Solar Physics最新文献

I will review the history of the helioseismic observations since the beginning of the field. I will explain how each instrument was designed based upon the required observables, and to which modes these instruments are sensitive. The impact of these sensitivities on the rotation and structure inversion will be developed. I will conclude with what remains to be done in this field for the future of detection.

The study of precursors preceding Forbush decreases belongs to the applied side of space research and to a relatively new area of modern science, that of Space Weather. Moreover, it is a pioneering and innovative research field with interesting results. In the framework of the above, the Athens Cosmic Ray Group of the National and Kapodistrian University of Athens (NKUA) and the Cosmic Ray Group of the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation of the Russian Academy of Sciences (IZMIRAN) have collaborated in investigating predecreases and/or preincreases of the cosmic-ray intensity before the development of a Forbush decrease, that could serve as precursory signs of the upcoming event and consequently play a significant role in the prediction of cosmic-ray and geomagnetic activity. In this work, the criterion of the increased anisotropy one hour before the onset of the event ((A_{mathit{xyb}}), %) is being examined for large Forbush decreases. Specifically, Forbush decreases with magnitude greater than 5%, accompanied with geomagnetic storms (i.e., geomagnetic index Dst < −100 nT and 5 ≤ Kp-index ≤ 9) and characterized by (A_{mathit{xyb}} geq ) 0.8% were analyzed. The catalog of Forbush Effects and Interplanetary Disturbances of IZMIRAN was used for analyzing the solar, interplanetary, and geomagnetic conditions during each event. Additionally, for a visual inspection of the precursory signs in each event the Ring of Stations method (i.e., asymptotic longitude–time diagram) was applied. Results revealed that the increased anisotropy one hour before the main phase of the Forbush decrease is a valid and reliable criterion of precursors that can be eventually used in the development of a Forbush decrease prognosis application tool.

The Hard X-ray Imager (HXI) aboard the Advanced Space-based Solar Observatory (ASO-S) is an instrument designed to observe hard X-ray (HXR) spectra and images of solar flares. Having 91 subcollimators to modulate incident X-rays, HXI can obtain 91 modulation data and 45 visibilities to reconstruct images with a spatial resolution as high as (sim 3.1) arcsec. HXI was launched on 9 October 2022 and powered up on 17 October 2022. After the on-orbit testing phase lasting for three months, HXI was ready for regular observations on 18 January 2023. With fine-tuning of the detectors and electronics, we were able to expand the energy range from (sim 30) – 200 keV to (sim 10) keV – 300 keV, which significantly raised the scientific values of the data and the number of detected flare events. This paper presents the changes and improvements of HXI instrument since 2019, the important ground tests, on-orbit tests, and calibration works. We also present the light curves, spectra, and reconstructed images of one flare observed by HXI on 6 January 2023.

The Extreme ultraviolet Variability Experiment (EVE) is one of three instruments onboard the Solar Dynamics Observatory (SDO). This paper focuses on using the “A” channel on the Multiple EUV Grating Spectrographs (MEGS-A) on EVE, which measures wavelengths of 5 – 37 nm, to improve the wavelength scale accuracy and spectral resolution during solar flares. EVE’s least processed (Level 0B) data product is used to create updated wavelength scales that are shown, through this analysis, to make more precise spectral measurements compared to EVE Level 2 data. An X2.2 class flare that occurred on 15 February 2011, SOL2011-02-15T0156, was used to derive the pixel-to-wavelength scales. An improvement range of 5.21% to 11.35% was found in the emission line widths. In the future, these measurements can be used for improved Doppler velocity calculations of the accelerated plasma of various temperatures during solar flares.

An experiment measuring the solar far-ultraviolet-ultraviolet (FUV-UV) irradiance with spectral resolution better than 0.1 nm in the wavelength range from 170 to 400 nm was carried out by the “HongHu-6” high-altitude balloon that flew to the bottom region of the near-space in September 2022. This experiment was based on the fact that solar FUV-UV penetrates through a complex cross-section window of the upper atmosphere, from outer to near space. The solar FUV-UV deposits energy in the upper atmosphere, which provides a key to answer scientific questions on the most important energy contributor to overall heating sources of the near space and how the near-space environment responds to solar activities. In the wavelength range between 150 and 210 nm, irradiance maps from active regions of the solar corona, the comparative small cross-section of molecular oxygen allows certain wavelengths of the band to arrive at altitudes between 20 and 30 km above the ground, indicating solar flares could directly impact the bottom region of the near space. Solar UV irradiance in the wavelength range 210 – 400 nm is absorbed by the upper atmosphere as a function of wavelength, and energy is deposited vertically in the lower regions of the near space. This experiment historically provides measurement data to fill a gap in the wavelength shorter than 280 nm in the lower regions of the near space. The solar FUV-UV spectrometer (SUVS) is a compact instrument based on improved Roland circle optics to adapt to the “HongHu-6” balloon payload platform. In this paper, we introduce the scientific goals of the solar FUV-UV spectrum measurement experiment, provide information on the SUVS instrument preflight calibration, and present the first results from the flight data.

The Mt. Wilson Observatory archive of observations of solar disk magnetic fields, Doppler velocities, and spectral line intensities is a resource for studying the Sun’s state from 1967 to 2013. Instrument changes/upgrades during this time must be considered when interpreting this record. Portions of this record have been previously released. This publication documents the data record in order to allow its independent interpretation. The archive is available through two directory trees which can be accessed at http://sha.stanford.edu/mwo/msm.html. The calibration of the observations is impacted by the solar surface convective flows, which produce offsets for both differential rotation and meridional circulation functions. The effects of these offsets have been reduced in this and other publications by temporal averaging.

We study the long-term variation of the zonal and meridional flows from Solar Cycle 23 to 25 derived with ring-diagram analysis applied to Global Oscillation Network Group (GONG) and Helioseismic and Magnetic Imager (HMI) Dopplergrams. We focus mainly on the subsurface flows averaged over depths from 2.0 Mm to 11.6 Mm since their long-term variations are sufficiently similar. First, we examine their temporal variations for systematic artifacts. We find that the GONG-derived zonal flows increase almost linearly with time until about 2020, which we correct with a linear regression. Then we determine the average differences between the GONG- and HMI-derived flows. The average offset is (0.15 pm 0.53) m s⁻¹ for the zonal flow and (0.65 pm 0.08) m s⁻¹ for the meridional flow within (pm 30.0^{circ }) latitude. The average difference of the meridional flow is nearly constant with latitude in this range, whereas that of the zonal flow varies similarly to that of the magnetic activity. At latitudes of 45.0^∘ and higher, the differences increase and are larger than those at lower latitudes, which is most likely due to the combined effect of different spatial resolution between GONG and HMI and geometric projection effects. Finally, we combine the GONG- and HMI-derived flows and find, as expected, that the solar-cycle variation is the dominant long-term variation. At each latitude within (pm 30.0^{circ }), the meridional-flow pattern appears ahead of the zonal-flow pattern by an average lag of (0.926 pm 0.126) years. The equatorward and poleward branches of the solar-cycle variation occur at 52.5^∘ with the poleward branches present near 60.0^∘ and the equatorward ones at lower latitudes. The zonal flows at 52.5^∘ and 60.0^∘ show an additional trend and decrease by (2.9 pm 0. 3) m s⁻¹ over 11 years. This decrease might nevertheless be related to the solar cycle and imply that the flow amplitudes are anticorrelated with the strength of the associated solar cycle.

This study explores the multi-fractal properties of cosmic-ray (CR) counts collected from two mid-latitude neutron-monitor stations, Newark (NEWK) and Irkutsk 3 (IRK3), and two high-latitude stations, Thule (THUL) and Inuvik (INVK), during periods of severe geomagnetic storms. By employing multi-fractal along with time-series analysis, we did an in-depth examination of CR count variations to demonstrate the effectiveness of these methods in analyzing complex signals associated with astrophysical and solar phenomena. The findings reveal that CR count rates across stations at different latitudes exhibit multi-fractal characteristics, reflecting a range of scaling exponents that capture varying degrees of correlation and variability within the system. The results underscore that solar activity, geomagnetic events, and interactions with Earth’s magnetic field play a more crucial role in determining multi-fractality than the geographic location of the measurement station. Moreover, the study shows that geomagnetic events exert a stronger influence on the multi-fractal properties of CR count rate than the geographic location of station, underscoring the impact of solar storms and Earth’s magnetic field on the distribution and intensity of CRs. This work emphasizes the value of multi-fractal analysis as a powerful tool for investigating the complex nature of CR counts and its sensitivity to both extraterrestrial and terrestrial factors.

Effective predicting sunspot numbers (SSN) is the complex task of studying space weather, solar activity, satellite communication, and Earth’s climate. Developing a reliable SSN forecasting model is difficult because SSN time series exhibit complex patterns, nonlinearity, and nonstationarity characteristics. The state-of-the-art shows that deep-learning models often need help capturing SSN data’s intricate dynamics and long-term dependencies. The SSN time series’ decomposed trend and seasonal and residual characteristics may provide better information on long-term dependencies and associated dynamics for effective learning. In this research, the vipin-deep-decomposed-recomposed rolling-window (vD2R2w) models have been proposed with a combination of time-series decomposition, deep-learning models, and a rolling-window method to predict the SSN accurately. The proposed vD2R2w models have been evaluated over four datasets and consistently outperform traditional deep-learning models. The model improves the performance in terms of RMSE, MAPE, and (R^{2}) over the datasets as SSN_Daily: 84.18% (RMSE), 10.38% (MAPE), and 3.504% ((R^{2})); SSN_Monthly: 39.5% (RMSE), 26.06% (MAPE), and 7.258% ((R^{2})); SSN_MonthlyMean: 178.32% (RMSE), 54.83% (MAPE), and 1.56% ((R^{2})); and SSN_Yearly: 6.06% (RMSE), 10.36% (MAPE), and 1.366% ((R^{2})). Further, the superiority of the vD2R2w models is validated through AIC & BIC, Diebold Mariano test, and Friedman ranking statistical tests. Additionally, the vD2R2w model has forecasted the peak value of Solar Cycles (SC) and time, i.e., SC25: 127.16 (± 6.83) in 2025 and SC26: 191.71 (± 43.37) in 2035. The analysis of proposed model performances and statistical validation over various measures with four SSNs have concluded that the vD2R2w model outperforms the traditional models and is a reliable framework for SSN time series forecasting. Implementing the proposed model may benefit domains such as space-weather monitoring, satellite communication planning, and solar energy forecasting that rely on accurate SSN predictions.

Solar type V radio bursts are associated with type III bursts. Several processes have been proposed to interpret the association, electron distribution, and emission. We present the observation of a unique type V event observed by e-CALLISTO on 7 May 2021. The type V radio emission follows a group of U bursts. Unlike the unpolarized U bursts, the type V burst is circularly polarized, leaving room for a different emission process. Its starting edge drifts to higher frequency four times slower than the descending branch of the associated U burst. The type V processes seem to be ruled by electrons of lower energy. The observations conform to a coherent scenario where a dense electron beam drives the two-stream instability (causing type III emission) and, in the nonlinear stage, becomes unstable to another instability, previously known as the electron firehose instability (EFI). The secondary instability scatters some beam electrons into velocities perpendicular to the magnetic field and produces, after particle loss, a trapped distribution prone to electron cyclotron masering (ECM). A reduction in beaming and the formation of an isotropic halo are predicted for electron beams continuing to interplanetary space, possibly observable by Parker Solar Probe and Solar Orbiter.