The THEMIS Fluxgate Magnetometer (FGM) measures the background magnetic field and its low frequency fluctuations (up to 64 Hz) in the near-Earth space. The FGM is capable of detecting variations of the magnetic field with amplitudes of 0.01 nT, and it is particularly designed to study abrupt reconfigurations of the Earth's magnetosphere during the substorm onset phase. The FGM uses an updated technology developed in Germany that digitizes the sensor signals directly and replaces the analog hardware by software. Use of the digital fluxgate technology results in lower mass of the instrument and improved robustness. The present paper gives a description of the FGM experimental design and the data products, the extended calibration tests made before spacecraft launch, and first results of its magnetic field measurements during the first half year in space. It is also shown that the FGM on board the five THEMIS spacecraft well meets and even exceeds the required conditions of the stability and the resolution for the magnetometer.

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This review describes the infrastructure and capabilities of the expanded and upgraded Canadian Array for Realtime InvestigationS of Magnetic Activity (CARISMA) magnetometer array in the era of the THEMIS mission. Formerly operated as the Canadian Auroral Network for the OPEN Program Unified Study (CANOPUS) magnetometer array until 2003, CARISMA capabilities have been extended with the deployment of additional fluxgate magnetometer stations (to a total of 28), the upgrading of the fluxgate magnetometer cadence to a standard data product of 1 sample/s (raw sampled 8 samples/s data stream available on request), and the deployment of a new network of 8 pairs of induction coils (100 samples per second). CARISMA data, GPS-timed and backed up at remote field stations, is collected using Very Small Aperture Terminal (VSAT) satellite internet in real-time providing a real-time monitor for magnetic activity on a continent-wide scale. Operating under the magnetic footprint of the THEMIS probes, data from 5 CARISMA stations at 29-30 samples/s also forms part of the formal THEMIS ground-based observatory (GBO) datastream. In addition to technical details, in this review we also outline some of the scientific capabilities of the CARISMA array for addressing all three of the scientific objectives of the THEMIS mission, namely: 1. Onset and evolution of the macroscale substorm instability, 414 I.R. Mann et al.2. Production of storm-time MeV electrons, and 3. Control of the solar wind-magnetosphere coupling by the bow shock, magnetosheath, and magnetopause. We further discuss some of the compelling questions related to these three THEMIS mission science objectives which can be addressed with CARISMA.

[1] A multipoint analysis of conjugate magnetospheric and ionospheric flow vortices during the formation of the substorm current wedge (SCW) on 19 February 2008 is presented. During the substorm, four Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft were located close to the neutral sheet in the premidnight region between 9 and 12 R E geocentric distance, of which three closely ($1-2 R E ) clustered at $23 MLT and one was farther west at $21 MLT. The closely clustered spacecraft were engulfed by a counterclockwise plasma flow vortex, while the single spacecraft recorded a clockwise plasma flow vortex. Simultaneously, a pair of conjugate flow vortices with clockwise and counterclockwise rotation appeared in the ionosphere, as inferred from equivalent ionospheric currents. The counterclockwise space vortex, which corresponded to a downward field-aligned current, was at least 1-2 R E in diameter and had rotational flow speeds of up to 900 km/s. Current density estimates associated with the formation of the space vortex in the first 30 s yielded 2.8 nA/m 2 (14 mA/m 2 mapped to the ionosphere), or a total current of 1.1 Â 10 5 A. Model calculations based on midlatitude ground magnetometer data show a gradual increase of the field-aligned current, with 1-2 Â 10 5 A within the first minute and a peak value of 7 Â 10 5 A after 10 min, associated with the SCW, and a matching meridian of the downward current of the SCW and the downward current (counterclockwise) space vortex. The combined ground and space observations, together with the model results, present a scenario in which the space vortices generated the field-aligned current of the SCW at the beginning of the substorm expansion phase and coupled to the ionosphere, causing the ionospheric vortices.

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[1] Following a long interval (many days) of sustained very quiet geomagnetic conditions, electromagnetic ion cyclotron (EMIC) wave activity was seen by the CARISMA array (www.carisma.ca) on the ground for several hours simultaneously with enhanced solar wind density and related magnetic compression seen at GOES 12 on 29th June 2007. The THEMIS C, D, and E satellites were outbound in a ''string-of-pearls'' configuration and each observed EMIC waves on L-shells ranging from 5 to 6.5. THEMIS resolved some of the spatial-temporal ambiguity and defined the radial extent of EMIC activity to be $1.3 Re. The band-limited EMIC waves were seen slightly further out in radial distance by each subsequent THEMIS satellite, but in each case were bounded at high-L by a decrease in density as monitored by spacecraft potential. The EMIC wave activity appears to be confined to a region of higher plasma density in the vicinity of the plasmapause, as verified by ground-based cross-phase analysis. The structured EMIC waves seen at THEMIS E and on the ground have the same repetition period, in contradiction to expectations from the bouncing wave packet hypothesis. Compression-related EMIC waves are usually thought to be preferentially confined to higher L's than observed here. Our observations suggest solar wind density enhancements may also play a role in the excitation of radially localised EMIC waves near the plasmapause. Citation: Usanova,

The Philae lander, part of the Rosetta mission to investigate comet 67P/Churyumov-Gerasimenko, was delivered to the cometary surface in November 2014. Here we report the precise circumstances of the multiple landings of Philae, including the bouncing trajectory and rebound parameters, based on engineering data in conjunction with operational instrument data. These data also provide information on the mechanical properties (strength and layering) of the comet surface. The first touchdown site, Agilkia, appears to have a granular soft surface (with a compressive strength of 1 kilopascal) at least ~20 cm thick, possibly on top of a more rigid layer. The final landing site, Abydos, has a hard surface.

[1] The intensification of the nightside whistler-mode chorus emissions is observed in the low-density region outside the plasmapause during the injection of anisotropic plasma sheet electrons into the inner magnetosphere. Time History of Events and Macroscale Interactions During Substorms data of the electron phase space density over the energy range between 0.1 keV and 30 keV are used to develop an analytical model for the distribution of injected suprathermal electrons. The path-integrated gain of chorus waves is then evaluated with the HOTRAY code by tracing whistler-mode chorus waves in a hot magnetized plasma. The simulated wave gain is compared to the observed wave electric field and magnetic field, respectively. The results indicate that lower-energy (<1 keV) plasma sheet electrons can penetrate deeper toward the Earth but cause little chorus intensification, while higher-energy (1 keV to tens of kiloelectron volts) electrons can be injected at relatively higher L-shells and are responsible for the intensification of lower-band and upper-band whistler-mode chorus. Compared to the lower-band chorus, a relatively higher electron anisotropy is required to generate upper-band chorus. In addition, higher plasma density results in stronger wave intensity and a broader frequency band of chorus waves.