EFW Team Meeting

Rutland Hotel, Sheffield, UK

Minutes by Anders.Eriksson@irfu.se


Mats André mats.andre@irfu.se
Stuart Bale bale@ssl.berkeley.edu
Rico Behlke rico@irfu.se
Jan Blecki jblecki@cbk.waw.pl
Patrick Canu canu@cetp.ipsl.fr
Tobia Carozzi tc@irfu.se
Nicole Cornilleau-Wehrlin nicole.cornilleau@cetp.ipsl.fr
Chris Cully cully@phys.ucalgary.ca
Anders Eriksson Anders.Eriksson@irfu.se
Andrew Fazakerley anf@mssl.ucl.ac.uk
Michael Fehringer michael.fehringer@esa.int
Rejean Grard rejean.grard@esa.int
Georg Gustafsson gg@irfu.se
Jan Holtet j.a.holtet@fys.uio.no
Craig Kletzing craig.kletzing@uiowa.edu
Vladimir Krasnoselskikh vkrasnos@cnrs-orleans.fr
Harri Laakso hlaakso@so.estec.esa.nl
Per-Arne Lindqvist lindqvist@plasma.kth.se
Elizabeth Lucek e.lucek@ic.ac.uk
Björn Lybekk bjorn.lybekk@fys.uio.no
Milan Maksimovic milan.maksimovic@obspm.fr
Arnaud Masson Arnaud.Masson@esa.int
Olivier Moullard om@so.estec.esa.nl
Forrest Mozer fmozer@ssl.berkeley.edu
Arne Pedersen arne.pedersen@fys.uio.no
Anders Tjulin Anders.Tjulin@irfu.se
Andris Vaivads andris@irfu.se
Claude de Villedary Claude.Devilledary@cetp.ipsl.fr
Simon Walker simon.walker@shef.ac.uk
Ieuan Willis i.willis@sheffield.ac.uk
Keith Yearby k.yearby@sheffield.ac.uk



1. Intro (Mats)

Mats welcomed everybody to this mainly technical meeting, the science issues being treated in the WEC meeting tomorrow as they are of interest to all the WEC community. Thanks to the dedicated work of the EFW team, not least by our former PI Georg Gustafsson, we now have four instruments performing excellently in space.


2. Cluster status (Mats)

Cluster works well, all instrument operational except ASPOC on SC1 and CIS on SC2. Commissioning review (Feb 1) succesfully ended commissioning, and we are now in the science phase of the mission. Extension of Cluster mission above the nominal two years lifetime may be possible, depending on the fuel consumption and hence on the operational scenarios.


3. EFW status


All OK, showed spin-fit data for full orbit and details of EFW and STAFF SA spectra to illustrate that large-scale as well as small-scale features can be studied using Cluster electric field data.


Spacecraft potential (Vsc): Comparison of CIS density to EFW Vsc. 40 V = 0.01 cm-3, 25 V = 0.1 cm-3, 10 V = 0.8 cm-3. Cannot use old relations for Vsc/density, need new relations for Cluster.

E-field: Showed offset tables for Ex and Ey for different probe pairs (derived from ground and on-board spin fits). Offsets generally constant and small (few tenths of mV/m). Plot of Ex and Ey from different probe pair spin fits show the pairs are equivalent. Shows consistency. To demonstrate absolute accuracy, he showed a plot of ExB velocity with s/c v removed (E.B = 0 assumed) showing the corotation velocity of the plasmasphere.

Comparison to ACE (and to some extent CIS) data very good:

short-circuiting effect of booms seem to be 10% or less, though further comparisons needed. Also showed integrated E (from spin fits and E.B = 0) using measured and model B in the Msphere - agrees perfectly.


Intro on s/c potential. Showed comparisons of Vsc to WHISPER and CIS (CSDS) data. WHISPER generally indicates higher density than CIS, though both gives higher density values for a given Vsc than expected from previous missions. Also, the probe-to-sc potential (which is what we measure) do not go so close to zero in high-density plasmas as could be expected from previous missions.


Vsc: Polar EFI/HYDRA comparison preliminary compares well with EFW/WHISPER comparison.


4. Interference (Anders, Arne, Forrest)

EDI: As yet, only I/F seen is lines at multiples of the square modulation frequency (multiples of 8/15 kHz) when looking at EFW internal burst data, and of course the slight change in Vsc due to the EDI current. The latter effect needs to be taken into account when using Vsc to study density.

WHISPER: The WHISPER synchronization in NM seems to work: not much WHISPER interference is seen in differential signals in NM sampling. We can see WHISPER when we have BM telemetry, where it contaminates the EFW data while transmitting. This creates no problems for spin fitted data, though it of course interferes with high resolution studies. Presently, WHISPER is transmitting every 7th spin in normal operations, and we certainly do not want more frequent transmissions.

ASPOC: When operating, ASPOC profoundly changes the electric field pattern in such a way that EFW cannot any longer measure the electric fields with any accuracy. The effect is worst in tenuous magneotspheric plasmas, where ASPOC operations completely disables our possibility of observing naturally occuring electric fields, but the problem is serious also in the magneotsheath and solar wind. Examples presented include complete shielding of the natural electric field in the magnetosphere, and enhanced sunward spurious field in the magnetosheath. The EFW team concludes that time sharing with ASPOC is necessary. The SDC manager may consider blanking E-field in CSDS prime parameters when ASPOC is on, and using SC1 (ASPOC not working) only for summary parameters.


5. Comparisons to EDI

Forrest: Not yet any good simultaneous EDI and EFW electric field data to compare, but expected to arrive soon.


6. Use of internal EFW burst memory

Ensure routine use of burst memory only within acquisition periods (as defined in the Master Science Plan, MSP). For explicit purposes, bursts can of course be taken also outside regular acquisition periods, but default should be to have them only within a period with NM1 or BM1 telemetry.

Nicole requests taking 2 E + 3 B at 9 ksamples/s with time-tagged bursts, so that we get full waveform data of the electromagnetic field up to 4 kHz simultaneously on all four s/c.


7. Special orbits

Andrew Fazakerley recapitulated the history of special orbits. Initial idea to put about 1/3 of all orbits as special orbits, where non-standard operations are suggested. The 1/3 disappeared very quickly, and now the number is about 1/8. PEACE maintains a web page with special orbit suggestions.

Special orbit suggestions:

a. We want to run EFW with 22 kbit/s, V1M, V2M, V34M in the BM1 period on orbit 118. ASPOC should be off and WHISPER passive or in low recurrence mode.

b. Forrest interested in the burst-dump-burst-dump mode. This needs BM telemetry to get reasonable coverage, and preferably at least 22 kbit/s to EFW.

c. Langmuir mode use of two probes is not a special orbit issue, but an internal WEC discussion. STAFF SA likes to keep one satellite with all probes in E mode not to loose all information on despun E.

d. Bandpass filter orbit: Forrest suggests using the Hx telemetry for BP/BPC instead of V12/V34 in the solar wind, in order to get high resolution measurements of Langmuir wave packets. We plan to run this on orbit 111.

We should start by implementing (a) and (d) as soon as possible.

Policy on special orbits and non-standard operations of EFW:

Suggestions should be sent to Mats. We are happy to consider anything anybody suggests, as long as there is some reasonable scientific background and it is certain that the data actually will be analyzed.


8. Operations

Anders summarized present operations. We run all four probes in E-field mode, except for the bias voltage sweeps about once every two hours. In BM1 mode, we have as yet always had 15 kbit/s. Burst memory is dumped in BM3 as regulated in MSP.


9. Sweeps

Arne raised the point if they are too fast. Anders thinks no, as there is no hysteresis effect on the bias voltage sweeps, though current and voltage bias sweeps may be different in this respect.

Bias voltage sweeps will be extended on the positive side to get info on solar wind and magnetosheath plasma. Presently, we run sweeps about every two hours. We may sweep more often on particular orbits.


10. CSDS

Per-Arne described the EFW CSDS parameters.


11. EFW associates and EFW science projects

Mats introduced the concept of EFW associates, which are people working with EFW data together with some EFW CoI without being CoIs themselves. Associates can be suggested at http://cluster.irfu.se, and are always associated with a particular CoI.

In order to encourage cooperation and to avoid confusion and duplication of work, ongoing science projects should also be reported to the PI using the same web page.


12. Documentation

Uppsala to update documentation list, removing old references, including new, and having EFW docs available directly under EFW, not only via the Isdat page.

Uppsala also to put up publications and presentations list.


13. FGM data

Mats described the FGM data policy, as formulated by the FGM PI and verified by Elizabeth Lucek (e.lucek@ic.ac.uk):

a. FGM as auxilliary data (pitch angles, E.B = 0): acknowledge the FGM PI.

b. FGM as part of the physics (identifying boundaries, finding coordinates): co-operation and co-authorship from FGM.

c. FGM data make up the main physics: not authorized outside the FGM team.

Elizabeth Lucek described the FGM data availability, and the status of FGM calibrations. There is a strong interest from the EFW team to have FGM prime parameters available in CSDS immediately.


14. Papers for the Annales Geophysicae special issue

Mats presented a list of the planned papers. Papers should not be published in other journals before the publication date of the Annales special issue, i.e. September 2001. After this date, publication is encouraged in all science journals.


15. Upcoming meetings

EGS, Nice, 25 - 30 March
AGU, Boston, 29 May - 2 June
Wolliscroft meeting, Sheffield, 24-26 April
SWT, ESTEC, 6 - 7 June
IAGA, Hanoi, 19 - 31 August
AGU, San Francisco, 10 - 14 December


16. Software tools

Tobia: ISDAT 2.7 released, with modules for all WEC instruments.
Requests to Tobia.Carozzi@irfu.se.

Forrest: SDT available to any EFW CoI who wants it. Requests to fmozer@ssl.berkeley.edu.


17. Next meeting

We do not aim for any EFW team meeting in at least four months.
Late summer or early autumn may be good times.

Summary of actions:

a. Negotiate ASPOC time sharing (PI group).
b. Ensure routine EFW internal bursts confined to MSP NM1/BM1 periods (PI group)
c. Update documentation on EFW web page (PI group)
d. Report EFW associates and ongoing science projects (CoIs)
e. Consider not providing EFW CSDS data products when ASPOC is on (SDC manager)
f. Implement special orbit suggestions (a) and (d) (Anders, Per-Arne)
g. Implement test run of internal burst using 3B + 2E (Anders)