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A Long-Term Dissipation of the EUV He?ii (30.4 nm) Segmentation in Full-Disk Solar Images
摘要： Some quiet-Sun days observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) during the time interval in 2010 – 2017 were used to continue our previous analyses reported by Didkovsky and Gurman (Solar Phys. 289, 153, 2014a) and Didkovsky, Wieman, and Korogodina (Solar Phys. 292, 32, 2017). The analysis consists of determining and comparing spatial spectral ratios (spectral densities over some time interval) from spatial (segmentation-cell length) power spectra. The ratios were compared using modeled compatible spatial frequencies for spectra from the Extreme ultraviolet Imaging Telescope (EIT) on-board the Solar and Heliospheric Observatory (SOHO) and from AIA images. With the new AIA data added to the EIT data we analyzed previously, the whole time interval from 1996 to 2017 reported here is approximately the length of two “standard” solar cycles (SC). The spectral ratios of segmentation-cell dimension structures show a signi?cant and steady increase with no detected indication of SC-related returns to the values that characterize the SC minima. This increase in spatial power at high spatial frequencies is interpreted as a dissipation of medium-size EUV network structures to smaller-size structures in the transition region. Each of the latest ratio changes for 2010 through 2017 spectra calculated for a number of consecutive short-term intervals has been converted into monthly mean ratio (MMR) changes. The MMR values demonstrate variable sign and magnitudes, thus con?rming the solar nature of the changes. These changes do not follow a “typical” trend of instrumental degradation or a long-term activity pro?le from the He II (30.4 nm) irradiance measured by the Extreme ultraviolet Spectrophotometer (ESP) either. The ESP is a channel of the Extreme ultraviolet Variability Experiment (EVE) on-board SDO.
关键词： Solar cycle, observations,Solar irradiance,Granulation
更新于2025-09-10 09:29:36
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Revision of the Sun’s Spectral Irradiance as Measured by SORCE SIM
摘要： The Spectral Irradiance Monitor (SIM) instrument on board the Solar Radiation and Climate Experiment (SORCE) performs daily measurements of the solar spectral irradiance (SSI) from 200 to 2400 nm. Both temporal and spectral corrections for instrument degradation have been built on physical models based on comparison of two independent channels with different solar exposure. The present study derives a novel correction for SIM degradation using the total solar irradiance (TSI) measurements from the Total Irradiance Monitor (TIM) on SORCE. The correction is applied to SIM SSI data from September 2004 to October 2012 over the wavelength range from 205 nm to 2300 nm. The change in corrected, integrated SSI agrees within 0.1 W m?2 (1σ ) with SORCE TIM TSI and independently shows agreement with the SATIRE-S and NRLSSI2 solar models within measurement uncertainties.
关键词： Solar spectral irradiance,Degradation correction,Solar spectrum,Solar variability,Solar cycle
更新于2025-09-04 15:30:14
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GONG p-Mode Parameters Through Two Solar Cycles
摘要： We investigate the parameters of global solar p-mode oscillations, namely damping width (cid:2), amplitude A, mean squared velocity (cid:2)v2(cid:3), energy E, and energy supply rate dE/dt, derived from two solar cycles’ worth (1996 – 2018) of Global Oscillation Network Group (GONG) time series for harmonic degrees l = 0 – 150. We correct for the effect of ?ll factor, apparent solar radius, and spurious jumps in the mode amplitudes. We ?nd that the amplitude of the activity-related changes of (cid:2) and A depends on both frequency and harmonic degree of the modes, with the largest variations of (cid:2) for modes with 2400 μ Hz ≤ ν ≤ 3300 μ Hz and 31 ≤ l ≤ 60 with a minimum-to-maximum variation of 26.6 ± 0.3% and of A for modes with 2400 μ Hz ≤ ν ≤ 3300 μ Hz and 61 ≤ l ≤ 100 with a minimum-to-maximum variation of 27.4 ± 0.4%. The level of correlation between the solar radio ?ux F10.7 and mode parameters also depends on mode frequency and harmonic degree. As a function of mode frequency, the mode amplitudes are found to follow an asymmetric Voigt pro?le with νmax = 3073.59 ± 0.18 μ Hz. From the mode parameters, we calculate physical mode quantities and average them over speci?c mode frequency ranges. In this way, we ?nd that the mean squared velocities (cid:2)v2(cid:3) and energies E of p modes are anticorrelated with the level of activity, varying by 14.7 ± 0.3% and 18.4 ± 0.3%, respectively, and that the mode energy supply rates show no signi?cant correlation with activity. With this study we expand previously published results on the temporal variation of solar p-mode parameters. Our results will be helpful to future studies of the excitation and damping of p modes, i.e., the interplay between convection, magnetic ?eld, and resonant acoustic oscillations.
关键词： Helioseismology, observations,Oscillations, solar,Solar Cycle, observations
更新于2025-09-04 15:30:14