[1] We statistically investigated features of the field-aligned current (FAC) distribution in plasma sheet boundary layers between 17 and 19 R E in the magnetotail using the curlometer technique to calculate the current from four-point magnetic field measurements taken in 2001. The results show that the FAC distribution in the plasma sheet boundary layers in the magnetotail has dusk-dawn asymmetry, earthward-tailward (polarity) asymmetry, and north-south asymmetry. The occurrence and polarities of FACs in the Northern Hemisphere are different from those in the Southern Hemisphere. The average density and the standard deviation of the FACs that are most likely to be connected to the Earth are 4.90 nA m −2 and 2.55 nA m −2 in the Northern Hemisphere and 4.21 nA m −2 and 1.80 nA m −2 in the Southern Hemisphere, respectively. For investigating the mechanism of the north-south asymmetry, we mapped the FACs along the field line into the polar region. The footprints of the FACs also show a difference between the Southern and Northern hemispheres (as a function of mapped latitude). These characteristics suggest a north-south asymmetry of the FACs in the magnetosphere. Further investigation is needed to identify the causes of this asymmetry, although the configuration of the magnetosphere, the polar cap boundary, the conductivity in the ionosphere, or the various solar wind-magnetosphere interaction processes all may be contributors. That the FAC densities are different between the hemispheres suggests that an important source of these currents must be a voltage generator.

As a novel X-ray focusing technology, lobster-eye micropore optics (MPO) feature both a wide observing field of view and true imaging capability, promising sky monitoring with significantly improved sensitivity and spatial resolution in soft X-rays. Since first proposed by Angel, the optics have been extensively studied, developed and trialed over the past decades. In this Letter, we report on the first-light results from a flight experiment of the Lobster Eye Imager for Astronomy, a pathfinder of the wide-field X-ray telescope of the Einstein Probe mission. The piggyback imager, launched in 2022 July, has a mostly unvignetted field of view of 18.°6 × 18.°6. Its spatial resolution is in the range of 4′–7′ in FWHM and the focal spot effective area is 2–3 cm2, both showing only mild fluctuations across the field of view. We present images of the Galactic center region, Sco X-1, and the diffuse Cygnus Loop nebular taken in snapshot observations over 0.5–4 keV. These are truly wide-field X-ray images of celestial bodies observed, for the first time, by a focusing imaging telescope. Initial analyses of the in-flight data show excellent agreement between the observed images and the on-ground calibration and simulations. The instrument and its characterization are briefly described, as well as the flight experiment. The results provide a solid basis for the development of the present and proposed wide-field X-ray missions using lobster-eye MPO.

[1] The influences of the interplanetary magnetic field (IMF) cone angle θ and clock angle φ on the field-aligned currents (FACs) at the plasma sheet boundary layers (PSBLs) have been investigated using Cluster Data. The FAC occurrence increases monotonically with IMF cone angle and has two peaks at À90°and +110°clock angle, respectively. The peak at +110°is distinctly larger than that at À90°. Overall, there are more FACs between 0°< φ < 180°, indicating that FACs occurrence is closely associated with duskward IMF. More FACs occur when 90°< |φ| < 180°, implying that FAC is closely associated with southward IMF. The large FAC densities occur when 60°< |φ| < 120°. The density also has two peaks and the peak at +90°clock angle (duskward IMF) is larger than that at À90°(dawnward IMF). These results indicate that the IMF influence on the FACs is from all IMF components and not only from a single component. Citation: Cheng, Z. W., J. K. Shi, M. Dunlop, and Z. X. Liu (2013), Influences of the interplanetary magnetic field clock angle and cone angle on the field-aligned currents in the magnetotail, Geophys. Res. Lett., 40,[5355][5356][5357][5358][5359]