ess 261energetic particles1 energetic particles & boundary remote sensing energetic particle...
TRANSCRIPT
ESS 261 Energetic Particles1
Energetic Particles & Boundary Remote Sensing
Energetic Particle Instruments: Operation and Data ProductsGeometric Factor. Contamination: Sunlight, Earth-glow, Neutrals
Background/Electronic Noise, Detector Capacitance and Leakage Current.Data Viewing, Removal of Noise and Analysis of Distribution Functions
Access, Use and Pitfalls of Analysis in Various Regions:Solar Wind, Magnetosphere, Radiation Belts and Ring Current
Remote Sensing of Particle Gradients: Magnetopause, Inner Magnetosphere and Low Frequency Waves
Contributions from:”Davin Larson, Thomas Moreau, Andrei Runov and Ryan CaronReferences: ISSI book on Analysis Methods for Multi-Spacecraft Data
ESS 261 Spring Quarter 2009
Lecture 05April 27, 2009
ESS 261 Energetic Particles2
Interaction of particles with matter [1]• The way in which energetic particles interact with matter
depends upon their mass and energy.– Photons - have “infinite range”- Their interaction is “all-or-nothing”
They do not slow down but instead “disappear”, typically through one of three interactions (I=I0e-x where is absorption coefficient ):
• Photoelectric effect (Low energy: E<~50 keV
• Compton Scattering (50 keV ~< E < 1 MeV)
• Pair production ( E >2 x 511 keV).
– Particles with non-zero mass (Electrons and Ions) will slow down as they pass through matter. They interact with electrons, phonons and nuclei.
• Electron interaction is long-range. Enectron-electron energy exchange peaks when incoming particle is close to the target electron energy. The material electrons have energies that are determined by
– The material temperature (phonon-electron interaction couples them) ~kT, ~105m/s
– The Fermi energy, i.e., the energy level of free electrons in absolute-zero temperature. This is about 5-10eV, which gives the Fermi speed of 106m/s.
ESS 261 Energetic Particles3
Photoelectric effect
Compton scattering
Pair production
ESS 261 Energetic Particles4
(/ often used: mass attenuation coefficient)
ESS 261 Energetic Particles5
Interaction of particles with matter [2]• Charged particles primarily interact with the
electrons in a material. Typically the energetic particle suffers numerous, distant collisions with a Fermi sea of electrons losing a small amount of energy with each interaction (much like a plasma!).
• The interaction is typically strongest when the velocity of the energetic particle is approximately the same as the Fermi speed.
• Energetic neutral atoms are quickly ionized soon after entering the solid.
• Neutrons are a different matter altogether
ESS 261 Energetic Particles6
• The stopping power for heavy particles (ions) is given by the Bethe-Bloch formula (1932):
Interaction of particles with matter [3]
: where,4
22
42
Bcm
ezN
dx
dE
e
A
2)1(
2ln 2
2
22
Z
C
I
cm
A
ZB e
Rate of energy loss is ~ inversely proportional to energy, and proportional to Z (the atomic number) and z2, z the projectile chargeI = average ionization potential, and C = density and shell corrections.
ESS 261 Energetic Particles7
• The range is given by:
– dE/dx is often expressed in units of keVcm2/gr which is dE/dx times the material density. This bundles the dE/dx curves into groups by normalizing away the material density from the electronic interactions.
– The range (typically in cm) is also often normalized to the density and expressed in units of grams/cm2, i.e., the equivalent mass per unit area required to stop the particle.
Interaction of particles with matter [4]
This formula is only useful for ions for reasons we will soon see.
dEdx
dER
Estart
0 1
ESS 261 Energetic Particles8
Interaction of particles with matter [8]• Electrons and Ions behave differently due to the
different mass ratio. The primary interaction of all energetic particles is with the sea of electrons.– Ions:
• Ions interact with a series of distant collisions. Each interaction results in a small energy loss and very little angular scattering. – They travel in nearly straight lines as they slow down. The dispersion is small. (Imagine a fast bowling ball thrown into a sea of slow moving ping pong balls.)
– Electrons:• Electrons can lose a large fraction of their energy and undergo large
angle scattering with each interaction (Imagine a high speed ping pong ball thrown into the same sea)
ESS 261 Energetic Particles9
Interaction of particles with matter [9]• When an electron hits an atom it can undergo a very large angle
deflection, often scattering it back out of the material.
• Bremstrahlung (braking) radiation is produced when electrons undergo extreme accelerations. X-rays are easily generated when energetic electrons strike high Z materials. (a good reason to avoid high Z materials on exposed surfaces)
ESS 261 Energetic Particles10
Protons in
Energy lost to ionization (collectable)
Energy lost to phonons (not collectable)
ESS 261 Energetic Particles11
Alphas in:
Energy lost to ionization (collectable)
Energy lost to phonons (not collectable)
ESS 261 Energetic Particles12
Electrons in
Energy lost toionization(collectable)
Energy lost toBremstrahlungradiation (notcollectable)
ESS 261 Energetic Particles13
Solid State Detectors• Solid State Detectors (SSDs) not only detect individual particles, they can be
used to measure particle energy with good energy resolution.
• Typically only good for E>20 keV
• Recent improvements push the limit to ~2 keV
• Two varieties of Silicon Diode Detectors– Implanted Ion (i.e. Canberra PIPS)
• Produced by implanting p-type material into an n-type silicon substrate
• Easy to produce pixelated surfaces
• Very rugged
– Surface Barrier• Chemical process to create diode surface
• Easily damaged, sensitive to solvents
• Not too common anymore
• Typically both varieties are run fully depleted (electric field extending throughout bulk of material)
• Maximum thickness is ~1000 microns – defines max energy particle that can be stopped within the detector
• Particles can be incident on either side of detector
ESS 261 Energetic Particles14
Operation Principle• With the application of a (large enough)
reverse bias voltage an electric field is established throughout the entire silicon volume (fully depleted detector).
• An energetic charged particle will leave an ionization trail in its wake.
• The electron hole pairs will separate and drift to opposite sides.
• The total charge is proportional to the electronic energy deposited. (3.61 eV per pair for Silicon).
• The signal contains only a few thousand electrons thus requiring sensitive electronics.
• The trick is to collect and measure this small signal.
p n++
--
E
p n++
--
E
Forward bias
p n++
--
E
Reverse biasparticle
-+
ESS 261 Energetic Particles15
Detector Electronics
Simulated A225response for typical 1MeV electron pulse through a Si detector.
The A225 integrates charge, with peak pulse equal to integrated charge.
A 20ns signal turns into an 8usec pulse!
ESS 261 Energetic Particles16
Front End Counting Electronics
ESS 261 Energetic Particles17
Sources of Noise• Capacitance
– Noise results inuncertainty inabsolute valueof energy
• Leakage (dark) current– When dark current is integrated by A225 results in baseline offset– Baseline restorer restores zero level– Leakage current results in error in absolute signal amplitude
ESS 261 Energetic Particles18
Examples of Detector Systems: WIND/3DPPredecessor of THEMIS/SST
ESS 261 Energetic Particles19
Cross section of the EPACT isotope telescope on Wind. The first two detectorsare two-dimensional position sensitive strip detectors (PSD1, PSD2). They are requiredso that path-length corrections may be made for the angle of incidence and fornon-uniformities in detector thickness. Tungsten rings are used to mask off circular areasfor each PSD. There are 6 solid-state detectors increasing in thickness with depth in thestack in order to minimize Landau fluctuations. From von Rosenvinge et al. [1995].
Examples of Detector Systems: WIND/EPACT
ESS 261 Energetic Particles20
Examples of Detector Systems: THEMIS/SST
Attenuator
Foil
Magnet
Detector Stack
Attenuator
Foil Collimator(for electrons)
Open Collimator(for ions)
ESS 261 Energetic Particles21
THEMIS/SST Sensor Unit Schematic
FoilCollimator(electron side)
Thick Detector
Sm-Co Magnet
Attenuator
Al/Polyamide/Al FoilOpen Detector
Foil Detector
Attenuator
Open Collimator (ion side)
ESS 261 Energetic Particles22
• Each sensor unit is a:– Dual-double ended solid state telescope
– Each double ended telescope (1/2 sensor) has:• Triplet stack of silicon solid state detectors
• Foil (on the side measuring electrons)– Filters out ions <~350 keV
– Leaves electron flux nearly unchanged
• Magnet / Open (on the side measuring ions)– Filters out electrons <400 keV
– Leaves ion flux nearly unchanged
• Mechanical Pinhole attenuator– Reduces count rate during periods of high flux
– Reduces radiation damage (caused by low energy ions) during periods of high flux
• Collimators
• Preamplifier / shaping electronics
THEMIS/SST Sensor Unit Details
ESS 261 Energetic Particles23
Detector Pixelation• Detectors similar to STEREO/STE
– Produced at LBNL/Craig Tindall PI
Active area
Guard ring
10 mm
5 mm
Additional Pixels not used for Themis
ESS 261 Energetic Particles24
T Out
+4.5 V
-2.5 V
O Out
-35 V
F Out
F Test in
T Test in
O Test in
~200 A Polysilicon + ~200 A Al
pn
np
np
pn
~200 A Polysilicon
T
F
O
300 micron thick detectors
225FB
225FB
225FB
Outside Grounded
Pixelated side ~1200 A Dead layer
Detector Wiring
ESS 261 Energetic Particles25
• Typical Electrical Connection Between Detector and Flex-Circuit
SST Detector Mechanical Design/Connections
Kapton Flex-Circuit
Detector (pixelated side)
Wirebond Loop
(NOT to scale – actual loop height < 300 micron)
ESS 261 Energetic Particles26
Detectors (4)
Spring Clamp
Spring Plate (2)
• Detector Board Composition (exploded view)
PEEK Spacer (4)
BeCu Gasket (3)
Kapton Flex-Circuit (4) AMPTEK Shield
KaptonHeater
Thermostat
• DFE Board Subassembly
SST Detector Mechanical Assembly
ESS 261 Energetic Particles27
SST Detector Mechanical: Real Life
ESS 261 Energetic Particles28
• DFE Board Subassembly Relative Positions • (2 per sensor)
AMPTEK Shielding
Detector Stack Subassembly
Multi-Layer Circuit Board (62 mil thickness)
Foil Frame
Thermostat
SST Mechanical Design
ESS 261 Energetic Particles29
SST Mechanical Design• Magnet-Yoke Assembly Co-Fe Yoke (2)
Sm-Co Magnet (4) (currently not visible)
Aluminum Magnet Cage
ESS 261 Energetic Particles30
• Attenuator Assembly
Attenuator (4)
Cam (2)
SMA Lever (2)
SST Mechanical Design
ESS 261 Energetic Particles31
• Actuators and Position Switches
Honeywell SPDT Hermetically Sealed Switch (2)
SMA Actuator (2)
SST Mechanical Design
ESS 261 Energetic Particles32
• Two Collimators Per SideElectron Side
Ion Side
SST Mechanical Design
ESS 261 Energetic Particles33
• Four Collimators Per Sensor
Ion Side
Electron Side
Electron SideIon Side
SST Mechanical Design
ESS 261 Energetic Particles34
• Support Structure • (back section)
Electrical Connector
Bottom Closeout Panel
Rigid Mounting Flange
SST Mechanical Design
ESS 261 Energetic Particles35
• Support Structure • (front section)
Kinematic Flexure (2)
Rigid Mounting Flange
SST Mechanical Design
ESS 261 Energetic Particles36
• Bi-Directional Fields-of-View
SST Mechanical Design
ESS 261 Energetic Particles37
• Sensor Orientation Relative to Spacecraft Bus
SST Mechanical Design
ESS 261 Energetic Particles38
• Sensor Unit Mounting Using Kinematic Flexures– Each sensor mounted to spacecraft panel at three points
• One rigid mounting flange• Two mounting flanges with kinematic flexures
– Allows relative motion due to CTE differences between sensor structure and spacecraft panel• Predicted expansion differential along instrument axes with 120
ºC temperature gradient:– X-Axis: 0.006” (0.15 mm)
– Y-Axis: 0.013” (0.33 mm)
– Flexure dimensions sized to keep maximum bending stresses below 6061-T6 yield strength• Factor of Safety (F.S.) > 1.4 per NASA-STD-5001
SST Mechanical Design
ESS 261 Energetic Particles39
• Attenuator Actuation – CLOSED position
Honeywell Switch (extended-position)
SMA Actuator (extended)
Honeywell Switch (compressed-position)
SMA Actuator (retracted)
SST Mechanical Design
ESS 261 Energetic Particles40
• Attenuator Actuation – OPEN position
Honeywell Switch (compressed-position)
SMA Actuator (retracted)
Honeywell Switch (extended-position)
SMA Actuator (extended)
SST Mechanical Design
ESS 261 Energetic Particles41
• Linear Actuators– Shaped Memory Alloy (SMA) actuator– Single direction 125 gram pull-force
• Required force < 42 gram => F.S. > 3.0– Operating temp range: -70°C to +75°C
Extended Position
Retracted Position
Relative Size(commercial model shown)
ESS 261 Energetic Particles42
Magnetics Testing• Magnet Cage assembly #1
• Measured Py for 19 magnets (All values were very close)
• Selected 4 magnets for assembly #1
• Measured dipole and quadrapole moments of assembly
• Found significant residual dipole moment along x-axis
• Contribution of dipole and quadrapole nearly equal at 2 m
• Conclusion: Px and Pz of individual magnets are important
ESS 261 Energetic Particles43
Magnetics Testing• Sent Magnet Cage assembly #2 to UCLA for testing
• Results are virtually the same
• Contribution of dipole and quadrapole fields are similar at 2 m:– B(dipole @ 2m) = .88 nT
– B(quad @ 2m) = .59 nT
• The sum of both contributions exceeds requirement (0.75 nT @ 2m)
• Relaxed requirement, since it is a DC field
-350
-300
-250
-200
-150
-100
-50
0
50
100
150
0 100 200 300 400 Series1
Series2
Series3
ESS 261 Energetic Particles44
Electronics Block Diagram• Signal chain: 1 of 12 channels shown
ADC
FPGACoincidence
Logic &Accumulators
Memory
DACThresh
Gain
PD
BLR
A225FPreampShaper
DFEBoard
DAP Board
Test Pulser
Bias Voltage
ESS 261 Energetic Particles45
FPGA Functions: Interface to ETC• Using Actel RT54SX72S (modeled on STEREO/STE)
– Controls 12 ADCs• Monitor / Count threshold events• Monitor peak detect signal• Produce convert strobe• Coincidence detection• Readout ADC (energy)
– Psuedo-logrithmic energy binning• ADC measurement used as address of LUT to increment accumulators
(LUTs and accumulators stored in SRAM)
– Data Readout (controlled by ETC board)– Command Data Interface (CDI) (loads tables)– Test Pulser control– Noise measurement
• Periodic conversions to measure “noise”
– Analog Housekeeping control
ESS 261 Energetic Particles46
SST Products• Products: Full, Reduced (Burst is same as full)
– Full: 16E x 64A– Reduced: 16E x 6A , or
16E x 1A (omni)
• Modes: Slow Survey, Fast Survey, Particle Burst• Slow Survey:
– Full distributions (ions and electrons) at 5min resolution– Reduced, omnidirectional distributions: every spin
• Fast Survey:– Ions: Full distributions every spin– Electrons: Reduced distributions (16E x 6A) every spin
• Burst:– Ions: same as above– Electrons: Full distributions every spin
ESS 261 Energetic Particles47
SSTs
Angelopoulos, 2008
SST Accommodation
ESS 261 Energetic Particles48
Angelopoulos, 2008
SST Accommodation
ESS 261 Energetic Particles49
Data Analysis Tools [1]• Pitfalls
– Sun contamination• ; Sun contamination is masked on board but often fails
; Use keyword: mask_remove to removed masked bins and interpolate across sectors
• ; Sun contamination is lefted unmasked recently (and most of the time) on board ; There is code to recognize the faulty bins (saturated) and remove them altogether.; This is called : method_sunpulse_clean='spin_fit' , or ‘median’ and tells the; programs to remove data beyond 2sigma away from spin-phase fit/median.
• ;Sun contamination/saturation also affects other channels due to electronic noise.;The code can remove the typical noise value and provide the remaining good; signal (assuming no saturation). The keyword is: enoise_bins and the; procedure is documented in: thm_crib_sst_contamination.pro
ESS 261 Energetic Particles50
Sun contamination (thm_crib_sst_contamination.pro) – ;PROCEDURE: thm_crib_sst_contamination
– ;Purpose: 1. Demonstrate the basic procedure for removal of sun contamination,
– ; electronic noise, and masking.
– ; 2.. Demonstrate removal of suncontamination via various methods.
– ; 3. Demonstrate the correction of inadvertant masking in SST data
– ; 4. Demonstrate scaling data for loss of solid angle in SST measurements.
– ; 5. Demonstrate substraction of electronic noise by selecting bins in a specific region
– ; 6. Show how to use these techniques for both angular spectrograms,energy spectrgrams, and moments.
– ;SEE ALSO:
– ; thm_sst_remove_sunpulse.pro(this routine has the majority of the documentation)
– ; thm_part_moments.pro, thm_part_moments2.pro, thm_part_getspec.pro
– ; thm_part_dist.pro, thm_sst_psif.pro, thm_sst_psef.pro,thm_sst_erange_bin_val.pro
– ; thm_crib_part_getspec.pro
Sun contamination (sst_remove_sunpulse.pro) – ; Routine to perform a variety of calibrations on full distribution sst data. These can remove sun
contamination and on-board masking. They can also scale the data to account for the loss of solid angle from the inability of the sst to measure directly along the probe geometric Z axis and the inability to measure directly along the probe geometric xy plane.(ie X=0,Y=0,Z = n or X=n,Y=m,Z=0, are SST 'blind spots') THM_REMOVE_SUNPULSE routine should not generally be called directly. Keywords to it will be passed down from higher level routines such as, thm_part_moments, thm_part_moments2, thm_part_dist,thm_part_getspec, thm_sst_psif, and thm_sst_psef
ESS 261 Energetic Particles51
Data Analysis Tools [3]• Pitfalls
– Sun contamination– Read crib sheets: thm_crib_sst_contamination.pro, and
documented procedure: thm_sst_remove_sunpulse.pro » ; » edit3dbins,thm_sst_psif(probe=sc, gettime(/c)), bins2mask» ; ON: Button1; OFF: Button2; QUIT: Button3» print,bins2mask
» thm_part_getspec, probe=probe, trange=[sdate, edate], $
» theta=[-45,0], phi=[0,360], $
» data_type=['psif'], start_angle=0,$
» angle='phi',method_sunpulse_clean='median',tplotsuffix='_ex2_t1',$
» enoise_bins = bins,enoise_bgnd_time=times,mask_remove=.99» tplot
ESS 261 Energetic Particles52
Ground processing (particles only)• Pitfalls
– Sun contamination: Bin selection » ;
ESS 261 Energetic Particles53
Density Correction• Interpolate densities• Add• date='2008-03-01'• startdate = '2008-03-01/00:00'• timespan,startdate, 4.0, /hour• Trange=['08-03-01/00:00','08-03-01/04:00']• Tzoom=['08-03-01/01:40','08-03-01/02:40']
• ;... select exact time interval to calculate join ESA/SST moments• tbeg = time_double(date+'/00:00')• tend = time_double(date+'/04:00')• ;select a probe• sc='b'• thm_load_state,probe=sc,coord='gsm',/get_support• thm_load_fit, level=1, probe=sc,
datatype=['efs', 'fgs'],/verbose• thm_cotrans,strjoin('th'+sc+'_fgs'),
out_suf='_gsm', in_c='dsl', out_c='gsm'• ;• ; SST now• thm_load_sst,probe=sc,lev=1• thm_part_moments, probe = sc, instr= ['ps?f'], $• moments = ['density', 'velocity', 't3'], $• mag_suffix='_peir_magt3', $• scpot_suffix='_peir_sc_pot';,/median• ; work in gsm• thm_cotrans,'th'+sc+'_ps?f_velocity',
in_coord='dsl',out_coord='gsm',out_suffix='_gsm'• ;• ; ESA now• thm_load_esa,probe=sc• ; Interpolate densities• tinterpol_mxn,'th'+sc+'_peer_density',
'th'+sc+'_peir_density',/overwrite,/nan_extrapolate• tinterpol_mxn,'th'+sc+'_ps?f_density',
'th'+sc+'_peir_density',/overwrite,/nan_extrapolate• …• ; ...total ion density• totNi = sst_i_n.y + esa_i_n.y
Ni
Ne
ESS 261 Energetic Particles54
Velocity Correction• Interpolate densities• Add flux• ;• ; • ; ...sst Flux• sstFi = sst_i_v.y*0.• sstFi[*,0] = sst_i_n.y*sst_i_v.y[*,0]• sstFi[*,1] = sst_i_n.y*sst_i_v.y[*,1]• sstFi[*,2] = sst_i_n.y*sst_i_v.y[*,2]
• ; ...esa Flux• esaFi = esa_i_v.y*0.• esaFi[*,0] = esa_i_n.y*esa_i_v.y[*,0]• esaFi[*,1] = esa_i_n.y*esa_i_v.y[*,1]• esaFi[*,2] = esa_i_n.y*esa_i_v.y[*,2]
• ; ...total ion density• totNi = sst_i_n.y + esa_i_n.y
• store_data, 'th'+sc+'_Ni',$data={x:esa_i_n.x, y:totNi}
• options, 'th'+sc+'_Ni', 'ytitle', $'Ni !C!C1/cm!U3'
• ylim, 'th'+sc+'_Ni', 0.01, 1., 1
• ; ...total ion velocity (GSM)• totVi = esa_i_v.y*0.• totVi[*,0] = (sstFi[*,0]+esaFi[*,0])/totNi• totVi[*,1] = (sstFi[*,1]+esaFi[*,1])/totNi• totVi[*,2] = (sstFi[*,2]+esaFi[*,2])/totNi
ESS 261 Energetic Particles55
Pressure Correction• Remove SST noise• Interpolate pressures• Then add• ;• ; SST now• ; SST now• thm_load_sst,probe=sc,lev=1• thm_part_moments, probe = sc, instr= ['ps?f'], $• moments = ['density', 'velocity', 't3'], $• mag_suffix='_peir_magt3', $• scpot_suffix='_peir_sc_pot';,/median• ; …interpolate• ; … add• ; ...pressure• ; ...SST: perpendicular temperature only• sst_Tperp = .5*(sst_i_t3.y[*,0]+sst_i_t3.y[*,1])• sst_i_p_nPa = 0.16*.001*sst_i_n.y * sst_Tperp • ; perp. pressure in nPa• store_data, 'th'+sc+'_psif_p_perp_nPa', $• data={x:sst_i_n.x, y:sst_i_p_nPa}• options, 'th'+sc+'_psif_p_perp_nPa', $• 'ytitle', 'sst Pi !C!CnPa'
• ; ...ESA: scalar temperature• esa_Ti = total(esa_i_T.y,2)/3.• store_data,'Ti_th'+sc+'_peir', $• data={x:esa_i_n.x, y:esa_Ti}• ; ...ESA ion pressure:• esa_i_p_nPa = 0.16 *.001 * esa_i_n.y*esa_Ti• ; scalar pressure in nPa• store_data, 'th'+sc+'_peir_p_nPa', $• data={x:esa_i_n.x, y:esa_i_p_nPa}• options, 'th'+sc+'_peir_p_nPa', $• 'ytitle', 'esa Pi !C!CnPa'
• ; ...Total ion pressure• totPi = sst_i_p_nPa + esa_i_p_nPa• store_data, 'th'+sc+'_i_p_nPa', $• data={x:esa_i_n.x, y:totPi}• options, 'th'+sc+'_i_p_nPa', 'ytitle', 'Pi !C!CnPa'
ESS 261 Energetic Particles56
Finite gyroradius techniques• Ion Gyroradius large compared to magnetospheric boundaries
– Can be used to remotely sense speedand thickness of boundaries
– Assumption is that boundary is sharpand flux has step function across
• Application at the magnetopause• Application at the magnetotail
– Can also be applied to waves ifparticle gradient is sufficiently high
• Application on ULF waves atinner magnetosphere
Method exploits finite iongyroradius to remotely senseapproaching ion boundary andmeasure boundary speed (V⊥)
THEMIS
To EarthTo Sun
To Tail
ESS 261 Energetic Particles57
At the magnetotaili,thermal-tail (4keV,20nT)= ~325kmi,super-thermal (50keV,20nT)= ~2200km
Plasma Sheet Thickness ~ 1-3 RE
Boundary Layer Thickness ~500-2000kmCurrent layer Thickness ~ 500-2000km
Waves Across Boundary: ~1000-10,000kmAlong Boundary: ~Normal : 1-10 RE
For magnetotail particles, the current layer and plasma sheet boundary layer are sharp compared to the superthermal ion gyroradius and the magnetic field is the same direction in the plasma sheet and outside (the lobe). This means we can use the measured field to determine gyrocenters both at the outer plasma sheet and the lobe, on either side of the hot magnetotail boundary.
ESS 261 Energetic Particles58
Side View (elevations)
To Sun
SpinAxis
ESA:Elevationdirection(DSL)
SST:Elevationdirection(DSL)
25o
52o
-25o
-52o
11.25o
33.75o
ESS 261 Energetic Particles59
Top View (sectors)For ESA and SST (0=Sun)
Spin motiondirection ( DSL)
11.25o
33.75o
To Sun (0o)
Spin axis
Normal to Sun, +90o
ESS 261 Energetic Particles60
(a)
(b)
(c)
(d)
(e)
TH-B
(a)
(b)
(c)
(d)
(e)
TH-B
Particle motion directionCoordinate: ( DSL)Energy: 125-175keV
Note: direction dependson spin axis.
B fieldazimuth(solid white)
-B fieldazimuth(dashed white)
You care to time this!(+/- 90o to Bfield azimuth)
ESS 261 Energetic Particles61
Multiple spacecraft, energies, elevations
A
B
D
E
….
Elev: 25deg E=30-50keV Elev: 25deg, E=80-120keV
ESS 261 Energetic Particles62
Vi_const 310km/sec/keV fci_cons 0.0152Hz/nT B 30nTTi 40keV rho_ion 683kmTi 100keV rho_ion 1081km Ti 150keV rho_ion 1323km Ti 300keV rho_ion 1872km
SC E (keV) detectord (deg) r time B 40 SPW -128.0 683.4 11:19:29 B 40 SPE -52.0 683.4 11:19:39 B 40 SEW -155.0 683.4 11:19:18 B 40 SEE -25.0 683.4 11:19:42 B 40 NPW 128.0 683.4 11:19:29 B 40 NPE 52.0 683.4 11:19:38 B 40 NEW 155.0 683.4 11:19:24 B 40 NEE 25.0 683.4 11:19:43 B 100 SPW -128.0 1080.5 11:19:17 B 100 SPE -52.0 1080.5 11:19:42 B 100 SEW -155.0 1080.5 11:19:20 B 100 SEE -25.0 1080.5 11:19:45 B 100 NPW 128.0 1080.5 11:19:20 B 100 NPE 52.0 1080.5 11:19:45 B 100 NEW 155.0 1080.5 11:19:23 B 100 NEE 25.0 1080.5 11:19:48 B 150 SPW -128.0 1323.4 11:19:10 B 150 SPE -52.0 1323.4 11:19:44 B 150 SEW -155.0 1323.4 11:19:14 B 150 SEE -25.0 1323.4 11:19:51 B 150 NPW 128.0 1323.4 11:19:23 B 150 NPE 52.0 1323.4 11:19:45 B 150 NEW 155.0 1323.4 11:19:13 B 150 NEE 25.0 1323.4 11:19:48 B 300 SPW -128.0 1871.5 11:19:10 B 300 SPE -52.0 1871.5 11:19:44 B 300 SEW -155.0 1871.5 11:19:14 B 300 SEE -25.0 1871.5 11:19:51 B 300 NPW 128.0 1871.5 11:19:23 B 300 NPE 52.0 1871.5 11:19:45 B 300 NEW 155.0 1871.5 11:19:13 B 300 NEE 25.0 1871.5 11:19:48
Note:NEE= North-Equatorial, EastNPW=North-Equatorial, WestAngles measured from East direction-25deg elevation, 90deg East = SEE+52deg elevation, 90deg East = NPE… Spin axis
B
NPW
NEW
SEW
SPW
NPE
NEE
SEE
SPE
Boundary
ESS 261 Energetic Particles63
Spin axis
BNPW
NEW
SEW
SPW
NPE
NEE
SEE
SPE
Boundary
V: NEE Part. direction
Hot/dense plasma
Cold/tenuous plasma Y
Z
GCNEE
n
Y
Y
n
Show: d=*sin(-)Note: d negative if moving towards spacecraft
d
SC
ESS 261 Energetic Particles64
• Procedure– For a given , determine variance of data for all – Find minimum in variance, this determines (boundary direction)– Speed distance as function of time determines boundary speed
– intro_ascii,'remote_sense_A.txt',delta,rho,hh,mm,ss,nskip=13,format="(25x,f6.1,f8.1,3(1x,i2))"– ;– angle=fltarr(73)– chisqrd=fltarr(73)– for ijk=0,72 do begin– epsilon=float(ijk*5)– get_d_vs_dt,epsilon,hh,mm,ss,rho,delta,dist,times– yfit=dist & yfit(*)=0.– chi2=dist & chi2(*)=0.– coeffs=svdfit(times,dist,2,yfit=yfit,chisq=chi2)– angle(ijk)=epsilon– chisqrd(ijk)=chi2– endfor– ipos=indgen(30)+43– chisqrd_min=min(chisqrd(ipos),imin)– plot,angle,chisqrd– print,angle(ipos(imin)),chisqrd(ipos(imin))– ;– stop
ESS 261 Energetic Particles65
Var
ianc
e,
2
Boundary orientation,
= 280o
Var
ianc
e,
2
Boundary orientation,
= 280o
1000
km
V ~ 70km/s
Z
Y
D
BA
• Procedure– Note two minima (identical solutions)
• One for approaching boundary at V>0• One for receding boundary at V<0
– Convention that d<0 if boundarymoves towards spacecraftallows us to pick one of the two(positive slope of d versus time)
ESS 261 Energetic Particles66
Probe: TH-BAngle to Y_east=280degD0 = -2224 kmV0 = 69.9 km/stcross= 11:19:31.81
Time since 11:19:00
Bou
ndar
y di
stan
ce (
km)
Probe: TH-BAngle to Y_east=280degD0 = -2224 kmV0 = 69.9 km/stcross= 11:19:31.81
Time since 11:19:00
Bou
ndar
y di
stan
ce (
km)
tcross V [km/s] [deg]
D 11:19:27.6 75 270
B 11:19:31.8 70 280
A 11:19:38.4 80 275
Table 1. Results of remote sensing analysis on the inner probes
Timing of the arrivals of the other signatures at the inner three spacecraft
ESS 261 Energetic Particles67
At the magnetopausei,sheath (0.5keV,10nT)= ~200kmi,m-sphere (10keV,10nT)= ~1000km
Magnetopause Thickness ~ 6000kmCurrent layer Thickness ~ 500km
FTE scale, Normal 2 Boundary: ~6000kmAlong Boundary: ~Normal : 1-3 RE
For leaking magnetospheric particles, the currentlayer is sharp compared to the ion gyroradius andthe magnetic field is the same direction in the sheath and the magnetopause outside the current layer. This means we can use the measured field outside themagnetopause to determine gyrocenters both at the magnetopause and the magnetosheath on either side of the hot magnetopause boundary.
ESS 261 Energetic Particles68
C
DTH-B AE
Ygse
Xgse
C
DTH-B AE
Ygse
Xgse
Magnetopause encounter on July 12, 2007
(a)(b)
(c)
(d)
(e)
(g)
(f)
(h)
(a)(b)
(c)
(d)
(e)
(g)
(f)
(h)
Magnetic field angle is 60deg below spin plane and +120deg in azimuth i.e., anti-Sunward and roughly tangent to the magnetopause. The particle velocities, centered at 52deg above the spin plane, have roughly 90o pitch angles, with gyro-centers that were on the Earthward side of the spacecraft. The energy spectra of the NP particles show clearly the arrival of the FTE ahead of its magnetic signature, remotely sensing its arrival due to the finite gyroradius effect of the energetic particles. T=55s, i,100keV, 28nT) =1150km, V=40km/s
ESS 261 Energetic Particles69
At the near-Earth magnetosphere
ESS 261 Energetic Particles70
At the near-Earth magnetosphere
ESS 261 Energetic Particles71
At the near-Earth magnetosphere
timespan,'7 11 07/10',2,/hours & sc='a'
thm_load_state,probe=sc,/get_supp
thm_load_fit,probe=sc,data='fgs',coord='gsm',suff='_gsm'
thm_load_mom,probe=sc ; L2: onboard processed moms
thm_load_esa,probe=sc ; L2: gmoms, omni spectra
tplot,'tha_fgs_gsm tha_pxxm_pot tha_pe?m_density tha_pe?r_en_eflux'
;
trange=['07-11-07/11:00','07-11-07/11:30']
thm_part_getspec, probe=['a'], trange=trange, angle='gyro', $
pitch=[45,135], other_dim='mPhism', $
; /normalize, $
data_type=['peir'], regrid=[32,16]
tplot,'tha_peir_an_eflux_gyro tha_fgs_gsm tha_pxxm_pot tha_pe?m_density tha_pe?r_en_eflux'
Remote sensing of wavesin ESA data, at the mostappropriate coordinateSystem, I.e, field alignedcoordinates. gyro=0o => Earthward particles
ESS 261 Energetic Particles72
At the near-Earth magnetosphere
trange=['07-11-07/11:00','07-11-07/11:30']
thm_part_getspec, probe=['a'], trange=trange, angle='gyro', $
pitch=[45,135], other_dim='mPhism', $
/normalize, $
data_type=['peir'], regrid=[32,16]
tplot,'tha_peir_an_eflux_gyro tha_fgs_gsm tha_pxxm_pot tha_pe?m_density tha_pe?r_en_eflux'
Same as before but using keyword: /normalizeI.e., anisotropy is normalized to 1, to ensure flux variations do not affect anisotropy calculation.