The long-term evolution of solar filaments, prominently observed in Hɑ, is closely related to the large-scale solar cycle, with their parameters tracing the solar surface magnetic fields and have been long thought to contribute to the polar fields of the next cycle. The Kodaikanal Solar Observatory (KoSO) hosts one of the longest reserves of archival data with the information of these features...
Solar activity is readily observed through the emergence of magnetic structures of varying sizes on the solar surface. While larger magnetic regions have been extensively studied and are well understood, Ephemeral Regions (ERs) represent small-scale, short-lived magnetic features that frequently emerge on the photosphere throughout all phases of the solar cycle. The magnetic flux of ERs ranges...
The growth of a large-scale magnetic field in the Sun and stars is usually possible when the dynamo number $(D)$ is above a critical value $D_c$. As the star ages, its rotation rate and thus $D$ decrease. Hence, the question is how far the solar dynamo is from the critical dynamo transition. To answer this question, we have performed a set of simulations using Babcock–Leighton type dynamo...
The Kodaikanal Solar Observatory (KoSO), one of the oldest solar observatories, possesses hand-drawn suncharts that depict various solar features such as plages, filaments, sunspots, and prominences, each marked with distinct colors. These suncharts are valuable for addressing the data gap in the Ca II K dataset of KoSO from 1980 to 2007, which resulted from plate damage and changes in...
The solar corona is a dynamic environment that contains various magnetic structures, such as coronal loops, coronal holes, polar plumes, etc. These structures are perturbed by energetic activities such as solar flares, coronal mass ejections, and magnetohydrodynamic waves, leading to oscillations that serve as indirect tools for investigating the properties of the coronal atmosphere. In this...
The Bipolar Magnetic Regions (BMRs) are intense magnetic regions on the Sun's surface, separated by a neutral line. These regions are thought to emerge in the form of magnetic bundles (flux tubes) due to magnetic buoyancy, rising through the convection zone (CZ) in an east-west orientation with a tilt relative to the equator. It has been observed that statistically, BMRs emerging at higher...
Active regions are one of the primary sources of solar eruptive events like flares and coronal mass ejections, causing adverse space weather conditions. Complex magnetic field distributions of observed active regions are often quantified using diverse tools and techniques, which are later used for measuring the chance of their eruptivity. Similar tools are also utilised to validate magnetic...
Theory suggests that an ion-neutral velocity drift may exist in the solar atmosphere if the collisional momentum exchange between both species is not large enough. This work aims to offer a fresh perspective on this issue by investigating the drift velocity within the Evershed flow. In a previous analysis (Khomenko et al. 2015), the authors derived the Evershed velocities associated to Fe I...
The solar activity is directly related to its variable magnetic field, which is generated in the Sun's convection zone. Solar activity increases and decreases with the solar cycle strength, popularly measured by the sunspot number (SSN). This activity creates space weather and impacts the interplanetary and Earth's atmosphere. The sunspot number (solar cycle) prediction provides a cutting-edge...
The correlation tracking and wave-front sensing cameras in an adaptive optics system correct the wavefront error by locking to a feature in the image acquired by the sensor. The feature is cross-correlated with a reference image to identify the relative shift between consecutive images in the sub-aperture images of a Shack-Hartmann wave-front sensor. The typical frequency of data acquisition...
Sunspots, dark features on the Sun’s surface, consist of a central, darker umbra and a surrounding, less dark, filamentary region called the penumbra. Their penumbra to umbra area size ratio is crucial for understanding sunspot radiation and its contribution to total solar irradiance. This study explores this penumbra-to-umbra area ratio (q) for sunspots across solar cycles 21 to 24...
We studied the sun’s chromosphere through Ca-K and H-alpha full-disk spectroheliograms from Kodaikanal archival data. Our study looks at the long-term correlation analysis of features such as plages, filaments, and active regions across these two chromospheric lines. By developing robust methodologies for feature extraction, we have tried to understand the long-term behavior of the...
In the coronal open-field regions, numerous transverse waves propagate along coronal plumes, typically interpreted as kink or Alfvénic waves. Previous studies have emphasized their potential role in coronal heating, solar wind acceleration, and seismological diagnostics of various physical parameters. However, these propagating kink waves have rarely been investigated with both vertical and...
We analyzed the inverse Evershed flow (IEF) around a sunspot (NOAA 13131) using line scan observations in the Fe I 6173 A and Ca II 8542 A lines. The line scan observations were acquired using a narrow band imager of the Multi-Aplication Solar Telescope (MAST), Udaipur, and were complimented with the data products of HMI onboard SDO. The line-of-sight velocities for different layers of the...
The toroidal to poloidal part of the solar dynamo mechanism involves some nonlinearity and stochasticity, which disturb the dynamo loop. Hence, the memory of the polar field decreases in every cycle. On the other hand, the dynamo
efficiency and, thus, the supercriticality of the dynamo decreases with the Sun's age. Previous studies indicate that the memory of the polar field decreases as the...
Various configurations of the magnetic field in the solar atmosphere effectively link plasma processes between the photosphere, chromosphere, and solar corona. In a majority of cases, these magnetic configurations are twisted. Therefore, studying excitation and propagation of magnetohydrodynamic waves in the magnetic flux tubes when twist is present is a key to understanding energy transport...
Kodaikanal solar observatory white light image data is used to explore the possible variation of sun's radius with respect to latitude. For the year 1904, very good calibrated digitized and limb darkening removed image is used. After unambiguously detected solar edge, circle is fitted, mean radius and central coordinates are estimated. By knowing these important parameters, heliographic...
Spicules have often been proposed as substantial contributors toward the mass and energy balance of the solar corona. While their transition region (TR) counterpart has unequivocally been established over the past decade or so, the observations concerning the coronal contribution of spicules have often been contested. This is mainly attributed to the lack of adequate coordinated observations,...
Helioseismic inferences show that sun's rotational gradient increases and is positive from base of convection zone to 0.935 radius of the sun. Whereas near surface (from 0.935 to 1.0 sun's radius) rotational gradient is decreasing and is negative.
First question arises why present day sun adopted two regions of positive and negative rotational gradients. Hence, any theoretical work should not...
The solar dynamo, believed to operate near the base of the convection
zone (BCZ), generates the magnetic fields responsible for solar activity and
solar cycles. Magnetic structures (flux tubes) formed near BCZ rise through
the convection zone, potentially fragmenting/branching into smaller
structures. These structures emerge as sunspots or active regions/sunspot groups
on the Sun's...
Pi2 pulsations are impulsive oscillations associated with magnetospheric substorm onsets. In this study, we investigate a geomagnetic Pi2 pulsation using the electric field data from the Van Allen Probe satellites (NASA’ mission) in the magnetosphere, and on the ground. The Pi2 oscillations in the compressional components are investigated. We noticed a high degree of similarity between the Pi2...
Magnetic flux tubes in the presence of background rotational flows are abundant throughout the solar atmosphere and may act as conduits for MHD waves to transport magnetic energy throughout the solar atmosphere. We investigate the Poynting flux associated with these waves within the presence of background rotational plasma flows. The MHD wave solutions of the equilibrium configuration are...
Coronal fan loops rooted in sunspot umbra constantly show 3-min period propagating slow magnetoacoustic waves (SMAWs) in the corona. However, the origin of these waves in the lower atmosphere is still unclear. Here, we present study of these waves along a clean fan loop system using the multi-wavelength imaging and spectroscopic observations from IRIS and SDO. We traced the origin of these...
The Solar Ultraviolet Imaging Telescope (SUIT) onboard Aditya-L1 performs spatially resolved full-disk imaging of the Sun across the 200–400 nm wavelength range with eleven bandpasses. SUIT provides a comprehensive view of different layers of the solar atmosphere, enabling the study of dynamic solar phenomena such as flares and jets, magnetic structures like plages, active regions, and network...
Segmentation of Full-Disk H-alpha Images to Understand the Lower Solar Chromospheric Variability
B. Prabhu Ramkumar (1), R. Kariyappa (2), H.N. Adithya (3), B. Ravindra (2), Y. Hanaoka (4) and K. Nishida (4)
(1) Kodaikanal Solar Observatory, Indian Institute of Astrophysics, Kodaikanal, India
(2) Indian Institute of Astrophysics, Bangalore, India
(3) Manipal Centre for Natural Science,...
Solar differential rotation plays an important role in the generation of Sun’s magnetic fields and its activities. For the present work, the digitized data of four chromospheric features viz plage area, enhanced network (EN), active network (AN), and quiet network (QN) obtained from Kodaikanal Observatory for the period 1907-1996 are used to investigate the differential rotation at different...
The coronal magnetic field (B) is predominant in forming structures such as streamers, holes, etc., and in determining their spatio-temporal evolution. Its routine estimation will most likely provide clues/answers to several unsolved problems in solar physics and, therefore, gain significance among solar physicists. Extrapolating the Photospheric magnetic field strength using the Potential...
The tilts of bipolar magnetic regions are believed to be caused by the action
of Coriolis force on rising magnetic flux tubes. Here we analysed the combined
Greenwich and Debrecen observatories sunspot-group data during the period
1874-2017 and the tilt angles of sunspot groups measured at Mt. Wilson
Observatory during the period 1917-1986 and Debrecen Observatory
during the period...
Solar EUV, UV & X-ray Irradiance Variability and Their Impacts on
Earth’s Climate and Space Weather
R. Kariyappa (1, 3), H.N. Adithya (2), S. Masuda (3), K. Kusano (3),
S. Imada (4), J. Zender (5), L. Dame (6), E. Deluca (7), M. Weber (7) & T. Matsumoto (3)
(1) Indian Institute of Astrophysics, Bangalore 560034, India
(2) Manipal Centre for Natural Sciences, Manipal University,...
Abstract
Space weather forecasts are of utmost importance in safeguarding navigation, communication, and electric power system operations, satellites from orbital drag, and the astronauts in the International Space Station from hazardous space radiation during extreme space weather conditions. The finest space weather prediction requires a clear understanding of solar wind-magnetosphere...
We perform high resolution spectroscopy of chromospheric fibrils near a plage network observed with the DKIST ViSP spectropolarimeter. The physical properties of the fibrils are inferred with the novel inversion approach of machine learning and k-means clustering. We infer the temperature and density structure of the fibrils with optical depth and analyze their variation along the fibrils....
We analyse chromospheric observations of NOAA AR 12765, which were
acquired using a narrow-band imaging spectrometer installed with the 50-cm
MAST at the Udaipur Solar Observatory. The active region included a large
plage region in the vicinity of a sunspot, and we employed the NICOLE
inversion code to determine 2D maps of temperature and velocity as a
function of height. Photospheric...
The "Equal-Contrast technique" (ECT) methodology is developed to generate uniform long time series of Ca-K images obtained during the 20th century from the Kodaikanal Observatory (KO), India for studying the long- and short-term variations in the solar chromosphere. We investigate temporal and periodic variations of the fractional Ca-K plage area time series of the full solar disk for cycle 14...
Heliospheric exploration has soared to unprecedented heights in recent decades thanks to innovative spaceborne missions, ground-based observatories, and advancements in computing, models, and theory. However, the progress of inner-heliospheric research is hindered by observing limitations, preventing resolving long-standing problems such as understanding the solar dynamo, solar cycle, solar...
Spicules are thin, elongated jet-like features ubiquitously seen shooting upwards in observations of the solar atmosphere, appearing to protrude into the corona before (mostly) falling back to the solar surface. These features exhibit highly complex dynamics during their short lifetimes of 5-10 minutes and seem to be a necessary connecting link between the cooler, denser solar chromosphere and...
Extending the record of solar activity is very important to improving our understanding of the origins and evolution of solar magnetism. To this end, we attempt to generate solar magnetograms using the valuable century-long Ca II K image database from the Kodaikanal Solar Observatory (KSO). We set up an image-to-image translation model using conditional Generative Adversarial Network (cGAN) to...
The Perseverance Rover has been on the Martian surface since February 2021. The rover has Mastcam-Z navigation stereo cameras (Kinch et al., 2020) that can capture direct images of the Sun’s surface. During periods of Mars’s orbit, the rover has a unique view-point of the Sun’s far-side (not visible from Earth at any given time). Solar scientists can use the rover’s conveniently positioned...
