Fast Plasma Flows Downstream of the Bow Shock Using MMS: Correlations and Generation Mechanisms

2021 ◽  
Author(s):  
Savvas Raptis ◽  
Tomas Karlsson ◽  
Ferdinand Plaschke ◽  
Anita Kullen ◽  
Per-Arne Lindqvist
Keyword(s):  
Dynamic Pressure ◽  
Bow Shock ◽  
Magnetic Islands ◽  
Plasma Flows ◽  
Outer Radiation Belt ◽  
Full Dataset ◽  
Close Proximity ◽  
Radiation Belt Electrons ◽  
Generation Mechanisms ◽  
Magnetosphere Plasma

<p>Fast plasma flows (magnetosheath jets) are localized and transient dynamic pressure enhancements found downstream of the Earth’s bow shock, in the magnetosheath region. They can be attributed to density and/or density enhancements and they are an energetic manifestation of the solar wind-magnetosphere coupling. They have been associated to several phenomena such as magnetopause reconnection, direct magnetosphere plasma inflow and the energization of the outer radiation belt electrons.</p><p>In this work, we are investigating the properties of a dataset of 9196 jets found by Magnetospheric Multiscale (MMS) from 09/2015 to 09/2020. These jets are classified into different classes based on their associated bow shock configuration. From the full dataset, about 300 jets are distinguished by being in very close proximity to a bow shock transition.</p><p>This subset of jet is then carefully pre-processed and statistically analyzed, providing information regarding the likelihood of existent (bow shock ripples, SLAMS penetration) and newly proposed (magnetic reconnection, magnetic islands) generation mechanisms for these jets. The initial results of these events support the pre-existing generation mechanism while giving indications to other possible effects that may take place.</p>

The Aerodynamics of Three-Dimensional Vaned Diffusers in Industrial Centrifugal Compressors

2005 ◽  
Author(s):  
Ahmed Abdelwahab
Keyword(s):  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Pressure Recovery ◽  
Navier Stokes ◽  
Spanwise Direction ◽  
Two Dimensional ◽  
Blade Loading ◽  
Recovery Capacity ◽  
Close Proximity

Vaned diffusers have been used successfully as efficient and compact dynamic pressure recovery devices in industrial centrifugal compressor stages. Typically such diffusers consist of a cascade of two-dimensional blades distributed circumferentially at close proximity to the impeller exit. In this paper three low-solidity diffuser blade geometries are numerically investigated. The first geometry employs variable stagger stacking of similar blade sections along the blade span. The second employs linearly inclined stacking to generate blade lean along the diffuser span. The third geometry employs the conventional two-dimensional low-solidity diffuser geometry with no variable stagger or lean. The variable stagger blade arrangement has the potential of better aligning the diffuser leading edges with the highly non-uniform flow leaving the impeller. Both variable stagger and linearly leaned diffuser blade arrangements, however, have the effect of redistributing the blade loading and flow streamlines in the spanwise direction leading to improved efficiency and pressure recovery capacity of the diffuser. In this paper a description of the proposed diffuser geometries is presented. The results of Three-dimensional Navier-Stokes numerical simulations of the three centrifugal compressor arrangements are discussed. Comparisons between the performance of the two and three-dimensional diffuser blade geometries are presented. The comparisons indeed show that the variable stagger and leaned diffusers present an improvement in the diffuser operating range and pressure recovery capacity over the conventional two-dimensional diffuser geometry.

scholarly journals Multi-satellite simultaneous observations of magnetopause and atmospheric losses of radiation belt electrons during an intense solar wind dynamic pressure pulse

2016 ◽  
Vol 34 (5) ◽  
pp. 493-509 ◽  
Author(s):  
Zheng Xiang ◽  
Binbin Ni ◽  
Chen Zhou ◽  
Zhengyang Zou ◽  
Xudong Gu ◽  
...  
Keyword(s):  
Solar Wind ◽  
Radiation Belt ◽  
Pressure Pulse ◽  
Electron Flux ◽  
Dynamic Pressure ◽  
Energetic Electron ◽  
Solar Wind Dynamic Pressure ◽  
Angle Scattering ◽  
Radiation Belt Electrons ◽  
Atmospheric Loss

<p><strong>Abstract.</strong> Radiation belt electron flux dropouts are a kind of drastic variation in the Earth's magnetosphere, understanding of which is of both scientific and societal importance. Using electron flux data from a group of 14 satellites, we report multi-satellite simultaneous observations of magnetopause and atmospheric losses of radiation belt electrons during an event of intense solar wind dynamic pressure pulse. When the pulse occurred, magnetopause and atmospheric loss could take effect concurrently contributing to the electron flux dropout. Losses through the magnetopause were observed to be efficient and significant at <i>L</i> ≳ 5, owing to the magnetopause intrusion into <i>L</i> ∼ 6 and outward radial diffusion associated with sharp negative gradient in electron phase space density. Losses to the atmosphere were directly identified from the precipitating electron flux observations, for which pitch angle scattering by plasma waves could be mainly responsible. While the convection and substorm injections strongly enhanced the energetic electron fluxes up to hundreds of keV, they could delay other than avoid the occurrence of electron flux dropout at these energies. It is demonstrated that the pulse-time radiation belt electron flux dropout depends strongly on the specific interplanetary and magnetospheric conditions and that losses through the magnetopause and to the atmosphere and enhancements of substorm injection play an essential role in combination, which should be incorporated as a whole into future simulations for comprehending the nature of radiation belt electron flux dropouts.</p>

scholarly journals Magnetospheric Response to Solar Wind Forcing: ULF Wave – Particle Interaction Perspective

2021 ◽  
Author(s):  
Qiugang Zong
Keyword(s):  
Solar Wind ◽  
Radiation Belt ◽  
Ring Current ◽  
Dynamic Pressure ◽  
Plasma Heating ◽  
Interplanetary Shock ◽  
Wind Forcing ◽  
Ulf Waves ◽  
Radiation Belt Electrons ◽  
The Impact

Abstract. Solar wind forcing, e.g. interplanetary shock and/or solar wind dynamic pressure pulses impact on the Earth’s magnetosphere manifests many fundamental important space physics phenomena including producing electromagnetic waves, plasma heating and energetic particle acceleration. This paper summarizes our present understanding of the magnetospheric response to solar wind forcing in the aspects of radiation belt electrons, ring current ions and plasmaspheric plasma physics based on in situ spacecraft measurements, ground-based magnetometer data, MHD and kinetic simulations. Magnetosphere response to solar wind forcing, is not just a “one-kick” scenario. It is found that after the impact of solar wind forcing on the Earth’s magnetosphere, plasma heating and energetic particle acceleration started nearly immediately and could last for a few hours. Even a small dynamic pressure change of interplanetary shock or solar wind pressure pulse can play a non-negligible role in magnetospheric physics. The impact leads to generate series kind of waves including poloidal mode ultra-low frequency (ULF) waves. The fast acceleration of energetic electrons in the radiation belt and energetic ions in the ring current region response to the impact usually contains two contributing steps: (1) the initial adiabatic acceleration due to the magnetospheric compression; (2) followed by the wave-particle resonant acceleration dominated by global or localized poloidal ULF waves excited at various L-shells. Generalized theory of drift and drift-bounce resonance with growth or decay localized ULF waves has been developed to explain in situ spacecraft observations. The wave related observational features like distorted energy spectrum, boomerang and fishbone pitch angle distributions of radiation belt electrons, ring current ions and plasmaspheric plasma can be explained in the frame work of this generalized theory. It is worthy to point out here that poloidal ULF waves are much more efficient to accelerate and modulate electrons (fundamental mode) in the radiation belt and charged ions (second harmonic) in the ring current region. The results presented in this paper can be widely used in solar wind interacting with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune, and other astrophysical objects with magnetic fields.

Simulations of the Relativistic Radiation Belt Electrons Using the VERB-3D Code

2021 ◽  
Author(s):  
Dedong Wang ◽  
Yuri Shprits ◽  
Alexander Drozdov ◽  
Nikita Aseev ◽  
Irina Zhelavskaya ◽  
...  
Keyword(s):  
Space Weather ◽  
Radiation Belt ◽  
Model Performance ◽  
Dynamic Evolution ◽  
Relativistic Electrons ◽  
Outer Radiation Belt ◽  
Chorus Waves ◽  
Van Allen Probes ◽  
Radiation Belt Electrons ◽  
Simulation Results

&lt;p&gt;Using the three-dimensional Versatile Electron Radiation Belt (VERB-3D) code, we perform simulations to investigate the dynamic evolution of relativistic electrons in the Earth&amp;#8217;s outer radiation belt. In our simulations, we use data from the Geostationary Operational Environmental Satellites (GOES) to set up the outer boundary condition, which is the only data input for simulations. The magnetopause shadowing effect is included by using last closed drift shell (LCDS), and it is shown to significantly contribute to the dropouts of relativistic electrons at high $L^*$. We validate our simulation results against measurements from Van Allen Probes. In long-term simulations, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modeling of megaelectron volt (MeV) electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they cannot only produce a net acceleration but also a net loss of MeV electrons. Decrease in high&amp;#8208;latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high&amp;#8208;latitude waves can result in a net loss of MeV electrons. Variations in high&amp;#8208;latitude chorus may account for some of the variability of MeV electrons.&amp;#160;&lt;/p&gt;&lt;p&gt;Our simulation results for the NSF GEM Challenge Events show that the position of the plasmapause plays a significant role in the dynamic evolution of relativistic electrons. We also perform simulations for the COSPAR International Space Weather Action Team (ISWAT) Challenge for the year 2017. The COSPAR ISWAT is a global hub for collaborations addressing challenges across the field of space weather. One of the objectives of the G3-04 team &amp;#8220;Internal Charging Effects and the Relevant Space Environment&amp;#8221; is model performance assessment and improvement. One of the expected outputs is a more systematic assessment of model performance under different conditions. The G3-04 team proposed performing benchmarking challenge runs. We &amp;#8216;fly&amp;#8217; a virtual satellite through our simulation results and compare the simulated differential electron fluxes at 0.9 MeV and 57.27 degrees local pitch-angle with the fluxes measured by the Van Allen Probes. In general, our simulation results show good agreement with observations. We calculated several different matrices to validate our simulation results against satellite observations.&lt;/p&gt;

scholarly journals On the alignment of velocity and magnetic fields within magnetosheath jets

2020 ◽  
Vol 38 (2) ◽  
pp. 287-296
Author(s):  
Ferdinand Plaschke ◽  
Maria Jernej ◽  
Heli Hietala ◽  
Laura Vuorinen
Keyword(s):  
Magnetic Fields ◽  
Entire Range ◽  
Dynamic Pressure ◽  
Bow Shock ◽  
Superposed Epoch Analysis ◽  
Magnetospheric Multiscale ◽  
Study Results ◽  
Epoch Analysis ◽  
The Magnetic Field

Abstract. Jets in the subsolar magnetosheath are localized enhancements in dynamic pressure that are able to propagate all the way from the bow shock to the magnetopause. Due to their excess velocity with respect to their environment, they push slower ambient plasma out of their way, creating a vortical plasma motion in and around them. Simulations and case study results suggest that jets also modify the magnetic field in the magnetosheath on their passage, aligning it more with their velocity. Based on Magnetospheric Multiscale (MMS) jet observations and corresponding superposed epoch analyses of the angles ϕ between the velocity and magnetic fields, we can confirm that this suggestion is correct. However, while the alignment is more significant for faster than for slower jets, and for jets observed close to the bow shock, the overall effect is small: typically, reductions in ϕ of around 10∘ are observed at jet core regions, where the jets' velocities are largest. Furthermore, time series of ϕ pertaining to individual jets significantly deviate from the superposed epoch analysis results. They usually exhibit large variations over the entire range of ϕ: 0 to 90∘. This variability is commonly somewhat larger within jets than outside them, masking the systematic decrease in ϕ at core regions of individual jets.

Examination of Bow-Shock Formation in Supersonic Radiatively Cooled Plasma Flows

2011 ◽  
Vol 39 (11) ◽  
pp. 2422-2423 ◽  
Author(s):  
Jonathan L. Peebles ◽  
Simon C. Bott ◽  
Kanchana Gunasekera ◽  
Joohwan Kim ◽  
Leonard Harpster ◽  
...  
Keyword(s):  
Bow Shock ◽  
Shock Formation ◽  
Plasma Flows

First Evidence of Flux Transfer Events Caused by Mangetosheath Jets

2020 ◽  
Author(s):  
Simon Thor ◽  
Anita Kullen ◽  
Tomas Karlsson ◽  
Savvas Raptis
Keyword(s):  
Formation Process ◽  
Statistical Study ◽  
Dynamic Pressure ◽  
Background Level ◽  
Jet Formation ◽  
Flux Transfer Events ◽  
Reconnection Region ◽  
Close Proximity ◽  
Flux Transfer ◽  
First Time

&lt;p&gt;Magnetosheath jets are local enhancements of dynamic pressure above the background level. Hietala et al. (2018) recently presented observational evidence of a jet collision with the magnetopause causing magnetic field line reconnection. In the present study, we show data which, for the first time, strongly indicates that magnetosheath jets can even create localized transient reconnection events, so-called flux transfer events (FTEs).&lt;/p&gt;&lt;p&gt;FTEs are commonly observed in cascades with an average separation time of 8-10 minutes, but may also appear as isolated events. Despite the fact that FTEs have gained major attraction during recent years, the formation process of FTEs is not yet fully understood. We showed in a recent statistical study (Kullen, Thor, and Karlsson; 2019) that isolated FTEs and FTE cascades occur during different IMF conditions and are differently distributed along the magnetopause. The results of the statistical study strongly suggest that the majority of the FTEs formed along the expected reconnection region for each respective IMF condition. However, for a subset of isolated FTEs, we proposed a different formation process. These events may have been caused by magnetosheath jets, as they occur during IMF conditions favorable for jet formation. Simulation results by Karimabadi et al. (2014) has shown that such a creation mechanism is possible. In his simulation, a magnetosheath jet collides with the magnetopause, creating an FTE.&lt;/p&gt;&lt;p&gt;In the present investigation, FTEs that may have been caused by magnetosheath jets were identified. To achieve this, we examined measurements from all four Cluster satellites, and searched for magnetosheath jets that appear in close proximity to FTEs listed in Wang et al. (2005)&amp;#8217;s FTE list. Our results show that approximately 15% of isolated FTEs appear in the vicinity of jets. These FTEs are further examined based on IMF and location across the magnetopause. For two of the FTEs, the associated jet appears close to the magnetopause. We present a detailed data analysis of these two events and discuss a possible formation mechanism for the FTEs, as there is strong evidence that the two FTEs are indeed caused by jets.&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document