Examination of Geotail measurements in the near‐tail (X > −30 R_E) has revealed the presence of small flux ropes in the plasma sheet. A total of 73 flux rope events were identified in the Geotail magnetic field measurements between November 1998 and April 1999. This corresponds to an estimated occurrence frequency of ∼1 flux rope per 5 hours of central plasma sheet observing time. All of the flux ropes were embedded within high‐speed plasma sheet flows with 35 directed Earthward, 〈V_x〉 = 431 km/s, and 38 moving tailward, 〈V_x〉 = −451 km/s. We refer to these two populations as “BBF‐type” and “plasmoid‐type” flux ropes. The flux ropes were usually several tens of seconds in duration, and the two types were readily distinguished by the sense of their quasisinusoidal ΔB_z perturbations, i.e., ∓ for the “BBF” events and ± for the “plasmoid” events. Most typically, a flux rope was observed to closely follow the onset of a high‐speed flow within ∼1–2 min. Application of the Lepping‐Burlaga constant‐α flux rope model (i.e., J = αB) to these events showed that approximately 60% of each class could be acceptably described as cylindrical, force‐free flux ropes. The modeling results yielded mean flux rope diameters and core field intensities of 1.4 R_E and 20 nT and 4.4 R_E and 14 nT for the BBF and plasmoid‐type events, respectively. The inclinations of the flux ropes were small relative to the GSM X–Y plane, but a wide range of azimuthal orientations were determined within that plane. The frequent presence of these flux ropes in the plasma sheet is interpreted as strong evidence for multiple reconnection X‐lines (MRX) in the near‐tail. Hence, our results suggest that reconnection in the near‐tail may closely resemble that at the dayside magnetopause where MRX reconnection has been hypothesized to be responsible for the generation of flux transfer events.

A new empirical model of the plasmapause location has been developed using density data from the plasma wave receiver onboard the CRRES spacecraft for nearly 1000 orbits. The “plasmapause” is identified here as the innermost sharp gradient in density (change of a factor of 5 in <0.5 L). Such a sharp gradient was observed on 73% of the CRRES inbound and outbound orbits that returned data. The plasmapause location is expressed as a linear function of Kp (previous 12 hour maximum) and local time. The model gives the linear best fit location of the plasmapause as well as the standard deviations of the model parameters. We found a slight noon‐midnight asymmetry with the plasmapause located on average an L shell farther from the Earth at midnight than in the noon sector. This is in the opposite sense to the noon‐midnight asymmetry found previously. Significant variability (with standard deviations up to +/− 1 L shell) in the plasmapause location is seen and suggests that though the mean plasmapause is roughly circular, the instantaneous plasmapause has significant time variable localized structure at all local times but most especially in the duskside sector.

Small‐scale magnetic flux ropes have been discovered in the solar wind at 1 AU in observations from the IMP 8 and WIND spacecraft. These small magnetic structures (diameter of 270 R_E, on average) have some similar properties to magnetic clouds (diameters of 0.2–0.3 AU or about 6000–8000 R_E), which are well known large‐scale magnetic flux ropes, but have durations of 10s of minutes as opposed to many hours or days for most magnetic clouds. The presence of these small helical field structures suggests that solar wind flux ropes may have a wide‐range of scale sizes, or possibly have a bimodal size distribution, and are perhaps more common than previously estimated. Similarities and differences with magnetic clouds will be discussed. We suggest that these small scale magnetic flux ropes are signatures of magnetic reconnection in the solar wind as opposed to in the solar corona.