Time Series Analysis of Particles and Fields data

1
Time Series Analysis of Particles and Fields data

• Potential subtraction
• Density computation from three sources (Ne, Ni,
  scpot)
• Cold plasma detection
• Next opportunity
• Velocity, pressure corrections from SST
• Waves analysis
• Suggested reading
• McFadden et al, THEMIS ESA instrument and
  calibration (Space Sci. Reviews)
• McFadden et al, ESA first results (Space Sci.
  Reviews)
• McFadden et al, Structure of plasmaspheric plumes
  (GRL)
• Materials in
• http//www.igpp.ucla.edu/public/vassilis/ESS265/20
  080519
• class_notes_time_series_analysis_B.ppt
• thm_code/thm_pot2dens.pro, thm_part_dist.pro,
  thm_part_moments.pro (for cleanup)
• esa_particles/get_th?_pe?r.pro
• potential_correction.pro density_all.pro
  cold_ions.pro

2
Potential Subtraction

• Automatic subtraction
• Read spacecraft potential (Vsc)
• From spheres Vsc-(V3V4)/2.
• Add 1V offset
• Accounts for spheres drivenabove plasma
  potential
• Correct to infinity ( x 1.15 )
• Sensor voltage is not exactly atzerooffset
  because Debye lengthis very large. A 15
  correctionto account for plasma potentialat
  infinite sphere distance.
• Reduce electron energies
• E'elec Eelec Vsccorrected
• Increase ion energies
• E'ion Eion Vsccorrected
• Cannot do if EFI is not deployed
• Right hand side is an example
• Must do manually
• Determine Vsc from spectrum
• Manually correct potential

Ni
Ne
3
Potential Subtraction

• Manual scpot subtraction
• When EFI not deployed
• Read scpot value (0)
• Correct based on spectra
• Recompute moments
• Use full or reduced distributions
• From peef get N,V,T
• From peer (6 angles) N,T

Ne Ni
gtgtgtgtgtgtpotential_correction.proltltltltltltltltltltltltltltltltltltlt
ltltltltltltltltlt timespan,'7 11 07/10',2,/hours sc'a th
m_load_state,probesc,/get_support thm_load_fit,pr
obesc,data'fgs',coord'gsm',suff'_gsm' thm_load
_fit,probesc,data'fgs',coord'dsl',suff'_dsl' t
hm_load_mom,probesc L2 onboard processed
moms thm_load_esa,probesc L2 ground processed
gmoms, omni spec Modify sc potential thm_load_
esa_pkt,probesc get_data,'tha_pxxm_pot',datatha_
pxxm_pot,dlimdlim tha_pxxm_pot.y()10.
eV store_data,'tha_pxxm_pot_corr',
dataxtha_pxxm_pot.x,ytha_pxxm_pot.y,
dlimdlim Recompute moments thm_part_moments,
probe sc, instrum 'peer', scpot_suffix
'_pxxm_pot_corr', mag_suffix '_fgs_dsl',
tplotnames tn options,'tha_peer_density','colors
','b' options,'tha_peim_density','colors','r'
store_data,'tha_pexm_density',
data'tha_peer_density tha_peim_density' options,'
tha_pexm_density','colors','b','r' options,'tha_
pe?m_density',yrange0,2 options,'tha_pexm_densi
ty',ylog0 tplot,'tha_fgs_gsm tha_pexm_density
tha_pe?r_en_eflux'
4
Density from S/C Potential, Other
gtgtgtgtgtgtdensity_all.proltltltltltltltltltltltltltltltltltltltltltltltltltltltlt
timespan,'8 1 16/1400',6,/hours sc'd' thm_load_
state,probesc,/get_supp thm_load_fit,probesc,dat
a'fgs',coord'gsm',suff'_gsm' thm_load_fit,probe
sc,data'fgs',coord'dsl',suff'_dsl' thm_load_mo
m,probesc L2 onboard processed
moms thm_load_esa,probesc L2 ground processed
gmoms, omni spectra thm_load_sst,level2,probesc
NOW CONSTRUCT DENSITY FROM SCPOT tinterpol_mxn,'
thd_peer_t3','thd_pxxm_pot',newname'thd_peer_t3_i
nt' get_data,'thd_pxxm_pot',datathd_pxxm_pot,dld
l get_data,'thd_peer_t3_int',datathd_peer_t3_int
thm_pot2dens,thd_pxxm_pot.y,thd_pxxm_potdens,
Tetotal(thd_peer_t3_int.y,2)/3. ?New code, in
class materials store_data,'thd_pxxm_potdens',
dataxthd_pxxm_pot.x,ythd_pxxm_potdens,dldl
NOW PLOT UNCORRECTED DENSITIES store_data,'thd_p
eer_en_eflux_pot',data'thd_peer_en_eflux
thd_esa_pot' options,'thd_fgs_gsm',yrange-150,15
0 options,'thd_peer_density',colors'r' options
,'thd_peir_density',colors'b' options,'thd_pxxm
_potdens',colors'g' options,'thd_pxxm_potdens',
ylog1 options,'thd_peer_t3',ylog0 options,'thd_p
xxm_pot',ylog0 options,'thd_pe?r_en_eflux',yrang
e7.,25000. store_data,'thd_densities',
data'thd_peir_density thd_peer_density
thd_pxxm_potdens' tplot,'thd_fgs_gsm thd_peer_t3
thd_pxxm_pot thd_densities '
'thd_psef_en_eflux thd_peer_en_eflux_pot
thd_peir_en_eflux'
Ne Ni
Nscpot
5
Correct Densities Issues

• Photoelectrons on Ne
• Have been corrected already, as EFI operating
• Both on board and through ground processing
• Primary and secondary electrons from gt10keV
  electrons entering i/e aperture
• Electron ESA, primaries and secondaries (below
  about 40eV) NegtNi
• Primaries, grazing incidence, degraded energy
• Secondaries from electron collisions with walls
• Secondary electrons in ion ESA (below about
  500eV) Ni gt Ne
• Must be gt2keV to overcome post-acceleration in
  front of McP
• When significant flux of energetic electrons is
  present
• See 1600 and 1630 UT injections on THD,
  2008-01-16
• Can result in either NegtNi or NigtNe depending on
• Scattered flux relative to electron/ion fluxes
• Correct by integrating density above secondaries
• gt 40eV for electrons
• gt 100eV for ions
• Background radiation near radiation belts
• Penetrates ESA walls
• Produces constant background eflux as function of
  energy

6
Correct Densities Solution
gtgtgtgtgtgtdensity_all.pro(continued)ltltltltltltltltltltltltltltltltlt
ltltlt CORRECT DENSITIES load L0 omni spectra,
all ESA data in memory thm_load_esa_pkt,probesc
PEIR MOMS/SPECTRA Remove radiation and
integrate above 40eV to remove scattered
electrons thm_part_moments, probe sc, instrum
'peir', scpot_suffix '_pxxm_pot',
trange'8 1 16/1400','8 1 16/2000',
erange0,31, mag_suffix '_fgs_dsl',
tplotnames tn, verbose 2, /bgnd_remove
names are output into tn ?New code, in class
materials PEER MOMS/SPECTRA Remove
radiation and integrate above 40eV to remove
scattered electrons thm_part_moments, probe sc,
instrum 'peer', scpot_suffix '_esa_pot',
trange'8 1 16/1400','8 1 16/2000',
erange0,24, mag_suffix '_fgs_dsl',
tplotnames tn, verbose 2, /bgnd_remove
names are output into tn ?New code, in class
materials scpot determination of density,
with (now/see above) better temperature tinterpo
l_mxn,'thd_peer_t3','thd_pxxm_pot',newname'thd_pe
er_t3_int' get_data,'thd_pxxm_pot',datathd_pxxm_p
ot,dldl get_data,'thd_peer_t3_int',datathd_peer_
t3_int thm_pot2dens,thd_pxxm_pot.y,thd_pxxm_potden
s, Tetotal(thd_peer_t3_int.y,2)/3. store_data
,'thd_pxxm_potdens', dataxthd_pxxm_pot.x,y
thd_pxxm_potdens,dldl tplot,'thd_fgs_gsm
thd_peer_t3 thd_pxxm_pot thd_densities '
'thd_psef_en_eflux thd_peer_en_eflux_pot
thd_peir_en_eflux'
Ni requires better background removal (in
progress)
7
Cold Ion Detection, Using Nscpot
gtgtgtgtgtgtcold_ions.proltltltltltltltltltltltltltltltltltltltlt timespan,
'7 6 8/2100',3,/hours sc'c' thm_load_state,pro
besc,/get_supp thm_load_fit,probesc,data'fgs',c
oord'gsm',suff'_gsm' thm_load_fit,probesc,data
'fgs',coord'dsl',suff'_dsl' thm_load_mom,probes
c thm_load_esa,probesc NOW CONSTRUCT DENSITY
FROM SCPOT tinterpol_mxn,'thc_peer_t3','thc_pxxm_p
ot', newname'thc_peer_t3_int' get_data,'thc_p
xxm_pot',datathc_pxxm_pot,dldl get_data,'thc_pee
r_t3_int',datathc_peer_t3_int thm_pot2dens,thc_px
xm_pot.y,thc_pxxm_potdens,
Tetotal(thc_peer_t3_int.y,2)/3. store_data,'thc_p
xxm_potdens', dataxthc_pxxm_pot.x,ythc_pxx
m_potdens,dldl NOW PLOT DENSITIES (NO
SCATTER/NO RADIATION) store_data,'thc_peer_en_eflu
x_pot', data'thc_peer_en_eflux
thc_pxxm_pot' options,'thc_fgs_gsm',yrange-70,10
0 options,'thc_peer_density',colors'r' options
,'thc_peir_density',colors'b' options,'thc_pxxm
_potdens',colors'g' options,'thc_pxxm_potdens',
ylog1 options,'thc_peer_t3',ylog0 options,'thc_p
xxm_pot',ylog0 options,'thc_pe?r_en_eflux',yrang
e7.,25000. store_data,'thc_densities',data'thc
_peir_density ' thc_peer_density
thc_pxxm_potdens' tplot,'thc_fgs_gsm
thc_peir_velocity_gsm thc_densities
thc_psef_en_eflux thc_peer_en_eflux_pot
thc_peir_en_eflux'
Nscpot gt NeNi Plasmasphere !
8
Cold Ion Detection, Issues

• When Vscpot gt Vthion then
• Cold ions cannot overcome barrier
• Ni lt Vscpot
• When Vscpot lt EESAmin then
• Electrons are missed
• Cold electrons missed Ne lt Ni
• Situation is improved when Vi large
• Cold ions can be detected
• Ni agrees with Nscpot
• When Ekinetic - eVsc gt EESAmin

Hot plasma (NeNiNscpot)
9
Cold Ion Detection, When Vi large

• Situation is improved when Vi large
• Cold ions can be detected
• Ni agrees with Nscpot
• When Ekinetic - eVsc gt EESAmin

gtgtgtgtgtgtcold_ions.pro (continued)ltltltltltltltltltltltltltltltltltlt
ltlt tvectot,'thc_peir_velocity_gsm',
newname'thc_peir_velocity_gsmt' tvectot,'thc_peir
_velocity_gsm',tot'thc_peir_velocity_t tinterp
ol_mxn,'thc_peir_velocity_t',
'thc_pxxm_pot',newname'thc_peir_velocity_tint' ge
t_data,'thc_peir_velocity_tint',datathc_peir_velo
city_tint get_data,'thc_pxxm_pot',datathc_pxxm_po
t eflow1000.(thc_peir_velocity_tint.y/310.)2
- thc_pxxm_pot.y in eV store_data,'thc_efl
ow',dataxthc_peir_velocity_tint.x,yeflow stor
e_data,'thc_peir_en_eflux-n-flow',
data'thc_peir_en_eflux thc_eflow' options,'thc_pe
ir_en_eflux',yrange7.,25000. tplot,'thc_fgs_
gsm thc_peir_velocity_gsmt thc_densities ',
thc_psef_en_eflux thc_peer_en_eflux_pot
thc_peir_en_eflux-n-flow' tlimit,'7 6
8/2200','7 6 8/2230'
10
Multi-spacecraft Analysis Calibration

• ESA instruments received first an absolute
  calibration
• In the sheath, avoid unmeasured plasmaspheric
  cold ions, electrons, or solar wind beam
• Correct for energy dependent efficiencies
• Detector anode relative efficiencies (north/south
  asymmetry)
• Electron-ion relative efficiencies (based on
  density, account for solar wind composition)
• FGM calibration was done independently for each
  spacecraft
• Spin plane offsets determined routinely
• In the solar wind determine spin axis offsets
• Spin axis offset variation 0.2nT over the mission

11
Multi-spacecraft Analysis ESA Inter-Calibration

• On all spacecraft, ions and electrons
• Detector anode relative efficiencies (north/south
  asymmetry)
• Sort ions and electrons separately in pitch-angle
• Apply low-order polynomial fit to pitch angle
• Determine anode efficiency that minimizes
  variance (a 1-2 effect)
• Large angle variance (systematic asymmetry)
  checked further
• Look at systematic flows during times expected to
  have zero
• Found none for ions in the magnetosphere
• Adjusted electron asymmetry (1-3) in the sheath
  such that Vi Ve

12
Multi-spacecraft Analysis ESA Inter-Calibration

• Detector energy relative efficiency
• Based on published data, private communications
  and simulations
• Main effect on ions is increase in g-factor due
  to fringe fields at grid
• Field from 2keV McP pre-acceleration potential
  leaks through zero volt grid into detector
• Collects scattered electrons, increases
  sensitivity of detector at low (lt2keV) energies

Themis, ions simulated
Electrons
Ions
13
Multi-spacecraft Analysis ESA Cross-Calibration

• THC was the trailblazer (EFI out) used as
  reference
• THC Electron sensor selected as reference
• THC Ion sensor caled for energy, anode
  efficiency
• THC Ion sensor g-factor adjusted to match
  electron
• All other spacecraft also internally calibrated
• Cross-calibration as follows
• Use early string of pearls configuration
• Adjust Ni/Ne (0.99) based on WIND/SWE 4 alphas
• Adjust THD/THC electron densities to match
• Adjust THE/THC etc.
• For THA
• Time varying calibration
• ESA McP scrubbing
• Efficiency decreases due to water molecules
  venting
• Stabilizes after few months of operations

Ignore
14
Multi-spacecraft Analysis ESA Absolute
Calibration
THC electrons

• THC and THD electrons versus WIND-SWE
• Time-shift WIND data
• WIND has plasma waves
• WIND density calibrated from plasma frequency
• Five intervals found in summer of 07
• Correct deficiency due to scpot below Emin
• Extend Maxwellian spectra to low energies
• Themis g-factors scaled to 70 in Fall07
• In retrospect, were due to overestimate ofenergy
  efficiency at low energies

THD electrons
Wind, B
THC, THD, B
THC, THD, Ne
Wind, B
15
Multi-spacecraft Analysis Calibration
verification

• Find magnetopause crossings and sheath waves
• Expect quasi-static pressure balance
• Determine total pressure
• Ptotal Pion Pelectron PB
• Show total pressure is constant across
• Method shows that pressure balance is observed
• Calibration is working, at least at low energies
• Higher energy component has been less tested

PTot
PB
Pi
Pe
16
Multi-spacecraft Analysis At the magnetopause
17
Homework

• Find a THEMIS 2-4 hour interval of your interest
• Use at least two satellites
• Plot ion and electron density
• Plot density derived from spacecraft potential
• Explain the differences