Author name code: bose ADS astronomy entries on 2022-09-14 =author:"Bose, Souvik" ------------------------------------------------------------------------ Title: ML pipeline for Solar Dynamics Observatory (SDO) data Authors: Salvatelli, Valentina; Neuberg, Brad; Dos Santos, Luiz F. G.; Bose, Souvik; Cheung, Mark C. M; Janvier, Miho; Jin, Meng; Gal, Yarin; Güneş Baydın, Atılım Bibcode: 2022zndo...6954828S Altcode: This software has been developed from the [FDL SDO Team](https://frontierdevelopmentlab.org/2019-sdo). The package contains: a configurable pipeline to train and test ML models on data from the Solar Dynamics Observatory some notebooks for data exploration and results analysis. It contains all the code supporting the publications: [Multi-Channel Auto-Calibration for the Atmospheric Imaging Assembly using Machine Learning](https://arxiv.org/abs/2012.14023) "Exploring the Limits of Synthetic Creation of Solar EUV Images via Image-to-Image Translation" Accepted for publication on ApJ (July 2022) Title: Exploring the Limits of Synthetic Creation of Solar EUV Images via Image-to-Image Translation Authors: Salvatelli, Valentina; dos Santos, Luiz F. G.; Bose, Souvik; Neuberg, Brad; Cheung, Mark C. M.; Janvier, Miho; Jin, Meng; Gal, Yarin; Gunes Baydin, Atilim Bibcode: 2022arXiv220809512S Altcode: The Solar Dynamics Observatory (SDO), a NASA multi-spectral decade-long mission that has been daily producing terabytes of observational data from the Sun, has been recently used as a use-case to demonstrate the potential of machine learning methodologies and to pave the way for future deep-space mission planning. In particular, the idea of using image-to-image translation to virtually produce extreme ultra-violet channels has been proposed in several recent studies, as a way to both enhance missions with less available channels and to alleviate the challenges due to the low downlink rate in deep space. This paper investigates the potential and the limitations of such a deep learning approach by focusing on the permutation of four channels and an encoder--decoder based architecture, with particular attention to how morphological traits and brightness of the solar surface affect the neural network predictions. In this work we want to answer the question: can synthetic images of the solar corona produced via image-to-image translation be used for scientific studies of the Sun? The analysis highlights that the neural network produces high-quality images over three orders of magnitude in count rate (pixel intensity) and can generally reproduce the covariance across channels within a 1% error. However the model performance drastically diminishes in correspondence of extremely high energetic events like flares, and we argue that the reason is related to the rareness of such events posing a challenge to model training. Title: A textbook example of magnetic flux emergence leading to EBs, UV bursts, surges and EUV signatures Authors: Cabello, Iballa; Moreno-Insertis, . Fernando, , Prof; Rouppe van der Voort, Luc; Bose, Souvik; Nóbrega Siverio, Daniel Bibcode: 2022cosp...44.2531C Altcode: Small-scale eruptive phenomena (like Ellerman bombs (EBs), UV bursts, surges) constitute both a true challenge and an opportunity for progress in understanding the solar atmosphere since they involve very different layers from the photosphere to the low corona. In our work, we are aiming to characterize small-scale eruptive phenomena related to emerging flux regions. In particular, we use coordinated observations from the Swedish $1-$m Solar Telescope (SST), the Interface Region Imaging Spectrograph (IRIS) and the Solar Dynamics Observatory (SDO, both HMI and AIA) to analyze an episode of magnetic flux emergence in an enhanced network that leads to an EB, a UV burst, a cool surge, and coronal signatures in the EUV. Through Milne-Eddington inversions of the {\ion{Fe}{I}} 6302 \AA\ line observed with SST/CRISP we obtain high-resolution (0.057"/pixel) magnetograms that allow us to reliably measure the magnetic field at the photosphere. A comparison with the corresponding SDO/HMI magnetograms reveals that this type of small-scale events are barely discernible in low-resolution (1") observations. During the emergence, a roundish dark bubble is visible in {\ion{Ca}{II} K} 3933 \AA\ at the location where the two opposite polarities of the emerging dipole are splitting apart. Several minutes later, indirect evidence of reconnection is found above the positive polarity of the dipole through the appearance of an EB in the wings of the {H$\alpha$} 6563 \AA\ and {\ion{Ca}{II} K} 3933 \AA\ lines from SST, and also in the SDO/AIA 1600 and 1700 \AA~data. Later, a surge shows up as an elongated structure visible in absorption in {H$\alpha$} and {\ion{Ca}{II} K}, extending over 12 Mm projected size on the disk. The shape of the surge is also apparent as an absorption feature in the SDO/AIA channels. Simultaneously with the surge (and at the location where the EB had appeared earlier on) a UV burst is clearly discernible as a strong and bright emission feature both in IRIS/SJI 1400 and 2796 \AA. Interestingly, this UV burst also has counterpart in SDO/AIA 94, 171, 193, 211, 304, and 335 \AA, meaning that we can find multi-thermal plasma up to a few MK in the reconnection site. This observation clearly shows the impact of the emergence of new magnetic field from the photosphere through the chromosphere and transition region and up into the corona. In addition, it provides an illustrative case to test new realistic simulations. Title: On the relationship between spicules and coronal bright points Authors: Bose, Souvik; De Pontieu, Bart; Rouppe van der Voort, Luc; Nóbrega Siverio, Daniel Bibcode: 2022cosp...44.2522B Altcode: Coronal bright points (CBPs) are a set of small-scale, lower coronal loop systems connecting opposite magnetic polarities and are primarily characterized by enhanced emission in the extreme ultraviolet (EUV) wavelengths and X-rays. Being ubiquitous they are thought to play a definite role in heating the solar corona. This study aims to explore the chromospheric components associated with a CBP by focusing on spicules and small-scaled flux emergence. We used high-resolution observations in H$\beta$ and Fe I 617.3 nm spectral lines obtained from the Swedish 1-m Solar Telescope (SST) in coordination with the images acquired from the Atmospheric Imaging Assembly (AIA) instrument on-board the Solar Dynamics Observatory (SDO). On-disk spicules were automatically detected by employing advanced image processing techniques on the Dopplergrams derived from H$\beta$, and Mile-Eddington inversions of the Fe I 617.3 nm line provided the photospheric vector magnetic field. The AIA co-observations were co-aligned to SST with the latter serving as a reference. We find abundant occurrences of chromospheric spicules close to the "footpoints" of the CBP. The orientation of the spicules is predominantly aligned along with CBP loops which further indicates that they form a fundamental part of the same magnetic structure. Several examples of the spatio-temporal evolution indicate that much of the chromospheric plasma is heated to coronal temperatures implying that spicules potentially supply mass and energy to the CBP loops. Furthermore, we study chromospheric and corresponding coronal responses to two magnetic flux emergence events and their impact on the dynamics of the CBP. This study presents unique and unambiguous evidence that connects chromospheric spicular dynamics and flux emergence with a CBP for the very first time using high-resolution observations. Title: Evidence of the multi-thermal nature of spicular downflows. Impact on solar atmospheric heating Authors: Bose, Souvik; Rouppe van der Voort, Luc; Joshi, Jayant; Henriques, Vasco M. J.; Nóbrega-Siverio, Daniel; Martínez-Sykora, Juan; De Pontieu, Bart Bibcode: 2021A&A...654A..51B Altcode: 2021arXiv210802153B Context. Spectroscopic observations of the emission lines formed in the solar transition region commonly show persistent downflows on the order of 10−15 km s−1. The cause of such downflows, however, is still not fully clear and has remained a matter of debate.
Aims: We aim to understand the cause of such downflows by studying the coronal and transition region responses to the recently reported chromospheric downflowing rapid redshifted excursions (RREs) and their impact on the heating of the solar atmosphere.
Methods: We have used two sets of coordinated data from the Swedish 1 m Solar Telescope, the Interface Region Imaging Spectrograph, and the Solar Dynamics Observatory for analyzing the response of the downflowing RREs in the transition region and corona. To provide theoretical support, we use an already existing 2.5D magnetohydrodynamic simulation of spicules performed with the Bifrost code.
Results: We find ample occurrences of downflowing RREs and show several examples of their spatio-temporal evolution, sampling multiple wavelength channels ranging from the cooler chromospheric to the hotter coronal channels. These downflowing features are thought to be likely associated with the returning components of the previously heated spicular plasma. Furthermore, the transition region Doppler shifts associated with them are close to the average redshifts observed in this region, which further implies that these flows could (partly) be responsible for the persistent downflows observed in the transition region. We also propose two mechanisms - (i) a typical upflow followed by a downflow and (ii) downflows along a loop -from the perspective of a numerical simulation that could explain the ubiquitous occurrence of such downflows. A detailed comparison between the synthetic and observed spectral characteristics reveals a distinctive match and further suggests an impact on the heating of the solar atmosphere.
Conclusions: We present evidence that suggests that at least some of the downflowing RREs are the chromospheric counterparts of the transition region and lower coronal downflows.

Movies associated to Figs. 1-3, 8, and 10 are available at https://www.aanda.org Title: On the dynamics of spicules and mass flows in the solar atmosphere Authors: Bose, Souvik Bibcode: 2021arXiv211010656B Altcode: Popular scientific summary -- The atmosphere of the Sun is envisioned as composed of inherently complex, non-homogeneous, and dynamic layers. A detailed understanding of the physical processes involved in these layers is still lacking. For example, it is largely unknown why the outermost layer of the Sun's atmosphere (the solar corona) is so much hotter than the photosphere by millions of degrees. Astrophysicists think that the layer sandwiched between the photosphere and the corona, known as the interface region, may hold the key to a better understanding of the nature of this enigma. With the help of coordinated high-resolution, ground- and space-based observations from the Swedish 1-m Solar Telescope (SST) on La Palma, Spain, and NASA's Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory (SDO), along with the support from an advanced numerical simulation, I aim to unlock some of the mysteries surrounding the dynamics of the interface region with a focus on small-scale jets, known as "spicules". Spicules are found almost everywhere on the Sun's surface and at any given moment there can be as many as 10 million of them rapidly shooting outwards. They are often found to be heated beyond chromospheric temperatures and appear in the transition region and (even) coronal passbands. Because of their "omnipresence", it is suggested that they play a major role in energizing the outer atmospheric layers of the Sun. This thesis focuses on the physical characteristics and dynamics of spicules, along with their role in mass-balance and heating of the solar atmosphere. Title: Signatures of ubiquitous magnetic reconnection in the deep atmosphere of sunspot penumbrae Authors: Rouppe van der Voort, Luc H. M.; Joshi, Jayant; Henriques, Vasco M. J.; Bose, Souvik Bibcode: 2021A&A...648A..54R Altcode: 2021arXiv210111321R Context. Ellerman bombs are regions with enhanced Balmer line wing emission and mark magnetic reconnection in the deep solar atmosphere in active regions and the quiet Sun. They are often found in regions where opposite magnetic polarities are in close proximity. Recent high-resolution observations suggest that Ellerman bombs are more prevalent than previously thought.
Aims: We aim to determine the occurrence of Ellerman bombs in the penumbra of sunspots.
Methods: We analyzed high spatial resolution observations of sunspots in the Balmer Hα and Hβ lines as well as auxiliary continuum channels obtained with the Swedish 1-m Solar Telescope and applied the k-means clustering technique to systematically detect and characterize Ellerman Bombs.
Results: Features with all the defining characteristics of Ellerman bombs are found in large numbers over the entire penumbra. The true prevalence of these events is only fully appreciated in the Hβ line due to the highest spatial resolution and lower chromospheric opacity. We find that the penumbra hosts some of the highest Ellerman bomb densities, surpassed only by the moat in the immediate surroundings of the sunspot. Some penumbral Ellerman bombs show flame morphology and rapid dynamical evolution. Many penumbral Ellerman bombs are fast moving with typical speed of 3.7 km s−1 and sometimes more than 10 km s−1. Many penumbral Ellerman bombs migrate from the inner to the outer penumbra over hundreds of km, and some continue moving beyond the outer penumbral boundary into the moat. Many penumbral Ellerman bombs are found in the vicinity of regions with opposite magnetic polarity.
Conclusions: We conclude that reconnection is a near continuous process in the low atmosphere of the penumbra of sunspots that manifest in the form of penumbral Ellerman bombs. These are so prevalent that they may be a major sink of sunspot magnetic energy.

Movies associated to Figs. 1 and 6 are available at https://www.aanda.org Title: Multichannel autocalibration for the Atmospheric Imaging Assembly using machine learning Authors: Dos Santos, Luiz F. G.; Bose, Souvik; Salvatelli, Valentina; Neuberg, Brad; Cheung, Mark C. M.; Janvier, Miho; Jin, Meng; Gal, Yarin; Boerner, Paul; Baydin, Atılım Güneş Bibcode: 2021A&A...648A..53D Altcode: 2020arXiv201214023D Context. Solar activity plays a quintessential role in affecting the interplanetary medium and space weather around Earth. Remote-sensing instruments on board heliophysics space missions provide a pool of information about solar activity by measuring the solar magnetic field and the emission of light from the multilayered, multithermal, and dynamic solar atmosphere. Extreme-UV (EUV) wavelength observations from space help in understanding the subtleties of the outer layers of the Sun, that is, the chromosphere and the corona. Unfortunately, instruments such as the Atmospheric Imaging Assembly (AIA) on board the NASA Solar Dynamics Observatory (SDO), suffer from time-dependent degradation that reduces their sensitivity. The current best calibration techniques rely on flights of sounding rockets to maintain absolute calibration. These flights are infrequent, complex, and limited to a single vantage point, however.
Aims: We aim to develop a novel method based on machine learning (ML) that exploits spatial patterns on the solar surface across multiwavelength observations to autocalibrate the instrument degradation.
Methods: We established two convolutional neural network (CNN) architectures that take either single-channel or multichannel input and trained the models using the SDOML dataset. The dataset was further augmented by randomly degrading images at each epoch, with the training dataset spanning nonoverlapping months with the test dataset. We also developed a non-ML baseline model to assess the gain of the CNN models. With the best trained models, we reconstructed the AIA multichannel degradation curves of 2010-2020 and compared them with the degradation curves based on sounding-rocket data.
Results: Our results indicate that the CNN-based models significantly outperform the non-ML baseline model in calibrating instrument degradation. Moreover, multichannel CNN outperforms the single-channel CNN, which suggests that cross-channel relations between different EUV channels are important to recover the degradation profiles. The CNN-based models reproduce the degradation corrections derived from the sounding-rocket cross-calibration measurements within the experimental measurement uncertainty, indicating that it performs equally well as current techniques.
Conclusions: Our approach establishes the framework for a novel technique based on CNNs to calibrate EUV instruments. We envision that this technique can be adapted to other imaging or spectral instruments operating at other wavelengths. Title: Spicules and downflows in the solar chromosphere Authors: Bose, Souvik; Joshi, Jayant; Henriques, Vasco M. J.; Rouppe van der Voort, Luc Bibcode: 2021A&A...647A.147B Altcode: 2021arXiv210107829B Context. High-speed downflows have been observed in the solar transition region (TR) and lower corona for many decades. Despite their abundance, it has been hard to find signatures of such downflows in the solar chromosphere.
Aims: In this work, we target an enhanced network region which shows ample occurrences of rapid spicular downflows in the Hα spectral line, which could potentially be linked to high-speed TR downflowing counterparts.
Methods: We used the k-means algorithm to classify the spectral profiles of on-disk spicules in Hα and Ca II K data observed from the Swedish 1 m Solar Telescope and employed an automated detection method based on advanced morphological image processing operations to detect such downflowing features, in conjunction with rapid blue-shifted and red-shifted excursions (RBEs and RREs).
Results: We report the existence of a new category of RREs (termed as downflowing RRE) for the first time that, contrary to earlier interpretation, are associated with chromospheric field aligned downflows moving toward the strong magnetic field regions. Statistical analysis performed on nearly 20 000 RBEs and 15 000 RREs (including the downflowing counterparts), which were detected in our 97 min long dataset, shows that the downflowing RREs are very similar to RBEs and RREs except for their oppositely directed plane-of-sky motion. Furthermore, we also find that RBEs, RREs, and downflowing RREs can be represented by a wide range of spectral profiles with varying Doppler offsets, and Hα line core widths, both along and perpendicular to the spicule axis, that causes them to be associated with multiple substructures which evolve together.
Conclusions: We speculate that these rapid plasma downflows could well be the chromospheric counterparts of the commonly observed TR downflows.

Movies are available at https://www.aanda.org Title: Characterization and formation of on-disk spicules in the Ca II K and Mg II k spectral lines (Corrigendum) Authors: Bose, Souvik; Henriques, Vasco M. J.; Joshi, Jayant; Rouppe van der Voort, Luc Bibcode: 2020A&A...637C...1B Altcode: No abstract at ADS Title: Auto-Calibration of Remote Sensing Solar Telescopes with Deep Learning Authors: Neuberg, Brad; Bose, Souvik; Salvatelli, Valentina; dos Santos, Luiz F. G.; Cheung, Mark; Janvier, Miho; Gunes Baydin, Atilim; Gal, Yarin; Jin, Meng Bibcode: 2019arXiv191104008N Altcode: As a part of NASA's Heliophysics System Observatory (HSO) fleet of satellites,the Solar Dynamics Observatory (SDO) has continuously monitored the Sun since2010. Ultraviolet (UV) and Extreme UV (EUV) instruments in orbit, such asSDO's Atmospheric Imaging Assembly (AIA) instrument, suffer time-dependent degradation which reduces instrument sensitivity. Accurate calibration for (E)UV instruments currently depends on periodic sounding rockets, which are infrequent and not practical for heliophysics missions in deep space. In the present work, we develop a Convolutional Neural Network (CNN) that auto-calibrates SDO/AIA channels and corrects sensitivity degradation by exploiting spatial patterns in multi-wavelength observations to arrive at a self-calibration of (E)UV imaging instruments. Our results remove a major impediment to developing future HSOmissions of the same scientific caliber as SDO but in deep space, able to observe the Sun from more vantage points than just SDO's current geosynchronous orbit.This approach can be adopted to perform autocalibration of other imaging systems exhibiting similar forms of degradation Title: Characterization and formation of on-disk spicules in the Ca II K and Mg II k spectral lines Authors: Bose, Souvik; Henriques, Vasco M. J.; Joshi, Jayant; Rouppe van der Voort, Luc Bibcode: 2019A&A...631L...5B Altcode: 2019arXiv191005533B We characterize, for the first time, type-II spicules in Ca II K 3934 Å using the CHROMIS instrument at the Swedish 1 m Solar Telescope. We find that their line formation is dominated by opacity shifts with the K3 minimum best representing the velocity of the spicules. The K2 features are either suppressed by the Doppler-shifted K3 or enhanced via increased contribution from the lower layers, leading to strongly enhanced but unshifted K2 peaks, with widening towards the line core as consistent with upper-layer opacity removal via Doppler-shift. We identify spicule spectra in concurrent IRIS Mg II k 2796Å observations with very similar properties. Using our interpretation of spicule chromospheric line formation, we produce synthetic profiles that match observations. Title: Using U-Nets to Create High-Fidelity Virtual Observations of the Solar Corona Authors: Salvatelli, Valentina; Bose, Souvik; Neuberg, Brad; dos Santos, Luiz F. G.; Cheung, Mark; Janvier, Miho; Gunes Baydin, Atilim; Gal, Yarin; Jin, Meng Bibcode: 2019arXiv191104006S Altcode: Understanding and monitoring the complex and dynamic processes of the Sun is important for a number of human activities on Earth and in space. For this reason, NASA's Solar Dynamics Observatory (SDO) has been continuously monitoring the multi-layered Sun's atmosphere in high-resolution since its launch in 2010, generating terabytes of observational data every day. The synergy between machine learning and this enormous amount of data has the potential, still largely unexploited, to advance our understanding of the Sun and extend the capabilities of heliophysics missions. In the present work, we show that deep learning applied to SDO data can be successfully used to create a high-fidelity virtual telescope that generates synthetic observations of the solar corona by image translation. Towards this end we developed a deep neural network, structured as an encoder-decoder with skip connections (U-Net), that reconstructs the Sun's image of one instrument channel given temporally aligned images in three other channels. The approach we present has the potential to reduce the telemetry needs of SDO, enhance the capabilities of missions that have less observing channels, and transform the concept development of future missions. Title: Semi-empirical model atmospheres for the chromosphere of the sunspot penumbra and umbral flashes Authors: Bose, Souvik; Henriques, Vasco M. J.; Rouppe van der Voort, Luc; Pereira, Tiago M. D. Bibcode: 2019A&A...627A..46B Altcode: 2019arXiv190508264B Context. The solar chromosphere and the lower transition region are believed to play a crucial role in the heating of the solar corona. Models that describe the chromosphere (and the lower transition region), accounting for its highly dynamic and structured character are, so far, found to be lacking. This is partly due to the breakdown of complete frequency redistribution (CRD) in the chromospheric layers and also because of the difficulty in obtaining complete sets of observations that adequately constrain the solar atmosphere at all relevant heights.
Aims: We aim to obtain semi-empirical model atmospheres that reproduce the features of the Mg II h&k line profiles that sample the middle chromosphere with focus on a sunspot.
Methods: We used spectropolarimetric observations of the Ca II 8542 Å spectra obtained with the Swedish 1 m Solar Telescope and used NICOLE inversions to obtain semi-empirical model atmospheres for different features in and around a sunspot. These were used to synthesize Mg II h&k spectra using the RH1.5D code, which we compared with observations taken with the Interface Region Imaging Spectrograph (IRIS).
Results: Comparison of the synthetic profiles with IRIS observations reveals that there are several areas, especially in the penumbra of the sunspot, where most of the observed Mg II h&k profiles are very well reproduced. In addition, we find that supersonic hot down-flows, present in our collection of models in the umbra, lead to synthetic profiles that agree well with the IRIS Mg II h&k profiles, with the exception of the line core.
Conclusions: We put forward and make available four semi-empirical model atmospheres. Two for the penumbra, reflecting the range of temperatures obtained for the chromosphere, one for umbral flashes, and a model representative of the quiet surroundings of a sunspot.

Data of semi-empirical model atmospheres are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/627/A46. Title: On the Variability of the Solar Mean Magnetic Field: Contributions from Various Magnetic Features on the Surface of the Sun Authors: Bose, Souvik; Nagaraju, K. Bibcode: 2018ApJ...862...35B Altcode: 2018arXiv180605291B The solar mean magnetic field (SMMF) is referred to as the disk-averaged line-of-sight (LOS) magnetic field that also reflects the polarity imbalance of the magnetic field on the Sun. The origin of the SMMF has been debated over the past few decades, with one school of thought suggesting that the contribution to the SMMF is mostly due to the large-scale magnetic field structure, also called the background magnetic field, whereas other and more recent studies have indicated that active regions have a major contribution to the observed SMMF. In this paper, we re-investigate the issue of the origin of the SMMF by decomposing the solar disk into plages, networks, sunspots, and background regions, thereby calculating the variation in the observed SMMF due to each of these features. We have used full-disk images from Solar Dynamics Observatory (SDO)/AIA recorded at 1600 Å for earmarking plages, networks, and background regions and 4500 Å images for separating the sunspots. The LOS fields corresponding to each of these regions are estimated from the co-temporal SDO/Helioseismic and Magnetic Imager full-disk magnetograms. The temporal variation of the SMMF shows a near one-to-one correspondence with that of the background field regions, suggesting that they constitute the major component of the observed SMMF. A linear regression analysis based on the coefficient of determination shows that the background field dominates and accounts for 89% of the variation in the SMMF, whereas the magnetic field from the other features accounts for the rest 11%. Title: Role of the background regimes towards the Solar Mean Magnetic Field (SMMF) Authors: Bose, Souvik; Nagaraju, K. Bibcode: 2018IAUS..340...85B Altcode: 2018arXiv180511151B The Solar Mean Magnetic Field (SMMF) is generally defined as the disc-averaged line-of-sight (LOS) magnetic field on the sun. The role of the active regions and the large-scale magnetic field structures (also called the background) has been debated over the past few decades to understand whether the origin of the SMMF is either due to the active regions or the background. We, in this paper have investigated contribution of sunspots, plages, networks and the background towards the variability of the SMMF using the datasets from the SDO-AIA & HMI, and found that 89% of the SMMF is due to the background whereas the remaining 11% originates from the active regions and the networks. Title: High Precision Full Stokes Spectropolarimetry of the Sun as a star-Instrument design aspects Authors: Bose, Souvik Bibcode: 2016arXiv161001581B Altcode: The magnetic field plays a major role in governing the dynamics of the sun. Many interesting features like sunspots, flares, prominences, and Coronal Mass Ejections (CMEs) occur on its surface due to the dynamics associated with the magnetic fields. The magnetic activity exhibits spatial scales ranging from very fine scale (below the resolution limit of the current largest telescope) to large scale such as sunspots, active regions and the spatial scales as large as the sun itself. While the major efforts in building large telescopes is going on towards the goal of resolving smallest structure possible we propose here to measure the magnetic field on the global scale. For this purpose we propose an instrument to carryout high precision and high accurate spectropolarimetry of sun-as-a-star. In this thesis, we explore various instrumental design aspects that are necessary to make such observations. As part of the design consideration we have analysed a major noise source i.e. seeing induced cross-talk through simulation as well as using the measured scintillation data. Further, we have analysed full disk Stokes images from SOLIS/VSM and SDO/HMI for the purpose of getting a rough idea on the disk averaged Stokes signal level. The instrument design aspects are mainly constrained by the need to modulate the light before it enters the telescope and image the full sun as a point source. Modulating the light before it enters the telescope has the advantage of completely avoiding the instrumental polarization which will enable us to carry out high accurate polarimetric measurements. We have explored in this thesis various concepts of polarization modulator and spectral discriminator and worked out their suitability for the purpose of carrying out high precision and high accurate spectropolarimetry of sun-as-a-star at high spectral resolution.