Single Power Law Research Articles

KiDS-1000: Weak lensing and intrinsic alignment around luminous red galaxies

We study the properties of luminous red galaxies (LRGs) selected from the fourth data release of the Kilo Degree Survey (KiDS-1000) via galaxy-galaxy lensing of the background galaxies from KiDS-1000. We used a halo model formalism to interpret our measurements and obtain estimates of the halo masses as well as the satellite fractions of the LRGs, resulting in halo masses of $2.7 h^ M ⊙ <M_ h h^ M ⊙ $. We studied the strength of intrinsic alignments (IA) using the position-shape correlations as a function of LRG luminosity, where we used a double power law to describe the relation between luminosity and halo mass to allow for a comparison with previous works. Here, we directly linked the observed IA of the (central) galaxy to the mass of the hosting halo, which is expected to be a fundamental quantity in establishing the alignment. We find that the dependence of the IA amplitude on halo mass is described well by a single power law, with an amplitude of A = 5.74 and slope of β_M = 0.44 in the range of $1.9 h^ M ⊙ <M_ h h^ M ⊙ $. We also find that both red and blue galaxies from the source sample associated with the LRGs are randomly oriented, with respect to the LRGs, although our detection significance is limited by the uncertainty in our photometric redshifts.

Random walks with long-range memory on networks.

We study an exactly solvable random walk model with long-range memory on arbitrary networks. The walker performs unbiased random steps to nearest-neighbor nodes and intermittently resets to previously visited nodes in a preferential way such that the most visited nodes have proportionally a higher probability to be chosen for revisit. The occupation probability can be expressed as a sum over the eigenmodes of the standard random walk matrix of the network, where the amplitudes slowly decay as power-laws at large times, instead of exponentially. The stationary state is the same as in the absence of memory, and detailed balance is fulfilled. However, the relaxation of the transient part becomes critically self-organized at late times, as it is dominated by a single power-law whose exponent depends on the second largest eigenvalue and on the resetting probability. We apply our findings to finite networks, such as rings, complete graphs, Watts-Strogatz, and Barabási-Albert networks, and to Barbell and comb-like graphs. Our study could be of interest for modeling complex transport phenomena, such as human mobility, epidemic spreading, or animal foraging.

The emergence of the MD − Ṁ* correlation in the magnetohydrodynamic wind scenario

Context. There is still much uncertainty around the mechanism that rules the accretion of proto-planetary disks. In recent years, magnetohydrondynamic (MHD) wind-driven accretion has been proposed as a valid alternative to the more conventional viscous accretion. In particular, winds have been shown to reproduce the observed correlation between the mass of the disk MD and the mass accretion rate onto the central star Ṁ*, but this has been done only for specific conditions. It is not clear whether this implies fine tuning or if it is a general result. Aims. We investigated under which conditions the observed correlation between the mass of the disk MD and the mass accretion rate onto the central star Ṁ*, can be obtained. Methods. We present mainly analytical calculations, supported by Monte Carlo simulations. We also perform a comparison with the observed data to test our predictions. Results. In the absence of a correlation between the initial mass M0 and the initial accretion timescale tacc,0 , we find that the slope of the MD − Ṁ* correlation depends on the value of the spread of the initial conditions of masses and lifetimes of disks. Then we clarify the conditions under which a disk population can be fitted with a single power law. Moreover, we derive an analytical expression for the spread of log(MD/Ṁ*) valid when the spread of tacc is taken to be constant. In the presence of a correlation between M0 and tacc,0, we derive an analytical expression for the slope of the MD−Ṁ* correlation in the initial conditions of disks and at late times. In this new scenario, we clarify under which conditions the disk population can be fitted by a single power law, and we provide empirical constraints on the parameters ruling the evolution of disks in our models. Conclusions. We conclude that MHD winds can predict the observed values of the slope and the spread of the MD−Ṁ* correlation under a broad range of initial conditions. This is a fundamental expansion of previous works on the MHD paradigm, exploring the establishment of this fundamental correlation beyond specific initial conditions.

Calculation of collisional line-broadening and shifting of acetylene using Complex Robert–Bonamy–Ma approach

A comprehensive semi-classical study of the collisional line broadening and shift coefficients of C2H2 by several key perturbers (H2, He, N2, C2H2, CO, and CO2) for astronomical applications using the Complex Robert–Bonamy–Ma (CRBM) framework is presented. Following the CRBM computational protocol, the intermolecular interaction potentials are constructed from atom–atom and electrostatic interactions, and then fitted to reproduce experimental room-temperature line-broadening parameters taken from the literature. In total, 657 experimental values are used in the fitting. The empirical potentials are then used to predict line broadening coefficients over a wide temperature range. Reference collisional line widths γ0 and temperature exponents n for the commonly used single-power law are produced, as well as a set of parameters for the double-power law, which better reproduces the temperature dependence of theoretical predictions. The vibrational dependence of the line widths is studied using a new ab initio isotropic polarizability surface of C2H2 and is found to be negligible. The computed line broadening parameters are found to agree well with the experimental data, while the modelling of line shifts of HCCH is not satisfactory when compared to the experiment. The new line broadening data of C2H2 with the J (or m) dependence have been used to populate the ExoMol database www.exomol.com as part of the ExoMol pressure-broadening diet and can be used to model opacities of atmosphere of (extrasolar) planets. The CRBM methodology tested here on C2H2 can be used for other similar (closed-shell) systems in ExoMol that are important for exoplanetary atmospheric studies.

The Radio Halo in PLCKESZ G171.94–40.65: Beacon of Merging Activity

We present the first multifrequency analysis of the candidate ultrasteep spectrum radio halo in the galaxy cluster PLCKESZ G171.94−40.65, using the upgraded Giant Metrewave Radio telescope (400 MHz), and Karl G. Jansky Very Large Array (1–2 GHz) observations. Our radio data have been complemented with archival Chandra X-ray observations to provide a crucial insight into the complex intracluster medium physics, happening at large scales. We detect the radio halo emission to the extent of ∼1.5 Mpc at 400 MHz, significantly larger than previously reported, along with five tailed galaxies in the central region. We also report the discovery of an unknown diffuse source “U,” at the cluster periphery, with an extent of 300 kpc. Using the available observations, we have found that the radio spectrum of the halo is well-fitted with a single power law, having a spectral index of −1.36 ± 0.05, indicating that it is not an ultrasteep spectrum radio halo. Our low-resolution (25″) resolved spectral map shows an overall uniform spectral index, with some patches of fluctuations. The X-ray and radio surface brightness are morphologically cospatial, with a slight extension along the northwest–southeast direction, seen in both maps. The radio and X-ray surface brightness indicates strong positive correlations, with sublinear correlation slopes (∼0.71). Multiple tailed galaxies and the radio halo indicate a high dynamical activity at the cluster central region.

Detection of Very High-energy Gamma-Ray Emission from the Radio Galaxy M87 with LHAASO

The nearby radio galaxy M87 is a very high-energy (VHE) gamma-ray emitter established by observations with ground-based gamma-ray detectors. Here we report the long-term monitoring of M87 from 2021 to 2024 with the Large High Altitude Air Shower Observatory (LHAASO). M87 has been detected by LHAASO with a statistical significance ∼ 9σ. The observed energy spectrum extends to 20 TeV, with a possible hardening at ∼20 TeV and then a clear softening at higher energies. Assuming that the intrinsic spectrum is described by a single power law up to 20 TeV, a tight upper bound on the extragalactic background light intensity is obtained. A strong VHE flare lasting 8 days, with a rise time of τrrise=1.05±0.49 days and decay time of τddecay=2.17±0.58 days, was found in early 2022. A possible GeV flare is seen also in Fermi Large Area Telescope data during the VHE flare period. The variability time as short as 1 day seen in the LHAASO data suggests a compact emission region with a size of ∼3 × 1015 δ cm (δ being the Doppler factor of the emitting region), corresponding to a few Schwarzschild radii of the central supermassive black hole in M87. The continuous monitoring of the source reveals a duty cycle of ∼1% for VHE flares with a flux above 10−11 erg cm−2 s−1.

Triggering the Untriggered: The First Einstein Probe-detected Gamma-Ray Burst 240219A and Its Implications

The Einstein Probe (EP) achieved its first detection and localization of a bright X-ray flare, EP240219a, on 2024 February 19, during its commissioning phase. Subsequent targeted searches triggered by the EP240219a alert identified a faint, untriggered gamma-ray burst (GRB) in the archived data of Fermi Gamma-ray Burst Monitor (GBM), Swift Burst Alert Telescope (BAT), and Insight-HXMT/HE. The EP Wide-field X-ray Telescope (WXT) light curve reveals a long duration of approximately 160 s with a slow decay, whereas the Fermi/GBM light curve shows a total duration of approximately 70 s. The peak in the Fermi/GBM light curve occurs slightly later with respect to the peak seen in the EP/WXT light curve. Our spectral analysis shows that a single cutoff power-law (PL) model effectively describes the joint EP/WXT–Fermi/GBM spectra in general, indicating coherent broad emission typical of GRBs. The model yielded a photon index of ∼–1.70 ± 0.05 and a peak energy of ∼257 ± 134 keV. After detection of GRB 240219A, long-term observations identified several candidates in optical and radio wavelengths, none of which was confirmed as the afterglow counterpart during subsequent optical and near-infrared follow-ups. The analysis of GRB 240219A classifies it as an X-ray-rich GRB (XRR) with a high peak energy, presenting both challenges and opportunities for studying the physical origins of X-ray flashes, XRRs, and classical GRBs. Furthermore, linking the cutoff PL component to nonthermal synchrotron radiation suggests that the burst is driven by a Poynting flux-dominated outflow.

Crater Equilibrium State Characterization given Crater Production from a Single Power Law

We generalize the crater equilibrium concept, a terminal state on a cratered surface where the balance of crater production and erasure apparently limits the crater population from further growth. Assuming the crater production consists of a single power law, our model identifies four classes of crater equilibrium. The first class is the most common state, where the power-law slope for the equilibrium size–frequency distribution is independent of the crater production slope power. The second class arises when there is efficient degradation of larger craters by smaller crater production, which results in dependence of the crater equilibrium slope power on the crater production slope power. The third class is another common state when a shallow production function causes a crater equilibrium state with a similarly shallow slope. This class results from the enhanced degradation of smaller craters by larger crater production. The fourth class is a combination of the second and third classes. We further compare the concept of geometric saturation, which has been widely used to quantify the level of crater equilibrium, and that of cookie-cutter saturation. We present a crucial update to the cookie-cutter saturation concept that brings models closer to the reality of crater accumulation over a range of sizes than the geometric saturation concept. Our model offers simpler analytical formulae for cookie-cutter saturation and proposes this concept as a more meaningful reference to argue the crater equilibrium level. Our work and earlier studies confirm the consistency of the crater equilibrium concepts, enabling deeper interpretations of crater equilibrium.

From Coasting to Energy-conserving: New Self-similar Solutions to the Interaction Phase of Strong Explosions

Astrophysical explosions that contain dense and ram-pressure-dominated ejecta evolve through an interaction phase, during which a forward shock (FS), contact discontinuity (CD), and reverse shock (RS) form and expand with time. We describe new self-similar solutions that apply to this phase and are most accurate in the limit that the ejecta density is large compared to the ambient density. These solutions predict that the FS, CD, and RS expand at different rates in time and not as single temporal power laws, are valid for explosions driven by steady winds and homologously expanding ejecta, and exist when the ambient density profile is a power law with a power-law index shallower than ∼3 (specifically when the FS does not accelerate). We find excellent agreement between the predictions of these solutions and hydrodynamical simulations, both for the temporal behavior of the discontinuities and for the variation of the fluid quantities. The self-similar solutions are applicable to a wide range of astrophysical phenomena and—although the details are described in future work—can be generalized to incorporate relativistic speeds with arbitrary Lorentz factors. We suggest that these solutions accurately interpolate between the initial “coasting” phase of the explosion and the later, energy-conserving phase (or, if the ejecta is homologous and the density profile is sufficiently steep, the self-similar phase described in R. A. Chevalier).

Assessment of the near-Sun magnetic field of the 10 March 2022 coronal mass ejection observed by Solar Orbiter

Aims. We estimate the near-Sun axial magnetic field of a coronal mass ejection (CME) on 10 March 2022. Solar Orbiter’s in situ measurements, 7.8 degrees east of the Sun-Earth line at 0.43 AU, provided a unique vantage point, along with the WIND measurements at 0.99 AU. We determine a single power-law index from near-Sun to L1, including in situ measurements from both vantage points. Methods. We tracked the temporal evolution of the instantaneous relative magnetic helicity of the source active region (AR), NOAA AR 12962. By estimating the helicity budget of the pre-and post-eruption AR, we estimated the helicity transported to the CME. Assuming a Lundquist flux-rope model and geometrical parameters obtained through the graduated cylindrical shell (GCS) CME forward modelling, we determined the CME axial magnetic field at a GCS-fitted height. Assuming a power-law variation of the axial magnetic field with heliocentric distance, we extrapolated the estimated near-Sun axial magnetic field to in situ measurements at 0.43 AU and 0.99 AU. Results. The net helicity difference between the post-and pre-eruption AR is ( − 7.1 ± 1.2)×1041 Mx2, which is assumed to be bodily transported to the CME. The estimated CME axial magnetic field at a near-Sun heliocentric distance of 0.03 AU is 2067 ± 405 nT. From 0.03 AU to L1, a single power-law falloff, including both vantage points at 0.43 AU and 0.99 AU, gives an index −1.23 ± 0.18. Conclusions. We observed a significant decrease in the pre-eruptive AR helicity budget. Extending previous studies on inner-heliospheric intervals from 0.3 AU to ∼1 AU, referring to estimates from 0.03 AU to measurements at ∼1 AU. Our findings indicate a less steep decline in the magnetic field strength with distance compared to previous studies, but they align with studies that include near-Sun in situ magnetic field measurements, such as from Parker Solar Probe.

Characterization of the Western Pictor A Hotspot in Hard X-Rays with NuSTAR

The origin of X-ray emission from the resolved kiloparsec-scale jets and hotspots of many active galactic nuclei remains uncertain, particularly where the X-ray emission is separate from the radio-optical synchrotron component. Possible explanations include synchrotron emission from a second electron population and external Compton or synchrotron self-Compton processes—alternatives which imply very different physical conditions within the jet. Until recently, X-ray studies of resolved jets and hotspots have been restricted to below ∼10 keV, often showing a hard spectral index indicating a spectral peak beyond this energy range. Here we present NuSTAR observations of the nearby powerful radio galaxy Pictor A, in which we clearly detect the western hotspot at approximately 4′ from the host galaxy, the most significant detection of hotspot emission above 10 keV to date. The NuSTAR spectrum is best fit by a single power law of index Γ = 2.03 ± 0.04; an exponential cutoff gives a 1σ lower limit on the cutoff energy of 40.7 keV. We confirm previous findings of variations in the soft X-ray flux detected by Chandra over the 2000 to 2015 period, at a significance of 6.5σ. This rises to >8σ in the common 3–8 keV band using the combined 22 yr span of Chandra and NuSTAR observations. The variability of the western Pictor A hotspot strongly confirms the previously argued synchrotron nature of the X-ray emission for the hotspot, while the lower bound to the spectral cutoff energy implies electron energies in the hotspot reach up to at least a few TeV.

Evidence for hybrid gamma-ray emission from the supernova remnant G150.3+4.5

The supernova remnant (SNR) G150.3+4.5 was first identified in radio, exhibiting a hard GeV spectrum and a ~1.5º radius. Radio observations revealed a bright arc with an index of ~−0.40, which stands in contrast to the index of ~−0.69 for the rest. This arc is coincident with the point-like Fermi source 4FGL J0426.5+5434 and KM2A source 1LHAASO J0428+5531. The rest of the SNR has a hard GeV spectrum and a soft TeV spectrum, implying a spectral cut-off or break near 1 TeV. Since there is no X-ray counterpart and no pulse signal detected, the gamma-ray (γ-ray) emission mechanism from the SNR and the point-like source appear puzzling. In this work, we reanalyse the γ-ray emission using 14 yr data recorded by Fermi Large Area Telescope and find that the spectrum of the northern half-sphere is compatible with a broken power law with a break at 146 ± 11 eV and photon indices of ΓNorthlobe = 1.54 ± 0.04stat ± 0.07syst (2.28 ± 0.08stat ± 0.12syst) below (above) the break. In addition, the southern half-sphere can be described well with a single power law with ΓSouthlobe =1.95 ± 0.07stat ± 0.09syst. Since the southern half-sphere is well correlated with CO emission, we propose that the γ-ray emission of the northern half-sphere could be dominated by relativistic electrons via inverse-Compton processes, while the southern half-sphere is dominated by cosmic rays via hadronic processes. 4FGL J0426.5+5434 may result from the illumination of a cloud by escaping cosmic rays or recent shock-cloud interaction. Observations from LHAASO-KM2A thus favour the possibility of a cosmic-ray PeVatron candidate, however, leptonic scenarios cannot be ruled out. Further multi-wavelength observations are warranted to confirm the hadronic nature of 1LHAASO J4028+5531.

A Comprehensive Analysis of Insight-HXMT Gamma-Ray Burst Data. I. Power Density Spectrum

The power density spectrum (PDS) is a powerful tool to study light curves of gamma-ray bursts (GRBs). We show the average PDS and individual PDS analysis with GRB data from the Hard X-ray Modulation Telescope (also named Insight-HXMT). The values of the power-law index of the average PDS ( αP¯ ) for long GRBs (LGRBs) vary from 1.58 to 1.29 (for 100–245, 245–600, and 600–2000 keV). The Insight-HXMT data allow us to extend the energy of the LGRBs up to 2000 keV, and a relation between αP¯ and energy E is obtained: αP¯∝E−0.09 (8–2000 keV). We first systematically investigate the average PDS and individual PDSs for short GRBs (SGRBs), and obtain αP¯∝E−0.07 (8–1000 keV), where the values of αP¯ vary from 1.86 to 1.34. The distribution of the power-law index of an individual PDS (α) of an SGRB is consistent with that of an LGRB, and the α value for the group with a dominant timescale (the bent power law) is higher than that for the group with no dominant timescale (the single power law). Both LGRBs and SGRBs show similar α and αP¯ , which indicates that they may be the result of similar stochastic processes. Typical values of the dominant timescale τ for LGRBs and SGRBs are 1.58 s and 0.02 s, respectively. It seems that τ varies in proportion to the duration of GRBs T 90, with a relation τ∝T900.86 . The GRB light curve may result from superposing a number of pulses with different timescales. No periodic or quasi-periodic signal above the 3σ significance threshold is found in our sample.

Plasmon Mediated Single Photon Emission from a Nanocrystal Ensemble.

Quantum photonic devices require robust sources of single photons to perform basic computational and communication protocols. Thus, developing scalable, integrable, and efficient quantum light sources has become crucial for the realization of quantum photonic devices. Single quantum dots are promising sources of quantum light due to their tunable emission wavelength. Here, we show the emergence of quantum-emitter-like antibunched emission behavior when multiple quantum dots are located in the vicinity of plasmonic particles. To evaluate the robustness of this phenomenon, we consider both monometallic and bimetallic particles. We find that the photoluminescence intensity of the plasmon coupled quantum dots fits well to a single sublinear power law exponent that is distinct from the behavior of CQD aggregates. Significantly, we find that plasmon coupling results in reduced flickering, thus enabling the realization of a more stable and reliable single photon source. Possible roles of emergent excitonic interactions in the coupled system are discussed.

Low-frequency solar radio type II bursts and their association with space weather events during the ascending phase of solar cycle 25

Abstract. Type II solar radio bursts are signatures of the coronal shocks and, therefore, particle acceleration events in the solar atmosphere and interplanetary space. Type II bursts can serve as a proxy to provide early warnings of incoming solar storm disturbances, such as geomagnetic storms and radiation storms, which may further lead to ionospheric effects. In this article, we report the first observation of 32 type II bursts by measuring various plasma parameters that occurred between May 2021 and December 2022 in solar cycle 25. We further evaluated their accompanying space weather events in terms of ionospheric total electron content (TEC) enhancement using the rate of TEC index (ROTI). In this study, we find that at heliocentric distance ∼1–2 R⊙, the shock and the Alfvén speeds are in the range 504–1282 and 368–826 km−1, respectively. The Alfvén Mach number is of the order of 1.2≤MA≤1.8 at the above-mentioned heliocentric distance. In addition, the measured magnetic field strength is consistent with the earlier reports and follows a single power law B(r)=6.07r-3.96G. Based on the current analysis, it is found that 19 out of 32 type II bursts are associated with immediate space weather events in terms of radio blackouts and polar cap absorption events, making them strong indications of space weather disruption. The ROTI enhancements, which indicate ionospheric irregularities, strongly correlate with GOES X-ray flares, which are associated with the type II radio bursts recorded. The diurnal variability in ROTI is proportional to the strength of the associated flare class, and the corresponding longitudinal variation is attributed to the difference in longitude. This article demonstrates that since type II bursts are connected to space weather hazards, understanding various physical parameters of type II bursts helps to predict and forecast the space weather.

Unraveling relationship between complex lifetimes and microscopic diffusion in deep eutectic solvents.

Aqueous mixtures of deep eutectic solvents (DESs) have emerged as a subject of interest in recent years for their tailored physicochemical properties. However, a comprehensive understanding of water's multifaceted influence on the microscopic dynamics, including its impact on improved transport properties of the DES, remains elusive. Additionally, the diffusion mechanisms within DESs manifest heterogeneous behavior, intricately tied to the formation and dissociation kinetics of complexes and hydrogen bonds. Therefore, it is imperative to explore the intricate interplay between bond kinetics, diffusion mechanism, and dynamical heterogeneity. This work employs water as an agent to explore their relationships by studying various relaxation phenomena in a DES based on acetamide and lithium perchlorate over a wide range of water concentrations. Notably, acetamide exhibits Fickian yet non-Gaussian diffusion across all water concentrations with Fickian (τf) and Gaussian (τg) timescales following a power-law relationship, τg∝τfγ, γ ∼ 1.4. The strength of coupling between bond kinetics and different diffusion timescales is estimated through various power-law relationships. Notably, acetamide-water hydrogen bond lifetime is linked to diffusive timescales through a single power-law over the entire water concentration studied. However, the relationship between diffusive timescales and the lifetime of acetamide-lithium complexes shows a sharp transition in behavior at 20 wt. % water, reflecting a change from vehicular diffusion below this concentration to structural diffusion above it. Our findings emphasize the critical importance of understanding bond dynamics within DESs, as they closely correlate with and regulate the molecular diffusion processes within these systems.

The radio properties of z>3.5 quasars: Are most high-redshift radio-loud active galactic nuclei obscured?

We explore the radio properties of powerful (rest-frame luminosity $ at 500 MHz) high-redshift ($z 3.5$) quasars. The aim of this study is to gain a better understanding of radio-loud sources at the epoch when they reach the highest space density. We selected 29 radio-loud quasars at low radio frequencies (76 MHz). Their radio spectra, covering the range from 76 MHz to 5 GHz, are generally well reproduced by a single power law. We created samples that were matched in radio luminosity at lower redshift (from $z to $z to investigate any spectral evolution. We find that the fraction of flat-spectrum radio quasars (FSRQs) strongly increases with redshift (from $ 8<!PCT!>$ at z=1.2 to $ 45<!PCT!>$ at z$>$3.5). This effect is also observed in quasars with lower luminosities (down to $ The increase in the fraction of FSRQs with redshift corresponds to a decrease in the steep- spectrum radio quasars. This result can be explained when we assume that the beaming factor and the slope of the luminosity function do not change with redshift and if high-redshift radio-loud sources can be recognized as quasars only when they are seen at a small viewing angle ($ but most of them, about 90<!PCT!> are obscured in the UV and optical bands. We also found a trend for the size of radio sources to decrease with increasing redshift. Because projection effects are insufficient to cause this trend, we suggest that the large amount of gas causing the nuclear obscuration also hampers the growth of the more distant sources.

Solar Eruptive Phenomena Associated with Solar Energetic Electron Spectral Types

The energy spectral shape of solar energetic electron events carries important information on the energetic electron source/acceleration at the Sun. We investigate the association of six newly identified solar energetic electron spectral types with solar eruptive phenomena, including the downward double-power-law (DDPL) spectrum with break energy E B above 20 keV (DDPL EB≥20keV ), DDPL with E B below 20 keV (DDPL EB<20keV ), upward double-power law (UDPL), single-power-law (SPL), Ellision–Ramaty–like (ER), and logarithmic-parabola (LP). We find that the SPL type shows (the other five types show) an association with hard X-ray flares of ∼38% (∼55%–82%) and an association with west-limb coronal mass ejections (CMEs) of ∼76% (∼85%–93%). Among the other five types, the DDPL EB<20keV and ER (LP and DDPL EB≥20keV ) types only have an association with type II radio bursts of ∼7%–8% (∼16%–20%) and an association with halo CMEs of ∼5%–9% (∼11%–21%); however, the UDPL type exhibits a significant (∼47% and ∼50%) association with type II bursts and halo CMEs, with a significantly faster median CME speed of 1000−120+550 km s−1. For DDPL EB≥20keV (DDPL EB<20keV ) with a positive (no) correlation between spectral indexes and no (a positive) correlation between the spectral index and break energy, the spectrum appears to be flatter as the associated CME (flare) becomes faster (stronger). These results suggest that the SPL type can result from the initial acceleration process that likely occurs high in the corona, and then provide seed populations for further acceleration processes to form the other five types: the DDPL EB<20keV and ER types via flare-related processes, the LP and DDPL EB≥20keV types via CME-related processes, and the UDPL type via CME-driven shocks.

Further Study of the Relationship between Transient Effects in Energetic Proton and Cosmic Ray Fluxes Induced by Coronal Mass Ejections

The study and better understanding of energetic transient phenomena caused by disturbances occurring on our Sun are of great importance, primarily due to the potential negative effects those events can have on Earth’s environment. Here, we present the continuation of our previous work on understanding the connection between disturbances in the flux of energetic particles induced in the near-Earth environment by the passage of interplanetary coronal mass ejections and related Forbush decrease events. The relationship between the shape of fluence spectra of energetic protons measured by the instruments on the SOHO/ERNE probe at Lagrange point L1, Forbush decrease parameters measured by the worldwide network of neutron monitors, and coronal mass ejection parameters measured in situ is investigated. Various parameters used to characterize transient phenomena and their impact on the heliosphere, provided by the WIND spacecraft, were utilized to improve the accuracy of the calculation of the associated energetic proton fluence. The single and double power laws with exponential rollover were used to model the fluence spectra, and their effectiveness was compared. Correlation analysis between exponents used to characterize the shape of fluence spectra and Forbush decrease parameters is presented, and the results obtained by the two models are discussed.

Properties of Cosmic Deuterons Measured by the Alpha Magnetic Spectrometer.

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of the deuteron (D) flux are presented. The measurements are based on 21×10^{6} D nuclei in the rigidity range from 1.9 to 21GV collected from May 2011 to April 2021. We observe that over the entire rigidity range the D flux exhibits nearly identical time variations with the p, ^{3}He, and ^{4}He fluxes. Above 4.5GV, the D/^{4}He flux ratio is time independent and its rigidity dependence is well described by a single power law ∝R^{Δ} with Δ_{D/^{4}He}=-0.108±0.005. This is in contrast with the ^{3}He/^{4}He flux ratio for which we find Δ_{^{3}He/^{4}He}=-0.289±0.003. Above ∼13 GV we find a nearly identical rigidity dependence of the D and p fluxes with a D/p flux ratio of 0.027±0.001. These unexpected observations indicate that cosmic deuterons have a sizable primarylike component. With a method independent of cosmic ray propagation, we obtain the primary component of the D flux equal to 9.4±0.5% of the ^{4}He flux and the secondary component of the D flux equal to 58±5% of the ^{3}He flux.