Observing the Electron Diffusion Region with MMS

Transcription

1 Yosemite Reconnection Observing the Electron Diffusion Region with MMS R.B. Torbert University of New Hampshire 1

2 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 is 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. 2

3 Magnetospheric MultiScale (MMS) Overview Solar Wind Mission Team NASA SMD Southwest Research Inst Science Leadership Instrument Suite Science Operations Center Science Data Analysis NASA GSFC Project Management Mission System Engineering Spacecraft Mission Operations Center NASA KSC Launch services Earth Earth Magnetic Field Lines Earth Science Objectives Discover the fundamental plasma physics process of reconnection in the Earth s magnetosphere Temporal scales of milliseconds to seconds Spatial scales of 10s to 100s of km Mission Description 4 identical satellites Formation flying in a tetrahedron with separations as close as 10 km 2 year operational mission Orbit Elliptical Earth orbits in 2 phases Phase 1 day side of magnetic field 1.2 R E by 12 R E Phase 2 night side of magnetic field 1.2 R E by 25 R E Significant orbit adjust and formation maintenance Instruments Identical in situ instruments on each satellite measure Electric and magnetic fields Fast plasma with composition Energetic particles Hot plasma composition Four Gbits/day/spacecraft Spacecraft Spin stabilized at 3 RPM Magnetic and electrostatic cleanliness Launch Vehicle 4 satellites launched together in one Atlas V Mission Status Currently in Phase C, Launch in

4 Challenges for MMS Time Resolution: Instrument resolution is sufficient, as required. Continuous data volume would be excessive. Burst Data Management is critical. Accuracy Ambitious, but achievable. Traded with Time Resolution. Identification Burst Mode Data selection Simulation and Modeling absolutely essential Separation Strategy Variable to 10 km. Traded with temporal and spatial resolution. 4

5 Instrument Suite Elements and Responsibilities The Instrument Suite is a collection of components to meet the overall objective of understanding magnetic reconnection Requires use of time-correlated measurements from entire suite of components across multiple s/c Measurements from observed plasma assimilated to theory predictions Instrument Suite implemented on a GSFC provided deck, with exceptions. GSFC accommodates components, mechanically reconciling all FOVs constraints and is responsible for integrated thermal analysis SwRI manages power and data interfaces and is responsible for implementation of IS deck integration SOC responsible for operating each IS, data management and archival of science data FIELDS - Electric and magnetic (E,B) measurements at >1 ms timing resolution Fast Plasma - Image full sky at 32 energies: electrons in 30 ms, ions in 150 ms. ( n, Ui, Ue, P, fe, fi) Energetic Particles - All-sky viewing of ion and electron energetic particles ( kev) using 2 sensor types (fe, fi) HPCA - Measures the composition resolved 3D ion energy distributions (fi) for H+, He++, He+, and O+ ASPOC Maintains s/c potential to <= 4 V. Enables valid (fi, E, B) data CIDP Power distribution and manages command and data flow burst data memory management

6 Important Scale Sizes From simulations: 100,000 km, MHD 500 km, Ion Scale 100 km. 10* Electron Scale Current sheets are < ~ 100 km thick by >1000 km length Current sheet speed is ~100 to 10 km/s. d i ~ km V A ~ km/s 1/ Ω ci ~ s d e ~ 5-10 km V te ~ km/s 1/ Ω ce ~ ms R L ~ 3 10 km 6

7 Instrument Requirements/Capabilities Measurement Time Resolution Accuracy DC B 3D B to ~ 1 ms <~ 0.1 nt DC E 3D E to <~ 1 ms SC Potential ( proxy for n e ) to ~ 1ms <~ 0.5 mv/m AC B Waveform, spectra to 6 khz < ~2x10-5 nt/hz 1 khz AC E Waveform, spectra to 100 khz < ~1x10-7 V/m-Hz 10 khz Electrons 3D f e (v) every 30 ms to 30 kev Electron beams at single E to 1 ms. <~20% ΔE/E resolution Poisson Statistics limited Fast Ions 3D f i (v) every 150 ms to >20 kev/q <~20% ΔE/E resolution Poisson Statistics limited Composition Energetic Electrons Energetic Ions 3D ion composition every 15 s 10 ev/q to 30 kev/q for H +, He ++, He +, O + 3D f e (v) every 10s to >500 kev 3D f i (v) every 30s to >500 kev/n 20% ΔE/E resolution 7

8 <(E + VxB) x > < T > Y 0 d e M i /M e =400 T i /T e =5 ω pe /ω ce = 2 n b = 0.3 n 0 Based on Daughton, et.al., 2006 X (d i ) mv/m

9 Topologies of fields and related quantities for asymmetric reconnection with no guide field. Color scales in all panels are saturated at half the maximum absolute value of the quantity of interest. From Pritchett and Mozer,2009

10 FIELDS Sensors on MMS SDP SDP SDP SDP

11 Magnetic Field Enhanced Time Resolution Frequency range of 1 Hz to 30 Hz is critical regime for magnetic field and current sheet measurements on MMS A new procedure has been tested on CLUSTER to merge Flux-gates and Search Coil data in this regime: Remove offsets from FG and SCM data of equal time length. FFT each component of FG and SCM separately Correct phase and amplitude with calibration data Also, compute noise figure on sensitivity and error in phase correction. Apply time offset (SCM versus FG) correction. Apply calibration matrices to common co-ord system Compute also adjusted errors in FFT components. Merge FFT components, weighted by respective errors. IFFT Overlap region uses respective errors. Above fh ( ~30 Hz), use only SCM Below fl ( ~ 1 Hz ), use only FG. Despin the data to inertial co-ordinate system. 11

12 FFT Comparison: FGM to STAFF 6 Comparison of Amplitudes for FGM-Z-FSR(rotated) and STAFF-2(Z) for C3 4 2 log PSD nt 2 /Hz freq (Hz) Day Start time Hrs 12

13 FFT Comparison: FGM to STAFF 12 Comparison of Amplitudes for FGM-Z-FSR(rotated) and STAFF-2(Z) for C log amplitude freq (Hz) Day Start time Hrs 13

14 Merged Data nt Seconds of Day X

15 Instrument Requirements/Capabilities Measurement Time Resolution Accuracy DC B 3D B to ~ 1 ms < 0.1 nt DC E 3D E to <~ 1 ms SC Potential ( proxy for n e ) to ~ 1ms <~ 0.5 mv/m AC B Waveform, spectra to 6 khz < ~2x10-5 nt/hz 1 khz AC E Waveform, spectra to 100 khz < ~1x10-7 V/m-Hz 10 khz Electrons 3D f e (v) every 30 ms to 30 kev Electron beams at single E to 1 ms. <~20% ΔE/E resolution Poisson Statistics limited Fast Ions 3D f i (v) every 150 ms to >20 kev/q <~20% ΔE/E resolution Poisson Statistics limited Composition Energetic Electrons Energetic Ions 3D ion composition every 15 s 10 ev/q to 30 kev/q for H +, He ++, He +, O + 3D f e (v) every 10s to >500 kev 3D f i (v) every 30s to >500 kev/n 20% ΔE/E resolution 15

16 FIELDS Sensors on MMS SDP SDP SDP SDP

17 Fast Plasma Instrument (FPI) First Video Plasma Analyzer Objective: Image full sky at 32 energies: electrons in 30 ms, ions in 150 ms Enhance time resolution by 10 2 Design Concept: Four ion and four electron dual deflecting-aperture top hat sensors for field of view and aperture Video compression methods(lossy) for data rate Dual Ion Sensor : DIS DES Specifications: Electrons: 1 ev to 30 kev resolving 17% at 30 ms cadence Ions: 1 ev to 30 kev resolving 8% at 150 ms cadence Angular: resolve 11 deg for electrons and ions Provide 8 ea 180 x 11 deg apertures, viewing ~radially Electrostatic deflection: ± 17 and ± 6 for each aperture Provide sufficient sensitivity to achieve required precision: Sensitivity (GdE/E) 1 x 10-3 (ions) cm2 sr ev/ev Sensitivitiy (GdE/E) 3 x 10-4 (e-) cm2 sr ev/ev DIS Fast Plasma Instrument Dual Electron Sensor DES DIS DES DES Cutaway DIS DES

18 From Chen, et.al, 2009.

19 MMS Data Rate Overview Daily Averages Duration (hours) Rate (kbits/s) Volume (GByte) Volume (Gbit) Slow Survey Fast Survey Burst ~0.338 ~2.7 House-keeping NA Total / Day ~0.5 Gbyte/Day ~4 Gbit/Day Values NOT exact. See R. Klar for more exact numbers. 19

20 MMS Burst System Basic Plan: Obtain ~20 minutes of burst per day. Phase 1 orbit: ~1 day -> 20 min. burst data. Phase 2 orbit: ~3 days -> 1 hour of burst data. 20

21 Challenges for MMS Time Resolution: Instrument resolution is sufficient, as required. Continuous data volume would be excessive. Burst Data Management is critical. Accuracy Ambitious, but achievable. Traded with Time Resolution. Identification Burst Mode Data selection Simulation and Modeling absolutely essential Separation Strategy Variable to 10 km. Traded with temporal and spatial resolution. 21

22 Instrument Requirements/Capabilities Measurement Time Resolution Accuracy DC B 3D B to ~ 1 ms < ~0.1 nt DC E 3D E to <~ 1 ms SC Potential ( proxy for n e ) to ~ 1ms <~ 0.5 mv/m AC B Waveform, spectra to 6 khz < ~2x10-5 nt/hz 1 khz AC E Waveform, spectra to 100 khz < ~1x10-7 V/m-Hz 10 khz Electrons 3D f e (v) every 30 ms to 30 kev Electron beams at single E to 1 ms. <~20% ΔE/E resolution Poisson Statistics limited Fast Ions 3D f i (v) every 150 ms to >20 kev/q <~20% ΔE/E resolution Poisson Statistics limited Composition Energetic Electrons Energetic Ions 3D ion composition every 15 s 10 ev/q to 30 kev/q for H +, He ++, He +, O + 3D f e (v) every 10s to >500 kev 3D f i (v) every 30s to >500 kev/n 20% ΔE/E resolution 22

23 On-orbit Calibration FIELDS has wide array of on-orbit cross-calibration methods. Each method can be used to compare between multiple spacecraft in suitably uniform regions. Calibrated Item Comparator Method Frequency AFG,DFG gains Field models Perigee pass analysis Initial, Yearly Phase 1,2 FG offsets none Variance Analysis, Solar Wind Yearly, as available FG gains, offsets EDI Direction, TOF comparison Weekly SCM gains AFG,DFG Overlapping frequency band Monthly SCM gains, phase, offsets none Waveform analysis of cal signals Daily SDP, ADP gains AFG,DFG - V sc x B perigee comparison Initial, Monthly Phase 1,2 SDP,ADP gains FPI, HPCA Solar Wind -VxB comparison As available SDP,ADP gains, offsets EDI Direct E perp comparison Continual, different plasma regimes SDP,ADP offsets DFG,AFG E B = 0 check Quiet regions SDP,ADP offsets HPCA - V O+ x B comparison Lobe outflow regions EDI MCP gains none ambient response: MCP,pre-amp Monthly 23

24 Integrated Instrument Complement Conversion of field energy to particle kinetic energy in reconnection is identified by using all field and particle data together to quantify terms in the generalized Ohm s law, as one example: Electric and magnetic field data (E, B), plasma distribution moments (n, U, Pe), adjusted by composition information, and derived quantities (η, J) are used to compute terms in this equation. Wave E,B contributions to η are computed and deduced from plasma distribution measurements (fe, fi). Energetic particle acceleration is measured and accounted for as dissipation terms, and explained using field wave information. E and vi x B through ion diffusion region [ Electron diffusion regions are smaller (~10 km) ]

25 Combined Double-Probe EDI Method B-perp plane (BPP) analysis Single-runner EDI beam with certain width Single L2 (25 Hz) EFW target (black dot) Move EFW point the shortest distance to the beam area (magenta line) New, composite target : magenta dot EFW Target (black dot) EDI Gun Composite Target (magenta dot) 25

26 Test Results: Ex-DSI Top panel: Pre-processing the EFW L2 data by shifting the x-component Middle panel: The Bestarg2 result for Ex (magenta) Bottom panel: How much are we moving the EFW Ex-DSI component to reach the EDI beam area? - Difference between Bestarg2 result and pre-processed EFW L2 data for x- component 26

27 Narrow Currents at MP using FGM 27

28 Narrow Currents using Merged Data 28

29 Narrow Events at MP 29

30 Fast Plasma Instrument (FPI) First Video Plasma Analyzer Objective: Image full sky at 32 energies: electrons in 30 ms, ions in 150 ms Enhance time resolution by 10 2 Design Concept: Four ion and four electron dual deflecting-aperture top hat sensors for field of view and aperture Video compression methods(lossy) for data rate Dual Ion Sensor : DIS DES Specifications: Electrons: 1 ev to 30 kev resolving 17% at 30 ms cadence Ions: 1 ev to 30 kev resolving 8% at 150 ms cadence Angular: resolve 11 deg for electrons and ions Provide 8 ea 180 x 11 deg apertures, viewing ~radially Electrostatic deflection: ± 17 and ± 6 for each aperture Provide sufficient sensitivity to achieve required precision: Sensitivity (GdE/E) 1 x 10-3 (ions) cm2 sr ev/ev Sensitivitiy (GdE/E) 3 x 10-4 (e-) cm2 sr ev/ev DIS Fast Plasma Instrument Dual Electron Sensor DES DIS DES DES Cutaway DIS DES

31 FPI Calibration Calibration Facilites at GSFC and MSFC. Backups at MSSL, ISAS, other sites. Ground Calibration Testing On-orbit Calibration, Maintenance Test Full (1 box) Std (3 box) Test Frequency Aperture MCP saturation Pixel Geometry Energy 32 pixels 8 energies 32 pixels 8 energies 8 pixels 16 energies 4 pixels 2 energies 4 pixels 2 energies 4 pixels 2 energies Aperture cal. against s/c potential, waves MCP sauturation Inter-calibration UV contamination Monthly Each orbit Each orbit UV rejection All pixels Quick scan HPCA, EPD cross cal 32 pixels 8 energies HPCA, EPD cross cal. Monthly Parallel path calibration assures sensors meet specifications and are inter-calibrated.

32 MMS SMART FPI Moment Error Bars Pixel errors dominated by Poisson statistics: n = Σ16384pix(Counts) kappa =10 ΔNe/Ne = ΔTe/Te = 1/ n ΔVe/Vth = 1/ n At low count rates producing ~ 400 counts in the array: 1/ n ~ 5% How many counts do we get for low plasma sheet densities at full time resolution (30 msec)? < 1% Error 1-5% Error > 5% Error Moore - FPI 32

33 Reduced electron distribution functions away from the center of the reconnection region. The top panel shows the location where particles were accumulated. The distribution shows small deviations from gyrotropy. From Hesse, et.al., 2004

34 Challenges for MMS Time Resolution: Sufficient, as required. Continuous data volume would be excessive. Burst Data Management is critical. Accuracy Ambitious, but achievable. Traded with Time Resolution. Identification Burst Mode Data selection Simulation and Modeling absolutely essential Separation Strategy Variable to 10 km. Traded with temporal and spatial resolution. 34

35 MMS Burst System 35

36 Burst Mode Strategy The 96-Gbyte on-board memory will store from one to three orbits of burst data, burst quality indices, and survey data for downlink at least once per orbit. Each downlink is limited to 4 Gbits so only a small fraction of the burst data can be sent to the ground. MMS will have two (perhaps three) ways of identifying burst data intervals. The first involves on board assessment of data quality and the assignment of burst quality indices to each burst data interval (2.5 minutes on the day side and 5 minutes on the night side). By assessing these indices for all four spacecraft on the ground, mission-level burst quality can be derived for each interval. The second method involves inspection of the fast survey data for identification of additional promising burst intervals for downlink. A third method may used automated analysis of fast survey data. By command the best burst intervals can be downlinked on the next pass. The on-board burst quality indices 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. 36

37 Selection of Burst Data - Layers Selection of Burst Data (Layered Architecture) Layer 1 - Simple Data Quality Algorithms Completely Automated Fully vetted prior to launch Layer 2 - Fast and Slow Survey Data Processing Algorithms Completely Automated Facilities for using input from these algorithms fully vetted prior to launch Algorithms themselves will likely be evolutionary (fully developed/vetted after instrument commissioning) Layer 3 - Scientist in the Loop Algorithms Data By Request Facilities for submitting requests fully vetted prior to launch 37

38 Quantity Source Algorithm Physical Signature Electrons: Pseudo-content variance Electrons: Pseudo-content of mean Electrons: Parallel Pseudo-flux variance Electrons: Parallel Pseudo-flux mean Electrons: Directional Pseudo-content variance Electrons: Directional Pseudo-content mean Ions: Pseudo-content variance Ions: Pseudo-content of mean DES DES DES DES DES DES DIS DIS FPI Trigger Data Measurements Sum (I:Emine->Emaxe) {EWe(n) * Sum(j:SAz, k:sei) {N(i,j,k)}} Sum (I:Emine->Emaxe) {EWe(n) * Sum(j:SAz, k:sei) { b p(j,k) * N(i,j,k)} for b -p >t1 (nom 0.33) Sum (I:Emine->Emaxe) {EWe(n) * Sum(j:SAz, k:sei) {N(i,j,k)} for t2< b -p <t3 (nom 0.33 to 1) Sum (I:Emini->Emaxi) {EWi(m) * Sum(j:SAz, k:sei) {N(i,j,k)} Density or pressure variability Density or pressure variability Parallel flow variability Parallel flow context Directional density or pressure context Directional density or pressure context Density or pressure variability Density or pressure context Ions: S/C Zs Pseudo-flux variance DIS Sum (I:Emini->Emaxi) {EWi(m) * Sum(j:SAz, k:sei) {pz(j,k) * N(i,j,k)} S/C Zs flow variability Ions: S/C Xs Pseudo-flux variance DIS Sum (I:Emini->Emaxi) {EWi(m) * Sum(j:SAz, k:sei) {px(j,k) * N(i,j,k)} S/C Xs flow variability Ions: S/C Ys Pseudo-flux variance DIS Sum (I:Emini->Emaxi) {EWi(m) * Sum(j:SAz, k:sei) {py(j,k) * N(i,j,k)} S/C Ys flow variability HPCA Trigger Data Measurements Quantity Source Spectral Range Amplitude Range Algorithm Physical Signature H+ energy flux H+ TOF/ energy spectrum 10eV to 40 kev 10^3 Sum over [H+ counts divided by energy]. Send out trigger when change in flux is larger than a threshold. Responds to H+ ions accelerated during reconnection events or in magnetopause crossing. O+ energy flux O+ TOF/ energy spectrum 10eV to 40 kev 10^3 Sum over [O+ counts divided by energy]. Send out trigger when change in flux is larger than a threshold. Responds to O+ ions accelerated during reconnection events or in magnetopause crossing.

39 FIELDS BURST Trigger Parameters Quantity Source Freq Range Algorithm Physical Signature E DSP (ΕΒ / Β ). DC-10Hz 0-50 mv/m Average of highest 4 Ε (peak) over twenty 0.5s internals J EDI (Ambient) To 1 KHz Parallel Electron Beam Fluxes Large parallel currents E E RMS 1 DSP SDP/ADP 10Hz-100Hz (V/m) 2 Hz E RMS 2 DSP SDP/ADP 100Hz-1kHz (V/m) 2 Hz E RMS 3 DSP SDP/ADP 1kHz-10kHz (V/m) 2 Hz E RMS 4 DSP SDP/ADP 10kHz-100kHz (V/m) 2 Hz AKR DSP SDP/ADP 10kHz-500kHz (V/m) 2 Hz Average of highest 4 average power densities in Ε Omni over twenty 0.5s internals Average of highest 4 average power densities in Ε Omni over twenty 0.5s internals Average of highest 4 average power densities in Ε Omni over twenty 0.5s internals Average of highest 4 average power densities in Ε Omni over twenty 0.5s internals Average of highest 4 average power densities in Ε Omni over twenty 0.5s internals Large Ε. Large electron currents Large Ε. Large electron currents Large Ε. Large electron currents Large Ε. Large electron currents Substorm E Structure s DSP SDP/ADP 100Hz-10kHz Number of electron holes in 10s interval. (ΕΗ is >4σ peak from RMS over 0.01s) Β n AFG/EDI DC-10Hz 0-25 nt Average of highest four maximum variations in Β over twenty 0.5s intervals 1 / Β AFG/EDI DC-10Hz nt -1 Average of highest four 1 / Β values over twenty 0.5s intervals B RMS 1 DSP SCM 10Hz-100Hz 0-25 nt Average of highest 4 average power densities in B Omni over twenty 0.5s intervals B RMS 2 DSP SCM 100Hz-1kHz 0-5 nt Average of highest 4 average power densities in B Omni over twenty 0.5s intervals B RMS 3 DSP SCM 1kHz-10kHz 0-1 nt Average of highest 4 average power densities in B Omni over twenty 0.5s intervals n CDPU DC-10 Hz Average of V1 + V2 + V3 + V4 over twenty 0.5s intervals Δn CDPU DC-10 Hz Average of highest 4 maximum variations in V1 + V2 + V3 + V4 over s intervals Large Ε. Large electron currents Large Β i, Β z. electron currents Large electron currents Large Β i, Β z. Large Β i, Β z. Large Β i, Β z. Density Density Change

40 1/B Trigger Data for BURST Mode Four Spacecraft Through simulation M i /M e =400 T i /T e =5 ω pe /ω ce = 2 n b = 0.3 n 0 Based on Daughton, et.al.,

41 Four Spacecraft Signatures 41

42 Spacecraft Separation Strategy 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). To determine kinetic processes driving reconnection we need to have smaller separations (down to 10 km) with spacecraft within the diffusion region (as shown). Time Scale~8 s Time Scale~ 0.2 s 42

43 reconnection rate

44 Ion Scale Separation M i /M e =400 T i /T e =5 ω pe /ω ce = 2 n b = 0.3 n 0 Based on Daughton, et.al.,

45 Signatures at Ion Scale 45

46 Cluster Quick-look Plot. (Not sufficient For MMS).

47 Narrow Currents using Merged Data 47

48 Challenges for MMS Time Resolution: Achieved, as required. Continuous data volume is excessive. Burst Data Management is critical. Accuracy Ambitious, but achievable with effort. Traded with Time Resolution. Identification Burst Mode Data selection challenging Simulation and Modeling absolutely essential Separation Strategy needs further refinement. Variable to 10 km. Traded with temporal and spatial resolution. 48

49 END 49