- ID:
- ivo://CDS.VizieR/J/A+A/329/721
- Title:
- Sensitivity indicators of Fraunhofer lines
- Short Name:
- J/A+A/329/721
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of calculations of the sensitivity indicators to the temperature, as well as the average geometrical heights of localization of the effective response to the temperature variations are presented for the central line depths, for the line depths on half-width, and for the equivalent widths of the 604 Fe I and 58 Fe II absorption lines. This list of unblended solar lines in the range of the wavelengths 401.0-901.0nm contains the maximum of lines suitable for the analysis of the fine structure of the line profiles and primarily for study of the line asymmetries.
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- ID:
- ivo://CDS.VizieR/J/ApJ/891/79
- Title:
- Single storms and the related ICMEs from 1998-2011
- Short Name:
- J/ApJ/891/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Interplanetary coronal mass ejections (ICMEs) could be classified into magnetic clouds (MCs) and non-MCs according to their magnetic field signatures, and into prominence-inside ICMEs (PIs) and non-PIs based on whether they contain colder and higher helium abundance plasmas than the solar wind. It is known that the MCs often lead to magnetic storms. However, whether or not the PIs have significant geoeffectiveness is unclear. This statistical work studies the southward interplanetary magnetic field (IMF) magnitude of the PIs, and the related magnetic storms' level. The data include the IMF and plasma moments measured by ACE and WIND, and the Dst index from 1998 to 2011. The hypothesis test based on the proportions of two groups is used to analyze 95 ICMEs related to single storms (SSs). The results show that the magnetic storms caused by the PIs mostly distribute at a strong level, while that caused by the non-PIs and by all the 95 ICMEs mostly distribute at a moderate level. The PIs have a significantly higher probability of generating SSs than the non-PIs. Moreover, the MCs containing carbon-cold and helium-enhanced materials (MC&PIs) have the highest fraction of minimum Bz, less than -11 nT. Since the MC&PIs have large-scale magnetic flux rope and prominence material, the stronger southward IMF is probably provided by the prominence. It is in accordance with the observed injection of enhanced twisted flux ropes to prominence. Therefore, the detailed eruption and propagation processes of the three-part coronal mass ejections deserve more concern from a space weather perspective.
- ID:
- ivo://CDS.VizieR/J/ApJS/239/12
- Title:
- Small-scale magnetic flux ropes in the solar wind
- Short Name:
- J/ApJS/239/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have developed a new automated small-scale magnetic flux ropes (SSMFR) detection algorithm based on the Grad-Shafranov (GS) reconstruction technique. We have applied this detection algorithm to the Wind spacecraft in situ measurements during 1996-2016, covering two solar cycles, and successfully detected a total number of 74241 small-scale magnetic flux rope events with duration from 9 to 361min. This large number of small-scale magnetic flux ropes has not been discovered by any other previous studies through this unique approach. We perform statistical analysis of the small-scale magnetic flux rope events based on our newly developed database, and summarize the main findings as follows. (1) The occurrence of small-scale flux ropes has strong solar-cycle dependency with a rate of a few hundred per month on average. (2) The small-scale magnetic flux ropes in the ecliptic plane tend to align along the Parker spiral. (3) In low-speed (<400km/s) solar wind, the flux ropes tend to have lower proton temperature and higher proton number density, while in high-speed (>=400km/s) solar wind, they tend to have higher proton temperature and lower proton number density. (4) Both the duration and scale size distributions of the small-scale magnetic flux ropes obey a power law. (5) The waiting time distribution of small-scale magnetic flux ropes can be fitted by an exponential function (for shorter waiting times) and a power-law function (for longer waiting times). (6) The wall-to-wall time distribution obeys double power laws with the break point at 60 minutes (corresponding to the correlation length). (7) The small-scale magnetic flux ropes tend to accumulate near the heliospheric current sheet (HCS).
- ID:
- ivo://CDS.VizieR/J/A+A/347/348
- Title:
- Solar abundance of iron
- Short Name:
- J/A+A/347/348
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Numerous papers on the solar photospheric abundance of iron have recently been published leading to a longstanding debate concerning rather different results obtained from the analyses of Fe I lines and, to a lesser extent, of Fe II lines. Based on a set of 65 solar Fe I lines, with accurate transition probabilities as well as new accurate damping constants, we construct a new empirical photospheric model. We succeed to reconcile abundance results obtained from low and high excitation Fe I lines as well as from Fe II lines and derive a solar photospheric abundance of iron, A_Fe_=7.50+/-0.05, which perfectly agrees with the meteoritic value.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A137
- Title:
- Solar acoustic modes in period 1996-2014
- Short Name:
- J/A+A/578/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Solar activity has significantly changed over the last two Schwabe cycles. After a long and deep minimum at the end of Cycle 23, the weaker activity of Cycle 24 contrasts with the previous cycles. In this work, the response of the solar acoustic oscillations to solar activity is used in order to provide insights into the structural and magnetic changes in the sub-surface layers of the Sun during this on-going unusual period of low activity. We analyze 18 years of continuous observations of the solar acoustic oscillations collected by the Sun-as-a-star GOLF instrument on board the SoHO spacecraft. From the fitted mode frequencies, the temporal variability of the frequency shifts of the radial, dipolar, and quadrupolar modes are studied for different frequency ranges that are sensitive to different layers in the solar sub-surface interior. The low-frequency modes show nearly unchanged frequency shifts between Cycles 23 and 24, with a time evolving signature of the quasi-biennial oscillation, which is particularly visible for the quadrupole component revealing the presence of a complex magnetic structure. The modes at higher frequencies show frequency shifts that are 30% smaller during Cycle 24, which is in agreement with the decrease observed in the surface activity between Cycles 23 and 24. The analysis of 18 years of GOLF oscillations indicates that the structural and magnetic changes responsible for the frequency shifts remained comparable between Cycle23 and Cycle 24 in the deeper sub-surface layers below 1400km as revealed by the low-frequency modes. The frequency shifts of the higher-frequency modes, sensitive to shallower regions, show that Cycle 24 is magnetically weaker in the upper layers of Sun
- ID:
- ivo://CDS.VizieR/J/A+A/587/A150
- Title:
- Solar activity during the Holocene
- Short Name:
- J/A+A/587/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cosmogenic isotopes provide the only quantitative proxy to analyze the long-term solar variability over the centennial time scale. While an essential progress has been achieved in both measurements and modelling of the cosmogenic proxy, uncertainties still remain in the determination of the geomagnetic dipole moment evolution. Here we aim at improving the reconstruction of solar activity over the past nine millennia using a multi-proxy approach. We use records of the ^14^C and ^10^Be cosmogenic isotopes, up-to-date numerical models of the isotope production and transport in the Earth's atmosphere, and available geomagnetic field reconstructions, including a new reconstruction relying on an updated archeo/paleointensity database. The obtained series were analyzed using the SSA (Singular Spectrum Analysis) method to study the millennial-scale trends. A new reconstruction of the geomagnetic dipole field moment, referred to as GMAG.9k, is built for the last nine millennia. New reconstructions of solar activity covering the last nine millennia, quantified in terms of sunspot numbers, are presented and analyzed. A conservative list of Grand minima and maxima is also provided. The primary components of the reconstructed solar activity, as determined using the SSA method, are different for the ^14^C and ^10^Be based series. This shows that these primary components can only be ascribed to long-term changes in the terrestrial system, and not to the Sun. These components have therefore been removed from the reconstructed series. In contrast, the secondary SSA components of the reconstructed solar activity are found to be dominated by a common ~2400-year quasi-periodicity, the so-called Hallstatt cycle, in both the ^14^C and ^10^Be based series. This Hallstatt cycle thus appears to be related to solar activity. Finally, it is shown that the Grand minima and Grand maxima occurred intermittently over the studied period, with clustering near highs and lows of the Hallstatt cycle, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/562/L10
- Title:
- Solar activity reconstructed for 3 millennia
- Short Name:
- J/A+A/562/L10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sun shows a large variability in its magnetic activity, from Grand minima to Grand maxima, but the nature of the variability is not fully understood, mostly because of an insufficient length of the directly observed solar activity records and of uncertainties related to long-term reconstructions. Here we present a new adjustment-free reconstruction of solar activity over three millennia and study its different modes. We present a new adjustment-free, physical reconstruction of solar activity over the past three millennia, using the latest verified carbon cycle, ^14^C production and archeomagnetic field models. This great improvement allows us to study different modes of solar activity at unprecedented level of details. The distribution of solar activity is clearly bi-modal implying the existence of distinct modes of activity. The main regular activity mode corresponds to moderate activity varying in a relatively narrow band between sunspot number 20 and 67. The existence of a separate Grand minimum mode with reduced solar activity, which cannot be explained by random fluctuations of the regular mode, is confirmed at a high confidence level. The possible existence of a separate Grand maximum mode is also suggested, but the statistics is too low for a confident conclusion to be reached. The Sun is shown to operate in distinct modes - a main general mode, a Grand minimum mode corresponding to an inactive Sun, and a possible Grand maximum mode corresponding to an unusually active Sun. These results provide important constraints for both dynamo models of Sun-like stars and investigations of possible solar influence on Earth's climate.
- ID:
- ivo://CDS.VizieR/VI/97
- Title:
- Solar and Lunar Eclipses: 1996-2020
- Short Name:
- VI/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Solar Eclipses - During the twenty-five year period 1996-2020, some portion of the Moon's shadow will sweep across the Earth a total of fifty-six times. Twenty-one of these events result in partial solar eclipses, seventeen of them are annular eclipses, sixteen more are total eclipses and the remaining two are both annular and total along sections of their narrow paths. Local circumstances at the instant of greatest eclipse1 for every event during this quarter century period are presented in solar.dat. The date and Universal Time of the instant of greatest eclipse are found in the first two columns. The eclipse type is given (T=Total, A=Annular, AT=Annular/Total or P=Partial) along with the Saros series, as defined by van den Bergh (1955). The magnitude of the eclipse is defined as the fraction of the Sun's diameter obscured at greatest eclipse. The latitude and longitude of the umbra are given for the instant of greatest eclipse, along with the Sun's altitude, the width of the path (kilometers) and the duration of totality or annularity. For partial eclipses, the latitude and longitude of the point closest to the umbra's axis at the instant of greatest eclipse are listed. The altitude of the Sun at this location is 0 degrees. Note: Greatest eclipse is defined as the instant when the axis of the Moon's shadow passes closest to the Earth's center. For total eclipses, the instant of greatest eclipse is virtually identical to the instants of greatest magnitude and greatest duration. However, for annular eclipses, the instant of greatest duration may occur at either the time of greatest eclipse or near the sunrise and sunset points of the eclipse path. Lunar Eclipses - During the twenty-five year period 1996-2020, the Moon will swing through some portion of Earth's shadow a total of fifty-eight times. Twenty-three of these events result in penumbral lunar eclipses, twelve of them are partial (umbral) eclipses, twenty-three more are total lunar eclipses. Local circumstances at the instant of greatest eclipse1 for every event during this quarter century period are presented in Table 1. The date and Universal Time of the instant of greatest eclipse are found in the first two columns. The eclipse type is given (T=Total, P=Partial [Umbral], or P=Penumbral) along with the Saros series, as defined by van den Bergh (1955). The penumbral and umbral magnitudes of the eclipse are defined as the fraction of the Moon's diameter obscured by either shadow at greatest eclipse. The partial and total semi-durations of the eclipse along with the Greenwich Siderial Time at midnight, and the Moon's Right Ascension and Declination are listed. The start and end times of the partial eclipse can be calculated by respectively subtacting and adding the partial semi-duration (i.e. - Par. SDur) to the instant of greatest eclipse. Likewise, the start and end times of the total eclipse can be calculated by respectively subtacting and adding the total semi-duration (i.e. - Total SDur) to the instant of greatest eclipse. Note: Greatest eclipse is defined as the instant when the Moon passes closest to the axis of Earth's shadow(s). This marks the instant when the Moon is deepest in Earth's shadow(s).
- ID:
- ivo://CDS.VizieR/J/A+A/539/A13
- Title:
- Solar bipolar magnetic fields
- Short Name:
- J/A+A/539/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The area asymmetry between the preceding and following regions of opposite magnetic polarity in a bipolar sunspot group has been known since the studies of Hale and his colleagues in the early 20th century. This area asymmetry, however, has not yet been investigated quantitatively using magnetograms. We quantitatively define the area asymmetry of bipolar magnetic fields in the photosphere of active regions on the Sun, and investigate correlations between the area asymmetry and other parameters.
- ID:
- ivo://CDS.VizieR/J/ApJ/709/1238
- Title:
- Solar Coronal Mass Ejection
- Short Name:
- J/ApJ/709/1238
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relative importance of different initiation mechanisms for coronal mass ejections (CMEs) on the Sun is uncertain. One possible mechanism is the loss of equilibrium of coronal magnetic flux ropes formed gradually by large-scale surface motions. In this paper, the locations of flux rope ejections in a recently developed quasi-static global evolution model are compared with observed CME source locations over a 4.5 month period in 1999. Using extreme ultraviolet data, the low-coronal source locations are determined unambiguously for 98 out of 330 CMEs. Our results suggest that while the gradual formation of magnetic flux ropes over weeks can account for many observed CMEs, especially at higher latitudes, there exists a second class of CMEs (at least half) for which dynamic active region flux emergence on shorter timescales must be the dominant factor.
