The Cluster Magnetic Field Investigation: overview of in-flight performance and initial results

Abstract

Abstract. The accurate measurement of the magnetic field along the orbits of the four Cluster spacecraft is a primary objective of the mission. The magnetic field is a key constituent of the plasma in and around the magnetosphere, and it plays an active role in all physical processes that define the structure and dynamics of magnetospheric phenomena on all scales. With the four-point measurements on Cluster, it has become possible to study the three-dimensional aspects of space plasma phenomena on scales commeasurable with the size of the spacecraft constellation, and to distinguish temporal and spatial dependences of small-scale processes. We present an overview of the instrumentation used to measure the magnetic field on the four Cluster spacecraft and an overview the performance of the operational modes used in flight. We also report on the results of the preliminary in-orbit calibration of the magnetometers; these results show that all components of the magnetic field are measured with an accuracy approaching 0.1 nT. Further data analysis is expected to bring an even more accurate determination of the calibration parameters. Several examples of the capabilities of the investigation are presented from the commissioning phase of the mission, and from the different regions visited by the spacecraft to date: the tail current sheet, the dusk side magnetopause and magnetosheath, the bow shock and the cusp. We also describe the data processing flow and the implementation of data distribution to other Cluster investigations and to the scientific community in general.

Modeling of remote sensing of thin current sheet

“…At 09:36 UT, high density, pulse-like disturbance passed by the Cluster, and subsequently the current sheet became very thin. By applying multi-spacecraft timing analysis to the FGM data [Balogh et al, 2001], we inferred the thickness of the current sheet to be about 1100 km, which is comparable to the Larmor radius of 5 keV protons in a magnetic field of 10 nT.…”

Double Star/Cluster observation of neutral sheet oscillations on 5 August 2004

“…Figure 1a shows Cluster FGM magnetic field data at 1-s resolution (Balogh et al, 2001). The data are shown in GSM Cartesian coordinates with a color scheme of black, red, green, and blue for spacecraft 1 to 4, respectively.…”

Foreshock cavitons for different interplanetary magnetic field geometries: Simulations and observations

“…There is a decrement of less than 10% in V x . Magnetic field data have a resolution of 5 vect/s [Balogh et al, 2001] and plasma moments from the Cluster Ion Spectrometry (CIS) instrument [Rème et al, 2001] are once per spin. Ion data from the CIS (HIA) experiment yield both the bulk solar wind plasma parameters and the threedimensional distribution functions of suprathermal ions in the range 0-32 keV.…”