We perform a number of numerical simulations of the solar corona with the aim to understand how it responds to different conditions in the photosphere. By changing parameters which govern the motion of the plasma at the photosphere we study the behavior of the corona, in particular, the effects on the current density generated. An MHD code is used to run simulations, using a 20×20×20 Mm box wit...

We present the first high-resolution soft X-ray spectral observations of the corona above an active region, using the Bragg crystal spectrometer (BCS) on board the Yohkoh satellite. We observed NOAA AR 7978 as it rotated beyond the solar limb so that the lower portions of the region were occulted. Long integrations from times after the region had totally disappeared some days later show a subst...

For those fortunate enough to have personally witnessed and photographed the visible corona surrounding the Sun during a solar eclipse, pictures are usually a let down for not living up to the visual view. After 150 years of investigating the corona, we understand it more fully and now know this difference to be real. The difference stems from our inability to either see or image the true distr...

vational facts, and then in another column compare them with the results of the theoretical program we have been carrying out at Chicago over the past few years. The purpose of this comparison will be to suggest experiments, some of which are already in progress, and which will perhaps resolve a few of the difficulties in our present knowledge of the dynamics of the interplanetary medium. I sha...

More than 1000 physicists will be on hand for the 2004 APS April meeting, to be held May 1-4 in Denver, Colorado. The April meeting traditionally covers a wide range of physics subfields, including astrophysics, nuclear and particle physics, the physics of beams, plasma physics, computational physics, gravitation, hadronic physics and few-body systems. There will also be numerous sessions on ph...

We compare observations of the non-flaring solar corona made simultaneously with Hinode/XRT and with RHESSI. The analyzed corona is dominated by a single active region on 12 November 2006. The comparison is made on emission measures. We derive emission measure distributions vs temperature of the entire active region from multifilter XRT data. We check the compatibility with the total emission m...

We present observations of the formation, propagation and decay of vortexshaped features in coronal images from the Solar Dynamics Observatory (SDO) associated with an eruption starting at about 2:30UT on Apr 8, 2010. The series of vortices formed along the interface between an erupting (dimming) region and the surrounding corona. They ranged in size from several to ten arcseconds, and traveled...

We present the first Hinode/EIS observations of 5 min quasi-periodic oscillations detected in a transition-region line (He II) and five coronal lines (Fe X, Fe XII, Fe XIII, Fe XIV, and Fe XV) at the footpoint of a coronal loop. The oscillations exist throughout the whole observation, characterized by a series of wave packets with nearly constant period, typically persisting for 4-6 cycles with...

We have simulated the 3D emergence and interaction of two twisted flux tubes, which rise from the interior into the outer atmosphere of the Sun. We present evidence for the multiple formation and eruption of flux ropes inside the emerging flux systems and hot arcade-like structures in between them. Their formation is due to internal reconnection, occurring between oppositely directed, highly st...

We present a model for the spontaneous onset of fast magnetic reconnection in a weakly collisional plasma, such as the solar corona. When a current layer of macroscopic width undergoes collisional (Sweet-Parker) reconnection, a narrow dissipation region forms around the X-line. This dissipation region naturally becomes narrower during the reconnection process as stronger magnetic fields are con...