ESA Science & Technology - Cluster Guest Investigator Operations, 2011-2013

Following a review in Spring/Summer 2011, by the Cluster Science Working Team and Science Operations Working Group, and by a panel organized by the Chair of the Solar System and Exploration Working Group, six GI proposals were selected.
 

Nominally, data is acquired all along the Cluster orbit as follows: 52.5 hours Normal Mode (NM) and 1.5 hours Burst Mode (BM). During the period of the GI operation implementation, the Cluster Science Operations Working Group defined a new style of spacecraft operations to enhance the amount of burst mode data per orbit, which benefitted the science objectives of the GI activities and other Cluster science targets. This was made possible by imposing a period of no data taking during another part of the orbit, to offset the increased load of the enhanced BM. The NM data rate is around 17 kbps (kbps: kilo bits per second) and BM is 105 kbps. So, for every extra hour of BM data, we impose 6 hours of no data taking. During the GI implementation, the maximum BM period implemented was 5 hours.

Information on specific operations is detailed below, including periods of enhanced/extended BM periods, in the order in which they were implemented.

It should be noted that the data periods discussed below were specially implemented for the GI programme and as such, the GIs have exclusive rights to the data for a 1 year proprietary period after the observations were made. 

Should you wish to analyse Cluster data from during the GI periods, you are strongly encouraged to contact the project scientist team at ESTEC, via Matt Taylor (email: mtaylorrssd.esa.int), who will liaise with the GI teams.

Guest Investigator: B. Walsh
Proposal Title: High Latitude Magnetopause Electrons

Abstract

We propose to study electrons along the magnetopause poleward of the cusp. Many observations show energetic electrons up to hundreds of keV within the exterior cusp. Some pitch angle measurements show these particles flowing along field lines out of the cusp. We plan to observe the region along the magnetopause poleward of the cusp to determine if the energetic electron population within the cusp can be contributing to a layer of energetic particles along the magnetopause.

Implementation

As the focus of the operations was energetic electrons and there were some constraints due to the observations being located close to payload off times due to eclipses, the so-called NM3 mode was implemented, which allowed for a higher resolution data to be taken by the RAPID IES electron instrument (9 polar and 16 azimuthal angular bins at spin resolution for all 8 energy bins (40 -400 keV)).

There were no constraints on the spacecraft formation or separation, but the maximum distance between spacecraft during the magnetopause target crossings was ~1.7 RE (between spacecraft 2 and 3).

Precise timing of the NM3 data periods were as follows (from JSOC planning database):

29/03/2011
C1: 10:03:00 – 15:00:00
C2: 10:46:00 – 15:03:00
C3: 11:36:00 – 16:01:00
C4: 11:40:00 – 16:40:00

31/03/2011
C1: 15:29:00 – 20:07:00
C2: 16:07:00 – 21:34:00
C3: 17:04:00 – 21:59:00
C4: 17:09:00 – 22:39:00

02/04/2011-03/04/2011
C1: 22:06:00 – 03:06:00
C2: 22:44:00 – 03:39:00
C3: 23:00:00 – 04:30:00
C4: 23:09:00 – 04:44:00

This set of GI operations are reported in:

Walsh, B.M., Haaland, S.E., Daly, P.W., Kronberg, E.A., and Fritz, T.A., Energetic electrons along the high-latitude magnetopause, Ann. Geophys., 30, 1003-1013, 2012; doi:10.5194/angeo-30-1003-2012.

Back to top

Guest Investigator: E. Yordanova
Proposal Title: Small-scale plasma turbulence

Abstract

The goal of the proposal is to address one of the hottest and still open questions in turbulence studies - the dissipation/dispersion range in plasma turbulence. In detail: what physical processes are responsible for the spectrum formation below the ion cyclotron scale; what turbulence is present in the dispersive range (whistler, Kinetic Alfvén Waves (KAWs), magnetoacoustic); what role does anisotropy and compressibility play in the dispersive cascade; and at which scales is the energy dissipated (ion or electron larmor radius) and what dissipation mechanism acts (ion cyclotron, electron Landau damping).

The difficulty in investigating this matter is that the small (kinetic) scales of turbulence are usually not well resolved or even inaccessible from satellite measurements. Another problem is that long data samples are necessary to ensure better quality of analysis. For this purpose, our proposal includes requests on burst mode operations when the Cluster spacecraft are in the solar wind and magnetosheath. The requests for particular instrument modes and Cluster configuration are described in the proposal.

The suggested proposal collaborates with an already running ISSI proposal: Team 185 "Dispersive cascade and dissipation in collisionless space plasma turbulence observations and simulations". Additional observations from the Artemis and STEREO missions will be used for cross-checking and comparison with the Cluster measurements.

The results from the investigation of the proposed scientific goals will help to establish the role of turbulence dissipation in processes such as plasma heating and acceleration, and small-scale magnetic reconnection, which is of general interest concerning a broader scientific (astrophysical, interplanetary and laboratory plasmas) community, as well as the design of future space missions.

Implementation

The goal was to examine turbulence anisotropy and the relative importance of the bulk speed and magnetic field direction on the plasma turbulence and development. Aligning parallel and perpendicular to the Sun–Earth direction was the closest configuration we could implement to match these requirements. This was carried out for a single pair of spacecraft, C3 and C4, which were targeted to have a separation of only ~40km shortly after apogee. The perpendicular configuration was implemented and optimised between 3 and 18 February 2012. Following manoeuvres from 20 February to 7 March, the parallel configuration was implemented and optimised between 7 and 22 March. These operations were carried out during the eclipse seasons. This constrains operations somewhat, as data must be downlink before the eclipse as, since the spacecraft is powered down during eclipse and hence the onboard memory is wiped.

The GI had identified a number of periods in the solar wind and magnetosheath suitable for the observations, with a mix of magnetosheath, and solar wind targets. Specific BM periods were then implemented within those periods as follows, in some cases with enhanced BM for the particular orbit (3 hours in stead of 1.5 hours).

2012-02-04T03:00:00 - 04:32:00
2012-02-04T11:15:00 - 12:43:00
2012-02-09T00:00:00 - 03:00:00
2012-02-11T00:00:00 - 03:00:00
2012-02-22T09:00:00 - 10:30:00
2012-02-22T13:30:00 - 15:00:00
2012-02-26T20:30:00 - 22:00:00
2012-02-27T02:30:00 - 04:00:00
2012-03-11T08:00:00 - 09:30:00
2012-03-11T17:00:00 - 18:30:00
2012-03-12T09:00:00 - 10:30:00
2012-03-12T18:00:00 - 19:30:00
2012-04-03T04:40:00 - 07:48:00

Back to top

Guest Investigator: A. Retinò

Proposal Title: Multi-scale observations of magnetic reconnection in the magnetosphere

Abstract

Magnetic reconnection is a universal process that is responsible for the major energy conversion/dissipation in the magnetosphere. A key but yet poorly understood aspect of reconnection is the coupling between electron, ion and fluid scales. Understanding this coupling requires simultaneous multi-point measurements at different scales. Such measurements are not yet available and are a current topic of discussion for future magnetospheric missions. At present the only way to investigate such coupling, although only partially, is using Cluster multi-scale configuration where two spacecraft are closely separated (~ 10 km ~ sub-ion scales) while having large separation from the others (~ 10000 km ~ MHD/fluid scales). The goal of this proposal is to investigate the cross-scale coupling at (1) the dayside magnetopause (2) near-Earth flow braking region, by using multi-instrument multi-point data from orbits in multi-scale configuration. The results expected from this study will be important to start understanding the scale coupling in reconnection and to provide a background for future multi-spacecraft spacecraft missions such as NASA/MMS and JAXA/SCOPE.

Implementation

As mentioned in the abstract above, the proposal was divided into two parts. The first part focused on multi-scale observations of the magnetopause. The observations were carried out in May 2012 and the spacecraft C1,C2 and C3 were configured in a large irregular triangle (4000-8000 km) parallel to the plane of the magnetopause. The fourth spacecraft was separated from Cluster 3 by ~65 km, in the direction perpendicular to the magnetopause. The specific GI intervals of BM are listed below:

2012-05-21T08:25:00 - 12:25:00
2012-05-23T14:19:00 - 16:19:00
2012-05-23T17:02:00 - 19:02:00
2012-05-25T21:05:00 - 2012-05-26T01:05:00
2012-05-28T03:25:00 - 07:25:00

In addition, a 40 minute period from 16:19:00-17:02:00 UT was sandwiched between BM periods and was used for WBD operations at the request of the GI. This is because WBD and BM telemetry mode are mutually exclusive.

The second part of this GI investigation focused on flow breaking in the magnetotail region. The criteria set by the GI was to focus on observations in the region (-12 < x < -9, -2 < y < 2, and -2 < z < 2, in Earth Radii in Geocentric Solar Magnetospheric coordinates). The spacecraft configuration was set up with a large-scale irregular triangle of side 9500 -5400 km formed by spacecraft C1, C2 and C3, with spacecraft C4 separated from spacecraft C3 by 310 km.

Back to top

Guest Investigator: C. Foullon

Proposal Title: Magnetopause boundary layer: evolution of plasma and turbulent characteristics along the flank

Abstract

The magnetopause and its adjacent boundary layers are a key science target for many satellite missions. They have been sampled, at the same time, either locally by a maximum of 4 to 5 closely spaced spacecraft (from the Cluster constellation and the Double Star TC-1 satellite) or on larger scales by missions such as Geotail, Cluster and THEMIS. Unfortunately, none of the spacecraft configurations has so far permitted the gevolutionh of perturbations along their main direction of propagation to be tracked. The study of the evolution of magnetic field and plasma perturbations, such as Kelvin-Helmholtz (KH) waves or Flux Transfer Events (FTEs), together with the (associated or not) generation of Kinetic Alfvén Waves (KAWs) and the turbulence developing at the flank magnetopause boundary layer, is important for our understanding of the mechanisms that mediate solar wind plasma entry into the magnetosphere, i.e. magnetic reconnection and diffusive processes. Complete study of the evolution of plasma perturbations at the magnetopause would require a series of spacecraft to be well aligned along the propagation track of the perturbations (i.e. along the flank magnetopause). We would therefore like to propose all four Cluster spacecraft to be manoeuvered along their orbits, so that they align as much as possible longitudinally along the flank at low latitudes, with approximately similar relative distances from a model magnetopause. Since the propagation speeds of the perturbations to be studied are much faster than the spacecraft speed, their tracking remains possible in this frame. Inter-spacecraft separations of ~1 Earth radii are necessary to relate the disturbances and deduce their evolution.

Implementation

As indicated in the abstract, this proposal targeted very large-scale spacecraft separations at the magnetopause, around 1 Earth radii for spacecraft pairs, resulting in separations of up to 36000 km across the constellation at the magnetopause. The resultant configuration for this set of operations was the largest separation ever for the Cluster mission. At other parts of the orbit, the spacecraft were separated along the orbit by up to 13 hours, providing very large-scale configurations in the inner magnetosphere. To obtain such a large separation with the limited fuel available was a challenge and was carried out by using a long drift time, where the spacecraft initiated a drift manoeuvre several weeks before the target period, with a secondary manoeuvre to arrest the drift just before the observation window. Due to the variable location of the magnetopause, a significant margin was used to ensure capture of the boundary and hence a large window of burst mode was implemented, bracketed by normal mode. Non-data taking periods were placed in between these and perigee so as to not lose coverage of the inner magnetosphere, to ensure conjugate measurements with the newly launched Radiation Belt Storm Probes (now renamed as the Van Allen Probes) would be lost.

The observation period spanned 9 orbits from 2 – 22 November 2012. The GI observations consisted of 10 hours of normal mode (NM), 5 hours of BM then another 10 hours of NM (although some orbits had more NM coverage later in the period). This 25-hour window was centred at the point at which the four spacecraft were almost the same distance from the magnetopause.

The specific observation times were:

2012-11-03T04:15:00 2012-11-03T14:15:00 NM
2012-11-03T14:15:00 2012-11-03T19:15:00 BM
2012-11-03T19:15:00 2012-11-04T05:15:00 NM
 
2012-11-05T10:40:00 2012-11-05T20:40:00 NM
2012-11-05T20:40:00 2012-11-06T01:40:00 BM
2012-11-06T01:40:00 2012-11-06T11:40:00 NM
 
2012-11-07T16:50:00 2012-11-08T02:50:00 NM
2012-11-08T02:50:00 2012-11-08T07:50:00 BM
2012-11-08T07:50:00 2012-11-08T17:50:00 NM
 
2012-11-09T23:10:00 2012-11-10T09:10:00 NM
2012-11-10T09:10:00 2012-11-10T14:10:00 BM
2012-11-10T14:10:00 2012-11-11T00:10:00 NM
 
2012-11-12T05:10:00 2012-11-12T15:10:00 NM
2012-11-12T15:10:00 2012-11-12T20:10:00 BM
2012-11-12T20:10:00 2012-11-13T06:10:00 NM
 
2012-11-14T11:20:00 2012-11-14T21:20:00 NM
2012-11-14T21:20:00 2012-11-15T02:20:00 BM
2012-11-15T02:20:00 2012-11-15T12:20:00 NM
 
2012-11-16T17:45:00 2012-11-17T03:45:00 NM
2012-11-17T03:45:00 2012-11-17T08:45:00 BM
2012-11-17T08:45:00 2012-11-17T18:45:00 NM
 
2012-11-18T03:55:00 2012-11-19T09:55:00 NM
2012-11-19T09:55:00 2012-11-19T14:55:00 BM
2012-11-19T14:55:00 2012-11-20T10:11:00 NM
 
2012-11-20T10:11:00 2012-11-21T16:05:00 NM
2012-11-21T16:05:00 2012-11-21T21:05:00 BM
2012-11-21T21:05:00 2012-11-22T16:28:00 NM

Back to top

Guest Investigator: Z. Pu

Proposal Title: Cluster Observations of generation and three-dimensional features of Flux Transfer events at the dayside magnetopause

Abstract

Flux transfer events (FTEs) at the magnetopause play an important role in solar wind-magnetosphere coupling. It is widely accepted that they are a result of transient magnetic reconnection (MR) near the sub-solar magnetopause. Despite many years of study, a number of fundamental questions still remain unclear. Of particular interest are the generation mechanism and three-dimensional (3D) structures of FTEs. A few well-known models have existed for more than 30 years. Nevertheless, we still do not know which model best represents reality. This is mainly due to the fact that generation of FTEs is 3D in nature, whereas the 3D features of FTEs can only be revealed through multiple spacecraft measurement, which only recently became possible after the launch of Cluster in 2000. This proposal aims to promote the study of FTEs a step further based on coming Cluster measurements at the subsolar magnetopause around February, 2013 and 2014 with focus on multi-spacecraft measurements of 3D features of FTEs. We are also going to examine the differences under solar maximum in 2013-2014 and contrast to already obtained data during solar minimum (2007-2008), when Cluster sampled the same region. Three or so orbits data from FGM, HIA, PEACE, (and RAPID /IES, EDI) are required. In addition, the studies will be carried out in conjunction with concurrent measurements by THEMIS P3, P4 and P5.

Implementation

The key aspect of this proposal is to make multi-scale observations of the magnetopause close to the sub-solar region. This region will be crossed by Cluster (due to its orbit evolution) in early 2013. The operations are complicated by being coincident with the eclipse season, which requires additional attention to ground station allocation before the spacecraft are powered down for eclipse, as was the situation with the Yordanova observations discussed previously. The spacecraft configuration forms an irregular large-scale triangle (C1, C2 and C3) of side 1600-4500 km, with C4 ~200 km perpendicular to this plane at the magnetopause crossing.

The periods of burst mode targeted were:

2013-01-22T07:20:00 2013-01-22T10:20:00
2013-01-26T20:25:00 2013-01-26T22:25:00
2013-01-31T08:25:00 2013-01-31T11:25:00 
2013-02-09T09:30:00 2013-02-09T12:30:00

Back to top

Guest Investigator: F. Pitout
Proposal Title: Particle acceleration and field aligned currents in the cusp

Abstract

The increasing tilt of Cluster spacecraft orbits allows us to access and probe new regions of the magnetosphere. Among these, the low-altitude dayside magnetosphere and cusp are key regions where injected magnetosheath particles may be accelerated. We propose first to use the CIS and PEACE particle sensors to probe this region. Then, once cases are clearly identified, we shall try to figure out what acceleration processes come into play with wave instruments (STAFF, EFW) since wave-particle interaction processes are expected. We shall also complement our observations with low-altitude satellites (DMSP, REIMEI) and ground-based instruments (EISCAT radars) whenever possible. We shall eventually be able to compare newly collected data with the work done at higher altitudes and have a full view in altitude of acceleration processes and field-aligned currents.

Implementation

The target of this proposal was the cusp region. The configuration has Cluster 1 and 2 roughly on the same field line, with C2 ~3000km below C1. Spacecraft C4, C3 and C1 are separated along track by 1800 km, with C1 and C2 offset by ~1000 km perpendicular to the orbit track of C3 and C4. Precise timing of observations has not yet been decided, but the observation period will cover October 2013-December 2013.

The periods of burst mode targeted were:

12/11/2013 14:10-14:50 UT
21/11/2013 14:50-15:50 UT
30/11/2013 15:30-16:30 UT
16/12/2013 11:50-12:50 UT
18/12/2013 13:50-16:10 UT
25/12/2013 12:50-13:50 UT

Back to top

For further details, please contact:

Philippe Escoubet, Cluster Project Scientist

Email: Philippe.Escoubetesa.int