen with equivalent widths 15.0 and 9.0 nm,
respectively."
Title: Supernova 1991T in NGC 4527
Authors: Sivaraman, K. R.; Prabhu, T. P.; Anupama, G. C.; Schmeer,
P.; Smith, H.; Royer, R.; Lubcke, G.; Villi, M.; Cortini, G.
Bibcode: 1991IAUC.5255....1S
Altcode:
K. R. Sivaraman, Indian Institute of Astrophysics, Bangalore, telexes:
"SN 1991T was observed by T. P. Prabhu and G. C. Anupama on Apr. 24,
25, and 27 using the 2.3-m telescope of Vainu Bappu Observatory,
Kavalur. The wavelength range 450-700 nm was covered at 0.5 nm per
pixel. Interstellar Na I D gives a velocity of 1700 km/s for the
parent galaxy, and the wavelengths mentioned below are corrected for
this velocity. The 500-nm dip was at 495.8 nm on Apr. 24 and began
to show structure due to Fe II (42). The Si II absorption feature
was at 614.7 nm. Weaker dips were visible at 450.4, 455.4, 466.0,
473.2, 485.4, 514.6, 530.8, and 545.7 nm. All features strengthened
with time. Identifying these with Fe II 462.9- and 473.1-nm; S II
481.5-nm; Fe II 492.4-, 501.8-, and 531.6-nm; S II 545.4- and 564.0-nm;
and stronger dips with Fe II 516.9-nm and Si II 635.5-nm, we derive
a mean expansion velocity of 10 000 +/- 1400 km/s (10 lines) and a
median of 9700 +/- 100 km/s (5 lines)." Visual magnitude estimates
(cf. IAUC 5251): Apr. 24.87 UT, 11.5 (P. Schmeer, Bischmisheim,
Germany); 25.14, 11.5 (H. Smith, Michigan State University; V + CCD);
26.17, 11.0 (R. Royer, Lakewood, CA); 27.21, 11.3 (Royer); 28.10, 11.3
(G. Lubcke, Middleton, WI); 29.25, 11.3 (Royer); 29.9, 11.7 (M. Villi
and G. Cortini, Monte Colombo, Italy).
Title: Sky conditions for infrared observations at Kavalur
Authors: Scaria, K. K.; Nair, R. M.; Sivaraman, K. R.
Bibcode: 1991BASI...19...65S
Altcode:
The extinction coefficients in the J, H, K near-IR bands are presented
that were derived for Kavalur during the years 1987, 1988, and
1989. Humidity and temperature observations made at Kavalur during
these years are used to ascertain the most suitable months for IR
observations. Mean values of the extinction coefficients in the J, H
and K bands are 0.20, 0.13, and 0.19, respectively. Absolute humidity
at Kavalur is lowest during the months of November, December, January,
February, and March.
Title: The Largescale Magnetic Field in the Global Solar Cycle -
Observational Aspects
Authors: Makarov, V. I.; Sivaraman, K. R.
Bibcode: 1991LNP...380..213M
Altcode: 1991IAUCo.130..213M; 1991sacs.coll..213M
The global solar cycle is considered as an interaction of 3 types of
activity: at low-latitude (sunspots), at high-latitude (polar faculae)
and the weak magnetic field. The properties of single and 3-fold
reversals of the polar magnetic field are considered. The variation
spectrum of the large-scale magnetic field of the Sun is analyzed in
the range of 1-30 nHz. A dependence between the rate of a poleward
meridional flow and phase of the global cycle is discussed.
Title: The Bright Points in the Ca II K-Line and Their Relation to
the Inner Network Magnetic Structures (With 1 Figure)
Authors: Sivaraman, K. R.
Bibcode: 1991mcch.conf...44S
Altcode:
No abstract at ADS
Title: Solar site testing: techniques and evaluation methods.
Authors: Sivaraman, K. R.
Bibcode: 1991nlt..work..132S
Altcode:
The parameters required to be measured in site survey work for selecting
an excellent site for establishing major solar telescope facilities are
described. The techniques to be adopted for these measurements as well
as the criteria for evaluation of the site from the survey data to judge
the worthiness of the site for astronomical work are also discussed.
Title: Global Evolution of Photospheric Magnetic Fields
Authors: Makarov, V. I.; Sivaraman, K. R.
Bibcode: 1990IAUS..138..281M
Altcode:
No abstract at ADS
Title: On the Location of Footpoints of Sub-Arc Magnetic Structures
in the Quiet Solar Photosphere
Authors: Sivaraman, K. R.; Bagare, S. P.; November, L. J.
Bibcode: 1990IAUS..142..192S
Altcode:
No abstract at ADS
Title: Largescale Flow Patterns in the Solar Atmosphere
Authors: Sivaraman, K. R.
Bibcode: 1990IAUS..142..101S
Altcode:
One of the results of a study on the migration of H-alpha filaments,
namely, the existence of meridional flow on the sun, is presented and
extended to show the participation of this meridional flow in the solar
cycle variation. The filament bands start their poleward migration with
small speeds ranging from 5 to 20 m/s synchronously with the rising
phase of the solar cycle. It is inferred from migration diagrams that
during the years of the solar minimum, the filament bands do not show
signs of a continuous migration toward the poles.
Title: Sunspot Motions from a Study of Kodaikanal and Mount Wilson
Observations
Authors: Howard, Robert F.; Sivaraman, K. R.; Gupta, S. S.; Gilman,
Pamela I.
Bibcode: 1990IAUS..142..107H
Altcode:
Results are presented of a study of the daily motions of individual
sunspots and of sunspot groups on the basis of Kodaikanal and Mount
Wilson white-light observations. A comparison of the two data sets show
a good agreement between them in spot areas and motions. Preliminary
rotation and latitude drift reduction from the combined data set
confirm earlier results from the Mount Wilson data alone.
Title: Narrow band photometry of Comet Halley in the emission bands
and the continuum
Authors: Babu, G. S. D.; Nathan, J. S.; Rajamohan, R.; Sivaraman, K. R.
Bibcode: 1989BASI...17..107B
Altcode:
IHW filter photometry of Comet Halley was carried out on seven nights
during pre-perihelion period and on six nights during post-perihelion
period, using the 40-cm telescope at the Vainu Bappu Observatory,
Kavalur, as a part of the Indian Halley Observation Program. The
pre-perihelion observations show large amplitude fluctuations in
the emission fluxes, superimposed on the general trend of their slow
increase with the decreasing R(h). The respective abundances of the
CN, C3, CO(+), C2 and H2O(+) molecules contained in a cylinder of
diameter 86 arcsec in the line of sight through the comet have also
been estimated. Their individual emission strengths are very low due
perhaps to the comet's several approaches to the sun.
Title: New Results Concerning the Global Solar-Cycle
Authors: Makarov, V. I.; Sivaraman, K. R.
Bibcode: 1989SoPh..123..367M
Altcode:
We derive the poleward migration trajectory diagram of the filament
bands for the years 1915-1982 from the H-alpha synoptic charts. We find
that the global solar activity commences soon after the polar field
reversal in the form of two components in each hemisphere. The first
component we identify with the polar faculae that appear at latitudes
40-70° and migrate polewards. The second and the more powerful
component representing the sunspots shows up at ∼40° latitudes
5-6 years later and drifts equatorward giving rise to the butterfly
diagram. Thus the global solar activity is described by the faculae and
the sunspots that occur at different latitude belts and displaced in
time by 5-6 years. This gives rise to the prolonged duration for the
global solar activity lasting for 16-18 years as against the 11 years
which has come about based only on the spots. The two components match
with the pattern of the coronal emission in 5303 Å line. Finally, we
show that the two components of activity also match with the pattern
of excess shear associated with the torsional oscillations on the Sun
and this provides a link between the torsional oscillations and the
magnetic activity.
Title: Evolution of latitude zonal structure of the large-scale
magnetic field in solar cycles
Authors: Makarov, V. I.; Sivaraman, K. R.
Bibcode: 1989SoPh..119...35M
Altcode:
Properties of a latitude zonal component of the large-scale
solar magnetic field are analyzed on the basis of Hα charts for
1905-1982. Poleward migration of prominences is used to determine
the time of reversal of the polar magnetic field for 1870-1905. It is
shown that in each hemisphere the polar, middle latitude and equatorial
zones of the predominant polarity of large-scale magnetic field can be
detected by calculating the average latitude of prominence samples
referred to one boundary of the large-scale magnetic field. The
cases of a single and three-fold polar magnetic field reversal are
investigated. It is shown that prominence samples referred to one
boundary of the large-scale magnetic field do not have any regular
equatorward drift. They manifest a poleward migration with a variable
velocity up to 30 m s-1 depending on the phase of the
cycle. The direction of migration is the same for both low-latitude
and high-latitude zones. Two different time intervals of poleward
migration are found. One lasts from the beginning of the cycle to
the time of polar magnetic field reversal and the other lasts from
the time of reversal to the time of minimum activity. The velocity of
poleward migration of prominences during the first period is from 5 m
s-1 to 30 m s-1 and the second period is devoid
of regular latitude drift.
Title: Do polar faculae on the sun predict a sunspot cycle?
Authors: Makarov, V. I.; Makarova, V. V.; Sivaraman, K. R.
Bibcode: 1989SoPh..119...45M
Altcode:
The paper reports the results of the analysis of the data on polar
faculae for three solar cycles (1960-1986) at the Kislovodsk Station of
the Pulkovo Observatory and on polar bright points in Ca II K line for
two solar cycles (1940-1957) at the Kodaikanal Station of the Indian
Institute of Astrophysics. We have noticed that the monthly numbers
of polar faculae and polar bright points in Ca II K line and monthly
sunspot areas in each hemisphere of the following solar cycle have a
correlation with each other. A new cycle of polar faculae and polar
bright points in the Ca II K line begins after the polar magnetic field
reversal. We find that the smaller the period between the ending of
the polar field reversal and the beginning of a new sunspot cycle is,
the more intense is the cycle itself. The intensity of the forthcoming
solar cycle (cycle 22) and the periods of strong fluctuations in
activity expected in this cycle are also discussed.
Title: SYSTEMATIC OBSERVATIONS OF THE SUN (In honour of Helen Dodson
Prince): Observations
Authors: McIntosh, P.; Snodgrass, H.; Mouradian, Z.; Harvey, K.;
Altrock, R.; Simon, P.; Legrand, J. -P.; Alissandrakis, G.; Neckel,
H.; Petropoulos, P.; Poulakis, X.; Gokhale, M. H.; Sivaraman, K. R.;
Pap, J.
Bibcode: 1989HiA.....8..672M
Altcode:
No abstract at ADS
Title: High Resolution Studies of [O I] and NH2 Line Emissions at
6300 A in Halley's Comet
Authors: Prasad, C. Debi; Chandrasekhar, T.; Desai, J. N.; Ashok,
N. M.; Sivaraman, K. R.; Rajmohan, R.
Bibcode: 1988PASP..100..702P
Altcode:
The forbidden O I line and NH2 (0-8-0) emissions of Comet Halley at
about 6300 A were observed during April 1986 using a Fabry-Perot
spectrometer with a resolution of about 0.14 A. The forbidden O
I line and NH2 rotational lines were spectrally well separated by
the interferometer and a NH2/O I ratio of about 0.5 was found. The
profile analysis shows the profiles of forbidden O I line and NH2 to
be symmetric with linewidths of about 3.5-3 km/s. The cometary Balmer
emission of hydrogen at 6563 A was barely detectable. An upper limit
for H(alpha) based on the instrumental sensitivity yields a value of
30 Rayleighs.
Title: Solar cycle variations of coronal neutral lines and polar
regions activity.
Authors: Makarov, V. I.; Makarova, V. V.; Koutchmy, S.; Sivaraman,
K. R.
Bibcode: 1988sscd.conf..362M
Altcode:
Observations of the corona, of prominences, of polar faculae and of
large scale magnetic fields show solar activity over all latitudes, in
contrast with sunspot activity, which is limited to mid-latitudes. The
global behaviour of the solar activity is considered here thanks to
the analysis of chromospheric synoptic maps which include the location
of Hα and Ca II K prominences. The process of "migration" of neutral
lines during the cycle (supposed to represent the large scale coronal
magnetic field) is shown.
Title: Spectrophotometry of Comet P/Halley. I - Flux, column density
and emission gradients within the coma in the emission bands and
the continuum
Authors: Sivaraman, K. R.; Babu, G. S. D.; Shylaja, B. S.; Rajamohan,
R.
Bibcode: 1987A&A...187..543S
Altcode:
The authors made spectral scans of comet P/Halley using the scanner
at the Cassegrain focus (f/13) of the 102 cm reflector at Kavalur. The
scans cover generally the wavelength region from 3900 to 6200 Å and are
at 40 Å resolution and on a few occasions in the blue region at 20 Å
resolution. The f/13 beam provided an image of the coma with a scale of
15arcsec.5 mm-1. The authors have obtained scans on several
consecutive nights in March and April, 1986 with a 25arcsec.9 entrance
aperture of the scanner at discrete and systematically displaced
locations within the coma in the anti-sunward direction as well as
normal to it about the position of the nucleus. They have derived the
brightness profiles of the neutrals and dust within the coma and have
discussed the variations of the spatial gradients of the profiles.
Title: Photopolarimetric Observations of Comet Halley
Authors: Sen, A. K.; Joshi, U. C.; Deshpande, M. R.; Kulshrestha,
A. K.; Sivaraman, K. R.
Bibcode: 1987BASI...15Q..23S
Altcode:
No abstract at ADS
Title: Infrared Photometer System for Astronomical Observation
Authors: Shivanandan, K.; Scaria, K. K.; Sivaraman, K. R.; Rajamohan,
R.; Nair, R. M.
Bibcode: 1987BASI...15...45S
Altcode:
No abstract at ADS
Title: Chromospheric CA II K-Line Variations in the Sun as a Star
over a Solar Cycle
Authors: Sivaraman, K. R.; Singh, Jagdev; Bagare, S. P.; Gupta, S. S.
Bibcode: 1987ApJ...313..456S
Altcode:
The disk-averaged Ca II K profiles obtained at the Kodaikanal solar
tower telescope for the period 1969-1984 are used to study the
chromospheric variations in the sun as a star. The 1A index shows
increases of 18 and 28 percent during the 20th and 21st cycles,
respectively. The corresponding enhancements in the central intensity
in the K line are 24 and 40 percent, respectively. The other K-line
parameters, such as the intensity of K2 emission, K-line widths,
and the V/R asymmetry, all show systematic variations over the solar
cycle. Although the plage seems to be responsible for almost all the
variations noticed, the participation of the bright points and the
network may have to be taken into consideration to account fully for
all the solar cycle-related changes.
Title: Magnetic neutral lines of the large-scale magnetic field and
solar activity.
Authors: Makarov, V. I.; Tavastsherna, K. S.; Sivaraman, K. R.
Bibcode: 1987SvA....30..317M
Altcode:
No abstract at ADS
Title: "Butterfly" diagram for polar faculae and sunspots during
1940 - 1985.
Authors: Makarov, V. I.; Makarova, V. V.; Sivaraman, K. R.
Bibcode: 1987BSolD1987R..62M
Altcode:
Data on the time-latitude distribution of polar faculae and sunspots
for 1940 - 1985 are given. They characterize two waves of the toroidal
component of the magnetic field of the global process of solar activity.
Title: Calibration on the Sun for Stellar Magnetic Fields
Authors: Sivaraman, K. R.; Bagare, S. P.; Gupta, S. S.; Kariyappa, R.
Bibcode: 1987LNP...291...47S
Altcode: 1987csss....5...47S; 1987LNP87.291...47S
The intimate association between the surface magnetic fields and the
Ca II K line emission known to exist on the sun, holds a promise for
using this property to detect the presence of global magnetic fields on
sun - like stars. We have obtained a large number of K line profiles
over a variety of plages on the sun and related the 1A emission flux
centred at the K3 minimum for these profiles with the corresponding
values of the longitudinal component of the photospheric magnetic
field. This provides a calibration for detecting and estimating the
surface magnetic fields on stars that show K emission.
Title: Spatial distribution of molecules and dust within the coma
of Comet Halley
Authors: Sivaraman, K. R.; Babu, G. S. D.; Shylaja, B. S.; Rajamohan,
R.
Bibcode: 1986ESASP.250a.479S
Altcode: 1986ehc1.conf..479S
Spectral scans of comet Halley were made at high spatial resolution
using the Cassegrain focus (f/13) of the 102 cm reflector at Kavalur
(India). The scans cover the wavelength region from 3900 to 6200 A and
at 40 A resolution and on a few occasions in the blue region at 20 A
resolution. The f/13 beam provided an image of the coma with a scale
of 15.5 arc sec/mm. Scans were obtained on several consecutive nights
in Mar. 1986 with a 25.9 arcsec entrance aperture of the scanner at
discrete and systematically displaced locations within the coma, in
the direction of the tail as well as normal to it about the position of
the nucleus. The spatial gradients of the distribution of the molecular
species and dust were derived from the brightness profiles.
Title: On the epochs of polarity reversals of the polar magnetic
field of the sun during 1870-1982
Authors: Makarov, V. I.; Sivaraman, K. R.
Bibcode: 1986BASI...14..163M
Altcode:
The H-alpha synoptic charts for the 1904-1982 period and data on the
polar prominences for the 1870-1905 period are used to investigate
the polarity reversal of the polar magnetic field on the sun for 11
solar cycles. Good agreement is found between polarity reversals
obtained from the drift trajectory of the neutral line and those
from magnetograph observations. A three-fold polarity reversal of the
sun's magnetic field was found in the 12th and 14th solar cycles in
the southern hemisphere, and in the 16th, 19th and 20th solar cycles
in the northern hemisphere. It is noted that the filament bands in
the two hemispheres do not reach the respective poles simultaneously.
Title: Magnetic Neutral Lines of the Largescale Magnetic Field and
Solar Activity
Authors: Makarov, V. I.; Tavastsherna, K. S.; Sivaraman, K. R.
Bibcode: 1986SvA....30..317M
Altcode:
No abstract at ADS
Title: Magnetic neutral lines of the large-scale magnetic field and
solar activity
Authors: Makarov, V. I.; Tavastsherna, K. S.; Sivaraman, K. R.
Bibcode: 1986AZh....63..534M
Altcode:
On the basis of Hα synoptic charts for the period 1955 - 1981 two
components in the distribution of the scales of structures of the
large-scale magnetic field are found. It is shown that the general
magnetic field of the sun has a latitudinal zonal structure which
is formed from the elements of the 1st and 2nd distributions. The
boundaries of latitude zones of the magnetic field either oscillate
near average latitudes or have only poleward migration. Three types of
quasi-periodic oscillations are noted, their periods being different
in the S and N hemispheres. The most probable period of oscillations
is found in the southern hemisphere and it equals to about 20 solar
rotations.
Title: On the latitudinal migration of polar faculae in their activity
cycle. II. Period: 1940 - 1968.
Authors: Makarov, V. I.; Sivaraman, K. R.
Bibcode: 1986BSolD1986...64M
Altcode:
Coordinates and the number of polar faculae are determined
at latitudinal higher 40° on K232-Ca+
spectroheliograms of the Kodaikanal Observatory for 2097 days for
the period 1940 - 1968. First polar faculae appear immediately after
the polarity reversal of the magnetic field as bright pairs of dots
against the chromospheric network. The polar faculae cycle is asymmetric
relative to the sunspot cycle, and the maximum of their number does not
always coincide with the sunspot minimum. The duration of the cycle of
polar faculae is equal to the interval between the neighbouring polarity
reversal of the magnetic field and lasts from 7 to 11 years. The zone
of the emergence of polar faculae migrates polewards with the mean
velocity 0.5 m/sec.
Title: Atlas of H-alpha synoptic charts for solar cycle 19 (1955 -
1964). Carrington solar rotations 1355 to 1486.
Authors: Makarov, V. I.; Sivaraman, K. R.
Bibcode: 1986KodOB...7.....M
Altcode:
No abstract at ADS
Title: K-Line Emission and the Integrated Surface Magnetic Field on
the Sun
Authors: Sivaraman, K. R.; Kariyappa, R.
Bibcode: 1986LNP...254..496S
Altcode: 1986csss....4..496S
We have made plots of the Ca II K line emission vs the global surface
magnetic field for the sun for the years 1975-1982 representing both
solar minimum as well as solar maximum epochs. These plots show that
the K-line emission is not related to the global magnetic fields. An
explanation for the absence of a correlation is offered. A direct
measurement of the global magnetic field of the sun or similar stars
will give an algebraic sum of the magnetic fields present on the
surface, whereas the K-line emission will be additive Irrespective of
the polarity of the fields. K-line emission being a sign insensitive
indicator of magnetic field, is advantageous and with a proper
calibration, the surface fields and the partition of fields according
to signs can be evaluated through a calibration. This possibility is
extended to sun-like stars where the presence of surface fields can
be established reliably.
Title: Observations of comet Crommelin.
Authors: Babu, G. S. D.; Shylaja; Sivaraman, K. R.
Bibcode: 1986IHWN....8...25B
Altcode:
No abstract at ADS
Title: On the Latitudinal Migration of Polar Faculae in Their Activity
Cycle - Part Two - 1940-1968
Authors: Makarov, V. I.; Sivaraman, K. R.
Bibcode: 1986BSolD...9...64M
Altcode:
No abstract at ADS
Title: Ca II K emission from the solar chromosphere.
Authors: Sivaraman, K. R.
Bibcode: 1986KodOB...6...11S
Altcode:
The role of the Ca II K line as a reliable diagnostic of the
chromospheric activity on the Sun is reviewed. The chromospheric
structures seen in this line serve as good indicators of the
photospheric magnetic structures and also mimic the morphological
changes in the surface magnetic features associated with the solar
cycle. Similar changes can be expected to take place in other sun-like
stars.
Title: Luminosity variations in the Ca II K lines and the solar cycle.
Authors: Sivaraman, K. R.; Singh, J.; Bagare, S. P.; Gupta, S. S.
Bibcode: 1985BASI...13Q..79S
Altcode:
No abstract at ADS
Title: Broad band photometry of the solar corona of 1983, June 11.
Authors: Sivaraman, K. R.; Singh, J.; Kapoor, R. C.; Kariyappa, R.
Bibcode: 1985KodOB...5...31S
Altcode:
The solar corona was photographed at an effective wavelength of
6300 Å during the total eclipse of 1983, June 11 at Indonesia. From
the isophotes of the corona, the intensity distributions along the
equator, poles, streamers and gaps have been derived. The brightness
distribution and the Ludendorff parameters of this corona are typical
of the intermediate phase of the solar cycle.
Title: Ca II K bright points and the solar cycle
Authors: Sivaraman, K. R.
Bibcode: 1984SoPh...94..235S
Altcode:
We have made number counts of the bright points that populate the
interior of the Ca II network in the solar chromosphere for four solar
cycles. We find that the number of these fine structures during the
solar maximum exceeds that during the minimum phase on an average
by 30%. The contribution due to this excess number would need to
be taken into account while explaining the variation in the Ca II K
emission profiles of the integrated sunlight from the solar minimum
to the maximum.
Title: Brightness, polarization and electron density of the solar
corona of 1980 February 16
Authors: Sivaraman, K. R.; Jayachandran, M.; Scaria, K. K.; Babu,
G. S. D.; Bagare, S. P.; Jayarajan, A. P.
Bibcode: 1984JApA....5..149S
Altcode:
During the eclipse of 1980 February 16 the authors photographed the
solar corona at an effective wavelength of 6300 Å. Using a quadruple
camera coronal pictures were obtained in polarized light for four
polaroid orientations. These observations are used to derive the coronal
brightness and polarization and from these the electron densities in
the corona out to a distance of about 2.5 R_sun; from the centre of
the disc. The coronal brightness matches well with that of the corona
of 1958 October 12.
Title: Fabry-Perot interferometric observations of the coronal red
and greenlines during the 1983 Indonesian eclipse.
Authors: Chandrasekhar, T.; Ashok, N. M.; Desai, J. N.; Pasachoff,
J. M.; Sivaraman, K. R.
Bibcode: 1984ApOpt..23..508C
Altcode:
A dual-channel Fabry-Perot interferometric system was used to study
simultaneously the coronal emission lines at 5303 Å (Fe XIV) and at
6374 Å (Fe X). Initial results indicate an emission corona confined
largely within 1.2 R_sun;. Doppler temperatures derived from the
width of the 5303-Å line appear to be appreciably lower than similar
temperatures determined during the solar-maximum eclipse of 1980.
Title: Observations of the Evershed Effect - Past and Present
Authors: Sivaraman, K. R.
Bibcode: 1984KodOB...4...11S
Altcode:
No abstract at ADS
Title: [Fe XIV] 5303 Å emission line profiles of the total solar
eclipseof 1983 June 11.
Authors: Singh, J.; Sivaraman, K. R.
Bibcode: 1984BASI...12R..78S
Altcode:
No abstract at ADS
Title: Magnetic field - plasma interaction on the Sun. Proceedings of
a colloquium held at Kodaikanal on January 23, 1984 in commemoration
of the 75th anniversary of the discovery of the Evershed effect.
Authors: Sivaraman, K. R.; Raju, P. K.; Bhattacharyya, J. C.;
Howard, R.
Bibcode: 1984mafi.book.....S
Altcode:
No abstract at ADS
Title: Fine structures in the interior of the chromospheric network
Authors: Sivaraman, K. R.
Bibcode: 1984stp..conf..459S
Altcode:
No abstract at ADS
Title: The EUV Structure of a Solar Active Region
Authors: Sivaraman, K. R.; Raju, P. K.
Bibcode: 1983ICRC....4..222S
Altcode: 1983ICRC...18d.222S
No abstract at ADS
Title: Solar Flare of April 14, 1982
Authors: Bagare, S. P.; Sivaraman, K. R.
Bibcode: 1983ICRC....4...20B
Altcode: 1983ICRC...18d..20B
No abstract at ADS
Title: Poleward Migration of the Magnetic Neutral Line and the
Reversal of the Polar Fields on the Sun - Part One - Period 1945-1981
Authors: Makarov, V. I.; Fatianov, M. P.; Sivaraman, K. R.
Bibcode: 1983SoPh...85..215M
Altcode:
Poleward migration of the magnetic neutral line on the Sun has been
calculated for the periods 1945-1950 and 1955-1981 using synoptic
charts based on Hα observations. Epochs of sign reversal of the solar
magnetic field at latitudes 50° to 90° have been determined for
these periods. During the cycles 19 and 20 a threefold sign reversal
took place in the northern hemisphere. During all the above cycles
both the solar poles were of one polarity for a period ranging from
0.5 to 1 year. The poleward drift velocity of the magnetic neutral
line varies from 6 to 29 m s−1 and seems to depend on
the strength of the cycle.
Title: Poleward Migration of the Magnetic Neutral Line and the
Reversal of the Polar Fields on the Sun - Part Two - Period 1904-1940
Authors: Makarov, V. I.; Sivaraman, K. R.
Bibcode: 1983SoPh...85..227M
Altcode:
Poleward migration of the magnetic neutral line on the Sun has been
computed for the period 1904-1940 using synoptic charts based on Hα
observations and the epochs of sign reversal of the solar magnetic
field at latitudes 50° to 90° have been determined for this
period. During the cycles 16 and 14, a threefold sign reversal took
place in the northern and southern hemispheres, respectively. During
all the cycles studied both the solar poles were of one polarity for
a period ranging from 0.6 to 1.6 years. The poleward drift velocity
of the neutral line varies from 4.2 to 8.2 m s−1. The
apparent relation between the velocity of the filament bands when
three bands are present with the bursts of solar activity is discussed.
Title: Morphology of H-alpha filaments and filament channel systems
Authors: Makarov, V. I.; Stoianova, M. N.; Sivaraman, K. R.
Bibcode: 1982JApA....3..379M
Altcode:
The results of a study of the morphology of the large-scale filament
structures of the sun and their relations with the distribution of
the large-scale magnetic field on the solar surface are reported. A
continuous filament which forms a closed circular contour has been
seen on spectroheliograms, particularly during the maximum phase of
the solar cycle. Their mean size seldom exceeds 10 degrees, while
their lifetimes occasionally span several days. In the core of the
H-alpha line, single filaments are seen connected with one another
by a regular structure of dark chromospheric elements several tens
of degrees in extent or at times by a conglomeration of absorption
grains one to three degrees in length. Occasionally, prominences can be
detected above filament channels. Some arches of the filament channel
may elongate with an associated local increase in coronal intensity.
Title: Ca ii K2V spectral features and their relation
to small-scale photospheric magnetic fields
Authors: Sivaraman, K. R.; Livingston, W. C.
Bibcode: 1982SoPh...80..227S
Altcode:
Although the Ca II K232 network is known to be cospatial with
magnetic elements there has been doubt as to the magnetic origin of
the fainter K2V points. We demonstrate that weak magnetic
elements also lie at the roots of the K2V points, and
because the latter are numerous they may contribute sensibly to the
integrated light profile of Ca II K.
Title: Phase Difference Between Two Components of the Solar Cycle
Authors: Gokhale, M. H.; Sivaraman, K. R.
Bibcode: 1982BASI...10..154G
Altcode:
No abstract at ADS
Title: Peculiarities in the ionic tail of Comet Ikeya-Seki (1965 f)
Authors: Krishan, V.; Sivaraman, K. R.
Bibcode: 1982M&P....26..209K
Altcode:
Direct photographs of Comet Ikeya-Seki obtained on four consecutive
days from October 29 to November 1, 1965, are used for an analysis of
the multiple helical structures in the ionised tail. The formation of
these structures is explained on the basis of plasma instabilities
excited in the tail containing twisted magnetic fields. The growth
rate of the modes excited at the mode rational surface agrees well
with the observed results. This model also accounts for the presence
of harmonic structures seen in the tail of the comet.
Title: K2V/K2R asymmetries in the sun and stars
Authors: Sivaraman, K. R.
Bibcode: 1982ApJ...254..814S
Altcode:
The K2V/K2R asymmetry in the self-reversed emission peaks of the Ca II
K line in the sun is the result of the redward displacement of K3. This
redward displacement is explained as caused by the dark condensations
in K3 and not due to the supergranulation flow pattern. Arguments are
presented to show that such asymmetries in the spectra of stars provide
evidence for the presence of these structures in their chromospheres.
Title: The two components in the distribution of sunspot groups with
respect to their maximum areas
Authors: Gokhale, M. H.; Sivaraman, K. R.
Bibcode: 1981JApA....2..365G
Altcode:
The frequency distribution of sunspot groups as a function of maximum
corrected group area is investigated in light of a phenomenological
model of the solar cycle driven by two distinct sets of magnetic flux
tube clusters. Analysis of the sunspot group distribution during the
last eight solar cycles (1889-1976) according to data contained in
the Greenwich Photoheliographic Results reveals the presence of a
two-component distribution, with the first component contributing to
spot groups of all possible areas and having a distribution density
varying as the exponential of the square root of the area, and a second
component contributing to spot groups of area less than 30 millionths
of a hemisphere and having a density distribution varying as the
exponential of the maximum area. Examination of the geometrical extents
of the two components also reveals differences in their latitudinal
distributions, supporting the existence of two families of flux tubes
as predicted by the model.
Title: The two component nature of the size-distribution of
sunspot-groups in a solar cycle.
Authors: Gokhale, M. H.; Sivaraman, K. R.
Bibcode: 1981BASI....9...86G
Altcode:
No abstract at ADS
Title: Polarisation of the solar corona of 1980 February 16.
Authors: Sivaraman, K. R.; Jayachandran, M.; Babu, G. S. D.
Bibcode: 1981BASI....9...70S
Altcode:
No abstract at ADS
Title: Emission band and continuum photometry of Comet West
/1975n/. II Emission profiles of the neutral coma, lifetimes of
molecules and distribution of the molecules and dust within the coma
Authors: Bappu, M. K. V.; Parthasarathy, M.; Sivaraman, K. R.; Babu,
G. S. D.
Bibcode: 1980MNRAS.192..641B
Altcode:
The scale lengths of the CN and C2 molecules and their parents are
derived based on Haser's model from drift scans across the coma of Comet
West in the light of CN (0,0), C2 (0,0) and the continuum
around 5000 Å. The analysis provides evidence to show that the CN
molecules are produced by the dissociation of two species of parent
molecules having entirely different lifetimes. A similar result is
also obtained for the C2 molecules. The step scans
of 1976 March 19.96, covering the spectral range 3700- 5300 Å and
at five independent locations inside the coma show that there is an
increase of reddening of the continuum, from the centre of the nucleus
outwards. These provide evidence that the coarser particles are to the
centre and the finer ones towards the periphery. A study of the radial
distribution of CN, C3 and C2 molecules and of
the dust particles shows that the C3 (4050 Å) intensities
fall most rapidly, compared to CN or C2.
Title: Preliminary Report of Solar Eclipse Observations
Authors: Sivaraman, K. R.
Bibcode: 1980BASI....8...93S
Altcode:
No abstract at ADS
Title: Emission band and continuum photometry of Comet West /1975n/. I
- Heliocentric dependence of the flux in the emission bands and
the continuum
Authors: Sivaraman, K. R.; Babu, G. S. D.; Bappu, M. K. V.;
Parthasarathy, M.
Bibcode: 1979MNRAS.189..897S
Altcode:
Spectrum scans of the coma of Comet West (1975n) covering the range
λλ3700--5700 Å were made on eight nights when the heliocentric
distance of the comet varied from 0.588 to 0.853 AU. These have been
used to derive the absolute flux in the CN(0,0), C3(4050),
C2(1, 0) and C2(0, 0) bands as well as in the
continuum. Enhancements in the band emissions were noticed on three
nights in CN(0,0), C3(4050) and C2(1, 0). The
column densities of neutral sodium atoms are derived from scans around
5900 Å on four nights. The column densities of CO+ ions
corresponding to four prominent band sequences are evaluated from two
scans of the tail.
Title: Possible amount of Magnetic Flux Reconnection Through Quiescent
Prominences Outside the Active Regions.
Authors: Gokhale, M. H.; Sivaraman, K. R.
Bibcode: 1979phsp.coll..189G
Altcode: 1979IAUCo..44..189G; 1979phsp.conf..189G
No abstract at ADS
Title: Emission band and continuum photometry of comet West (1975n).
Authors: Babu, G. S. D.; Bappu, M. K. V.; Parthasarathy, M.; Sivaraman,
K. R.
Bibcode: 1978BASI....6R..51B
Altcode:
No abstract at ADS
Title: K emission line widths in the Sun and the stars.
Authors: Bappu, M. K. V.; Sivaraman, K. R.
Bibcode: 1977MNRAS.178..279B
Altcode:
K-emission line widths measured with a micrometer on integrated spectra
of the sun have a mean value of 38.2 km/s. A definition is proposed
whereby the width is a measure in km/s at the inverse-e value of the
difference between the intensity of the brighter K2 peak over the
K1 background, reckoned from this latter level. Averaged spectra over
different parts of the solar disk show the very appreciable contribution
by rotation to the emission line width, making it imperative for any
calibration of width with absolute magnitude to use a solar value
derived from an integrated spectrum. Arguments are presented showing
that the K-emission profile observed in other stars is the profile
of the typical bright mottle that should enable the derivation of
chromospheric parameters. From measures of Doppler displacements of
both K2 and K3, 'dark condensations' as seen on the sun play a role
in the atmospheres of stars with K emission.
Title: Intensity Fluctuations in the Solar Chromosphere
Authors: Sivaraman, K. R.; Venkitachalam, P. P.
Bibcode: 1977KodOB...2...34S
Altcode:
No abstract at ADS
Title: Emission band photometry of comet West (1975n).
Authors: Parthasarathy, M.; Sivaraman, K. R.
Bibcode: 1976BASI....4...80P
Altcode:
No abstract at ADS
Title: Time evolution studies of the fine structure of the solar
chromosphere.
Authors: Sivaraman, K. R.; Venkitachalam, P. P.
Bibcode: 1975BASI....3R..27S
Altcode:
No abstract at ADS
Title: Centre-limb observations of the intensity fluctuations in
the Balmer lines in the solar atmosphere.
Authors: Sivaraman, K. R.; Venkitachalam, P. P.
Bibcode: 1975BASI....3Q..27S
Altcode:
No abstract at ADS
Title: An interpretation of the correlation of the intensity
fluctuations in the K-line of Ca II and b1 of Mg I.
Authors: Sivaraman, K. R.
Bibcode: 1974BASI....2...40S
Altcode:
No abstract at ADS
Title: An Interpretation of the Correlation in the Intensity
Fluctuations in H and K of Ca II and b1 of Mg I
Authors: Sivaraman, K. R.
Bibcode: 1974SoPh...36...49S
Altcode:
No abstract at ADS
Title: Sodium emission in comet Kohoutek (1973f).
Authors: Bappu, M. K. V.; Parthasarathy, M.; Sivaraman, K. R.
Bibcode: 1974BASI....2R..35B
Altcode:
No abstract at ADS
Title: Observational Study of the Five-Minute Oscillations in the
Solar Atmosphere - I. Oscillatory Velocity and Intensity Fields
Authors: Sivaraman, K. R.
Bibcode: 1973SoPh...33..319S
Altcode:
The 5-min oscillations in the photospheric velocity fields have been
studied in detail from measurements on 14 absorption lines from three
time sequences of spectrograms of high quality. The lines cover a range
of heights in the solar atmosphere from log τ = + 0.2 to -1.2. Regions
oscillating coherently are seen to have an average dimension of 8000
km and the oscillations in general last for 2 to 3 periods. The power
spectrum analysis of high resolution enabled to determine the period
of oscillation at each level very precisely. The period decreases with
increase in height, being 304 s at the level log τ = + 0.2 and 295 s
at the level log τ = -1.2. The low level lines possess considerable
power in the low frequency range representing the convective overshoot
from below. The oscillatory power increases with height, while the
low frequency power decreases and the high frequency component remains
substantially constant in the heights studied.
Title: Comet Kohoutek (1973f).
Authors: Bappu, M. K. V.; Parthasarathy, M.; Sivaraman, K. R.;
Matchett, V. L.; Mayo, M.; Truxton, J.; Sherrod, C.
Bibcode: 1973IAUC.2608....1B
Altcode:
No abstract at ADS
Title: Comets.
Authors: Sivaraman, K. R.
Bibcode: 1973BASI....1...35S
Altcode:
No abstract at ADS
Title: The Indian Institute of Astrophysics
Authors: Sivaraman, K. R.
Bibcode: 1973BASI....1....4S
Altcode:
No abstract at ADS
Title: Photometry of the solar corona of March 7, 1970.
Authors: Bappu, M. K. V.; Bhattacharyya, J. C.; Sivaraman, K. R.
Bibcode: 1973Prama...1..117B
Altcode:
No abstract at ADS
Title: On Emission Lines of Hydrogen, Helium and Ionized Calcium
Seen on a Coronal Spectrogram of the March 7, 1970 Eclipse
Authors: Bappu, M. K. V.; Bhattacharyya, J. C.; Sivaraman, K. R.
Bibcode: 1972SoPh...26..366B
Altcode:
Emission lines of the Balmer series, D3 and H and K are
reported present on a coronal spectrogram obtained at the March 7,
1970 eclipse. Arguments are presented to show that these could not
have originated from scattering in the Earth's atmosphere and hence
possibly have a coronal origin.
Title: K Emission-Line Widths and the Solar Chromosphere
Authors: Bappu, M. K. V.; Sivaraman, K. R.
Bibcode: 1971SoPh...17..316B
Altcode:
Closely spaced microphotometer tracings parallel to the dispersion of
one excellent frame of a K-line time sequence have been utilized for a
study of the nature of the K2v, K2R intensities
in the case of the solar chromosphere. The frequency of occurrence
of the categories of intensity ratio are as follows: per cent; per
cent; per cent; per cent; per cent. Two types of absorbing components
are postulated to explain the pattern of observed K2v,
k2R intensity ratios. One component with minor Doppler
displacements acting on the normal K232 profile, where
K2V >K2R, produces the cases K2v
≫ K2R, K2v = K2R, K2v
<K2R. The other component arises from `dark condensations'
which are of size 3500 kms as seen in K2R. They have
principally large down flowing velocities in the range 5-8 km/sec and
are seen on K3 spectroheliograms with sizes of about 5000
kms, within the coarse network of emission. These `dark condensations'
give rise to the situation K2R = 0.
Title: Some characteristics of the solar wind inferred from the
study of sodium emission from cometary nuclei
Authors: Bappu, M. K. V.; Sivaraman, K. R.
Bibcode: 1969SoPh...10..496B
Altcode:
Seventeen comets, having information on sodium D-line emission during
their apparition, have been studied. The heliocentric distances
corresponding to the sodium emission commencement or termination epoch
are found to have a dependence on the phase of the solar cycle. For
comets appearing during a solar maximum the sodium emission is
detectable out to greater distances than, for the comets appearing
during solar minimum. The sodium emission is also found to depend on
heliographic latitude of the comet. It is concluded that the spatial
properties of the solar wind during a solar maximum and minimum are
responsible for the observed dependence.
Title: On the Relation between Sunspot Area Changes and Flare
Occurrences
Authors: Sivaraman, K. R.
Bibcode: 1969SoPh....6..152S
Altcode:
No abstract at ADS
Title: Comet Ikeya-Seki (1965) and the nature of the interplanetary
medium during its apparition.
Authors: Bappu, M. K. V.; Sivaraman, K. R.
Bibcode: 1969KodOB.187.....B
Altcode:
No abstract at ADS
Title: A Doppler comparator for solar spectra.
Authors: Kubicela, A.; Sivaraman, K. R.
Bibcode: 1969KodOB.189.....K
Altcode:
No abstract at ADS
Title: Chromospheric Heights in Active Regions
Authors: Bappu, M. K. V.; Sivaraman, K. R.
Bibcode: 1968IAUS...35..247B
Altcode:
No abstract at ADS
Title: Monochromatic polarization measures of comet Ikeya-Seki (1965f)
Authors: Bappu, M. K. V.; Sivaraman, K. R.; Bhatnagar, A.; Natarajan,
V.
Bibcode: 1967MNRAS.136...19B
Altcode:
Monochromatic measures of polarization of Comet Ikeya-Seki (I 965f)
at 3 890 A, 4 300 A, 4 740 A and 5 875 A are described. The relative
contributions of emission and continuum to radiation transmitted by
the fflters at 3 890 A and 4740 A are evaluated. The polarization
at phase angle 900 of the CN (o,o) band is 6'9% while that of the C2
(1,0) band is %, in close agreement with the theoretical values for
resonance fluorescence. The polarization value of the continuum is
% at phase angle 900, while for the same phase angle, a measure of
the polarization in the tail, 3' away from the head, is 13' 6%. The
agencies responsible for the continuum in both head and tail are likely
to have a difference in the major constituent. The role of ices and
iron particles as scattering agencies is discussed. -
Title: Emission band photometry of comet Ikeya-Seki (1965f)
Authors: Bappu, M. K. V.; Sivaraman, K. R.
Bibcode: 1967MNRAS.137..151B
Altcode:
Photoelectric measures of emission band intensities of C2 (I, o) and
CN (o, o) of the coma of Comet Ikeya-Seki (1965f) are reported. The
measured fluxes are utilized to determine the number of molecules of
C2 and CN that contribute to the observed emission.
Title: Lunar Geomagnetic Tides at Kodaikanal
Authors: Raja Rao, K. S.; Sivaraman, K. S.
Bibcode: 1958JGR....63..727R
Altcode:
Following the mathematical development of Chapman and Miller, Tschu has
described a practical method of determining the lunar diurnal variation
of geophysical elements. By the application of Tschu's method, the lunar
semi-diurnal variation of the horizontal intensity of earth's magnetic
field at Kodaikanal in the geomagnetic equatorial region is worked
out for the winter solstice by making use of the hourly values of the
horizontal intensity for the period 1950 to 1954. The expression ΔH -
3.32 sin (2τ - 39° 04') γ is obtained for the lunar semi-diurnal
wave. A graph of ΔH against the age of the moon is drawn. From the
graph, it is seen that the amplitude of the lunar geomagnetic tide is
maximum when the sun and the moon are 135° apart. The solar diurnal
variation is also determined up to four harmonics.