Solar Physics最新文献

In this article, Part 1, we have synthetically resonance scattered and Thomson scattered a measured solar chromospheric (mathrm{Ly}alpha ) spectral radiance (CLSR) spectrum off the neutral hydrogen [(N_{1})] atoms in ground state and free electrons [(N_{mathrm{e}})], respectively, contained in a 3D coronal model of the 14 July 2000 (“Bastille Day”) Coronal Mass Ejection (CME). From these two scatters, we have computed maps of the associated resonance scattered spectral radiance (RSSR) spectrum and the Thomson scattered spectral radiance (TSSR) spectrum in ultraviolet (UV) from 121.3 to 121.8 nm with a wavelength resolution of 0.1 nm, which encompasses the (mathrm{Ly}alpha ) center line at 121.57 nm. We then integrated the maps over the above wavelength range and have created two 2D resonance scattered radiance (RSR) and Thomson scattered radiance (TSR) maps. As expected, the TSSR spectrum is (approx 1000) times dimmer than the RSSR spectrum, which we can deem for it to contribute towards noise in the center of the RSSR spectrum. In a follow up article, Part 2, we intend to do the following with these maps. First, we will use the computed RSSR spectra along each line of sight (LOS) to derive the proton temperature [(T_{mathrm{p}})] and speed [(V_{mathrm{p}})] using the Doppler Dimming technique (DDT). Second, we will compare these derived proton parameters along each LOS with the actual values contained within the Bastille Day CME model at the plane of the sky and compute the differences. If we find they are different we will then determine where along the LOS they closely match and their distances from the plane of the sky. Finally, we will quantify an estimate of the systematic error from using DDT to measure the proton parameters at the plane of the sky, which is different from the statistical error margins reported in the literature from real RSSR experiments conducted from space-based instruments.

We report on the 2024 September 9 sustained gamma-ray emission (SGRE) event observed by the Large Area Telescope (LAT) on board the Fermi satellite. The hevent was associated with a backside solar eruption observed by multiple spacecraft such as the Solar and Heliospheric Observatory (SOHO), Solar Terrestrial Relations Observatory (STEREO), Parker Solar Probe (PSP), Solar Orbiter (SolO), Solar Dynamics Observatory (SDO), Wind, and GOES, and by ground-based radio telescopes. Fermi/LAT observed the SGRE after the EUV wave from the backside eruption crossed the limb to the frontside of the Sun. SolO’s Spectrometer Telescope for Imaging X-rays (STIX) imaged an intense (X3.3) flare, which occurred ≈ 41° behind the east limb, from heliographic coordinates S13E131. Forward modeling of the coronal mass ejection (CME) flux rope revealed that it impulsively accelerated (3.54 km s⁻²) to attain a peak speed of 2162 km s⁻¹. SolO’s energetic particle detectors (EPD) observed protons up to ≈ 1 GeV from the extended shock and electrons that produced a complex type II burst and possibly type III bursts. The durations of SGRE and type II burst are consistent with the linear relation between these quantities obtained from longer duration (> 3 hours) SGRE events. All these observations are consistent with an extended shock surrounding the CME flux rope, which is the likely source of high-energy protons required for the SGRE event. We compare this event with six other behind-the-limb (BTL) SGRE eruptions and find that they are all consistent with energetic shock-driving CMEs. We also find a significant east-west asymmetry (3:1) in the BTL source locations.

We study solar differential rotation for solar cycle No. 19 (1954 – 1964) by tracing sunspot groups on the sunspot drawings of Kanzelhöhe Observatory for Solar and Environmental Research (KSO). Our aim is to extend previous differential rotation (DR) analysis from the KSO data (1964 – 2016) to the years prior to 1964 to create a catalog of sunspot group positions and photospheric DR parameters from KSO sunspot drawings and white light images. Synodic angular rotation velocities were first determined using the daily shift (DS) and robust linear least-squares fit (rLSQ) methods, then converted to sidereal velocities, and subsequently used to derive solar DR parameters. We compare the DR parameters obtained from different sources and analyse the north–south asymmetry of rotation for solar cycle No. 19. It has been shown that our results for the equatorial rotation velocity (parameter (A)) and the gradient of DR (parameter (B)) coincide with earlier results from the KSO data (performed with a different method), as well as with results from the Kodaikanal Solar Observatory (KoSO) and the Yunnan Observatories (YNAO). In contrast, the values of parameter (A) from three different earlier studies based on the Greenwich Photoheliographic Results (GPR) exhibit statistically significant differences when compared to the values of parameter (A) derived from KSO, KoSO and YNAO. These findings suggest that the GPR data have the largest inconsistency compared to the other three data sources, highlighting the need for further analysis to identify the causes of these discrepancies. The analysis of the north-south asymmetry in the solar rotation profile using two different methods shows that the DR parameters of the hemispheres coincide, indicating a rotational symmetry around the equator. This is consistent with previous results from KSO and YNAO data. However, all sources indicate slightly higher equatorial rotation velocities in the southern hemisphere.

Understanding the long-term variability of the solar dynamo remains a key challenge in solar physics. In this work, we apply the Sparse Identification of Nonlinear Dynamical Systems (SINDy) framework to reconstruct a low-order dynamo model directly from 275 years of sunspot number data. Our data-driven approach for discovering governing equations from time series enables us to identify a minimal yet accurate dynamical system that captures the essential features of solar activity cycles. We demonstrate that, when interpreted as a low-order dynamo model, the solar dynamo is governed by an unstable saddle point, with nonlinear evolution leading to cyclic behavior. In particular we find that the underlying dynamics is described by a cubic nonlinearity driven by a (B_{phi }dot{B}_{phi }^{2}) term, which results in a phase space not necessarily of the Van der Pol universality class. Additionally, we show that higher-order nonlinearities are disfavored, and we discuss how to interpret our findings in terms of a mean-field dynamo model with a novel quenching term.

In this work we compare the full-disk line-of-sight magnetic field measurements of the Helioseismic and Magnetic Imager (HMI) with the magnetograms from multiple sources including the Global Oscillation Network Group (GONG), the Michelson Doppler Imager (MDI), the Synoptic Optical Long-term Investigations of the Sun (SOLIS) instrument, the Mount Wilson Observatory (MWO), and the Wilcox Solar Observatory (WSO). A scaling factor is then derived that matches the magnetograms from these instruments to those of HMI. The scaling factors are (1.438pm 0.000) for GONG, (0.701pm 0.001) for MDI, (1.038pm 0.001) for SOLIS, (2.795pm 0.002) for MWO, and ({3.582pm 0.006}) for WSO. This scaling factor varies with the center-to-limb distance and field strength. Distortion maps for these instruments are also determined using the HMI data as a reference.

Solar activity seems quite understandable when considered on the scales comparable with a solar cycle, i.e. about 11 years, and on a short time scale of about a year. A solar cycle looks basically (anti)symmetric with respect to the solar equator, while the sunspot distribution is more or less random. We investigated the difference in the spatial distribution of magnetic structures on both time scales in terms of sunspots and the surface large-scale magnetic field and arrived at the conclusion that the structures of each type are created by a specific mechanism. For long-term structures, it is the mean-field dynamo. For the short-term ones, it is the spot production considered as a separate physical mechanism. The relationship between the mean-field dynamo mechanism and the processes of sunspot formation is a complex problem of current interest. The 11-year cycle itself is created by the mean-field dynamo and is most likely determined by processes in the convection zone. However, the transformation of magnetic flux into spots and active regions occurs, apparently, on significantly shorter time scales and probably develops directly in the subsurface layers, i.e., Near-Surface Shear Layer (NSSL) or leptocline.

We investigate the relationship between the gamma-ray emission measured with the Large Area Telescope on board Fermi (Fermi-LAT9 and radio signatures of coronal shock waves in four behind-the-limb (BTL) solar flares. All events were associated with metric type II radio bursts. Both start and end times of the radio bursts were synchronized with the gamma-ray emission. The type II bursts associated with the BTL gamma-ray flares had higher speeds and lower formation heights than those of an average sample. These findings support the notion that the highly relativistic ions that produce the gamma-rays in BTL flares are accelerated at CME-driven propagating coronal shock waves rather than in large-scale coronal loops.

Solar eruptive events such as flares and coronal mass ejections can accelerate charged particles up to nearly relativistic energies producing so-called solar energetic particles (SEPs). Some of those SEPs can propagate towards Earth and be registered by, e.g., particle detectors onboard satellites. Favourable acceleration conditions make strong SEP events possible with a high flux of high-energy (> 500 MeV) protons, which can be registered even on the ground by neutron monitors (NMs) as rapid enhancements of their count rate over the background. Such events are accordingly called ground-level enhancements (GLEs). GLEs are rare, with only 73 events registered from 1942 to 2023, and three more GLEs 74 – 76 occurred in 2024, close to the maximum of solar activity. In this work, we report GLE 75 that happened on 8 June 2024, initially missed during real-time monitoring, but identified retrospectively. The SEP event, which induced the GLE, was associated with a flare from the solar active region 13697 (13664 on the previous solar rotation). It caused statistically significant increases in the count rate of NMs Dome C, South Pole, and Peawanuck, as well as in the proton intensity measured by Geostationary Operational Environmental Satellite GOES-16. Here, we show the GLE in NM data, describe the procedure of evaluation of its statistical significance, and present the analysis with reconstruction of the spectral and angular SEP distributions.

Sunrise iii is a balloon-borne solar observatory dedicated to investigating the physics governing the magnetism and dynamics in the lower solar atmosphere. The observatory is designed to operate in the stratosphere, at heights around 36 km (above 99% of Earth’s atmosphere), to avoid image degradation due to turbulence in the Earth’s lower atmosphere, to gain access to the NUV wavelengths down to 309 nm, and to enable (when flown during summer solstice) observing the Sun uninterruptedly 24 hours/day. It is composed of a balloon gondola (equivalent to a spacecraft bus) carrying a 1-m aperture telescope (the largest solar telescope to-date to fly in the stratosphere on a balloon) feeding an imaging vector magnetograph and two spectropolarimeters aiming at acquiring high spatial resolution high cadence time series maps of the solar vector magnetic fields, plasma flows, and temperature in the photosphere and chromosphere.

In July 2024 Sunrise iii successfully completed a six and a half days long stratospheric flight from Kiruna (Sweden) to Northern Canada at an average altitude of 36 km. This was the third successful flight of the Sunrise observatory, which had previously flown in 2009 and 2013. For this flight it was upgraded substantially with a new and improved suite of three instruments carried by a completely new gondola with upgraded pointing control system.

This article focuses on describing the design and flight performance of the Sunrise iii gondola and all its subsystems. It describes the gondola mechanical structure, its power system, its command and control system, and in particular its pointing control system which was key for achieving high spatial and spectral resolution images of the solar photosphere and chromosphere by the three instruments.

Solar active regions are where sunspots are located and photospheric magnetic fluxes are concentrated, therefore being the sources of energetic eruptions in the solar atmosphere. The detection and statistics of solar active regions have been forefront topics in solar physics. In this study, we developed a solar active region detector (SARD) based on the advanced object detection model YOLOv8. First, we applied image processing techniques including thresholding and morphological operations to 6975 line-of-sight magnetograms from 2010 to 2019 at a cadence of 12 h, obtained by the Helioseismic and Magnetic Imager onboard the Solar Dynamic Observatory. With manual refinement in accordance with the NOAA catalog, we labeled each individual active regions in the dataset, and obtained a total of 26,531 labels for training and testing the SARD. Without any overlap between the training and test sets, the superior performance of SARD is demonstrated by an average precision rate as high as 94%. We then performed a statistical analysis on the area and magnetic flux of the detected active regions, both of which yield log-normal distributions. This result sheds light on the underlying complexity and multi-scale nature of solar active regions.