scholarly journals Simulating Siberian Radioheliograph response to the quiet Sun

2018 ◽  
Vol 4 (4) ◽  
pp. 82-87 ◽  
Author(s):  
Сергей Лесовой ◽  
Sergey Lesovoi ◽  
Вероника Кобец ◽  
Veronika Kobets
Keyword(s):  
Flux Density ◽  
Solar Disk ◽  
Beam Pattern ◽  
Microwave Emission ◽  
The Sun ◽  
Extended Source ◽  
Microwave Source ◽  
Quiet Sun ◽  
Correlation Plot ◽  
The Impact

The Siberian Radioheliograph (SRH) correlation plot is the time dependence of the sum of absolute values of complex correlations over all baselines. These plots are built for each operating frequency of SRH. The correlation is related not only to the spatial coherence of the incident microwave emission but also to antenna gains. That is why we have to consider real SRH antenna gains and shadowings. Correlation plots obtained by SRH are related to microwave flux density of the Sun and spatial features of microwave sources. Also the correlation plots show variability of SRH beam pattern in time with constant flux density and spatial structure of sources. The SRH beam pattern depends on position of the Sun with respect to SRH, which changes with time. This leads to variations of these plots, which can be confused, for example, with the quasi-harmonic oscillations of the microwave flux produced by sources located above sunspots. Because the solar disk is an extended source, the correlation plot variability is mostly due to the SRH response to the quiet Sun. The smaller is the microwave source, the smaller are the correlation plot variations caused by a change of the beam pattern. Relatively fast variations result from long baseline responses, so it is undesirable to exclude them from the plots. Moreover, the sensitivity of the plots is better when all baselines are taken in account. The impact of the correlation plot variations on the eruptive event response is especially strong because variations of microwave flux during such events are comparable with those of the correlation plots in magnitude and time. From the above it seems reasonable to simulate the SRH response to the quiet solar disk and correct the correlation plots. In this work, we propose a method for simulating correlation plots, which allows us to correct their variations caused by time and frequency dependence of SRH response to the solar disk. The correlation plots are simulated either by summing all model antenna pair responses to the model solar disk or by summing the corresponding values of the solar disk visibility under the assumption that the visibility is ~J1(x)/x, where J1(x) is the Bessel function of the first kind. Also we consider the shadowing of antennas nearest to the center of the SRH antenna array.

scholarly journals Simulating Siberian Radioheliograph response to the quiet Sun

2018 ◽  
Vol 4 (4) ◽  
pp. 106-113
Author(s):  
Сергей Лесовой ◽  
Sergey Lesovoi ◽  
Вероника Кобец ◽  
Veronika Kobets
Keyword(s):  
Flux Density ◽  
Solar Disk ◽  
Beam Pattern ◽  
Microwave Emission ◽  
The Sun ◽  
Extended Source ◽  
Microwave Source ◽  
Quiet Sun ◽  
Correlation Plot ◽  
The Impact

The Siberian Radioheliograph (SRH) correlation plot is the time dependence of the sum of absolute values of complex correlations over all baselines. These plots are built for each operating frequency of SRH. The correlation is related not only to the spatial coherence of the incident microwave emission but also to antenna gains. That is why we have to consider real SRH antenna gains and shadowings. Correlation plots obtained by SRH are related to microwave flux density of the Sun and spatial features of microwave sources. Also the correlation plots show variability of SRH beam pattern in time with constant flux density and spatial structure of sources. The SRH beam pattern depends on position of the Sun with respect to SRH, which changes with time. This leads to variations of these plots, which can be confused, for example, with the quasi-harmonic oscillations of the microwave flux produced by sources located above sunspots. Because the solar disk is an extended source, the correlation plot variability is mostly due to the SRH response to the quiet Sun. The smaller is the microwave source, the smaller are the correlation plot variations caused by a change of the beam pattern. Relatively fast variations result from long baseline responses, so it is undesirable to exclude them from the plots. Moreover, the sensitivity of the plots is better when all baselines are taken in account. The impact of the correlation plot variations on the eruptive event response is especially strong because variations of microwave flux during such events are comparable with those of the correlation plots in magnitude and time. From the above it seems reasonable to simulate the SRH response to the quiet solar disk and correct the correlation plots. In this work, we propose a method for simulating correlation plots, which allows us to correct their variations caused by time and frequency dependence of SRH response to the solar disk. The correlation plots are simulated either by summing all model antenna pair responses to the model solar disk or by summing the corresponding values of the solar disk visibility under the assumption that the visibility is ~J1(x)/x, where J1(x) is the Bessel function of the first kind. Also we consider the shadowing of antennas nearest to the center of the SRH antenna array.

Synoptic maps in three wavelengths of the Chromospheric Telescope

2018 ◽  
Vol 14 (A30) ◽  
pp. 339-341
Author(s):  
Andrea Diercke ◽  
Carsten Denker
Keyword(s):  
Time Series ◽  
Solar Cycle ◽  
Solar Disk ◽  
The Sun ◽  
Observational Period ◽  
Quiet Sun ◽  
Solar Cycle 24 ◽  
Cycle 24 ◽  
Spectral Ranges ◽  
Full Disk

Abstracthe Chromospheric Telescope (ChroTel) observes the entire solar disk since 2011 in three different chromospheric wavelengths: Hα, Ca ii K, and He i. The instrument records full-disk images of the Sun every three minutes in these different spectral ranges. The ChroTel observations cover the rising and decaying phase of solar cycle 24. We started analyzing the ChroTel time-series and created synoptic maps of the entire observational period in all three wavelength bands. The maps will be used to analyze the poleward migration of quiet-Sun filaments in solar cycle 24.

scholarly journals Solar chromospheric emission and magnetic structures from plages to intranetwork: Contribution of the very quiet Sun

2018 ◽  
Vol 615 ◽  
pp. A87 ◽  
Author(s):  
N. Meunier
Keyword(s):  
Time Series ◽  
Solar Cycle ◽  
Radial Velocity ◽  
Activity Level ◽  
The Sun ◽  
Stellar Activity ◽  
Quiet Sun ◽  
Magnetic Structures ◽  
Chromospheric Emission ◽  
The Impact

Context. We need to establish a correspondence between the magnetic structures generated by models and usual stellar activity indexes to simulate radial velocity time series for stars less active than the Sun. This is necessary to compare the outputs of such models with observed radial velocity jitters and is critical to better understand the impact of stellar activity on exoplanet detectability. Aims. We propose a coherent picture to describe the relationship between magnetic activity, including the so-called quiet Sun regions, and the chromospheric emission using the Sun as a test-bench and a reference. Methods. We analyzed a long time series of Michelson Doppler imaging (MDI) magnetograms jointly with chromospheric emission time series obtained at Sacramento Peak and Kitt Peak observatories. This has allowed us to study the variability in the quiet Sun over the solar cycle, and then, based on available relations between magnetic fields in active structures and chromospheric emission, to propose an empirical reconstruction of the solar chromospheric emission based on all contributions. Results. We show that the magnetic flux covering the solar surface, including in the quieted regions, varies in phase with the solar cycle, suggesting a long-term relationship between the global dynamo and the contribution of all components of solar activity. We have been able to propose a reconstruction of the solar S-index, including a relationship between the weak field component and its chomospheric emission, which is in good agreement with the literature. This allows us to explain that stars with a low average chromospheric emission level exhibit a low variability. Conclusions. We conclude that weak flux regions significantly contribute to the chromospheric emission; these regions should be critical in explaining the lower variability associated with the lower average activity level in other stars as compared to the Sun and estimated from their chromospheric emission.

The Homeland, Imprisoned and Illegal: The Impact of Marginalisation on Views of the Homeland in Kanafānī's and Khalīfa's Work

2019 ◽  
Vol 13 (1) ◽  
pp. 1-18
Author(s):  
Jedidiah Anderson
Keyword(s):  
Affect Theory ◽  
The Sun ◽  
Minor Literature ◽  
War Machine ◽  
Ghassan Kanafani ◽  
The Impact

This paper deals with the concept of Al-Waṭan, or ‘the homeland’, in Arabic in The Shell (Al-Qawqʿa) by Muṣṭafā Khalifa and Men in the Sun (Rijāl fīsh-Shams) by Ghassān Kanafānī. Analysis of how alienation from this concept has affected both Khalifa's and Kanafānī's characters is carried out through the lenses of Deleuze and Guattari's theories of rhizomatic associations and minor literature, as well as through the lens of affect theory. The paper also examines parallels between definitions of Al-Waṭan/the homeland in Ibn Manẓūr's classical dictionary Lisān al-ʿArab and Deleuze and Guattari's concepts of the war machine and the apparatus of capture.

scholarly journals Quasi-Band-Limited Coronagraph for Extended Sources

2021 ◽  
Vol 10 (01) ◽  
pp. 2150002
Author(s):  
Igor Loutsenko ◽  
Oksana Yermolayeva
Keyword(s):  
High Resolution ◽  
High Ratio ◽  
Gravitational Lens ◽  
High Resolution Imaging ◽  
The Sun ◽  
Extended Source ◽  
Amplitude Image ◽  
Extended Sources ◽  
Resolution Imaging ◽  
Band Limited

We propose a class of graded coronagraphic “amplitude” image masks for a high throughput Lyot-type coronagraph that transmits light from an annular region around an extended source and suppresses light, with extremely high ratio, from elsewhere. The interior radius of the region is comparable with its exterior radius. The masks are designed using an idea inspired by approach due M. J. Kuchner and W. A. Traub (“band-limited” masks) and approach to optimal apodization by D. Slepian. One potential application of our masks is direct high-resolution imaging of exo-planets with the help of the Solar Gravitational Lens, where apparent radius of the “Einstein ring” image of a planet is of the order of an arc-second and is comparable with the apparent radius of the sun and solar corona.

scholarly journals Models and data analysis tools for the Solar Orbiter mission

2020 ◽  
Vol 642 ◽  
pp. A2 ◽  
Author(s):  
A. P. Rouillard ◽  
R. F. Pinto ◽  
A. Vourlidas ◽  
A. De Groof ◽  
W. T. Thompson ◽  
...  
Keyword(s):  
Data Analysis ◽  
Solar Disk ◽  
Source Region ◽  
Solar Interior ◽  
The Sun ◽  
Science Operations ◽  
Wide Range ◽  
Tools And Techniques ◽  
Orbiter Mission ◽  
Current Modelling

Context. The Solar Orbiter spacecraft will be equipped with a wide range of remote-sensing (RS) and in situ (IS) instruments to record novel and unprecedented measurements of the solar atmosphere and the inner heliosphere. To take full advantage of these new datasets, tools and techniques must be developed to ease multi-instrument and multi-spacecraft studies. In particular the currently inaccessible low solar corona below two solar radii can only be observed remotely. Furthermore techniques must be used to retrieve coronal plasma properties in time and in three dimensional (3D) space. Solar Orbiter will run complex observation campaigns that provide interesting opportunities to maximise the likelihood of linking IS data to their source region near the Sun. Several RS instruments can be directed to specific targets situated on the solar disk just days before data acquisition. To compare IS and RS, data we must improve our understanding of how heliospheric probes magnetically connect to the solar disk. Aims. The aim of the present paper is to briefly review how the current modelling of the Sun and its atmosphere can support Solar Orbiter science. We describe the results of a community-led effort by European Space Agency’s Modelling and Data Analysis Working Group (MADAWG) to develop different models, tools, and techniques deemed necessary to test different theories for the physical processes that may occur in the solar plasma. The focus here is on the large scales and little is described with regards to kinetic processes. To exploit future IS and RS data fully, many techniques have been adapted to model the evolving 3D solar magneto-plasma from the solar interior to the solar wind. A particular focus in the paper is placed on techniques that can estimate how Solar Orbiter will connect magnetically through the complex coronal magnetic fields to various photospheric and coronal features in support of spacecraft operations and future scientific studies. Methods. Recent missions such as STEREO, provided great opportunities for RS, IS, and multi-spacecraft studies. We summarise the achievements and highlight the challenges faced during these investigations, many of which motivated the Solar Orbiter mission. We present the new tools and techniques developed by the MADAWG to support the science operations and the analysis of the data from the many instruments on Solar Orbiter. Results. This article reviews current modelling and tool developments that ease the comparison of model results with RS and IS data made available by current and upcoming missions. It also describes the modelling strategy to support the science operations and subsequent exploitation of Solar Orbiter data in order to maximise the scientific output of the mission. Conclusions. The on-going community effort presented in this paper has provided new models and tools necessary to support mission operations as well as the science exploitation of the Solar Orbiter data. The tools and techniques will no doubt evolve significantly as we refine our procedure and methodology during the first year of operations of this highly promising mission.

Post hoc analysis of the CLEAR study in advanced renal cell carcinoma (RCC): Effect of subsequent therapy on survival outcomes in the lenvatinib (LEN) + everolimus (EVE) versus sunitinib (SUN) treatment arms.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 4562-4562
Author(s):  
Thomas E. Hutson ◽  
Toni K. Choueiri ◽  
Robert J. Motzer ◽  
Sun Young Rha ◽  
Anna Alyasova ◽  
...  
Keyword(s):  
Median Duration ◽  
Proportional Hazards Model ◽  
Objective Response ◽  
Anticancer Therapy ◽  
Cox Proportional Hazards ◽  
Cox Proportional Hazards Model ◽  
The Sun ◽  
Post Hoc ◽  
The Impact

4562 Background: The multicenter, open-label, randomized, phase 3 CLEAR study showed that LEN + EVE had a significant PFS benefit (HR 0.65, 95% CI 0.53-0.80, P<0.001) and improved objective response rate (relative risk 1.48, 95% CI 1.26-1.74) vs SUN in the first-line treatment of patients (pts) with advanced RCC. The difference in overall survival (OS) for LEN + EVE vs SUN was not statistically significant (HR 1.15, 95% CI 0.88-1.50) (Motzer R et al. NEJM. 2021). Post hoc subgroup analyses were performed to assess the impact of subsequent therapy on OS. Methods: Pts in the CLEAR study were randomly assigned (1:1:1) to 1 of 3 treatment arms, including LEN 18 mg + EVE 5 mg once daily (QD) and SUN 50 mg QD (4 weeks on then 2 weeks off). These post hoc analyses examined OS by subsequent systemic anticancer medication in the LEN + EVE and SUN arms. Hazard ratios (HR; LEN + EVE vs SUN) were based on stratified (geographic region and MSKCC prognostic risk groups) Cox proportional hazards model. Results: Among 1069 pts with advanced RCC randomized in the CLEAR study, 714 pts were randomly assigned to the LEN + EVE and SUN arms (N=357/each). The median duration of survival follow-up was 27 months in the LEN + EVE arm and 26 months in the SUN arm. Given the shorter median duration of study treatment with SUN (7.8 months) vs LEN + EVE (11.0 months), more pts in the SUN arm received subsequent anticancer therapy during survival follow-up (LEN + EVE, n=167; SUN, n=206). Among pts who received subsequent therapy, pts in the LEN + EVE arm had a longer median time from randomization to initiation of subsequent therapy vs those in the SUN arm (8.0 vs 6.6 months, respectively). OS for the overall population, for pts with no subsequent anticancer therapy, and for pts with no subsequent immunotherapy is shown in the table. In the US population subgroup (LEN + EVE, n=62; SUN, n=61) of the CLEAR study, in which a similar number of pts received subsequent systemic anticancer therapies in the LEN + EVE vs SUN arms (62.9% vs 65.6%, respectively), OS was comparable among the 2 arms (HR 0.95, 95% CI 0.51-1.76). Overall, the safety profile was consistent with the known safety profiles of LEN + EVE and SUN. In both arms, most treatment-emergent deaths were due to progressive disease; there were few treatment-related deaths (<1%, per arm) and no clustering of events. Conclusions: In the CLEAR study, LEN + EVE met the primary endpoint of a significant benefit in PFS vs SUN. The results of these exploratory analyses suggest that subsequent systemic anticancer therapy affected the OS outcome results for LEN + EVE vs SUN in the CLEAR study. Clinical trial information: NCT02811861. [Table: see text]

When Caddy's Went Viral

10.28945/4750 ◽  
2021 ◽  
Vol 6 ◽  
pp. 001-025
Author(s):  
Samuel Barrington ◽  
Randy Esponda ◽  
Timothy E Newsome ◽  
Say Sengsouvanna ◽  
Cynthia L Steel
Keyword(s):  
Health And Safety ◽  
The Other ◽  
The Sun ◽  
Executive Order ◽  
Summer Vacation ◽  
White Sand ◽  
The Face ◽  
Treasure Island ◽  
The Impact ◽  
Loyal Customers

With the sun losing its glare and now appearing as a beautiful orange orb just above the distant horizon where the sky meets the sea, Barry O’Connor thought to himself, “This is as close to paradise as you can get.” Yet, the vast empty sea of white sand surrounding him told a very different story. It was July 17, 2020, and this beautiful area should have been overrun with college students and young families as they enjoyed their summer vacation. Instead, the executive order that came as a result of the COVID-19 epidemic four months earlier forced him to immediately close his four bars and six Caddy’s Waterfront Dining restaurants, laying off 600 employees and dashing his dreams of another lucrative season. Barry gazed at the beautiful sunset one more time before turning his thoughts to the monumental problem that faced him. While he agreed that the health and safety of his employees and loyal customers was paramount, he couldn’t help but feel the pang that losing a few million dollars a month brings. Now, as businesses began to reopen their doors in the face of new restrictions brought about by COVID, Barry was left to figure out how to navigate the uncharted landscape of new in-house capacity restrictions, everyone’s fear of contracting the virus, and the unknown of when this pandemic would end. All the while, Barry’s bar business was in shambles due to a second government shutdown of bars, which only added pressure on the Caddy’s brand to drive revenue and keep the other half of the business afloat. A potential solution loomed on the horizon, however. This Caddy’s location in Treasure Island had an extensive beach immediately outside its doors, which could expand its footprint, allowing an additional 450-500 customers to enjoy the Caddy’s experience in the safety of an outdoor arena. However, due to local government zoning restrictions, Caddy’s was not legally allowed to treat this area as a traditional restaurant setting. But Barry had become a self-made man because he understood that the nature of business was never static. He knew that the best way forward was to disregard the inconvenience of circumstances beyond his control, and instead pour his efforts into a search for the opportunities that always accompanied such impacts. But just what opportunities did the pandemic create? How could he best leverage technology to exploit them? How would he manage the impact of the changes on his customers and employees?

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