1. Summary of EFI splinter
Delft (NL)
Summary of EFI splinter
Raffaella D’Amicis
7th Data Quality Workshop
27 October 2017

2. Contents We had a very rich and fruitful EFI splinter session
EFI science
Thermal Ion Imagers: anomaly, operations and datasets, validation
Langmuir Probes: status, operations and datasets
Validation: faceplate, ISR, radio occultation
Summary of open points and recommendations

3. EFI science EFI keeps delivering scientifically valuable measurements
Several published and submitted papers in 2017
Published:
Birkeland Current Boundary Flows, Archer et al., JGR
630 nm auroral emission height, Gillies et al., JGR
EFI Instrument and performance, Knudsen et al., JGR
Electron heating in pulsating aurora, Liang et al., JGR
High-latitude Poynting flux, Park et al., JGR
Multiple arc current systems, Wu et al., JGR
Submitted:
Distinguishing BCBFs and SAIDs, Archer & Knudsen, JGR
“STEVE” arcs– MacDonald et al., Science Advances
Alfvén waves in a dual-arc system, Miles et al., GRL
Alfvén waves in MI Coupling, Pakhotin et al., JGR
Langmuir probe cal/val, Lomidze et al., Radio Science
Birkeland Current Boundary Flows
vs Sub-Auroral Ion Drifts
Archer and Knudsen, JGR, submitted

4. EFI science EFI keeps delivering scientifically valuable measurements
Several published and submitted papers in 2017
Published:
Birkeland Current Boundary Flows, Archer et al., JGR
630 nm auroral emission height, Gillies et al., JGR
EFI Instrument and performance, Knudsen et al., JGR
Electron heating in pulsating aurora, Liang et al., JGR
High-latitude Poynting flux, Park et al., JGR
Multiple arc current systems, Wu et al., JGR
Submitted:
Distinguishing BCBFs and SAIDs, Archer & Knudsen, JGR
“STEVE” arcs– MacDonald et al., Science Advances
Alfvén waves in a dual-arc system, Miles et al., GRL
Alfvén waves in MI Coupling, Pakhotin et al., JGR
Langmuir probe cal/val, Lomidze et al., Radio Science
Correlated E and dB from
FACs and Alfvén waves
Pakhotin et al., JGR, submitted

5. TII imaging anomaly
Swarm A and B EFI TII’s continue to provide good data with reduced operations (now 3 orbits per day) Good Poor Numerous tests have been conducted to investigate H2O hypothesis, and to mitigate the problem, including scrubbing, heater tests and high-voltage supply commissioning. Tests are still on-going and are designed to improve image anomaly although we are aware that moisture might never be fully removed within operating lifetime.
Good vs Poor images showing “ring” and “wing” anomalies
(Courtesy of J. Burchill and Torr Scientific)

6. EFI-TII operations Anomaly workaround: Special operations:
Reduced number of daily operational orbits:
6 in 2016 and 3 in 2017 on Alpha (since July 2017) and Bravo
3 then 1 (since June 2017) on Charlie
Daily scrubbing of Inner Dome implemented since Spring 2017
Full scrubbing of Phosphor Plate, MCP and Inner Dome sequentially (TBC)
Special operations:
Commissioning of MCP from 2.2 kV to 2.4 kV (to allow improved scrubbing) on all spacecraft
Commissioning of Phosphor Plate from 5 kV to 7 kV (to allow improved scrubbing) on Charlie, and on Alpha and Bravo next month
Bravo yaw-manoeuvred 15°during 1 week in March to test heating the TII sensor
Image performance tested under various Inner Dome voltage (60 to 100 V) and Phosphor Screen voltage (3 to 5 kV)

7. EFI science operations
03/2017
SW-B Heating test with yaw bias
08/2017
Sw-A/B MCP commissioning to 2400V
04/2017
Scrubbing included in R&C and OPF
(Courtesy of Serenella Di Betta)
08/2017
Investigation on spikes in phosphor plate voltage.
08/2017
SW-C Phosphor Plate commissioning to 7000V
11/2016
Sw-A/B MCP commissioning to 2250V
05/2017
TPF commanding as part of the nominal Ramp-Up event in R&C
05/2015
EFI Active only for few orbits per day Regular activity
09/2017
SW-C both LP in high gain during the TII Ready state
09/2016
Sw-C EFI Heating test
09/2017
HK sampling rate to 1Hz around the Ramp-Up to support detection of spikes in the voltages – automatized via R&C
08/2016
Sw-C MCP commissioning to 2250V
04/2014
End of official commissioning for EFI
10/2015
Introduction of OPF to handle EFI state transitions
06/2017
Sw-A TII inner dome ring test
07/2016
Different TII Image rate for different EFI state
07/2017
Sw-C MCP commissioning to 2400V
11/2017
SW-A/B Phosphor Plate commissioning to 7000V
22/11/2013
Launch
Tests to investigate the anomaly of the TII image
05/2016
Start of scrubbings
2014
2015
2016
2017

8. TII datasets 2 Hz Cross-track flow datasets 16 Hz
(Courtesy of J. Burchill)

9. EFI cross-track flow data validation
Why cross-track flow? All the measurements are based on the so-called signal angle, so they are species-independent. Within this context the Origin location (x-not, y-not) is the only parameters we need to find out in the signal angle.
Hypothesis of stationarity works. Day-side equatorial plasma flows show evidence for westward ion drift of order 40 m/s  Consistent with statistical diurnal measurements by ISR
Known ion drift associated with plasma corotation and satellite yaw enable calibration of TII H detector
Vertical detector signal modulation is not sufficient for its calibration  Is it possible to modulate satellite pitch angle on a regular basis?
(from A. Kouznetsov’s talk)

10. Preparing TII measurements
L1b Prototype is complex to calibrate
Derive cross-track flows from flow angles, assuming 7.6 km/s ram speeds as is done for some products for DE2, DMSP
Use reference frame co-rotating with Earth, remove flows arising from yaw and pitch motions
Calibrate cross-track horizontal flow against (co-rotation + yaw) signal
Exclude noisy data
Send latest measurements to ESA
Expert judgment needed

11. Validation of TII E field data
The optimization procedure consists in minimising the difference between electric conductances computed with SECS and a proxy derived from Robinson formula:
Provides better results when the ionospheric current (and its magnetic effect at Swarm) is stronger.
Needs to be tuned to the latitudinal range of the ionospheric current.
When swA and swB are longitudinally ‘conjugate’ and the event is roughly 1D, both the 2D and 1D optimization provide roughly similar results (as they should).
For 1D events, often observed in the auroral region:
Optimization of Ect-V looks promising, though in general will depend on the geometry.
Once again, the optimization should be tuned to the latitude range of Jion.
The tilt, q, of the 1D aurora, with respect to the E-V direction, matters.
Move the parametrization, (a, b) and (c, d), to the TII system, and perhaps apply it to v instead of E.
Parametrize also the possible tilt, q, of the 1D aurora.
Analysis of more events, ideally assisted by optical data.
(courtesy of O. Marghitu)

12. Equatorial plasma depletions as observed by Swarm
Correlation E and B field
Study of the direction of electromagnetic energy flux associated with equatorial plasma depletions.
Asymmetry in Poynting flux to be caused probably by an asymmetry between the hemispheres on the ionospheric conductivity
(Rodriguez-Zuluaga et al 2017)

13. Recommendation
Different TII measurements (datasets) under study. Since for example in 2016 only few EPD had EFI TIICT (19%), a recommendation to take into account the occurrence of equatorial plasma depletions.

14. A comparison of Swarm cross-track ion-drifts and SuperDARN line-of-sight velocities
Since Swarm EFI gives better quality data for the cross-track drift component, a comparison is performed with paths that are almost perpendicular to one or several SuperDARN radar beams. Basically agreement consistent with the analysis by Fiori et al. (2016) based on Su perDARN statistical model. Advantage of combining data as for example in convection reversal boundary.
(Courtesy of A. Koustov)
Year 2016

15. LP overview and status
Longterm behaviour, no signs of degradation or erosion
Solar activity presently helps against the 0-tracking failures which now minimized
Signs of effects from different surfaces, TiN (Titanium Nitride) vs gold-plated
“Samegain” of probes provides opportunities for investigations, perhaps new data products

16. LP datasets Provisional LP data (/Advanced folder)
Preliminary data provided by IRF whose main products are electron density and temperature and s/c potential. Coverage: all s/c, BOM – 17/07/2015
Operational LP data (/Level1b folder)
Data from PLASMA operational chain produced at ESA PDGS. Coverage: 18/07/ present
The two datasets are interoperable. The LP provisional dataset is still kept for providing users data before 18/07/2015. This dataset will be dismissed as soon as a complete reprocessing of operational plasma data will be executed.
2 Hz Langmuir Probe Extended Dataset: electron temperature and spacecraft potential derived from the two probes separately (not blended).
To add also the currrents, complex admittances and bias
1/128 Hz Sweep mode dataset: to add also currents
16 Hz Faceplate currents plasma density: improved version recently published with coordinates correction, “re-sizing” of FP area. Coverage 02/10/2014 – 08/07/2017 for all s/c.

17. LP data validation
Several detailed studies on LP parameters validation were performed.

18. LP validation of Ne: comparing LP and faceplate
The comparison with the empirical ISO-standard model IRI-2016 suggests that Swarm Ne values are too low by about 10%-15%
The comparison of Faceplate ion density estimations with the LP measurements seems to pinpoint as well on the effect of variable effective (or reduced) ion masses
The assumption of a pure O+ (amu = 16) ion plasma is certainly wrong, in particular for nighttime conditions, and should be reconsidered; estimates of real ion composition (meff) appears to be feasible and worth pursuing
meff = ( ∑i=1,n pi / mi ) -1
with ∑i=1,n pi = 1
50% [O+] & 50% [H+] => meff =
95% [O+] & 5% [N+] => meff =
(courtesy of M. Förster)

19. Mass composition and ion flow estimates
Swarm faceplate current and Langmuir probe ion admittance measurements can be combined to solve for any two of ‘ion ram speed’, ‘ion density’, and ‘effective ion mass’ under the OML Langmuir probe approximation (assuming vi,ram = 7.6 km/s and mi = 16 a.m.u).
Resulting ion ram speed estimates show evidence of geophysical flow variability.
Comparison with TII flows provides an initial validation of the LP-Faceplate technique.
Effective ion mass estimates at low-latitude are of right order of magnitude.
Various error sources are likely present, including effect of minor ions on the density (>10%) and flow estimates (>1 km/s).

20. Validation of LP electron temperature on the basis of the IRI model
Operational dataset (but can be applied also to the other datasets), all s/c
Differences between data and IRI depend on local time and latitude (probably
Ne dependent)
Corrected Te values using spherical harmonics up to grade 6 (available on request ing to
Comparisons with Jicamarca data, Swarm results (Stolle et al., JGR 2011) and numerical simulation using the FLIP model show a substantial improvement with respect to original Te OPER data (some differences during daytime at high Ne density region still remain)
(courtesy of V. Truhlik)

21. LP validation (Ne and Te) with ISR and others
Independent measurements (ISRs, Ionosondes and Radio occultation) indicate that on average, Swarm LP
plasma frequencies (densities) are systematically underestimated by ~10 % (18 %) for densities > 105 cm-3
Electron temperatures are systematically overestimated by ~350 K (18 %) for high-gain LPs and ~700 K (40 %) for the low-gain LPs.
The correlations of both density and temperature from Swarm with data from other measurements are usually very high ( ).
The ISR-based corrections (initial comparison and calibration) of Swarm LP densities and temperatures removes systematic biases.
The other measurements are used for validation.
(courtesy of L. Lomidze)

22. ISRs Ionosondes initial initial COSMIC initial
(courtesy of L. Lomidze)
ISRs
Corrected
initial
Ionosondes
initial
ISR-corrected
COSMIC
initial
ISR-corrected

23. Te validation Low-gain LP vs high-gain LP vs IRI
The data from the high-gain LPs are more accurate and reliable.
Zonally and seasonally averaged electron temperatures agree significantly better with the corresponding IRI-2016 values, globally after the ISR-based corrections.
(courtesy of L. Lomidze)
25°≤|Mlat|≤50°
initial
ISR-corrected
low-gain
high-gain
IRI-2016

24. Summary of open points and recommendations
Continue operations (scrubbing, commissioning, etc) on TII to improve image anomaly, keeping S/C C for tests
LP probes both in high gain now as a test on S/C C but then as a normal mode of operation also on S/C A and B
Validation still on going with several interesting results; open point discrepancies with different datasets still under study; study on the estimate of real ion composition;
After the full reprocessing of L1b operational plasma data, dismission of preliminary LP dataset
Extended 2 Hz LP dataset to be updated asap with other parameters (currents, complex admittances and bias) and extended in time
Also sweep mode to be updated with currents but with a lower priority
Continue updating TII cross track ion flow dataset, extending also to Swarm C and introducing likely also ion temperature in the next future