Dynamics and stability of relativistic GRB blast waves

In gamma-ray-bursts (GRB), ultra-relativistic blast waves are ejected into the circumburst medium. We analyse in unprecedented detail the deceleration of a self-similar Blandford-McKee blast wave from a Lorentz factor 25 to the nonrelativistic Sedov phase. Our goal is to determine the stability properties of its frontal shock. We carried out a grid-adaptive relativistic 2D hydro-simulation at extreme resolving power, following the GRB jet during the entire afterglow phase. We investigate the effect of the finite initial jet opening angle on the deceleration of the blast wave, and identify the growth of various instabilities throughout the coasting shock front. We find that during the relativistic phase, the blast wave is subject to pressure-ram pressure instabilities that ripple and fragment the frontal shock. These instabilities manifest themselves in the ultra-relativistic phase alone, remain in full agreement with causality arguments, and decay slowly to finally disappear in the near-Newtonian phase as the shell Lorentz factor drops below 3. From then on, the compression rate decreases to levels predicted to be stable by a linear analysis of the Sedov phase. Our simulations confirm previous findings that the shell also spreads laterally because a rarefaction wave slowly propagates to the jet axis, inducing a clear shell deformation from its initial spherical shape. The blast front becomes meridionally stratified, with decreasing speed from axis to jet edge.Comment: accepted for publication in A&

Transverse stability of relativistic two-component jets

Context: Astrophysical jets from various sources seem to be stratified, with a fast inner jet and a slower outer jet. As it is likely that the launching mechanism for each component is different, their interface will develop differential rotation, while the outer jet radius represents a second interface where disruptions may occur. Aims: We explore the stability of stratified, rotating, relativistic two-component jets, in turn embedded in static interstellar medium. Methods: In a grid-adaptive relativistic hydrodynamic simulation with the AMRVAC code, the non-linear azimuthal stability of two-component relativistic jets is investigated. We simulate until multiple inner jet rotations have been completed. Results: We find evidence for the development of an extended shear flow layer between the two jet components, resulting from the growth of a body mode in the inner jet, Kelvin-Helmholtz surface modes at their original interface, and their nonlinear interaction. Both wave modes are excited by acoustic waves which are reflected between the symmetry axis and the interface of the two jet components. Their interaction induces the growth of near stationary, counterrotating vortices at the outer edge of the shear flow layer. The presence of a heavy external jet allows to slow down their further development, and maintain a collimated flow. At the outer jet boundary, small-scale Rayleigh-Taylor instabilities develop, without disrupting the jet configuration. Conclusion: We demonstrate that the cross-section of two-component relativistic jets, with a heavy, cold outer jet, is non-linearly stable.Comment: Accepted in A&A 24/09/200

Faktor-Faktor yang Berhubungan dengan Kepatuhan Mengkonsumsi Tablet Fe Pada Ibu Hamil di Puskemas Pembina Palembang Tahun 2022

Masalah gizi pada bayi dan anak disebabkan kebiasaan pemberian ASI dan MP-ASI yang tidak tepat (kuantitas dan kualitas). Selain itu, para ibu kurang menyadari bahwa sejak bayi berusia lebih dari 6 bulan sudah memerlukan MP-ASI dalam jumlah dan mutu yang baik. Tujuan penelitian ini untuk mengetahui hubungan pengetahuan, sikap ibu dan dukungan keluarga terhadap ketepatan pemberian MP-ASI. Data Dinkes Provinsi Sumatera Selatan tentang cakupan pemberian ASI eksklusif pada tahun 2020 sebesar 52,71% masih dibawah target rencana strategi sebesar 64%. Jenis penelitian ini adalah analitik korelasional dengan pendekatan cross sectional. Populasi dalam penelitian ini adalah semua ibu yang mempunyai anak usia lebih dari 6 bulan - 24 bulan di wilayah kerja Puskesmas Pematang Panggang II tahun 2022 adalah 135 orang. Sampel diambil menggunakan tehnik Simple Random Sampling, dan diperoleh sampel sebanyak 57 responden. Pengumpulan data dilakukan dengan kuesioner dan dianalisis dengan uji Chi-square. Hasil penelitian menunjukkan ada hubungan yang bermakna antara pengetahuan, sikap ibu dan dukungan keluarga secara simultan dengan ketepatan pemberian MP-ASI, dengan nilai masing-masing variabel pengetahuan (p=<0,001), sikap ibu (p=<0,001), dukungan keluarga (p=<0,001). Disarankan agar ibu balita menambah pengetahuan dan mempertahankan sikap positif terhadap ketepatan pemberian MP-ASI, selain itu, tenaga kesehatan juga harus mensosialisasikan tentang dukungan keluarga terhadap ketepatan pemberian MP-ASI

Effect of angular opening on the dynamics of relativistic hydro jets

Context. Relativistic jets emerging from AGN cores transfer energy from the core to their surrounding ISM/IGM. Because jets are observed to have finite opening angles, one needs to quantify the role of conical versus cylindrical jet propagation in this energy transfer. Aims. We use FR-II AGN jets parameter with finite opening angles. We study the effect of the variation of the opening angle on the dynamics and energy transfer of the jet. We also point out how the characteristics of this external medium, such as its density profile, play a role in the dynamics. Methods. This study exploits our parallel AMR code MPI-AMRVAC with its special relativistic hydrodynamic model, incorporating an equation of state with varying effective polytropic index. We studied mildly under-dense jets up to opening angles of 10 degrees, at Lorentz factors of about 10, inspired by observations. Instantaneous quantification of the various ISM volumes and their energy content allows one to quantify the role of mixing versus shock-heated cocoon regions over the time intervals. Results. We show that a wider opening angle jet results in a faster deceleration of the jet and leads to a wider cocoon dominated by Kelvin-Helmholtz and Rayleigh-Taylor instabilities. The energy transfer mainly occurs in the shocked ISM region by both the frontal bow shock and cocoon-traversing shock waves, in a roughly 3 to 1 ratio to the energy transfer of the mixing zone, for a 5 degree opening angle jet. A rarefaction wave induces a dynamically formed layered structure of the jet beam. Conclusions. Finite opening angle jets can efficiently transfer significant fractions (25 % up to 70 %) of their injected energy over a growing region of shocked ISM matter. The role of the ISM stratification is prominent for determining the overall volume that is affected by relativistic jet injection

DRIVING FACTOR ANALYSIS OF LAND USE CHANGE USING ANALYTICAL HIERARCHY PROCESS (AHP) METHOD (CASE: DAS WAERUHU OF AMBON CITY)

Land development in the Waeruhu watershed moves dynamically due to changes in land cover/land use. The phenomenon of land use change is inseparable from the demand for land along with the increasing population in Ambon City. The aim of this study was to determine the factors that influence changes in land cover/land use in the Waeruhu watershed. Analysis of the factors that influence land use change using the AHP (Analytical Hierarchy Process) method. Factors analyzed in this study include settlements, trade and service centers, educational facilities, roads and rivers. Determination of respondents in this study was determined by purposive sampling, namely Bapedalitbang Ambon City, Maluku River Hall, and Academics. The results showed that settlements had a weighted factor (0.40) which had the most influence on land use changes in the Waeruhu watershed, while the least influential factor was river network with a factor weight of (0.06). Changes in land use that occur in the Waeruhu watershed are thought to be triggered by the increasing rate of population growth which has an impact on increasing the need for land to be built up. &nbsp

ANALISIS FAKTOR-FAKTOR SELF REGULATED LEARNING MAHASISWA PENDIDIKAN TEKNOLOGI AGROINDUSTRI SETELAH MENGGUNAKAN APLIKASI SPOT UPI (SISTEM PEMBELAJARAN ONLINE TERPADU)

Penelitian ini bertujuan untuk mengetahui faktor-faktor self regulated learning yang dominan pada mahasiswa Pendidikan Teknologi Agroindustri setelah menggunakan Sistem Pembelajaran Online Terpadu (SPOT) dan mengetahui kemampuan self regulated learning pada mahasiswa Pendidikan Teknologi Agroindustri setelah menggunakan SPOT. Metode penelitian yang digunakan yaitu metode deskriptif kuantitatif. Instrumen yang digunakan yaitu angket mengenai self regulated learning dan angket mengenai penggunaan SPOT. Aspek yang dinilai pada angket self regulated learning terdiri dari (A) goal setting and planning, (B) rehearsing and memorizing, (C) organizing and transforming, (D) self evaluating, (E) self consequence, (F) seeking social assistance, (G) environmental structuring, (H) keeping records and monitoring, (I) seeking information, (J) reviewing records dan (K) other (help seeking). Teknik pengambilan sampel menggunakan teknik purposive sampling sebanyak 102 responden. Hasil penelitian menunjukkan kebanyakan mahasiswa menggunakan aplikasi SPOT UPI karena dosen pengampu mata kuliah juga menggunakan SPOT dan mahasiswa menggunakan SPOT untuk mengunduh materi perkuliahan. Hasil penelitian menunjukkan bahwa aplikasi SPOT UPI dapat mengembangkan dua kemampuan self regulated learning yaitu organizing and transforming (pengorganisasian dan pentransformasian) sebesar 70,59%. dan seeking information (mencari informasi) sebesar 70,59%. Faktor perilaku merupakan faktor yang paling dominan pada mahasiswa Pendidikan Teknologi Agroindustri setelah menggunakan aplikasi SPOT UPI dengan persentase sebesar 65,33%. Hasil penelitian ini menunjukkan bahwa aplikasi SPOT UPI dapat mendukung atau menunjang dua kemampuan self regulated learning yaitu organizing and transforming dan seeking information. ;---The study aims was to determine the dominant factors of self-regulated learning on students of Study program Agroindustry Technology Education after using the Integrated Online Learning System (SPOT) and to know the ability of self-regulated learning in the Agroindustry Technology Education students after using SPOT. The research method used was descriptive quantitative method. Instruments used was questionnaire about self-regulated learning and questionnaire about the use of SPOT. Aspects assessed in self-regulated learning questionnaire consist of (A) goal setting and planning, (B) rehearsing and memorizing, (C) organizing and transforming, (D) self evaluating, (E) self consequence, (F) seeking social assistance, (G) environmental structuring, (H) keeping records and monitoring, (I) seeking information, (J) reviewing records and (K) other (help seeking). Sampling technique using purposive sampling technique to 102 respondents. The result showed that most student use SPOT because lecturers also use SPOT and students use SPOT to download the course material. The result showed that SPOT UPI application can develop two capabilities of self-regulated learning that is organizing and transforming equal to 70,59% and seeking information (70,59%). Behavioral factor was the most dominant factor in the students of Agroindustry Technology Education after using SPOT UPI application with the percentage of 65,33%. The result showed that SPOT UPI application can support the two capabilities of self-regulated learning that is organizing and transforming and seeking information

Shape and evolution of wind-blown bubbles of massive stars: on the effect of the interstellar magnetic field

The winds of massive stars create large (>10 pc) bubbles around their progenitors. As these bubbles expand they encounter the interstellar coherent magnetic field which, depending on its strength, can influence the shape of the bubble. We wish to investigate if, and how much, the interstellar magnetic field can contribute to the shape of an expanding circumstellar bubble around a massive star. We use the MPI-AMRVAC code to make magneto-hydrodynamical simulations of bubbles, using a single star model, combined with several different field strengths: B = 5, 10, and 20 muG for the interstellar magnetic field. This covers the typical field strengths of the interstellar magnetic fields found in the galactic disk and bulge. Furthermore, we present two simulations that include both a 5 muG interstellar magnetic field and a 10,000 K interstellar medium and two different ISM densities to demonstrate how the magnetic field can combine with other external factors to influence the morphology of the circumstellar bubbles. Our results show that low magnetic fields, as found in the galactic disk, inhibit the growth of the circumstellar bubbles in the direction perpendicular to the field. As a result, the bubbles become ovoid, rather than spherical. Strong interstellar fields, such as observed for the galactic bulge, can completely stop the expansion of the bubble in the direction perpendicular to the field, leading to the formation of a tube-like bubble. When combined with a warm, high-density ISM the bubble is greatly reduced in size, causing a dramatic change in the evolution of temporary features inside the bubble. The magnetic field of the interstellar medium can affect the shape of circumstellar bubbles. This effect may have consequences for the shape and evolution of circumstellar nebulae and supernova remnants, which are formed within the main wind-blown bubble.Comment: Proposed for acceptance for publication in Astronomy & Astrophysics. The published version will contain animations of each simulatio

Synchrotron radiation of self-collimating relativistic MHD jets

The goal of this paper is to derive signatures of synchrotron radiation from state-of-the-art simulation models of collimating relativistic magnetohydrodynamic (MHD) jets featuring a large-scale helical magnetic field. We perform axisymmetric special relativistic MHD simulations of the jet acceleration region using the PLUTO code. The computational domain extends from the slow magnetosonic launching surface of the disk up to 6000^2 Schwarzschild radii allowing to reach highly relativistic Lorentz factors. The Poynting dominated disk wind develops into a jet with Lorentz factors of 8 and is collimated to 1 degree. In addition to the disk jet, we evolve a thermally driven spine jet, emanating from a hypothetical black hole corona. Solving the linearly polarized synchrotron radiation transport within the jet, we derive VLBI radio and (sub-) mm diagnostics such as core shift, polarization structure, intensity maps, spectra and Faraday rotation measure (RM), directly from the Stokes parameters. We also investigate depolarization and the detectability of a lambda^2-law RM depending on beam resolution and observing frequency. We find non-monotonic intrinsic RM profiles which could be detected at a resolution of 100 Schwarzschild radii. In our collimating jet geometry, the strict bi-modality in polarization direction (as predicted by Pariev et al.) can be circumvented. Due to relativistic aberration, asymmetries in the polarization vectors across the jet can hint to the spin direction of the central engine.Comment: Submitted to Ap

AMRVAC and Relativistic Hydrodynamic simulations for GRB afterglow phases

We apply a novel adaptive mesh refinement code, AMRVAC, to numerically investigate the various evolutionary phases in the interaction of a relativistic shell with its surrounding cold Interstellar Medium (ISM). We do this for both 1D isotropic as well as full 2D jetlike fireball models. This is relevant for Gamma Ray Bursts, and we demonstrate that, thanks to the AMR strategy, we resolve the internal structure of the shocked shell-ISM matter, which will leave its imprint on the GRB afterglow. We determine the deceleration from an initial Lorentz factor $\gamma=100$ up to the almost Newtonian $\gamma\sim{\cal O}(2)$ phase of the flow. We present axisymmetric 2D shell evolutions, with the 2D extent characterized by their initial opening angle. In such jetlike GRB models, we discuss the differences with the 1D isotropic GRB equivalents. These are mainly due to thermally induced sideways expansions of both the shocked shell and shocked ISM regions. We found that the propagating 2D ultrarelativistic shell does not accrete all the surrounding medium located within its initial opening angle. Part of this ISM matter gets pushed away laterally and forms a wide bow-shock configuration with swirling flow patterns trailing the thin shell. The resulting shell deceleration is quite different from that found in isotropic GRB models. As long as the lateral shell expansion is merely due to ballistic spreading of the shell, isotropic and 2D models agree perfectly. As thermally induced expansions eventually lead to significantly higher lateral speeds, the 2D shell interacts with comparably more ISM matter and decelerates earlier than its isotropic counterpart.Comment: 12 pages, accepted in MNRAS, 12/01/200