Presentation on theme: "The Magnetospheric Multiscale Mission Jim Burch Southwest Research Institute San Antonio, TX 2008 Huntsville Workshop: The Physical Processes for Energy."— Presentation transcript:
The Magnetospheric Multiscale Mission Jim Burch Southwest Research Institute San Antonio, TX 2008 Huntsville Workshop: The Physical Processes for Energy and Plasma Transport Across Magnetic Boundaries October 27, 2008
Universal Significance of Reconnection In general, reconnection is a candidate to explain any phenomena exhibiting plasma heating, particle acceleration, magnetic field collapse, or magnetic topology changes. This includes solar, stellar and planetary magnetic fields, solar and stellar winds, laboratory plasmas and even planetary dynamos. Reconnection is extremely important in the laboratory, especially in limiting plasma heating in Tokamaks. Moreover, recent advances have allowed for laboratory experiments in the collisionless regime. However, the very small temporal and spatial scales limit the measurements that can be made within the reconnection sites. Remote sensing of these phenomena (particularly in the solar context) provides vast amounts of information on their scale sizes, temporal development, and energy transfer; but high-resolution in-situ measurements are needed to determine the processes that drive reconnection. Reconnection is the most important process driving the Earth’s magnetosphere. Groundbreaking measurements by spacecraft such as Polar and Cluster, along with rapid advancements in numerical simulations have set the stage for a definitive experiment on magnetospheric reconnection.
A Fundamental Universal Process (a) (b) (c) Magnetic reconnection is important in the (a) Earth’s magnetosphere, (b) in the solar corona (solar flares and CMEs) and throughout the universe (high energy particle acceleration). Simulations (c) guide the MMS measurement strategy.
Sawtooth Crashes Sudden flattening (or crashes) of the electron temperature profile limit plasma heating within Tokamaks, thereby defeating their purpose. These crashes are explained by reconnection with a strong guide field within the device as shown in laboratory experiments. Current Density Reconnection Rate Edegal et al.  Yamada et al. 
Astrophysical Contexts Some of the most energetic phenomena in the universe result from supernova explosions. After the explosion the star collapses into a neutron star and often into a black hole. Later any nearby stars can be distorted and drawn into the black hole trough an accretion disk that is magnetically connected through reconnection to the black hole and neutron star. The transfer of angular momentum by the magnetic field to the neutron star results in the ejection of jets of material from the star. The neutron star can evolve into a pulsar or, in extreme cases, into a magnetar, which exhibits very energetic flare-type emissions that, by analogy with the solar corona, are likely produced by magnetic reconnection. Crab Nebula Magnetar
Is it Laminar or Turbulent? Standard “Petschek” model has laminar flow with only two field lines reconnecting at a time. Turbulent model, in which many field lines reconnect at once may be required to explain reconnection that rapidly progresses over vast astrophysical distances.
A Fundamental Universal Process [Nakamura, 2006]
Magnetospheric Multiscale Mission The MMS Mission science will be conducted by the SMART (Solving Magnetospheric Acceleration, Reconnection and Turbulence) Instrument Suite Science Team and a group of three Interdiscliplinary Science (IDS) teams. Launch is scheduled for October
MMS Science Objectives Scientific Objective: Understand the microphysics of magnetic reconnection by determining the kinetic processes occurring in the electron diffusion region that are responsible for collisionless magnetic reconnection, especially how reconnection in initiated. Specific Objectives: Determine the role played by electron inertial effects and turbulent dissipation in driving magnetic reconnection in the electron diffusion region. Determine the rate of magnetic reconnection and the parameters that control it. Determine the role played by ion inertial effects in the physics of magnetic reconnection.
100,000 km 500 km 100 km Unstable, thin current sheets have thickness < 1000 km “Electron diffusion region” thickness is of order 10 km Current sheet motion is typically 10 to 100 km/s Required resolution for electron diffusion region is ~30 ms Important Scale Sizes From simulations:
To identify reconnection events we need to have larger separations (up to 400 km) with spacecraft in the two inflow regions and in the two outflow regions (blue and red arrows). Need for 4 Spacecraft To determine processes driving reconnection we need to have smaller separations (down to 10 km) with spacecraft within the diffusion region (as shown).
Orbital Phases MMS employs two mission phases with inclination of 28 deg. to optimize encounters with both dayside and nightside reconnection regions.
Burst-Mode Data Acquisition
Tetrahedron configuration and burst data acquisition maintained throughout region of interest (> 9 R E day side, >15 R E night side).
Burst Mode Strategy MMS will have two ways of capturing burst data. The first involves on board assessment of data quality, the sharing of data quality indices among the spacecraft, and the assignment of priorities to each burst data interval (2.5 minutes on the day side and 5 minutes on the night side). –The 24-Gbyte on-board memory will store 960 minutes of prioritized burst data along with survey data for downlink once per orbit. The downlink is limited to 4 Gbits so only a small fraction of the burst data can be sent to the ground. The second method involves inspection of the fast survey data for identification of promising burst intervals that did not originally have a high enough priority for downlink. By command these intervals can be assigned higher priority so that they can be downlinked on the next pass. The on-board burst quality triggers involve parameters such as parallel electric fields, particle flux variability, parallel electron fluxes, large delta-B, high fluxes of heavy ions or energetic particles, etc.
MMS Payload Fields (Lead: Roy Torbert, UNH) Search Coil Magnetometer (up to 6 kHz) Analog Flux Gate Magnetometer (0.5 nT/10 ms) Digital Flux Gate Magnetometer (0.5 nT/10 ms) Electron Drift Instrument (E , 0.5 mV/m, DC to 1 Hz) Double-Probe E- Field ( kHz, 0.5 mV/m spin-plane, 1 mV/m axial) Fast Plasma (Lead: Tom Moore, GSFC) Ion Sensor (10 eV - 30 keV) Electron Sensor (10 eV - 30 keV) High time resolution (30 ms for electrons, 150 ms for ions) using multiple sensors with electrostatic scanning of FOV. Hot Plasma Composition (Lead: Dave Young, SwRI) Toroidal tophat with TOF (10 eV - 30 keV H +, He ++, He +, O + per half spin) RF technique to reduce proton flux by 10 3 to eliminate spillover problem. Energetic Particles (Lead: Barry Mauk, APL) Fly’s Eye Detector (all-sky electrons and ions to 500 keV) Energetic Ion Spectrometer (3D per spin with TOF mass analysis) ASPOC (Lead: Klaus Torkar, IWG, Austria) S/C neutralization to <4 V as on Cluster.
Theory and Modeling Key to the success of the SMART science plan is the coupling of theory and observation. The SMART Theory and Modeling Team has developed the latest and most sophisticated numerical models of the reconnection process. –These models have been used to define the MMS measurement requirements and guide mission design. –During the development phase, the models will be refined further, and procedures for assimilating the MMS data into the models will be defined. –In the mission operations and data analysis phase, the Theory and Modeling team will work closely with the instrument scientists to ensure optimum science return. Significant additional expertise and models have been added with the selection of the three IDS teams.
Co-Investigators and Participating Scientists
Interdisciplinary Science Teams PI in Bold Letters
Summary MMS will conduct definitive experiments on the universally-important plasma physics of magnetic reconnection. The four payloads will sample reconnection regions with separations and data rates sufficient to determine the kinetic processes responsible for magnetic interconnection and the resulting conversion of magnetic energy to heat and particle energy. The most critical region to be probed is the electron diffusion region within which specific predictions about the electric fields, currents, and electron dynamics will be tested. The measurement requirements are based on theoretical results from the latest reconnection models as well as on recent measurements from Cluster and Polar. The MMS theory and modeling program will provide a bridge for applying the magnetospheric results to the broader astrophysical context.
After MMS? ESA Cross-Scale Mission Study
After MMS? ESA Cross-Scale Mission Study MMS: km Cluster: ion scale and larger