Reverse Shock Research Articles

The contemporaneous phase of GRB afterglows – application to GRB 221009A

ABSTRACT The TeV observations of GRB 221009A provided us with a unique opportunity to analyse the contemporaneous phase in which both prompt and afterglow emissions are seen simultaneously. To describe this initial phase of gamma-ray burst afterglows, we suggest a model for a blast wave with an intermittent energy supply. We treat the blast wave as a two-element structure. The central engine supplies energy to the inner part (shocked ejecta material) via the reverse shock. As the shocked ejecta material expands, its internal energy is transferred to the shocked external matter. We take into account the inertia of the shocked external material so that the pressure difference across this region determines the derivative of the blast wave’s Lorentz factor. Applied to GRB 221009A, the model yields a very good fit to the observations of the entire TeV light curve except for three regions where there are excesses in the data with respect to the model. Those are well correlated with the three largest episodes of the prompt activity and thus, we interpret them as the reverse shock emission. Our best-fitting solution for GRB 221009A is an extremely narrow jet with an opening angle θj ≈ 0.07° (500/Γ0) propagating into a wind-like external medium. This extremely narrow angle is consistent with the huge isotropic equivalent energy of this burst, and its inverse jet break explains the very rapid rise of the afterglow. Such inverse jet break occurs in an accelerating blast wave when the relativistic beaming becomes narrower than the jet’s opening angle. Interestingly, photon–photon annihilation does not play a decisive role in the best-fitting model.

귀국 직장인의 민족정체성과 심리사회적 적응의 관계

Objectives The aim of this study was to examine the moderated mediating effect of the acculturation strategy on the relationship with the impact of changed ethnic identity on reverse cultural shock and psychological social adaption to adults who returned to work after living abroad.
 Methods The survey was conducted between February 22 and March 27, 2020 on 202 adults who returned to Korea and are working after living abroad for at least 3 years, and collected data that did not consent to the collec-tion and use of personal information, excluding those, 199 copies were used as final analysis data. The mediation effect, the moderation effect and the moderated mediating effect were analyzed through SPSS 25.0 and SPSS Macro.
 Results The results were as follows; The reverse culture shock was significant on the relationship between the ethnic identity and psychological social adaption. Also the moderation effect of assimilation and separation strat-egies was verified on the relationship between reverse cultural shock and psychological social adaption even though there was a limitation in investigating the moderated mediating effect of the integration strategy, which is a sub-strategies of acculturation strategy due to the reliability problem. Lastly, assimilation and separation strategies moderated the mediating effect of reverse cultural shock between internalized ethnic identity and psy-chological social adaption.
 Conclusions These findings showed the impact of ethnic identity and reverse cultural shock on psychological so-cial adaptation, and high level of assimilation and low level of separation strategies were expected to be risks for psychological social adaptation. Finally, the implications and limitations of this study were discussed.

Reverse shock index multiplied by simplified motor score as a predictor of clinical outcomes for patients with COVID-19

BackgroundThe reverse shock index (rSI) combined with the Simplified Motor Score (sMS), that is, the rSI-sMS, is a novel and efficient prehospital triage scoring system for patients with COVID-19. In this study, we evaluated the predictive accuracy of the rSI-sMS for general ward and intensive care unit (ICU) admission among patients with COVID-19 and compared it with that of other measures, including the shock index (SI), modified SI (mSI), rSI combined with the Glasgow Coma Scale (rSI-GCS), and rSI combined with the GCS motor subscale (rSI-GCSM).MethodsAll patients who visited the emergency department of Taipei Tzu Chi Hospital between January 2021 and June 2022 were included in this retrospective cohort. A diagnosis of COVID-19 was confirmed through a SARS-CoV-2 reverse-transcription polymerase chain reaction test or SARS-CoV-2 rapid test with oropharyngeal or nasopharyngeal swabs and was double confirmed by checking International Classification of Diseases, Tenth Revision, Clinical Modification codes in electronic medical records. In-hospital mortality was regarded as the primary outcome, and sepsis, general ward or ICU admission, endotracheal intubation, and total hospital length of stay (LOS) were regarded as secondary outcomes. Multivariate logistic regression was used to determine the relationship between the scoring systems and the three major outcomes of patients with COVID-19, including. The discriminant ability of the predictive scoring systems was investigated using the area under the receiver operating characteristic curve, and the most favorable cutoff value of the rSI-sMS for each major outcome was determined using Youden’s index.ResultsAfter 74,183 patients younger than 20 years (n = 11,572) and without COVID-19 (n = 62,611) were excluded, 9,282 patients with COVID-19 (median age: 45 years, interquartile range: 33–60 years, 46.1% men) were identified as eligible for inclusion in the study. The rate of in-hospital mortality was determined to be 0.75%. The rSI-sMS scores were significantly lower in the patient groups with sepsis, hyperlactatemia, admission to a general ward, admission to the ICU, total length of stay ≥ 14 days, and mortality. Compared with the SI, mSI, and rSI-GCSM, the rSI-sMS exhibited a significantly higher accuracy for predicting general ward admission, ICU admission, and mortality but a similar accuracy to that of the rSI-GCS. The optimal cutoff values of the rSI-sMS for predicting general ward admission, ICU admission, and mortality were calculated to be 3.17, 3.45, and 3.15, respectively, with a predictive accuracy of 86.83%, 81.94%%, and 90.96%, respectively.ConclusionsCompared with the SI, mSI, and rSI-GCSM, the rSI-sMS has a higher predictive accuracy for general ward admission, ICU admission, and mortality among patients with COVID-19.

From total destruction to complete survival: dust processing at different evolutionary stages in the supernova remnant Cassiopeia A

ABSTRACT The expanding ejecta of supernova remnants (SNRs) are believed to form dust in dense clumps of gas. Before the dust can be expelled into the interstellar medium and contribute to the interstellar dust budget, it has to survive the reverse shock that is generated through the interaction of the preceding supernova blast wave with the surrounding medium. The conditions under which the reverse shock hits the clumps change with remnant age and define the dust survival rate. To study the dust destruction in the SNR Cassiopeia A, we conduct magnetohydrodynamical simulations of the evolution of a supernova blast wave and of the reverse shock. In a second step, we use these evolving conditions to model clumps that are disrupted by the reverse shock at different remnant ages. Finally, we compute the amount of dust that is destroyed by the impact of the reverse shock. We find that most of the dust in the SNR is hit by the reverse shock within the first 350 yr after the SN explosion. While the dust destruction in the first 200 yr is almost complete, we expect greater dust survival rates at later times and almost total survival for clumps that are first impacted at ages beyond 1000 yr. Integrated over the entire evolution of the SNR, the dust mass shows the lowest survival fraction (17 per cent) for the smallest grains (1 nm) and the highest survival fraction (28 per cent) for the largest grains (1000 nm).

Particle acceleration test with Cas A multiwavelength emission

AbstractThe investigation of supernova remnants (SNRs) across the electromagnetic spectrum from radio up to very high energy gamma‐rays can serve as a test of the particle acceleration and touches on one of the unresolved problems of modern astrophysics, namely the origin of cosmic rays and the Galaxy's contribution to the overall cosmic ray spectrum. The multiwavelength observations of Cas A SNR demonstrated that structure and spectral features have clear signs of young SNRs and its overall properties make this object the best target to test a hypothesis of cosmic ray origin in SNRs. Studies of Cas A at very high energies by SHALON telescope showed the location of TeV gamma‐ray emission region relative to the position of reveres shock. Also, the spectral energy distribution was obtained at high and very high energies. To describe the spectral and structural features of this SNR viewed in non‐thermal emission, two approaches involving reverse and also both reverse and forward shocks to the mechanism of diffusive shock acceleration of cosmic rays in Cas A were applied. It is demonstrated that the observational properties of Cas A are well reproduced by the hadronic model with significant contribution of both the forward and reverse shocks in the generation of broadband emission. Calculation results suggest that the very high efficiency of particle acceleration in Cas A, which value is up to 25% of the supernova explosion energy with energy of accelerated particles not exceeding of eV. Whereas, the forward shock model predicts the spectral characteristics of the TeV‐gamma‐emission corresponding to ones detected at 800 GeV–40 TeV that are the evidence of acceleration of the hadronic cosmic rays in shells of SNRs up to eV

Jet Structure and Burst Environment of GRB 221009A

We conducted a comprehensive investigation of the brightest-of-all-time GRB 221009A, using new insights from very high-energy (VHE) observations from LHAASO and a complete multiwavelength afterglow data set. Through data fitting, we imposed constraints on the jet structure, radiation mechanisms, and burst environment of GRB 221009A. Our findings reveal a structured jet morphology characterized by a core+wing configuration. A smooth transition of energy within the jet takes place between the core and wing, but with a discontinuity in the bulk Lorentz factor. The jet structure differs from both the case of the short GRB 170817A and the results of numerical simulations for long-duration bursts. The VHE emission can be explained by the forward shock synchrotron self-Compton radiation of the core component, but requiring a distinctive transition of the burst environment from uniform to wind-like, suggesting the presence of complex pre-burst mass ejection processes. The low-energy multiwavelength afterglow is mainly governed by the synchrotron radiation from the forward and reverse shocks of the wing component. Our analysis indicates a magnetization factor of 5 for the wing component. Additionally, by comparing the forward shock parameters of the core and wing components, we find a potential correlation between the electron acceleration efficiency and both the Lorentz factor of the shock and the magnetic field equipartition factor. We discuss the significance of our findings, potential interpretations, and remaining issues.

Strangers in Their Homeland

This study explored reverse culture shock faced by the first-generation Thai diasporas residing in Western countries upon visiting Thailand. A qualitative research approach guided it. Semi-structured interviews were employed to obtain data from 21 respondents. Thematic analysis revealed that all Thai diaspora tourists experienced reverse culture shock, which could be categorized into five main aspects: cultural, interpersonal, emotional, moral, and environmental. Further, the study suggested that reverse culture shock did not always result from the elements in a home country that caused difficulties, discomfort or unpleasant feelings but could also come from the attributes which tourists sought but could not find in their current country of residence and the realization of the significance of things in their home country that were previously overlooked.

Predicting outcomes in trauma patients by using reverse shock index multiplied by Glasgow coma scores (rSIG): A retrospective cross-sectional study

Introduction: This study aimed to determine the predictive value of the reverse shock index (rSI) using the Glasgow Coma Score (GCS) to predict the outcome of traumatic patients. Methods: This study included all patients with a traumatic injury aged≥18 years with ISS score≥16 and head Abbreviated Injury Scale (AIS)≥2 admitted to the Imam Reza hospital of Tabriz, Iran from 1 March, 2021 to 1 July, 2021. After excluding the patients with incomplete data, 216 patients were enrolled. In this study, the rSIG is the product of rSI multiplied by the GCS score. The patients’ symptoms were recorded routinely in the summary section of all patients’ records using the studied indexes. Data collection was performed using the researcher-made forms. The SPSS software v.21 was used to analyze the data. A P-value<0.05 was considered as statistically significant. Results: The results of data analysis demonstrated that the regression model by two predicting variables of rSI and rSIG was statistically significant. Also, the model can distinguish between the patients who died and those who were discharged. In addition, the Hosmer-Lemeshow test confirmed the model’s advantage and its accuracy (χ2=14.12, df=8, P>0.05). Conclusion: So, the predictive value of rSI with GCS in predicting the outcome of traumatic patients was high.

Reverse shock index multiplied by the motor component of the Glasgow Coma Scale predicts mortality and need for intervention in pediatric trauma patients.

Timely identification of high-risk pediatric trauma patients and appropriate resource mobilization may lead to improved outcomes. We hypothesized that reverse shock index times the motor component of the Glasgow Coma Scale (GCS) (rSIM) would perform equivalently to reverse shock index times the total GCS (rSIG) in the prediction of mortality and the need for intervention following pediatric trauma. The 2017-2020 National Trauma Data Bank data sets were used. We included all patients 16 years or younger who had a documented prehospital and trauma bay systolic blood pressure, heart rate, and total GCS. We excluded all patients who arrived at the trauma center without vital signs and interfacility transport patients. Receiver operating characteristic curves were used to model the performance of each metric as a classifier with respect to our primary and secondary outcomes, and the area under the receiver operating characteristic curve (AUROC) was used for comparison. Our primary outcome was mortality before hospital discharge. Secondary outcomes included blood product administration or hemorrhage control intervention (surgery or angiography) <4 hours following hospital arrival and intensive care unit admission. After application of exclusion criteria, 77,996 patients were included in our analysis. Reverse shock index times GCS-motor and rSIG performed equivalently as predictors of mortality in the 1- to 2- ( p = 0.05) and 3- to 5-year-old categories ( p = 0.28), but rSIM was statistically outperformed by rSIG in the 6- to 12- (AUROC, 0.96 vs. 0.95; p = 0.04) and 13- to 16-year-old age categories (AUROC, 0.96 vs. 0.95; p < 0.01). Reverse shock index times GCS-motor and rSIG also performed similarly with respect to prediction of secondary outcomes. Reverse shock index times GCS-total and rSIM are both outstanding predictors of mortality following pediatric trauma. Statistically significant differences in favor of rSIG were noted in some age groups. Because of the simplicity of calculation, rSIM may be a useful tool for pediatric trauma triage. Diagnostic Tests or Criteria; Level III.

Reverse shock emission in an off-axis top-hat jet model for gamma-ray bursts

ABSTRACT The afterglow of a gamma-ray burst (GRB) has been widely argued to arise from the interaction of a relativistic outflow with its ambient medium. During such an interaction, a pair of shocks are generated: a forward shock that propagates into the medium and a reverse shock that propagates into the outflow. Extensive studies have been conducted on the emission from the forward shock viewed off-axis. Furthermore, the observation of a reverse shock in an on-axis short GRB suggests that the reverse shock can produce an electromagnetic counterpart to a gravitational wave-detected merger. In this paper, we investigate the contribution of the reverse shock to the afterglow from a top-hat jet viewed off-axis, and apply our model to some short GRBs previously modelled by an off-axis emission. We employ the Markov Chain Monte Carlo (MCMC) method to get the model parameters (i.e. the jet’s half-opeaning angle θj, the viewing angle θobs, the initial Lorentz factor Γ0, and the isotropic energy Eiso). Our model successfully reproduces off-axis afterglow emission without a structured jet. In addition, our calculations suggest that the reverse shock may produce a prominent feature in an early afterglow, which can be potentially observed in an orphan optical afterglow.

Numerical investigation on turbulent flame jet characteristics of a pre-chamber fueled with CH4/O2 and CH4/NH3/O2 mixture under different initial pressures

Ammonia is a very potential carbon-free alternative fuel with extremely low reactivity. The application of ammonia in internal combustion engines faces the risks of ignition failure, low burning rate, and poor combustion stability. Pre-chamber turbulent jet ignition (TJI), which can provide much more ignition energy, is a promising method to ignite ammonia fuel. However, the transient propagation process of pre-chamber jet flame has not been fully investigated yet. In this paper, the propagation characteristic of methane jet flame was numerically studied based on a constant volume combustion system. The supersonic jet flame propagation and Mach disk phenomenon were further analyzed with numerical methods. And the propagation characteristic of methane/ammonia mixed jet flame was investigated. According to the results, the formation and propagation process of methane jet flame has different characteristics at different stages. In High-speed development stage (Stage II) and Low-speed oscillation development stage (Stage III), the penetration distance of flame jet tip is almost proportional to the penetration time. However, the penetration speed of the two stages is significantly different. The change trend of the jet velocity at the outlet of orifice hole can also be divided into four stages: slow increasing, rapid increasing, gradual decreasing, and periodic oscillation. The periodic oscillation of the jet tip velocity and the jet velocity at the outlet of orifice hole is caused by the effect of forward and reverse shock waves. The calculation results of CH4/NH3/O2 mixture jet flame show that the addition of ammonia has significant effects on the flame propagation process in PC, the thermodynamic state of PC, and the propagation characteristics of jet flame. With the increase of ammonia proportion, the maximum pressure of PC gradually decreases and the pressure rise rate slows down. Meanwhile, the two-stage (the high-speed development stage and the low-speed development stage) characteristic of jet propagation process gradually disappears. And the addition of ammonia is more likely to destroy the two-stage characteristic under low initial pressure.

The BOAT GRB 221009A: A Poynting-flux-dominated narrow jet surrounded by a matter-dominated structured jet wing

We argue that the broad-band observations of the brightest-of-all-time (BOAT) GRB 221009A reveal a physical picture involving two jet components: a narrow (∼0.6 degree half opening angle) pencil-beam jet that has a Poynting-flux-dominated jet composition, and a broader matter-dominated jet with an angular structure. We discuss various observational evidence that supports such a picture. To treat the problem, we develop an analytical structured jet model for both forward and reverse shock emission from the matter dominated structured jet wing during the deceleration phase. We discuss the physical implications of such a two-component jet configuration for this particular burst and for GRBs in general. We argue that in a quasi-universal structured jet scenario, some bright X-ray flares could be similar narrow jets viewed slightly outside the narrow jet cone and that narrow jets may exist in many more GRBs without being detected.

Relativistic shocks in conductive media

Context. Relativistic shocks are present in all high-energy astrophysical processes involving relativistic plasma outflows interacting with their ambient medium. While they are well understood in the context of relativistic hydrodynamics and ideal magnetohydrodynamics (MHD), there is a limited understanding of the properties related to their propagation in media characterized by finite electrical conductivity. Aims. This work presents a systematic method for the derivation and solution of the jump conditions for relativistic shocks propagating in MHD media with finite electrical conductivity. This method is applied to the numerical solution of the Riemann problem and the determination of the conditions inside the blastwave that is formed when ultrarelativistic magnetized ejecta interact with the circumburst medium during a gamma-ray burst. Methods. We derived the covariant relations expressing the jump conditions in a frame-independent manner. The resulting algebraic equations expressing the Rankine-Hugoniot conditions in the propagation medium’s frame were then solved numerically. A variable adiabatic index equation of state was used in order to obtain a realistic description of the post-shock fluid’s thermodynamics. This method was then employed for the solution of the Riemann problem for the case of a forward and a reverse shock, both of which form during the interaction of a gamma-ray burst ejecta with the circumburst medium. This allowed us to determine the kinematics of the resulting blastwave and the dynamical conditions in its interior. Results. Our solutions clearly depict the impact of the plasma’s electrical conductivity in the properties of the post-shock medium. Two characteristic regimes are identified with respect to the value of a dimensionless parameter that has a linear dependence on the conductivity. For small values of this parameter, the shock affects only the hydrodynamic properties of the propagation medium and leaves its electromagnetic field unaffected. No current layer forms in the shock front; thus, we refer to this as the current-free regime. For large values of this parameter, the ideal MHD regime has been retrieved. We also show that the assumption of a finite electrical conductivity can lead to higher efficiencies in the conversion of the ejecta energy into thermal energy of the blastwave through the reverse shock. The theory developed in this work can be applied to the construction of Riemann solvers for resistive relativistic MHD (RR4MHD).

Fast as Potoroo: Radio continuum detection of a bow-shock pulsar wind nebula powered by pulsar J1638–4713

Abstract We report the discovery of a bow-shock pulsar wind nebula (PWN), named Potoroo, and the detection of a young pulsar J1638 $-$ 4713 that powers the nebula. We present a radio continuum study of the PWN based on 20-cm observations obtained from the Australian Square Kilometre Array Pathfinder (ASKAP) and MeerKAT. PSR J1638 $-$ 4713 was identified using Parkes radio telescope observations at frequencies above 3 GHz. The pulsar has the second-highest dispersion measure of all known radio pulsars (1 553 pc cm $^{-3}$ ), a spin period of 65.74 ms and a spin-down luminosity of $\dot{E}=6.1\times10^{36}$ erg s $^{-1}$ . The PWN has a cometary morphology and one of the greatest projected lengths among all the observed pulsar radio tails, measuring over 21 pc for an assumed distance of 10 kpc. The remarkably long tail and atypically steep radio spectral index are attributed to the interplay of a supernova reverse shock and the PWN. The originating supernova remnant is not known so far. We estimated the pulsar kick velocity to be in the range of 1 000–2 000 km s $^{-1}$ for ages between 23 and 10 kyr. The X-ray counterpart found in Chandra data, CXOU J163802.6 $-$ 471358, shows the same tail morphology as the radio source but is shorter by a factor of 10. The peak of the X-ray emission is offset from the peak of the radio total intensity (Stokes $\rm I$ ) emission by approximately 4.7 $^{\prime\prime}$ , but coincides well with circularly polarised (Stokes $\rm V$ ) emission. No infrared counterpart was found.

Assessing Reverse Shock Index as a Survival Predictor for Trauma Patients in Emergency Settings: A Retrospective Observational Study

ntroduction: Identifying trauma patients with shock is crucial, as early intervention and prompt treatment improve patient prognosis and survival. To address this, the ratio of Systolic Blood Pressure (SBP) and Heart Rate (HR), known as the Reverse Shock Index (RSI), is measured. Aim: To evaluate the effectiveness of RSI calculation in assessing prognosis. Materials and Methods: This was a retrospective observational study in which data were retrospectively collected on trauma patients treated in the Emergency Room (ER) at Dhiraj Hospital, Sumandeep Vidyapeeth Deemed to be University, Vadodara, Gujarat, India, from January 2021 to December 2022. Patients involved in road traffic accidents, fall from a height of ≥6 m, assault, and machinery injuries were included. Upon arrival, vital signs such as HR, SBP, Respiratory Rate (RR), Glasgow Coma Scale (GCS), associated injuries, and in-hospital mortality were documented. Any resuscitative procedures required, such as Cardiopulmonary Resuscitation (CPR), intubation, oxygen therapy, chest tube insertion, and blood transfusion, were also recorded. The RSI was calculated for all trauma patients and divided into two groups (RSI &lt;1 and RSI ≥1). The t-test was performed with a 95% Confidence Interval (CI). Results: Out of 363 patients, data from 320 patients were included. Among them, 55 patients (17.2%) had RSI &lt;1, and 265 patients (82.8%) had RSI ≥1. Patients with RSI &lt;1 exhibited lower GCS scores, tachypnoea (RR &gt;29), or bradypnoea (RR &lt;10), along with higher mortality rates. These patients also required resuscitative interventions. Those with RSI &lt;1 experienced more head injuries, thoracic trauma, and maxillofacial injuries (p&lt;0.001). Conclusion: The RSI &lt;1 in trauma patients demonstrated significantly higher predictive accuracy for adverse outcomes, serving as a primary tool for early intervention and aggressive care in the ER.

A Multiwavelength Investigation of PSR J2229+6114 and its Pulsar Wind Nebula in the Radio, X-Ray, and Gamma-Ray Bands

G106.3+2.7, commonly considered to be a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct (“head” and “tail”) regions in the radio band. A discovery of very-high-energy gamma-ray emission (E γ > 100 GeV) followed by the recent detection of ultrahigh-energy gamma-ray emission (E γ > 100 TeV) from the tail region suggests that G106.3+2.7 is a PeVatron candidate. We present a comprehensive multiwavelength study of the Boomerang PWN (100″ around PSR J2229+6114) using archival radio and Chandra data obtained two decades ago, a new NuSTAR X-ray observation from 2020, and upper limits on gamma-ray fluxes obtained by Fermi-LAT and VERITAS observatories. The NuSTAR observation allowed us to detect a 51.67 ms spin period from the pulsar PSR J2229+6114 and the PWN emission characterized by a power-law model with Γ = 1.52 ± 0.06 up to 20 keV. Contrary to the previous radio study by Kothes et al., we prefer a much lower PWN B-field (B ∼ 3 μG) and larger distance (d ∼ 8 kpc) based on (1) the nonvarying X-ray flux over the last two decades, (2) the energy-dependent X-ray size of the PWN resulting from synchrotron burn-off, and (3) the multiwavelength spectral energy distribution (SED) data. Our SED model suggests that the PWN is currently re-expanding after being compressed by the SNR reverse shock ∼1000 yr ago. In this case, the head region should be formed by GeV–TeV electrons injected earlier by the pulsar propagating into the low-density environment.

Stream Interaction Regions in the Minimum of Solar Cycles 23 and 24

AbstractStream interaction regions (SIRs) dominate the large‐scale solar wind dynamics during the minimum of the solar cycle. The interaction of SIRs with the magnetosphere causes most of geomagnetic storms during this epoch. We used in‐situ solar wind observations at 1 AU to study 62 SIRs detected in the interval 2007–2008 (minimum of cycle 23) and 61 SIRs in the interval 2018–2019 (minimum of cycle 24). We compared distinct characteristics of SIRs, such as the solar wind streams velocities, the presence of forward and/or reverse shocks (RS), SIR radial widths, the relative position of the stream interface within the SIRs, SIR latitudinal orientation, and the geoeffectiveness. There were more geomagnetic storms driven by SIRs in cycle 23 than in cycle 24. The pattern of fast solar wind streams in cycle 23 tended to be faster than in cycle 24. We found more SIRs with RS in cycle 23 than in cycle 24. For the geoeffective SIRs, the momentum flows from the fast solar wind to the slow solar wind, as well as their stream interface is closer to the SIR front. Coronal holes associated with SIRs registered in cycle 23 tended to be wider in longitude near the solar equator and/or at midlatitudes. We did not find a clear relation between the geoeffectiveness of the SIRs and their latitudinal inclinations.

Internal shocks hydrodynamics: the collision of two cold shells in detail

ABSTRACT Emission in many astrophysical transients originates from a shocked fluid. A central engine typically produces an outflow with varying speeds, leading to internal collisions within the outflow at finite distances from the source. Each such collision produces a pair of forward and reverse shocks with the two shocked regions separated by a contact discontinuity (CD). As a useful approximation, we consider the head-on collision between two cold and uniform shells (a slower leading shell and a faster trailing shell) of finite radial width, and study the dynamics of shock propagation in planar geometry. We find significant differences between the forward and reverse shocks, in terms of their strength, internal energy production efficiency, and the time it takes for the shocks to sweep through the respective shells. We consider the subsequent propagation of rarefaction waves in the shocked regions and explore the cases where these waves can catch up with the shock fronts and thereby limit the internal energy dissipation. We demonstrate the importance of energy transfer from the trailing to leading shell through pdV work across the CD. We outline the parameter space regions relevant for models of different transients,e.g. Gamma-ray burst internal shock model, fast radio burst blast wave model, Giant flare due to magnetars, and superluminous supernovae ejecta. We find that the reverse shock likely dominates the internal energy production for many astrophysical transients.

Reverse Shock Index multiplied by Glasgow Coma Scale score as a point-of-care severity assessment for initial trauma management: a nationwide cohort study

BackgroundSevere trauma patients often require emergent interventions, such as massive transfusion, resuscitative procedures, and surgical procedures, and consume considerable human and medical resources. However, few practical indices can be easily used for emergent interventions. In recent years, it has become clear that rSIG (Reverse Shock Index multiplied by Glasgow Coma Scale [GCS] score), which can be easily calculated from vital signs, is a promising predictor of mortality. However, it is unclear whether rSIG is useful for emergent interventions. MethodsData collected by the Japan Trauma Data Bank for adult patients admitted directly from the scene of trauma between April 2019 and December 2020 were analysed. The outcomes were massive transfusion, resuscitative procedures, surgical procedures and emergent interventions. Emergent interventions were defined as the composite outcome of massive transfusion, resuscitative procedures, and surgical procedures. The ability of rSIG to predict massive transfusion was compared with that of the ABC score and FASILA score by receiver-operating characteristic curve analysis. The ability of rSIG to predict resuscitative and surgical procedures was compared with that of the Shock Index (SI), GCS, Triage Revised Trauma score (T-RTS), and Previous Simple Prediction (PSP) score. The ability of rSIG to predict emergent interventions was compared with that of T-RTS, PSP, ABC, and FASILA. In addition to rSIG, rSIM (Reverse Shock Index multiplied by best motor response score) was also analysed as a supplement. ResultsThe study included 32,201 patients, 6,371 of whom required emergent interventions. The area under the receiver-operating characteristic curve (AUROC) for massive transfusion was highest for rSIG (0.846 [95% confidence interval 0.832–0.859]) and significantly higher for rSIG than for rSIM, ABC and FASILA (all p<0.0001). AUROCs for resuscitative and surgical procedures were highest for rSIG (0.777 [0.769–0.785] and 0.731 [0.720–0.741], respectively) and significantly higher than those for rSIM, SI, GCS, T-RTS, and PSP (all p<0.0001). The AUROC for emergent interventions was highest for rSIG (0.760 [0.753–0.768]) and significantly higher for rSIG than for rSIM, T-RTS, PSP, ABC, or FASILA (all p<0.0001). ConclusionsrSIG is a simple and effective point-of-care predictor of emergent interventions during initial management of trauma.

Reverse shock index (RSI) as a predictor of post-intubation cardiac arrest (PICA)

BackgroundEndotracheal intubation (ETI) in critically ill patients is a high-risk procedure due to the increased risk of cardiac arrest, and several factors may predict poor outcomes in these patients. The aim of this study was to investigate the role of some factors, especially newly introduced vital signs such as the reverse shock index (RSI), in predicting post-intubation cardiac arrest (PICA) in critically ill adult patients.MethodsThis cross-sectional study was conducted on critically ill patients over 18 years of age who were admitted to the emergency department (ED) and underwent ETI within 1 year. Patients who developed PICA and those without this event were included in the study, and their features were compared. The primary outcome was cardiac arrest.ResultsOf 394 patients, 127 patients were included, of whom 95 (74.8%) developed PICA, and 32 (25.2%) did not experience cardiac arrest after intubation. In multivariate analysis, age, RSI, oxygen saturation, and total bilirubin were significantly associated with PICA. In addition, patients with RSI < 1 had a significantly higher risk of developing PICA (odds ratio = 5.22, 95% CI 1.83–14.86, p = 0.002). The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for predicting PICA were 51.11%, 83.33%, 90.2%, 36.23%, and 59.17%, respectively. The ROC curve for RSI showed an area under the curve (AUC) of 0.66.ConclusionRSI may be useful in predicting PICA with higher diagnostic accuracy compared to the shock index. Furthermore, advanced age, hypoxia, and hyperbilirubinemia may increase the risk of PICA in patients admitted to the ED.