Transcript Document

ESS 261 Spring Quarter 2009
Energetic Particles & Boundary Remote
Sensing
Energetic Particle Instruments: Operation and Data Products
Geometric 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 Caron
References: ISSI book on Analysis Methods for Multi-Spacecraft Data
Lecture 05
April 27, 2009
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Energetic Particles1
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.
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Energetic Particles2
Pair production
Photoelectric effect
Compton scattering
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Energetic Particles3
(/ often used: mass attenuation coefficient)
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Energetic Particles4
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
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Energetic Particles5
Interaction of particles with matter [3]
• The stopping power for heavy particles (ions)
is given by the Bethe-Bloch formula (1932):
dE 4N A z e


B, where:
2 2
dx
me c 
2 4
2 2

 2me c  
Z
C 
2
B
   
ln 
2 
A   I (1   ) 
Z 2
Rate of energy loss is ~ inversely proportional to energy, and
proportional to Z (the atomic number) and z2, z the projectile charge
I = average ionization potential,  and C = density and shell corrections.
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Energetic Particles6
Interaction of particles with matter [4]
• The range is given by:
1
 dE 
R  
 dE
dx 
Estart 
0
– 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.
This formula is only useful for ions for reasons we will soon see.
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Energetic Particles7
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)
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Energetic Particles8
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)
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Energetic Particles9
Protons in
Energy lost to ionization (collectable)
Energy lost to phonons (not collectable)
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Energetic Particles10
Alphas in:
Energy lost to ionization (collectable)
Energy lost to phonons (not collectable)
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Energetic Particles11
Electrons in
Energy lost to
ionization
(collectable)
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Energetic Particles12
Energy lost to
Bremstrahlung
radiation (not
collectable)
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
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Energetic Particles13
• Particles can be incident on either side of detector
Operation Principle
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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.
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Energetic Particles14
p
- +
n
- +
E
Forward bias
p
-+
n
-+
E
particle
Reverse bias
p
- +
n
-+ +E
Detector Electronics
Simulated A225
response 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!
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Energetic Particles15
Front End Counting Electronics
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Energetic Particles16
Sources of Noise
• Capacitance
– Noise results in
uncertainty in
absolute value
of 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
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Energetic Particles17
Examples of Detector Systems: WIND/3DP
Predecessor of THEMIS/SST
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Energetic Particles18
Examples of Detector Systems: WIND/EPACT
Cross section of the EPACT isotope telescope on Wind. The first two detectors
are two-dimensional position sensitive strip detectors (PSD1, PSD2). They are required
so that path-length corrections may be made for the angle of incidence and for
non-uniformities in detector thickness. Tungsten rings are used to mask off circular areas
for each PSD. There are 6 solid-state detectors increasing in thickness with depth in the
stack in order to minimize Landau fluctuations. From von Rosenvinge et al. [1995].
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Energetic Particles19
Examples of Detector Systems: THEMIS/SST
Foil Collimator
(for electrons)
Attenuator
Foil
Detector Stack
Magnet
Attenuator
Open Collimator
(for ions)
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Energetic Particles20
THEMIS/SST Sensor Unit Schematic
Al/Polyamide/Al Foil
Foil Detector
Thick Detector
Open Detector
Foil
Collimator
(electron side)
Attenuator
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Open Collimator (ion side)
Attenuator
Sm-Co Magnet
Energetic Particles21
THEMIS/SST Sensor Unit Details
• 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
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Energetic Particles22
• Preamplifier / shaping electronics
Detector Pixelation
• Detectors similar to STEREO/STE
– Produced at LBNL/Craig Tindall PI
Active area
5 mm
Guard ring
10 mm
Additional Pixels not used for Themis
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Energetic Particles23
Detector Wiring
-35 V
~200 A Polysilicon
n
p
F
+4.5 V
225FB
F Out
-2.5 V
Pixelated side
~1200 A Dead layer
F Test in
p
n
n
p
T
225FB
T Out
T Test in
p
n
O
225FB
Outside Grounded
O Test in
~200 A Polysilicon +
~200 A Al
300 micron thick detectors
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O Out
Energetic Particles24
SST Detector Mechanical Design/Connections
• Typical Electrical Connection Between Detector and Flex-Circuit
Wirebond Loop
(NOT to scale – actual
loop height < 300 micron)
Kapton FlexCircuit
Detector
(pixelated side)
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Energetic Particles25
SST Detector Mechanical Assembly
• DFE Board
Subassembly
BeCu Gasket (3)
Detectors (4)
Kapton
Heater
Spring Clamp
PEEK Spacer (4)
Spring Plate (2)
Kapton Flex-Circuit (4)
AMPTEK Shield
Thermostat
• Detector Board Composition (exploded view)
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Energetic Particles26
SST Detector Mechanical: Real Life
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Energetic Particles27
SST Mechanical Design
• DFE Board Subassembly Relative Positions
•
(2 per sensor)
Detector Stack
Subassembly
Foil Frame
Multi-Layer Circuit Board
(62 mil thickness)
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Thermostat
Energetic Particles28
AMPTEK Shielding
SST Mechanical Design
• Magnet-Yoke Assembly
Co-Fe Yoke (2)
Sm-Co Magnet (4)
(currently not visible)
Aluminum Magnet Cage
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Energetic Particles29
SST Mechanical Design
• Attenuator Assembly
SMA Lever (2)
Attenuator (4)
Cam (2)
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Energetic Particles30
SST Mechanical Design
• Actuators and Position Switches
Honeywell SPDT Hermetically
Sealed Switch (2)
SMA Actuator (2)
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Energetic Particles31
SST Mechanical Design
• Two Collimators Per Side
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Energetic Particles32
Ion Side
Electron Side
SST Mechanical Design
• Four Collimators Per Sensor
Electron Side
Ion Side
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Ion Side
Electron Side
SST Mechanical Design
• Support Structure
• (back section)
Rigid Mounting
Flange
Electrical Connector
Bottom Closeout Panel
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Energetic Particles34
SST Mechanical Design
• Support Structure
• (front section)
Rigid Mounting
Flange
Kinematic Flexure (2)
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SST Mechanical Design
• Bi-Directional Fields-of-View
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SST Mechanical Design
• Sensor Orientation Relative to Spacecraft Bus
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Energetic Particles37
SST Mechanical Design
• 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:
Y-Axis:
0.006” (0.15 mm)
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
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Energetic Particles38
SST Mechanical Design
• Attenuator Actuation – CLOSED position
Honeywell Switch
(compressed-position)
Honeywell Switch
(extended-position)
SMA Actuator (retracted)
SMA Actuator (extended)
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Energetic Particles39
SST Mechanical Design
• Attenuator Actuation – OPEN position
Honeywell Switch
(extended-position)
Honeywell Switch
(compressed-position)
SMA Actuator (extended)
SMA Actuator (retracted)
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Energetic Particles40
• 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
Relative Size
(commercial model shown)
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Retracted
Position
Energetic Particles41
Magnetics Testing
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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
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Energetic Particles42
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
150
100
50
0
-50 0
-100
-150
-200
-250
-300
-350
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100
200
300
400
Series1
Series2
Series3
Energetic Particles43
Electronics Block Diagram
• Signal chain: 1 of 12 channels shown
Bias Voltage
Test Pulser
DAC
Thresh
Gain
PD
A225F
Preamp
Shaper
ADC
Memory
BLR
DFE
Board
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FPGA
Coincidence
Logic &
Accumulators
DAP Board
Energetic Particles44
FPGA Functions: Interface to ETC
• Using Actel RT54SX72S (modeled on STEREO/STE)
– Controls 12 ADCs
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Monitor / Count threshold events
Monitor peak detect signal
Produce convert strobe
Coincidence detection
Readout ADC (energy)
– Psuedo-logrithmic energy binning
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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
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Energetic Particles45
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
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Energetic Particles46
SST Accommodation
SSTs
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Angelopoulos, 2008
SST Accommodation
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Angelopoulos, 2008
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
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Sun contamination (thm_crib_sst_contamination.pro)
–
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;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
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Data Analysis Tools [3]
• Pitfalls
– Sun contamination
– Read crib sheets:
documented procedure:
»
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»
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thm_crib_sst_contamination.pro, and
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
Energetic Particles51
Ground processing (particles only)
• Pitfalls
– Sun contamination: Bin selection
» ;
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Density Correction
• Interpolate densities
• Add
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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']
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;... 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
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Ni
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Ne
Energetic Particles53
Velocity Correction
• Interpolate densities
• Add flux
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;
;
; ...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]
•
•
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•
; ...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
•
•
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•
; ...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
•
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Pressure Correction
• Remove SST noise
• Interpolate pressures
• Then add
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; 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'
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; ...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'
•
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; ...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'
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Energetic Particles55
Finite gyroradius techniques
• Ion Gyroradius large compared to magnetospheric boundaries
– Can be used to remotely sense speed
and thickness of boundaries
– Assumption is that boundary is sharp
and flux has step function across
• Application at the magnetopause
• Application at the magnetotail
To Tail
THEMIS
– Can also be applied to waves if
particle gradient is sufficiently high
• Application on ULF waves at
inner magnetosphere
To Earth
To Sun
ESS 261
Energetic Particles56
Method exploits finite ion
gyroradius to remotely sense
approaching ion boundary and
measure boundary speed (V⊥)
At the magnetotail
i,thermal-tail (4keV,20nT)=
i,super-thermal (50keV,20nT)=
~325km
~2200km
Plasma Sheet Thickness
Boundary Layer Thickness
Current layer Thickness
~ 1-3 RE
~500-2000km
~ 500-2000km
Waves Across Boundary:
Along Boundary:
~1000-10,000km
~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 Particles57
52o
Side View (elevations)
Spin
Axis
To Sun
o
25
SST:
Elevation
direction
(qDSL)
-25o
-52o
ESA:
Elevation
direction
(qDSL)
ESS 261
Energetic Particles58
33.75o
11.25o
Top View (sectors)
For ESA and SST (0=Sun)
Spin axis
To Sun (0o)
11.25o
33.75o
Spin motion
direction ( f DSL)
ESS 261
Normal to Sun, +90o
Energetic Particles59
TH-B
(a)
(b)
B field
azimuth
(solid white)
You care to time
this!
(c)
(+/- 90o to Bfield azimuth)
Particle motion direction
Coordinate: ( f DSL)
Energy: 125-175keV
(d)
(e)
Note: direction depends
on spin axis.
-B field
ESS 261
azimuth
(dashed white)
Energetic Particles60
Multiple spacecraft, energies, elevations
A
B
….
D
E
Elev: 25deg E=30-50keV Elev: 25deg, E=80-120keV
ESS 261
Energetic Particles61
Vi_const
310km/sec/keV
Ti
40keV rho_ion
683km
Ti
100keV rho_ion
1081km
Ti
150keV rho_ion
1323km
Ti
300keV rho_ion
1872km
SC
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
E (keV) detectord (deg)
40
SPW
-128.0
40
SPE
-52.0
40
SEW
-155.0
40
SEE
-25.0
40
NPW
128.0
40
NPE
52.0
40
NEW
155.0
40
NEE
25.0
100
SPW
-128.0
100
SPE
-52.0
100
SEW
-155.0
100
SEE
-25.0
100
NPW
128.0
100
NPE
52.0
100
NEW
155.0
100
NEE
25.0
150
SPW
-128.0
150
SPE
-52.0
150
SEW
-155.0
150
SEE
-25.0
150
NPW
128.0
150
NPE
52.0
150
NEW
155.0
150
NEE
25.0
300
SPW
-128.0
300
SPE
-52.0
300
SEW
-155.0
300
SEE
-25.0
300
NPW
128.0
300
NPE
52.0
300
NEW
155.0
300
NEE
25.0
ESS 261
fci_cons
r
683.4
683.4
683.4
683.4
683.4
683.4
683.4
683.4
1080.5
1080.5
1080.5
1080.5
1080.5
1080.5
1080.5
1080.5
1323.4
1323.4
1323.4
1323.4
1323.4
1323.4
1323.4
1323.4
1871.5
1871.5
1871.5
1871.5
1871.5
1871.5
1871.5
1871.5
0.0152Hz/nT
time
11:19:29
11:19:39
11:19:18
11:19:42
11:19:29
11:19:38
11:19:24
11:19:43
11:19:17
11:19:42
11:19:20
11:19:45
11:19:20
11:19:45
11:19:23
11:19:48
11:19:10
11:19:44
11:19:14
11:19:51
11:19:23
11:19:45
11:19:13
11:19:48
11:19:10
11:19:44
11:19:14
11:19:51
11:19:23
11:19:45
11:19:13
11:19:48
B
30nT
Note:
NEE= North-Equatorial, East
NPW=North-Equatorial, West
Angles measured from East direction
-25deg elevation, 90deg East = SEE
+52deg elevation, 90deg East = NPE
…
NPW
NEW
Spin axis
NPE
NEE
B
SEW
SPW
Energetic Particles62
SEE
SPE
Boundary
NPW
B
NEW
Spin axis
NPE
V: NEE Part. direction
NEE
d
SC
SEW
SPW
SEE d
SPE
Y

Z
n
Cold/tenuous plasma
n
Hot/dense plasma
GCNEE
e
Show: d=*sin(d-e)
Note: d negative if moving towards spacecraft
ESS 261
Energetic Particles63
Y
Y
d
Boundary
•
Procedure
– For a given e, determine variance of data for all d
– Find minimum in variance, this determines e (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 Particles64
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 boundary
moves towards spacecraft
allows us to pick one of the two
(positive slope of d versus time)
A
1000 km
–
Y
D
B
V ~ 70km/s
e= 280o
Variance, 2
•
Z
Boundary orientation, e
ESS 261
Energetic Particles65
Boundary distance (km)
Probe: TH-B
Angle to Y_east=280deg
D0 = -2224 km
V0 = 69.9 km/s
tcross=
11:19:31.81
Time since 11:19:00
tcross
V [km/s]
e[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 Particles66
At the magnetopause
i,sheath (0.5keV,10nT)=
i,m-sphere (10keV,10nT)=
~200km
~1000km
Magnetopause Thickness
Current layer Thickness
~ 6000km
~ 500km
FTE scale, Normal 2 Boundary: ~6000km
Along Boundary:
~Normal : 1-3 RE
For leaking magnetospheric particles, the current
layer is sharp compared to the ion gyroradius and
the 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 the
magnetopause to determine gyrocenters both at the
magnetopause and the magnetosheath on either side
of the hot magnetopause boundary.
ESS 261
Energetic Particles67
Magnetopause encounter on July 12, 2007
(a)
(b)
(c)
(d)
(e)
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
(f)
(g)
(h)
Energetic Particles68
At the near-Earth magnetosphere
ESS 261
Energetic Particles69
At the near-Earth magnetosphere
ESS 261
Energetic Particles70
At the near-Earth magnetosphere
Remote sensing of waves
in ESA data, at the most
appropriate coordinate
System, I.e, field aligned
coordinates.
gyro=0o => Earthward particles
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'
ESS 261
Energetic Particles71
At the near-Earth magnetosphere
Same as before but using
keyword: /normalize
I.e., anisotropy is normalized
to 1, to ensure flux variations
do not affect anisotropy
calculation.
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'
ESS 261
Energetic Particles72