- ID:
- ivo://CDS.VizieR/J/ApJ/789/117
- Title:
- Solar spectral irradiance
- Short Name:
- J/ApJ/789/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use solar spectra obtained by the Ozone Monitoring Instrument (OMI) on board the Aura satellite to detect and follow long-term (years) and short-term (weeks) changes in the solar spectral irradiance (SSI) in the 265-500 nm spectral range. During solar Cycle 24, in the relatively line-free regions the SSI changed by ~0.6%+/-0.2% around 265 nm. These changes gradually diminish to 0.15%+/-0.20% at 500 nm. All strong spectral lines and blends, with the notable exception of the upper Balmer lines, vary in unison with the solar "continuum." Besides the lines with strong chromospheric components, the most involved species include Fe I blends and all prominent CH, NH, and CN spectral bands. Following the general trend seen in the solar "continuum," the variability of spectral lines also decreases toward longer wavelengths. The long-term solar cycle SSI changes are closely, to within the quoted 0.1%-0.2% uncertainties, matched by the appropriately adjusted short-term SSI variations derived from the 27 day rotational modulation cycles. This further strengthens and broadens the prevailing notion about the general scalability of the UV SSI variability to the emissivity changes in the Mg II 280 nm doublet on timescales from weeks to years. We also detect subtle deviations from this general rule: the prominent spectral lines and blends at {lambda} >~ 350 nm show slightly more pronounced 27 day SSI changes when compared to the long-term (years) trends. We merge the solar data from Cycle 21 with the current Cycle 24 OMI and GOME-2 observations and provide normalized SSI variations for the 170-795 nm spectral region.
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- ID:
- ivo://CDS.VizieR/J/A+A/645/A2
- Title:
- Solar spectral irradiance during Solar Cycle 24
- Short Name:
- J/A+A/645/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Solar spectral irradiance (SSI) is the wavelength-dependent energy input to the top of the Earth's atmosphere. Solar ultraviolet (UV) irradiance represents the primary forcing mechanism for the photochemistry, heating, and dynamics of the Earth's atmosphere. Hence, both temporal and spectral variations in solar UV irradiance represent crucial inputs to the modeling and understanding of the behavior of the Earth's atmosphere. Therefore, measuring the long-term solar UV irradiance variations over the 11-year solar activity cycle (and over longer timescales) is fundamental. Thus, each new solar spectral irradiance dataset based on long-term observations represents a major interest and can be used for further investigations of the long-term trend of solar activity and the construction of a homogeneous solar spectral irradiance record. The main objective of this article is to present a new solar spectral irradiance database (SOLAR-v) with the associated uncertainties. This dataset is based on solar UV irradiance observations (165-300nm) of the SOLAR/SOLSPEC space-based instrument, which provides measurements of the full-disk SSI during solar cycle 24. SOLAR/SOLSPEC made solar acquisitions between April 5, 2008 and February 10, 2017. During this period, the instrument was affected by the harsh space environment that introduces instrumental trends (degradation) in the SSI measurements. A new method based on an adaptation of the Multiple Same-Irradiance-Level (MuSIL) technique was used to separate solar variability and any uncorrected instrumental trends in the SOLAR/SOLSPEC UV irradiance measurements. A new method for correcting degradation has been applied to the SOLAR/SOLSPEC UV irradiance records to provide new solar cycle variability results during solar cycle 24. Irradiances are reported at a mean solar distance of 1 astronomical unit (AU). In the 165-242nm spectral region, the SOLAR/SOLSPEC data agrees with the observations (SORCE/SOLSTICE) and models (SATIRE-S, NRLSSI 2) to within the 1-sigma error envelope. Between 242 and 300nm, SOLAR/SOLSPEC agrees only with the models.
- ID:
- ivo://CDS.VizieR/J/ApJ/787/10
- Title:
- Solar s-process contributions with GCE model
- Short Name:
- J/ApJ/787/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the s-process abundances (A>~90) at the epoch of the solar system formation. Asymptotic giant branch yields are computed with an updated neutron capture network and updated initial solar abundances. We confirm our previous results obtained with a Galactic chemical evolution (GCE) model: (1) as suggested by the s-process spread observed in disk stars and in presolar meteoritic SiC grains, a weighted average of s-process strengths is needed to reproduce the solar s distribution of isotopes with A>130; and (2) an additional contribution (of about 25%) is required in order to represent the solar s-process abundances of isotopes from A=90 to 130. Furthermore, we investigate the effect of different internal structures of the ^13^C pocket, which may affect the efficiency of the ^13^C({alpha},n)^16^O reaction, the major neutron source of the s process. First, keeping the same ^13^C profile adopted so far, we modify by a factor of two the mass involved in the pocket; second, we assume a flat ^13^C profile in the pocket, and we test again the effects of the variation of the mass of the pocket. We find that GCE s predictions at the epoch of the solar system formation marginally depend on the size and shape of the ^13^C pocket once a different weighted range of ^13^C-pocket strengths is assumed. We obtain that, independently of the internal structure of the ^13^C pocket, the missing solar system s-process contribution in the range from A=90 to 130 remains essentially the same.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A67
- Title:
- Solar supergranular velocity profiles
- Short Name:
- J/A+A/581/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Flow vorticity is a fundamental property of turbulent convection in rotating systems. Solar supergranules exhibit a preferred sense of rotation, which depends on the hemisphere. This is due to the Coriolis force acting on the diverging horizontal flows. We aim to spatially resolve the vertical flow vorticity of the average supergranule at different latitudes, both for outflow and inflow regions. To measure the vertical vorticity, we use two independent techniques: time-distance helioseismology (TD) and local correlation tracking of granules in intensity images (LCT) using data from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). Both maps are corrected for center-to-limb systematic errors. We find that 8 h TD and LCT maps of vertical vorticity are highly correlated at large spatial scales.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A165
- Title:
- Solar type III radio burst
- Short Name:
- J/A+A/618/A165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We design an event recognition-analysis system that can automatically detect solar type III radio burst and can mine information of the burst from the dynamic spectra observed by Nancay Decameter Array (NDA). We investigate the frequency drift rate of type III bursts and the speed of electron beams responsible for the generation of the bursts. Several computer vision methods are used in this automatic analysis system. The Hough transform is performed to recognize the line segment associated with type III bursts in the dynamic spectra. A modified active contour model is used to track the backbone of the burst and estimate the frequency drift rate at different frequency channels. We run this system on the NDA data from 2012 to 2017, and give a statistical survey of the event number distribution, the starting and stopping frequencies of bursts, the frequency dependence of the drift rate, and the exciter speed using three corona density models. The median value of the average frequency drift rates is about 6.94MHz/s for 1389 simple well-isolated type III bursts detected in the frequency range 10-80MHz of NDA observation. The frequency drift rate changes with frequency as df/dt=-0.0672f^1.23^ from a least-squares fitting. The average exciter speed is about 0.2c based the density models. We do not find any significant dependence of the drift rate and the exciter speed on the solar activity cycle.
- ID:
- ivo://CDS.VizieR/J/A+AS/119/489
- Title:
- Solar Type II Radio Bursts, 1990.09 - 1993.12
- Short Name:
- J/A+AS/119/489
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Solar type II radio bursts represent the radio signature of shock waves travelling through the solar corona. They are associated with flares, coronal mass ejections (CME's) and interplanetary shocks. Type II radio bursts appear as emission stripes slowly drifting from high to low frequencies in dynamic radio spectra. The spectral features of all solar type II radio bursts observed by the new radiospectrograph of the Astrophysikalisches Institut Potsdam in Tremsdorf during the time period from September 1, 1990 to December 31, 1993, i.e., during the first part of the ULYSSES spacecraft mission, are summarized and statistically investigated.
- ID:
- ivo://CDS.VizieR/J/A+A/390/717
- Title:
- Solar Velocities of the Sun in 1989-99 (IRIS++)
- Short Name:
- J/A+A/390/717
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The IRIS (International Research of Interior of the Sun) network has been operated continuously since July 1st 1989. To date, it has acquired more than a complete solar cycle of full-disk helioseismic data which has been used to constrain the structure and rotation of the deep solar interior. However, the duty cycle of the network data has never reached initial expectations. To improve this situation, several cooperations have been developed with teams collecting observations with similar instruments. This paper demonstrates that we are able to merge data from these different instruments in a consistent manner resulting in a very significant improvement in network duty cycle over more than one solar cycle initiating what we call the IRIS++ network.
- ID:
- ivo://CDS.VizieR/J/ApJS/230/21
- Title:
- Solar wind 3D magnetohydrodynamic simulation
- Short Name:
- J/ApJS/230/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a three-dimensional magnetohydrodynamic simulation of the solar wind to calculate cosmic-ray diffusion coefficients throughout the inner heliosphere (2R_{sun}_-3au). The simulation resolves large-scale solar wind flow, which is coupled to small-scale fluctuations through a turbulence model. Simulation results specify background solar wind fields and turbulence parameters, which are used to compute diffusion coefficients and study their behavior in the inner heliosphere. The parallel mean free path (mfp) is evaluated using quasi-linear theory, while the perpendicular mfp is determined from nonlinear guiding center theory with the random ballistic interpretation. Several runs examine varying turbulent energy and different solar source dipole tilts. We find that for most of the inner heliosphere, the radial mfp is dominated by diffusion parallel to the mean magnetic field; the parallel mfp remains at least an order of magnitude larger than the perpendicular mfp, except in the heliospheric current sheet, where the perpendicular mfp may be a few times larger than the parallel mfp. In the ecliptic region, the perpendicular mfp may influence the radial mfp at heliocentric distances larger than 1.5au; our estimations of the parallel mfp in the ecliptic region at 1 au agree well with the Palmer "consensus" range of 0.08-0.3au. Solar activity increases perpendicular diffusion and reduces parallel diffusion. The parallel mfp mostly varies with rigidity (P) as P^.33^, and the perpendicular mfp is weakly dependent on P. The mfps are weakly influenced by the choice of long-wavelength power spectra.
- ID:
- ivo://CDS.VizieR/J/ApJ/871/93
- Title:
- Solar wind speed from 5yr data with ACE spacecraft
- Short Name:
- J/ApJ/871/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The slow wind anisotropy is observed by Dasso+ 2005ApJ...635L.181D as elongation along the magnetic field direction in the magnetic self-correlation contours calculated from data sets of two-day-long data and averaged for five years in 1998-2002, which is consistent with prediction by the "critical balance cascade theory". More pronounced elongation at smaller scales than at larger scales has also been predicted by this theory. However, this prediction has not yet been checked by observations. Here, we present a check of the variation trend of the anisotropy with scales by presenting level contours of magnetic field and velocity self-correlations using intervals with durations varying from two days to one hour as observed by the Advanced Composition Explorer during 1998-2002 in the slow wind. We find that the level contours elongate along the magnetic field direction at durations of two days and one day. But they become isotropic for shorter intervals from about 10 hours to 1 hour. We also find that in the fast wind, the variation of the anisotropy with the scale has the same trend as in the slow wind. The 2D isotropic feature of the solar wind fluctuations shown by these statistical results is not consistent with the existing theory and will open a new avenue for studying solar wind turbulence.
- ID:
- ivo://CDS.VizieR/J/ApJ/891/54
- Title:
- Solar X-ray flares and associated CME speeds & widths
- Short Name:
- J/ApJ/891/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We recently repeated an earlier analysis by Garcia showing that large (>=M3.0) solar X-ray flares associated with solar energetic particle (SEP) events have significantly lower peak X-ray flux ratios R=(0.04-0.5nm)/(0.1-0.8nm), proxies for flare peak temperatures, than those without SEP events. As we expect SEP events to be produced by shocks ahead of fast coronal mass ejections (CMEs), a smaller R for an X-ray flare of a given peak flux Fp should also be more likely to be accompanied by a fast (Vcme>1000km/s) CME. We confirm this expectation, examine the role played by the ratios R in correlations between Fp and CME speeds Vcme, and then compare CME widths W, Vcme, and R with each other. We consider an apparent conflict between a global scaling model of eruptive events showing Vcme scaling with higher R and our confirmation that the Garcia analysis implies that faster CMEs are associated with flares of lower R. The R values are examined for 16 large flares of the well-studied AR 12192, for which nearly all flares had no associated CMEs. Those flares share the same high values of R as other active region (AR) flares with no CMEs. We also find that small (<M3.0) flares of filament eruptions leading to SEP events share the lower R values of larger flares with fast CMEs.
