Drift Instabilities in Thin Current Sheets Using a Two‐Fluid Model With Pressure Tensor Effects
Year: 2019
Type: article
Abstract: The integration of kinetic effects in fluid models is important for global simulations of the Earth's magnetosphere. We use a two‐fluid 10‐moment model, which includes the pressure tensor and has been used to study reconnection, to study the drift kink and lower hybrid drift instabilities. Using a nonlocal linear eigenmode analysis, we find that for the kink mode, the 10‐moment model shows good agreement with kinetic calculations with the same closure model used in reconnection simulations, while the electromagnetic and electrostatic lower hybrid instabilities require modeling the effects of the ion resonance using a Landau fluid closure. Comparisons with kinetic simulations and the implications of the results for global magnetospheric simulations are discussed.
DOI: 10.1029/2018ja026313
Authors: Jonathan Ng, Ammar Hakim, J. Juno, A. Bhattacharjee
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Awards: G1286236842, G1632040200, G1863003419, A KEY GOAL PUT FORWARD BY NASA S HELIOPHYSICS DIVISION IS TO "EXPLORE THE PHYSICAL PROCESSES IN THE SPACE ENVIRONMENT FROM THE SUN TO THE EARTH AND THROUGHOUT THE SOLAR SYSTEM." ONE SUCH PHYSICAL PROCESS OF GREAT SCIENTIFIC INTEREST IS TURBULENCE THROUGHOUT THE HELIOSPHERE. BY TURBULENCE WE MEAN THE PLASMA S FLOW AND ELECTROMAGNETIC FIELDS ARE CHAOTIC AND STOCHASTIC AND CHARACTERIZED BY ROTATIONALITY DIFFUSIVITY AND MOST IMPORTANTLY DISSIPATION. IN THIS CASE DISSIPATION REFERS TO PHYSICAL PROCESSES WHICH TRANSFER ENERGY FROM THE TURBULENT ELECTROMAGNETIC FIELDS INTO THE PLASMA PARTICLES WHEREBY THE PLASMA IS ULTIMATELY IRREVERSIBLY HEATED VIA COLLISIONS. TURBULENCE AND TURBULENT HEATING MAY BE A PARTIAL OR COMPLETE EXPLANATION FOR OUTSTANDING QUESTIONS SUCH AS WHY THE CORONA AND SOLAR WIND ARE SO HOT WHERE MEASUREMENTS OF THE TEMPERATURE OF THE CORONA ARE MUCH LARGER THAN THE SURFACE OF THE SUN AND THE SOLAR WIND'S TEMPERATURE IS LARGER THAN WE WOULD EXPECT FROM SIMPLE ADIABATIC EXPANSION. IN FACT A SIGNIFICANT NUMBER OF ONGOING PROPOSED AND SOON-TO-BE-LAUNCHED MISSIONS HAVE AS PART OF THEIR SCIENCE MISSIONS THE EXPLICIT OBJECTIVE TO CHARACTERIZE THIS TURBULENCE IN THE VARIETY OF PLASMA ENVIRONMENTS FOUND THROUGHOUT THE HELIOSPHERE. THE MAGNETOSPHERIC MULTISCALE MISSION IS PROVIDING MAGNETOSHEATH TURBULENCE DATA OF UNPRECEDENTED RESOLUTION AND CADENCE. SOLAR PROBE PLUS WILL FLY CLOSER TO THE SUN THAN WE EVER HAVE AND IN THE PROCESS WILL REVEAL HOW TURBULENCE MAY PLAY A ROLE NEAR THE ALFVEN POINT WHERE THE SOLAR WIND BECOMES SUPER-ALFVENIC. BEYOND THESE MISSIONS TURBULENT DISSIPATION IS BECOMING A CORE AMBITION OF PROPOSED MISSIONS SUCH AS THE TURBULENCE HEATING OBSERVER. WE PROPOSE TO DO COMPLEMENTARY NUMERICAL STUDIES OF TURBULENCE WITH A VARIETY OF PARAMETERS CHARACTERISTIC OF THE HELIOSPHERE TO BETTER UNDERSTAND THE DISSIPATIVE PROCESSES WHICH MAY BE OCCURRING AND HOW THIS TURBULENCE HEATS THE PLASMA THROUGHOUT THE HELIOSPHERE. UNFORTUNATELY DISSIPATION CAN ONLY BE TREATED BY MODELING THE PLASMA KINETICALLY WHICH IS OFTEN COMPUTATIONALLY PROHIBITIVE; HOWEVER USING THE DISCONTINUOUS GALERKIN FINITE ELEMENT METHOD AND THE OPEN-SOURCE GKEYLL NUMERICAL SIMULATION FRAMEWORK WE HAVE DEVELOPED A NEW TOOL FOR THE DISCRETIZATION OF THE VLASOV-MAXWELL SYSTEM OF EQUATIONS. THIS NEW TOOL IS ROBUST AND EFFICIENT SCALING TO THOUSANDS OF PROCESSORS AND ALLOWING US TO ACCESS THE FULL PLASMA DISTRIBUTION FUNCTION FOR BOTH IONS AND ELECTRONS FREE OF NOISE AND APPROXIMATION. WITH THE PLASMA DISTRIBUTION FUNCTION IN HAND WE CAN MORE CAREFULLY PROBE QUESTIONS ABOUT WHAT WAVE-PARTICLE RESONANCES MAY BE ONGOING IN THE TURBULENCE AND HOW EVEN A WEAK COLLISIONS AFFECT THE MEASURED DISSIPATION. IN PARTICULAR THE AIM OF THIS PROPOSAL IS TO ANSWER QUESTIONS OF HOW IMPORTANT LANDAU AND CYCLOTRON DAMPING MAY BE IN THE DISSIPATION OF THE TURBULENT PLASMA THAT MAKES UP THE HELIOSPHERE BY EXPLORING THE STABILITY OF PLATEAU FORMATION IN A WEAKLY COLLISIONAL STRONGLY TURBULENT PLASMA AND HOW THE CASCADE OF TURBULENT FLUCTUATIONS BEHAVES ABOVE THE CYCLOTRON FREQUENCY., G3083819904, G419881185, G42916606, G4501827968, Collaborative Research: Integration of Extended Magnetohydrodynamic (MHD) and Kinetic Effects in Global Magnetosphere Models, G4896746546, G498139845, G516483051, G586700770, G663282964, G969889393
OpenAlex ID: W2923089802