scholarly journals Variations in EUV Irradiance: Comparison between LYRA, ESP, and SWAP Integrated Flux

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Mehmet Sarp Yalim ◽  
Stefaan Poedts
Keyword(s):  
Solar Disk ◽  
Extreme Ultraviolet ◽  
Coronal Holes ◽  
Active Regions ◽  
The Sun ◽  
The Moon ◽  
Large Yield ◽  
Active Pixel ◽  
Observation Instruments ◽  
The Difference

The Sun Watcher Using Active Pixel System Detector and Image Processing (SWAP) telescope and Large Yield Radiometer (LYRA) are the two Sun observation instruments on-board PROBA2. SWAP extreme ultraviolet images, if presented in terms of the integrated flux over solar disk, in general, correlate well with LYRA channel 2–4 (zirconium filter) and channels QD and 18 of EVE/ESP on-board SDO between 2010 and 2013. Hence, SWAP can be considered as an additional radiometric channel. We compare in detail LYRA channel 2–4 and SWAP integrated flux in July 2010 and in particular during the solar eclipse that occurred on July 11, 2010. During this eclipse, the discrepancy between the two data channels can be explained to be related to the occultation of active region 11087 by the Moon. In the second half of July 2010, LYRA channel 2–4 and SWAP integrated flux deviate from each other, but these differences can also be explained in terms of features appearing on the solar disk such as coronal holes and active regions. By additionally comparing with timeline of EVE/ESP, we can preliminarily interpret these differences in terms of the difference between the broad bandpass of LYRA channel 2–4 and the, relatively speaking, narrower bandpass of SWAP.

scholarly journals LUCI onboard Lagrange, the next generation of EUV space weather monitoring

2020 ◽  
Vol 10 ◽  
pp. 49
Author(s):  
Matthew J. West ◽  
Christian Kintziger ◽  
Margit Haberreiter ◽  
Manfred Gyo ◽  
David Berghmans ◽  
...  
Keyword(s):  
Space Weather ◽  
Extreme Ultraviolet ◽  
Coronal Holes ◽  
Active Regions ◽  
Pass Band ◽  
The Sun ◽  
Lower Corona ◽  
Transient Phenomena ◽  
Weather Forecasts ◽  
Active Pixel

Lagrange eUv Coronal Imager (LUCI) is a solar imager in the Extreme UltraViolet (EUV) that is being developed as part of the Lagrange mission, a mission designed to be positioned at the L5 Lagrangian point to monitor space weather from its source on the Sun, through the heliosphere, to the Earth. LUCI will use an off-axis two mirror design equipped with an EUV enhanced active pixel sensor. This type of detector has advantages that promise to be very beneficial for monitoring the source of space weather in the EUV. LUCI will also have a novel off-axis wide field-of-view, designed to observe the solar disk, the lower corona, and the extended solar atmosphere close to the Sun–Earth line. LUCI will provide solar coronal images at a 2–3 min cadence in a pass-band centred on 19.5. Observations made through this pass-band allow for the detection and monitoring of semi-static coronal structures such as coronal holes, prominences, and active regions; as well as transient phenomena such as solar flares, limb coronal mass ejections (CMEs), EUV waves, and coronal dimmings. The LUCI data will complement EUV solar observations provided by instruments located along the Sun–Earth line such as PROBA2-SWAP, SUVI-GOES and SDO-AIA, as well as provide unique observations to improve space weather forecasts. Together with a suite of other remote-sensing and in-situ instruments onboard Lagrange, LUCI will provide science quality operational observations for space weather monitoring.

Ibn al-Ḥadib’s Tables for Finding True Syzygy

2019 ◽  
Vol 50 (4) ◽  
pp. 428-446
Author(s):  
Bernard R. Goldstein ◽  
José Chabás
Keyword(s):  
Middle Ages ◽  
The Sun ◽  
The Moon ◽  
Focus Attention ◽  
Important Work ◽  
The Difference ◽  
The Middle Ages

Isaac ben Solomon Ibn al-Ḥadib (or al-Aḥdab) emigrated from Castile to Sicily no later than 1396. In astronomy, his most important work, written in Hebrew, is The paved way ( Oraḥ selula), a set of tables for the motions of the Sun and the Moon. Here, we focus attention on his unusual tables for finding the difference in time and the difference in longitude between mean and true syzygy, where syzygy refers to the conjunction and opposition of the Sun and the Moon. It is shown that he took into account the effect of Ptolemy’s second lunar model on the velocity of the Moon at syzygy, which was done by very few astronomers in the Middle Ages. It is also noteworthy that he took some parameters from the zij of al-Battānī and others from the Parisian Alfonsine Tables, using them inconsistently in these tables.

scholarly journals Extreme ultraviolet observations of active regions in the solar corona

1968 ◽  
Vol 35 ◽  
pp. 395-402
Author(s):  
W. M. Burton
Keyword(s):  
High Temperature ◽  
Extreme Ultraviolet ◽  
Active Regions ◽  
Pinhole Camera ◽  
Emission Region ◽  
The Sun ◽  
Coronal Emission ◽  
Improved Design ◽  
Ultraviolet Observations ◽  
Plane Diffraction

The coronal features associated with solar active regions can be observed by recording images of the Sun at extreme ultraviolet (XUV) wavelengths. Pinhole cameras have been flown on stabilized sun-pointing ‘Skylark’ rockets to obtain broad-waveband XUV solar images. These images show localised emission from high-temperature regions located in the corona above calcium-plage areas. An improved design of pinhole camera, which uses a plane-diffraction grating to give increased spectral resolution, has recorded spectroheliograms in several intense solar lines including He II (304 Å), Fe IX–XI (180 Å), and Si X–XII (50 Å). Estimates are made of the size and brightness of the coronal emission region associated with a developing calcium-plage area.

scholarly journals I. Observations of temperature during two eclipses of the sun (in 1858 and 1867)

1867 ◽  
Vol 15 ◽  
pp. 421-423
Keyword(s):  
Solar Disk ◽  
Open Space ◽  
The Sun ◽  
The Moon ◽  
The Third ◽  
The Moment ◽  
The Village

On the 15th of March 1858, occurred an annular eclipse of the sun, whose entral line of shadow passed near the village of Steeple Aston, a few miles orth of Oxford. Ample preparations were made for observing it by resi­dents in Oxford, and they were met on the ground by many persons from distance; Mr. Lasseli being one of the party, there was no lack of telescopic power. The day was unfavourable—cold and cloudy, with some ccasional feeble and delusive gleams, scarcely permitting a sight of the rogress of the eclipse, which, however, was obvious enough by the grow-g and diminishing darkness. Under these circumstances I devoted my trincipal attention to three thermometers, carefully selected and compared forehand—one mercurial with blackened bulb, another mercurial with lear bulb (these were placed in an open space exposed to the sun); the third, minimum- spirit thermometer, tint red, was placed in a shaded situation. The observations began at 11 h 30 m and lasted till 2 h 30 m , thus including he whole period of the eclipse, which began at 11 h 35 m , reached the maxium of obscuration at 0 h 54 m , and ended at 2 h 11 m . The apparent semi-ameters of the sun and moon were so nearly equal that the eclipse was lmost total (997/1000). The observations were recorded as follows:— During the late partial eclipse of the sun on the 6th of March 1867 observations of'the ingress of the moon were favoured at Oxford by brilliant weather; within fire minutes after the moment of maximum obscuration (742/1000) Clouds appeared; and from this time till the end of the eclips they never wholly disappeared, but did not prevent the progress of the moon and the degrees of obscuration from being correctly marked. At the very end it was only just possible to observe the egress by a momentary attenuation of the clouds; the remainder of the day was cold, cloudy, and finally snowy. The observations began at 8 h and ended at 10 h 50 s , thus including the whole period of the eclipse, which began at 8 h 12 m 15 s , reached the greatest obscuration at 9 h 26 m , and ceased at 10 h 45 m 8 s . At the mo­ment of greatest obscuration the light-giving area was reduced to one-third of the solar disk.

scholarly journals On the Lithium Abundance in Sunspots and the Undisturbed Solar Atmosphere

1968 ◽  
Vol 1 ◽  
pp. 247-250
Author(s):  
E. Dubov ◽  
V. Prokof’ev ◽  
A. Severny
Keyword(s):  
Solar Atmosphere ◽  
Active Regions ◽  
Resolving Power ◽  
The Sun ◽  
Diffuse Band ◽  
Lithium Abundance ◽  
Echelle Grating ◽  
The Difference ◽  
Preliminary Consideration ◽  
Important Indication

The difference between abundances of such elements as Li, Be, B in active regions on the Sun and in the undisturbed atmosphere, if it exists at all, could be considered a very important indication on the possible nuclear reaction in active regions and on the rate of diffusion of elements inside magnetic fields of sunspots. One of the authors from the considerations of λ6707 Å has an estimated (Dubov, 1955) Li abundance in the undisturbed solar atmosphere as log N(Li) = 0·93 (taking log N(H) = 12·0), which is close to the later results (Goldberg et al., 1960). In sunspots we can expect that the first doublet λ6103 of Li diffuse series appears. The preliminary consideration (Dubov, 1964) showed that Li abundance in sunspots could be several times larger than the above estimate for the undisturbed atmosphere. This result forced us to consider as carefully as possible the region of λ6103 in eight spectra of four sunspots taken with the aid of the echelle-grating spectrograph of the Crimean observatory with a dispersion of 1 Å/mm and measured resolving power 0·03 Å. The consideration of the Zeeman pattern of this line shows that at the field strengths we had in sunspots (2000–3000 gs) the line should be diffuse band with width ~0·23 Å, and taking into account the broadening of the line the halfwidth of the line has not to be smaller than 0·25 Å.

scholarly journals The moon phases influence on the beginning of astronomical dawn determination in Yogyakarta

2017 ◽  
Vol 2 (1) ◽  
pp. 1
Author(s):  
Abu Yazid Raisal ◽  
Yudhiakto Pramudya ◽  
Okimustava Okimustava ◽  
Muchlas Muchlas
Keyword(s):  
Full Moon ◽  
Moving Average ◽  
Weather Condition ◽  
The Sun ◽  
The Moon ◽  
Moon Phases ◽  
Brightness Level ◽  
Sky Brightness ◽  
New Moon ◽  
The Difference

<p class="Abstract">In astronomy, there are three types of dawn. They are astronomical, nautical, and civil dawn. The sunlight is starting to appear on the east horizon when the Sun altitude is 18<sup>o</sup> below the horizon. Hence, there is a change on the sky brightness. The sky brightness can be affected by the moon phases. The sky brightness level is monitored by Sky Quality Meter (SQM). The SQM was installed upward to the zenith. There are 4 locations of measurement in Yogyakarta. The data has been collected for nine months to obtain the complete moon phases. The beginning of astronomical dawn is time when the sky brightness level is starting to decrease. The moving average algorithm was employed to determine the beginning of astronomical dawn. The time when the astronomical dawn begins is compared with the sun altitude calculation. The sun altitude calculation has been done using accurate times software. The difference of the beginning of astronomical dawn by measurement and calculation are 18.61±6.81 minutes, 19.12±3.28 minutes, 31.12±7.76 minutes, and 27.24±8.04 minutes, on the new moon (0), on the first quarter (0.25), on the full moon (0.5) and on the last quarter (0.75), respectively. The weather condition is also contributing to the results.</p>

scholarly journals The design of solar synoptic chart for space weather forecast

2015 ◽  
Vol 11 (S320) ◽  
pp. 324-329 ◽  
Author(s):  
Qiao Song ◽  
Jing-Song Wang ◽  
Xue-Shang Feng ◽  
Xiao-Xin Zhang
Keyword(s):  
Public Education ◽  
Space Weather ◽  
Coronal Holes ◽  
Active Regions ◽  
Weather Forecast ◽  
The Sun ◽  
The Public ◽  
The Past ◽  
The Earth ◽  
Synoptic Chart

AbstractThe Sun drives most events of space weather in the vicinity of the Earth. Because the activities of the Sun are complicated, a visualized chart with key objects of solar activities is needed for space weather forecast. This work investigates the key objects in research during the past forty years and surveys a variety of solar observational data. We design the solar synoptic chart (SSC) that covers the key objects of solar activities, i.e., active regions, coronal holes, filaments/prominences, flares and coronal mass ejections, and synthesizes images from different heights and temperatures of solar atmosphere. The SSC is used to analyze the condition of the Sun in March 2012 and October 2014 as examples. The result shows that the SSC is timely, comprehensive, concise and easy to understand. It has the potentiality for space weather forecast and can help in improving the public education.

scholarly journals First Year of Observations with SOHO/EIT of the “Quiet” Sun Corona

1998 ◽  
Vol 167 ◽  
pp. 41-44
Author(s):  
F. Portier-Fozzani ◽  
A.J. Maucherat ◽  
EIT Team
Keyword(s):  
Extreme Ultraviolet ◽  
Coronal Holes ◽  
Active Regions ◽  
Emission Lines ◽  
Magnetic Interactions ◽  
First Year ◽  
Wide Field ◽  
Morphology Evolution ◽  
Magnetic Structures

AbstractSince January 1996 (EIT first light) the Extreme Ultraviolet Telescope aboard SOHO has produced about 20,000 wide-field images of the corona and transition regions. Four different emission lines (He II, Fe IX/X, Fe XII, Fe XV) were selected to detail morphologies of magnetic structures in the corona. They show the different structures present in the corona with information about their topologies (Neupert et al. 1998). They provide the global temperature distribution in the quiet corona in the range 0.5 to 3 × 106 K.The evolution of the corona during the first year of the SOHO mission revealed its nonuniform aspect and the nonregularity of the appearance of new active regions. Changes observed in active regions and coronal holes (e.g., August–September 1996) showed the complex role of magnetic fields including magnetic interactions and possible reconnections needed to explain some loop morphology evolution.

scholarly journals Relativistic positioning: including the influence of the gravitational action of the Sun and the Moon and the Earth’s oblateness on Galileo satellites

2021 ◽  
Vol 366 (7) ◽  
Author(s):  
Neus Puchades Colmenero ◽  
José Vicente Arnau Córdoba ◽  
Màrius Josep Fullana i Alfonso
Keyword(s):  
Space Time ◽  
Satellite Orbits ◽  
The Sun ◽  
The Moon ◽  
Schwarzschild Metric ◽  
Positioning Systems ◽  
Positioning Errors ◽  
The Earth ◽  
Realistic Description ◽  
The Difference

AbstractUncertainties in the satellite world lines lead to dominant positioning errors. In the present work, using the approach presented in Puchades and Sáez (Astrophys. Space Sci. 352, 307–320, 2014), a new analysis of these errors is developed inside a great region surrounding Earth. This analysis is performed in the framework of the so-called Relativistic Positioning Systems (RPS). Schwarzschild metric is used to describe the satellite orbits corresponding to the Galileo Satellites Constellation. Those orbits are circular with the Earth as their centre. They are defined as the nominal orbits. The satellite orbits are not circular due to the perturbations they have and to achieve a more realistic description such perturbations need to be taken into account. In Puchades and Sáez (Astrophys. Space Sci. 352, 307–320, 2014) perturbations of the nominal orbits were statistically simulated. Using the formula from Coll et al. (Class. Quantum Gravity. 27, 065013, 2010) a user location is determined with the four satellites proper times that the user receives and with the satellite world lines. This formula can be used with any satellite description, although photons need to travel in a Minkowskian space-time. For our purposes, the computation of the photon geodesics in Minkowski space-time is sufficient as demonstrated in Puchades and Sáez (Adv. Space Res. 57, 499–508, 2016). The difference of the user position determined with the nominal and the perturbed satellite orbits is computed. This difference is defined as the U-error. Now we compute the perturbed orbits of the satellites considering a metric that takes into account the gravitational effects of the Earth, the Moon and the Sun and also the Earth oblateness. A study of the satellite orbits in this new metric is first introduced. Then we compute the U-errors comparing the positions given with the Schwarzschild metric and the metric introduced here. A Runge-Kutta method is used to solve the satellite geodesic equations. Some improvements in the computation of the U-errors using both metrics are introduced with respect to our previous works. Conclusions and perspectives are also presented.

scholarly journals Soft X-Radiation from Single Active Regions

1975 ◽  
Vol 68 ◽  
pp. 101-102
Author(s):  
D. H. Brabban ◽  
E. B. Dorling ◽  
W. M. Glencross ◽  
J. R. H. Herring
Keyword(s):  
Solar Disk ◽  
Active Regions ◽  
Angular Width ◽  
Entrance Window ◽  
The Sun ◽  
Proportional Counters

SummaryThe MSSL/Leicester University package on OSO 5 contained proportional counters having fields of view small compared with the area of the solar disk (Herring et al., 1971). Results discussed here were obtained with a detector sensitive in the band 0.3–0.9 nm. This had an entrance window collimated to examine a strip of angular width 2′ lying across the Sun.

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