We use an E × B‐driven plasmapause test particle (PTP) simulation to provide global contextual information for in situ measurements by the Van Allen Probes (Radiation Belt Storm Probes (RBSP)) during 15–20 January 2013. During 120 h of simulation time beginning on 15 January, geomagnetic activity produced three plumes. The third and largest simulated plume formed during enhanced convection on 17 January, and survived as a rotating, wrapped, residual plume for tens of hours. To validate the simulation, we compare its output with RBSP data. Virtual RBSP satellites recorded 28 virtual plasmapause encounters during 15–19 January. For 26 of 28 (92%) virtual crossings, there were corresponding actual RBSP encounters with plasmapause density gradients. The mean difference in encounter time between model and data is 36 min. The mean model‐data difference in radial location is 0.40 ± 0.05 RE. The model‐data agreement is better for strong convection than for quiet or weakly disturbed conditions. On 18 January, both RBSP spacecraft crossed a tenuous, detached plasma feature at approximately the same time and nightside location as a wrapped residual plume, predicted by the model to have formed 32 h earlier on 17 January. The agreement between simulation and data indicates that the model‐provided global information is adequate to correctly interpret the RBSP density observations.

[1] On March 18, 2002, under northward interplanetary magnetic field (IMF) and high ($15 nPa) solar wind dynamic pressure conditions, Cluster observed reconnection signatures and the passage of an X-line at the large ($175°) magnetic-shear high-latitude magnetopause (MP). The observations are consistent with the occurrence of a reconnection site tailward of the cusp and in the vicinity of the spacecraft. At the same time IMAGE observed a bright spot poleward of the dayside auroral oval resulting from precipitating protons into the atmosphere. The intensity of the proton spot is consistent with the energy flux contained in the plasma jets observed by Cluster. Using the Tsyganenko-01 magnetic field model with enhanced solar wind pressure, the Cluster MP location is mapped to the vicinity of the IMAGE proton spot. Mapping the auroral spot out to the MP implies an X-line of at least 3.6 R E in y GSM . In addition to confirming the reconnection source of the dayside auroral proton spot, the Cluster observations also reveal sub-Alfvénic flows and a plasma depletion layer in the magnetosheath next to the MP, in a region where gas dynamic models predict super-Alfvénic flows.

[1] We report a clear encounter by the Cluster spacecraft of a magnetic reconnection diffusion region in the near-Earth magnetotail at X GSM = À17.5 R E on September 19, 2003. In addition to the reversals of the plasma jets and of GSM-z ($normal) component of the magnetic field, clear signatures of Hall quadrupolar (GSM-y) magnetic fields as well as bipolar Hall (GSM-z) electric fields with amplitude up to 80 mV/m directed toward the neutral sheet in both hemispheres were observed. Furthermore, large fluctuations in the electric field perpendicular to the magnetic field with amplitudes reaching 65 mV/m were observed near the separatrices in both hemispheres and in association with local density minima. Citation:

[1] We have used the ion composition data from the CIS/CODIF instrument on the Cluster spacecraft to determine how the H + and O + contribution to the plasma sheet density changes as a function of geomagnetic conditions and solar activity. The Cluster spacecraft are in a polar orbit that cut through the equatorial plasma sheet at ∼19 Re downtail for the first 5 years of the mission. We have restricted the data set to apogee time periods, from 15 to 19 Re, in order to give the composition at a clear position, which can then be used, for example, as a boundary condition for models. The geomagnetic conditions are described using the Kp index, while the solar activity is represented by the use of F10.7 index. Functional forms for these dependencies are provided. The statistical study covers the years from 2001 to 2005, which covers solar maximum, and the declining stage of the solar cycle. We find, as expected, that the O + density in this region depends strongly on both solar EUV and geomagnetic activity. In addition, we find that there is a gradient in the O + /H + density ratio, from the 15 to 19 Re plasma sheet to the 6.6 Re plasma sheet, indicating that there is significant additional entry of O + inside of 15 Re.

Magnetic field data from nine spacecraft in the magnetospheric plasma sheet and the solar wind are employed to determine the correlation scale and the magnetic Taylor microscale from simultaneous multiple‐point measurements for multiple intervals with a range of mean magnetic field directions. We have determined that in the solar wind the Taylor scale is independent of direction relative to the mean magnetic field, but the correlation scale along the mean magnetic field (2.7 × 106 ± 0.2 × 106 km) is longer than along the perpendicular direction (1.5 × 106 ± 0.1 × 106 km). Within the plasma sheet we found that the correlation scale varies from 16,400 ± 1000 km along the mean magnetic field direction to 9200 ± 600 km in the perpendicular direction. The Taylor scale is also longer parallel to the magnetic field (2900 ± 100 km) than perpendicular to it (1100 ± 100 km). In the solar wind the ratio of the parallel correlation scale to the perpendicular correlation scale is 2.62 ± 0.79; in the plasma sheet the ratio is 1.78 ± 0.16, which indicates that the turbulence in both regions is anisotropic. The correlation and Taylor scales may be used to estimate effective magnetic Reynolds numbers separately for each angular channel. Reynolds numbers were found to be approximately independent of the angle relative to the mean magnetic field. These results may be useful in magnetohydrodynamic modeling of the solar wind and the magnetosphere and can contribute to our understanding of solar and galactic cosmic ray diffusion in the heliosphere.