Visible Emission Line Coronagraph on Aditya-L1

Prasad, B. Raghavendra; Banerjee, D.; Singh, Jagdev; Nagabhushana, S.; Kumar, Amit; Kamath, Pritish; Srinivasan, Kathiravan; Venkata, Suresh; Rajkumar, N.; Natarajan, Vasant; Juneja, Madhur; Somu, Pawan; Pant, Vaibhav; Shaji, Nigar; Sankarsubramanian, K.; Patra, Asit; Venkateswaran, R.; Adoni, Abhijit A.; Narendra, Shiradkar; Haridas, T. R.; Mathew, Shibu K.; Krishna, R. Mohan; Amareswari, K.; Jaiswal, Bhavesh

doi:10.18520/cs/v113/i04/613-615

Cited by 53 publications

(21 citation statements)

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“…In order to apply their theorem in our setting, a number of differences in the setup of this paper and [41] [41,42] are formulated for the sum-of-squares SDP hierarchy, which is equivalent to the Lasserre SDP hierarchy: the kth level of the sums-of-squares SDP hierarchy is the same as the (k/2)th level of the Lasserre SDP hierarchy. Third, while the results in [41,42] are formulated for constraint languages consisting of a single {0, 1}-valued weighted relation, the proofs give the same result for constraint languages (of finite size) consisting of [0, 1]-valued weighted relations of different arities [46]. Finally, while the work in [41,42] deals with maximisation problems, for exact solvability we can equivalently turn to minimisation problems.…”

Section: Resultsmentioning

confidence: 88%

The Limits of SDP Relaxations for General-Valued CSPs

Thapper

Živný

2018

ACM Trans. Comput. Theory

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It has been shown that for a general-valued constraint language Γ the following statements are equivalent: (1) any instance of VCSP(Γ) can be solved to optimality using a constant level of the Sherali-Adams LP hierarchy; (2) any instance of VCSP(Γ) can be solved to optimality using the third level of the Sherali-Adams LP hierarchy; (3) the support of Γ satisfies the "bounded width condition", i.e., it contains weak near-unanimity operations of all arities.We show that if the support of Γ violates the bounded width condition then not only is VCSP(Γ) not solved by a constant level of the Sherali-Adams LP hierarchy but it requires linear levels of the Lasserre SDP hierarchy (also known as the sum-of-squares SDP hierarchy). For Γ corresponding to linear equations in an Abelian group, this result follows from existing work on inapproximability of Max-CSPs. By a breakthrough result of Lee, Raghavendra, and Steurer [STOC'15], our result implies that for any Γ whose support violates the bounded width condition no SDP relaxation of polynomial-size solves VCSP(Γ).We establish our result by proving that various reductions preserve exact solvability by the Lasserre SDP hierarchy (up to a constant factor in the level of the hierarchy). Our results hold for general-valued constraint languages, i.e., sets of functions on a fixed finite domain that take on rational or infinite values, and thus also hold in notable special cases of {0, ∞}-valued languages (CSPs), {0, 1}-valued languages (Min-CSPs/Max-CSPs), and Q-valued languages (finite-valued CSPs).The dichotomy conjecture of Feder and Vardi has been verified in several important special cases by Schaefer [47], Hell and Nešetřil [27], Bulatov [8,11], and Barto, Kozik, and Niven [6] mostly using the so-called algebraic approach [10,4]. Remarkably, the dichotomy conjecture has recently been solved independently by Bulatov [9] and Zhuk [58], respectively.Using concepts from the extensions of the algebraic approach to optimisation problems [17], the exact solvability of purely optimisation CSPs, known as finite-valued CSPs, has been established by the authors [50] (these include Min/Max-CSPs as a special case). Putting together decision and optimisation problems in one framework, the exact complexity of socalled general-valued CSPs has been established, modulo the (now proved) classification of decision CSPs, by the works of Kozik and Ochremiak [35] and Kolmogorov, Krokhin, and Rolínek [31]. A result that proved useful when classifying both finite-valued and generalvalued CSPs is an algebraic characterisation of the power of the basic linear programming relaxation for decision CSPs [36] and general-valued CSPs [32]. ApproximationConvex relaxations, such as linear programming (LP) and semidefinite programming (SDP), have long been powerful tools for designing efficient exact and approximation algorithms [55,56]. In particular, for many combinatorial problems, the introduction of semidefinite programming relaxations allowed for a new structural and computational perspective [23, 30...

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Section: Resultsmentioning

confidence: 88%

The Limits of SDP Relaxations for General-Valued CSPs

Thapper

Živný

2018

ACM Trans. Comput. Theory

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“…Progress in CME physics is of course not dependent on radio observations alone, and a host of new multiwavelength observations will be available with new and upcoming spacebased missions. Imaging of the inner corona from coronagraphs such as Metis (Antonucci et al, 2019) on Solar Orbiter, the Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun (ASPIICS; Galy et al, 2015) onboard PROBA-3, the Visible Emission Line Coronagraph (VELC; Prasad et al, 2017) onboard Aditya-L1, as well as from EUV imagers such as SUVI and the Extreme Ultraviolet Imager (EUI; Rochus et al, 2020) on Solar Orbiter will provide excellent synergies alongside the radio instrumentation described above. Radio and multiwavelength studies can provide powerful diagnostics in CME physics from the CME nascent stages to eruption and eventual propagation into the heliosphere and promise to make significant advances in the understanding of this phenomenon in the near future and beyond.…”

Section: Discussionmentioning

confidence: 99%

Radio Observations of Coronal Mass Ejection Initiation and Development in the Low Solar Corona

Carley

Vilmer

Vourlidas

2020

Front. Astron. Space Sci.

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Coronal mass ejections (CMEs) are large eruptions of plasma and magnetic field from the low solar corona into the heliosphere. These eruptions are often associated with energetic electrons that produce various kinds of radio emission. However, there is ongoing investigation into exactly where, when, and how the electron acceleration occurs during flaring and eruption, and how the associated radio emission can be exploited as a diagnostic of both particle acceleration and CME eruptive physics. Here, we review past and present developments in radio observations of flaring and eruption, from the destabilization of flux ropes to the development of a CME and the eventual driving of shocks in the corona. We concentrate primarily on the progress made in CME radio physics in the past two decades and show how radio imaging spectroscopy provides the ability to diagnose the locations and kinds of electron acceleration during eruption, which provides insight into CME eruptive models in the early stages of their evolution ( < 10 R ⊙ ). We finally discuss how new instrumentation in the radio domain will pave the way for a deeper understanding of CME physics in the near future.

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“…These include the ground-based facilities DKIST and CoMP (Tomczyk et al 2008). ISRO's Aditya-L1 space mission, currently under development, will fly the Solar Ultraviolet Imaging Telescope (SUIT; Tripathi et al 2017) and the Variable Emission Line Coronagraph (VELC; Prasad et al 2017) instruments which would simultaneously observe filament-prominence-arcade systems and coronal magnetic fields. We expect these multiviewpoint, multi-wavelength observations to revolutionize the field of coronal magnetometry.…”

Section: Concluding Discussionmentioning

confidence: 99%

Prediction of the Sun’s Coronal Magnetic Field and Forward-modeled Polarization Characteristics for the 2019 July 2 Total Solar Eclipse

Dash

Bhowmik

Athira

et al. 2020

ApJ

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On 2019 July 2 a total solar eclipse—visible across parts of the Southern Pacific Ocean, Chile, and Argentina—enabled observations of the Sun’s corona. The structure and emission characteristics of the corona are determined by underlying magnetic fields, which also govern coronal heating and solar eruptive events. However, coronal magnetic field measurements remain an outstanding challenge. Coronal magnetic field models serve an important purpose in this context. Earlier work has demonstrated that the large-scale coronal structure is governed by surface flux evolution and memory buildup, which allows for its prediction on solar rotational timescales. Utilizing this idea and based upon a 51 day forward run of a predictive solar surface flux transport model and a potential field source surface model, we predict the coronal structure of the 2019 July 2 solar eclipse. We also forward model the polarization characteristics of the coronal emission. Our prediction of two large-scale streamer structures and their locations on the east and west limbs of the Sun match eclipse observations reasonably well. We demonstrate that the Sun’s polar fields strongly influence the modeled corona, concluding that accurate polar field observations are critical. This study is relevant for coronal magnetometry initiatives envisaged with the Daniel K. Inouye Solar Telescope, Coronal Multichannel Polarimeter and upcoming space-based instruments such as Solar Orbiter, Solar Ultraviolet Imaging Telescope and the Variable Emission Line Coronagraph on board the Indian Space Research Organisation’s Aditya-L1 space mission.

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Visible Emission Line Coronagraph on Aditya-L1

Cited by 53 publications

References 0 publications

The Limits of SDP Relaxations for General-Valued CSPs

The Limits of SDP Relaxations for General-Valued CSPs

Radio Observations of Coronal Mass Ejection Initiation and Development in the Low Solar Corona

Prediction of the Sun’s Coronal Magnetic Field and Forward-modeled Polarization Characteristics for the 2019 July 2 Total Solar Eclipse

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