- ID:
- ivo://CDS.VizieR/J/ApJS/91/461
- Title:
- EUV spectrum of solar active region
- Short Name:
- J/ApJS/91/461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present wavelengths and absolute intensities for 269 emission lines from a single active region observed by the Solar EUV Rocket Telescope and Spectrograph (SERTS) on 1989 May 5. For this catalog, the imaged spectra have been spatially averaged over a field of view 7"x276" cutting through the center of AR5464 at S18 W45. Wavelength coverage is 170-450A with a spectral resolution approaching 10,000. Most of the line positions are determined to 5mA or better, representing the highest accuracy yet obtained for solar wavelengths throughout this spectral interval. The relative photometric calibration of the instrument is good to +/-20% over its first-order range, and has been placed onto an absolute scale that should be correct to within a factor less than 2. Where known, identifications, atomic transitions and formation temperatures are also given. The identified lines arise from temperatures that cover the range 4.7<=logT<=6.8, providing information about the Sun's corona and upper transition region. Upper limits to the intensity of any emission line not included here can be estimated from the measured instrumental sensitivity. This averaged EUV spectrum should prove useful as a source of accurate wavelengths and intensities for emission characteristic of the high-temperature plasma associated with a solar active region and small subflare.
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- ID:
- ivo://CDS.VizieR/J/ApJ/543/1016
- Title:
- EUV spectrum of solar active region from SERTS-97
- Short Name:
- J/ApJ/543/1016
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Goddard Space Flight Center's Solar EUV Research Telescope and Spectrograph was flown on 1997 November 18, carrying an intensified CCD detector and a multilayer-coated toroidal diffraction grating with enhanced sensitivity over that of a standard gold-coated grating throughout the instrument's 299-353{AA} spectral bandpass. Spectra and spectroheliograms of NOAA Active Region 8108 (N21{deg}, E18{deg}) were obtained with a spectral resolution (instrumental FWHM) of 115m{AA}. Nearly 100 emission lines were observed in the spatially averaged active region spectrum. Spectra and spectroheliograms of quiet areas south of the region were also obtained. An end-to-end radiometric calibration of the rocket instrument was carried out at the Rutherford-Appleton Laboratory in the same facility that was used to calibrate the Coronal Diagnostic Spectrometer experiment on SOHO and using the same EUV light source. The accuracy of this calibration is confirmed by the excellent agreement between the measured and theoretical values of density- and temperature-insensitive line intensity ratios. Nine emission lines of Fe XV are identified in our spectrum; however, large differences between wavelengths in the CHIANTI database and some of the measured solar wavelengths, as well as inconsistencies of various theoretical intensity ratios, suggest a need for improvement in the Fe XV atomic physics parameters and/or the presence of unidentified blending lines.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A6
- Title:
- Evolution of solar irradiance during Holocene
- Short Name:
- J/A+A/531/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Long-term records of solar radiative output are vital for understanding solar variability and past climate change. Measurements of solar irradiance are available for only the last three decades, which calls for reconstructions of this quantity over longer time scales using suitable models. We present a physically consistent reconstruction of the total solar irradiance for the Holocene.
- ID:
- ivo://CDS.VizieR/J/A+AS/129/41
- Title:
- Fe I line shifts in the Sun
- Short Name:
- J/A+AS/129/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Central wavelengths measured in the FTS disc-centre spectrum, in the FTS flux spectrum, rest wavelengths, excitation potentials, transition probabilities (log(gfs)) and line equivalent widths at the centre of the disc when available (from Moore et al. 1966 (The Solar Spectrum 2935{AA} to 8770{AA}, National Bureau of Standards Monograph 61) and compiled by A. D. Wittmann, private communication). An asterisk in the equivalent width means that the line has a blend.
- ID:
- ivo://CDS.VizieR/J/A+A/370/1071
- Title:
- Fe XII UV line intensity ratios
- Short Name:
- J/A+A/370/1071
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new set of radiative and electron collisional data for Fe XII was presented in two earlier papers. In the present work, we derive level populations and theoretical line intensities for a range of plasma densities and temperatures. Observations of Fe XII lines obtained with the Solar EUV Rocket Telescope and Spectrograph are analysed both as a check on the quality of the new atomic data and to determine the electron density in active regions and the quiet Sun. The discrepancy between the electron density values determined from Fe XII line intensity ratios and those obtained from other ions is investigated.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A132
- Title:
- GLE integral intensities
- Short Name:
- J/A+A/647/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Fluences of solar energetic particles (SEPs) are not easy to evaluate, especially for high-energy events (i.e. ground-level enhancements, GLEs). Earlier estimates of event-integrated SEP fluences for GLEs were based on partly outdated assumptions and data, and they required revisions. Here, we present the results of a full revision of the spectral fluences for most major SEP events (GLEs) for the period from 1956-2017 using updated low-energy flux estimates along with greatly revisited high-energy flux data and applying the newly invented reconstruction method including an improved neutron-monitor yield function. Low- and high-energy parts of the SEP fluence were estimated using a revised space-borne/ionospheric data and ground-based neutron monitors, respectively. The measured data were fitted by the modified Band function spectral shape. The best-fit parameters and their uncertainties were assessed using a direct Monte Carlo method. A full reconstruction of the event-integrated spectral fluences was performed in the energy range above 30MeV, parametrised and tabulated for easy use, along with estimates of the 68% confidence intervals. This forms a solid basis for more precise studies of the physics of solar eruptive events and the transport of energetic particles in the interplanetary medium, as well as the related applications.
- ID:
- ivo://CDS.VizieR/J/ApJ/797/50
- Title:
- Global energetics of solar flares. I.
- Short Name:
- J/ApJ/797/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first part of a project on the global energetics of solar flares and coronal mass ejections that includes about 400 M- and X-class flares observed with Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). We calculate the potential (E_p_), the nonpotential (E_np_) or free energies (E_free_=E_np_-E_p_), and the flare-dissipated magnetic energies (E_diss_). We calculate these magnetic parameters using two different NLFFF codes: the COR-NLFFF code uses the line-of-sight magnetic field component B_z_ from HMI to define the potential field, and the two-dimensional (2D) coordinates of automatically detected coronal loops in six coronal wavelengths from AIA to measure the helical twist of coronal loops caused by vertical currents, while the PHOT-NLFFF code extrapolates the photospheric three-dimensional (3D) vector fields. We find agreement between the two codes in the measurement of free energies and dissipated energies within a factor of <~3. The size distributions of magnetic parameters exhibit powerlaw slopes that are approximately consistent with the fractal-diffusive self-organized criticality model. The magnetic parameters exhibit scaling laws for the nonpotential energy, E_np_{propto}E_p_^1.02^, for the free energy, E_free_{propto}E_p_^1.7^ and E_free_{propto}B_{phi}_^1.0^L^1.5^, for the dissipated energy, E_diss_{propto}E_p_^1.6^ and E_diss_{propto}E_free_^0.9^ , and the energy dissipation volume, V{propto}E_diss_^1.2^. The potential energies vary in the range of E_p_=1x10^31^-4x10^33^erg, while the free energy has a ratio of E_free_/E_p_{approx}1%-25%. The Poynting flux amounts to F_flare_{approx}5x10^8^-10^10^erg/cm2/s during flares, which averages to F_AR_{approx}6x10^6^erg/cm2/s during the entire observation period and is comparable with the coronal heating rate requirement in active regions.
- ID:
- ivo://CDS.VizieR/J/ApJ/802/53
- Title:
- Global energetics of solar flares. II.
- Short Name:
- J/ApJ/802/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the second part of a project on the global energetics of solar flares and coronal mass ejections that includes about 400 M- and X-class flares observed with the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) during the first 3.5yr of its mission. In this Paper II we compute the differential emission measure (DEM) distribution functions and associated multithermal energies, using a spatially-synthesized Gaussian DEM forward-fitting method. The multithermal DEM function yields a significantly higher (by an average factor of ~14), but more comprehensive (multi-) thermal energy than an isothermal energy estimate from the same AIA data. We find a statistical energy ratio of E_th_/E_diss_~2-40% between the multithermal energy E_th_ and the magnetically dissipated energy E_diss_, which is an order of magnitude higher than the estimates of Emslie et al. (2012ApJ...759...71E). For the analyzed set of M- and X-class flares we find the following physical parameter ranges: L=10^8.2^-10^9.7^cm for the length scale of the flare areas, T_p_=10^5.7^-10^7.4^K for the DEM peak temperature, T_w_=10^6.8^-10^7.6^K for the emission measure-weighted temperature, n_p_=10^10.3^-10^11.8^/cm3 for the average electron density, EM_p_=10^47.3^-10^50.3^/cm3 for the DEM peak emission measure, and E_th_=10^26.8^-10^32.0^erg for the multithermal energies. The deduced multithermal energies are consistent with the RTV scaling law E_th,RTV_=73x10^-10^T_p_^3^L_p_^2^, which predicts extremal values of E_th,max_~1.5x10^33^erg for the largest flare and E_th,min_~1x10^24^erg for the smallest coronal nanoflare. The size distributions of the spatial parameters exhibit powerlaw tails that are consistent with the predictions of the fractal-diffusive self-organized criticality model combined with the RTV scaling law.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/27
- Title:
- Global energetics of solar flares. III.
- Short Name:
- J/ApJ/832/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study entails the third part of a global flare energetics project, in which Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) data of 191 M and X-class flare events from the first 3.5yrs of the Solar Dynamics Observatory mission are analyzed. We fit a thermal and a nonthermal component to RHESSI spectra, yielding the temperature of the differential emission measure (DEM) tail, the nonthermal power-law slope and flux, and the thermal/nonthermal cross-over energy e_co_. From these parameters, we calculate the total nonthermal energy E_nt_ in electrons with two different methods: (1) using the observed cross-over energy e_co_ as low-energy cutoff, and (2) using the low-energy cutoff e_wt_ predicted by the warm thick-target bremsstrahlung model of Kontar et al. Based on a mean temperature of T_e_=8.6MK in active regions, we find low-energy cutoff energies of e_wt_=6.2+/-1.6keV for the warm-target model, which is significantly lower than the cross-over energies e_co_=21+/-6keV. Comparing with the statistics of magnetically dissipated energies E_mag_ and thermal energies E_th_ from the two previous studies, we find the following mean (logarithmic) energy ratios with the warm-target model: E_nt_=0.41E_mag_, E_th_=0.08E_mag_, and E_th_=0.15E_nt_. The total dissipated magnetic energy exceeds the thermal energy in 95% and the nonthermal energy in 71% of the flare events, which confirms that magnetic reconnection processes are sufficient to explain flare energies. The nonthermal energy exceeds the thermal energy in 85% of the events, which largely confirms the warm thick-target model.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/105
- Title:
- Global energetics of solar flares. IV. CME
- Short Name:
- J/ApJ/831/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study entails the fourth part of a global flare energetics project, in which the mass m_cme_, kinetic energy E_kin_, and the gravitational potential energy E_grav_ of coronal mass ejections (CMEs) is measured in 399 M and X-class flare events observed during the first 3.5 years of the Solar Dynamics Observatory (SDO) mission, using a new method based on the extreme ultraviolet (EUV) dimming effect. EUV dimming is modeled in terms of a radial adiabatic expansion process, which is fitted to the observed evolution of the total emission measure of the CME source region. The model derives the evolution of the mean electron density, the emission measure, the bulk plasma expansion velocity, the mass, and the energy in the CME source region. The EUV dimming method is truly complementary to the Thomson scattering method in white light, which probes the CME evolution in the heliosphere at r>~2R_{sun}_, while the EUV dimming method tracks the CME launch in the corona. We compare the CME parameters obtained in white light with the LASCO/C2 coronagraph with those obtained from EUV dimming with the Atmospheric Imaging Assembly onboard the SDO for all identical events in both data sets. We investigate correlations between CME parameters, the relative timing with flare parameters, frequency occurrence distributions, and the energy partition between magnetic, thermal, nonthermal, and CME energies. CME energies are found to be systematically lower than the dissipated magnetic energies, which is consistent with a magnetic origin of CMEs.
