The magnetic field in the Sun's corona: The solar corona is the outermost layer of the Sun's atmosphere, consisting of hot, diffuse, and highly ionized plasma. The magnetic field in this region is expected to drive many of its physical properties but has been difficult to measure with observations. Yang et al. used near-infrared imaging spectroscopy to determine the electron density and magnetohydrodynamic wave speed in the corona. By combining these measurements, they derived maps of the magnetic field throughout the entire observable corona. The method could potentially be used to produce routine magnetic field maps for the corona that are similar to those already available for the Sun's surface. Science , this issue p. 694

Solid evidence of magnetic reconnection is rarely reported within sunspots, the darkest regions with the strongest magnetic fields and lowest temperatures in the solar atmosphere. Using the world’s largest solar telescope, the 1.6 m Goode Solar Telescope, we detect prevalent reconnection through frequently occurring fine-scale jets in the Hα line wings at light bridges, the bright lanes that may divide the dark sunspot core into multiple parts. Many jets have an inverted Y-shape, shown by models to be typical of reconnection in a unipolar field environment. Simultaneous spectral imaging data from the Interface Region Imaging Spectrograph show that the reconnection drives bidirectional flows up to 200 km s⁻¹, and that the weakly ionized plasma is heated by at least an order of magnitude up to ∼80,000 K. Such highly dynamic reconnection jets and efficient heating should be properly accounted for in future modeling efforts of sunspots. Our observations also reveal that the surge-like activity previously reported above light bridges in some chromospheric passbands such as the Hα core has two components: the ever-present short surges likely to be related to the upward leakage of magnetoacoustic waves from the photosphere, and the occasionally occurring long and fast surges that are obviously caused by the intermittent reconnection jets.

The anisotropy of solar wind turbulence is a critical issue in understanding the physics of energy transfer between scales and energy conversion between fields and particles in the heliosphere. Using the measurement of Parker Solar Probe (PSP), we present an observation of the anisotropy at kinetic scales in the slow, Alfvénic, solar wind in the inner heliosphere. The magnetic compressibility behaves as expected for kinetic Alfvénic turbulence below the ion scale. A steepened transition range is found between the inertial and kinetic ranges in all directions with respect to the local background magnetic field direction. The anisotropy of k _⊥ ≫ k _∥ is found evident in both transition and kinetic ranges, with the power anisotropy P _⊥/P _∥ > 10 in the kinetic range leading over that in the transition range and being stronger than that at 1 au. The spectral index varies from α _t∥ = −5.7 ± 1.0 to α _t⊥ = −3.7 ± 0.3 in the transition range and α _k∥ = −3.12 ± 0.22 to α _k⊥ = −2.57 ± 0.09 in the kinetic range. The corresponding wavevector anisotropy has the scaling of k ∥ ∼ k ⊥ 0.71 ± 0.17 in the transition range, and changes to k ∥ ∼ k ⊥ 0.38 ± 0.09 in the kinetic range, consistent with the kinetic Alfvénic turbulence at sub-ion scales.

We present observations of the power spectral anisotropy in the wavevector space of solar wind turbulence and study how it evolves in interplanetary space with increasing heliocentric distance. We use magnetic field measurements from the Helios 2 spacecraft within 1 AU. To derive the power spectral density (PSD) in the (k ∥, k ⊥) space based on single-satellite measurements is a challenging task that had not been accomplished previously. Here, we derive the spectrum PSD2D(k ∥, ) from the spatial correlation function CF2D(r ∥, r ⊥) by a transformation according to the projection-slice theorem. We find the so-constructed PSDs to be distributed in k space mainly along a ridge that is more inclined toward the axis than the axis. Furthermore, this ridge of the distribution is found to gradually get closer to the axis as the outer scale length of the turbulence becomes larger with increasing radial distance. In the vicinity of the axis, a minor spectral component appears that probably corresponds to quasi-parallel Alfvénic fluctuations. Their relative contribution to the total spectral density tends to decrease with radial distance. These findings suggest that solar wind turbulence undergoes an anisotropic cascade transporting most of its magnetic energy toward larger and that the anisotropy in the inertial range is radially developing further at scales that are relatively far from the ever increasing outer scale. For the ion-scale fluctuations, we speculate, from the radial evolution of the extended oblique major component, a transition tendency from dominance by oblique Alfvén/ion-cyclotron waves (1 AU).