Ultra-high-resolution observations of persistent null-point reconnection in the solar corona

Magnetic reconnection is a key mechanism involved in solar eruptions and is also a prime possibility to heat the low corona to millions of degrees. Here, we present ultra-high-resolution extreme ultraviolet observations of persistent null-point reconnection in the corona at a scale of about 390 km over one hour observations of the Extreme-Ultraviolet Imager on board Solar Orbiter spacecraft. The observations show formation of a null-point configuration above a minor positive polarity embedded within a region of dominant negative polarity near a sunspot. The gentle phase of the persistent null-point reconnection is evidenced by sustained point-like high-temperature plasma (about 10 MK) near the null-point and constant outflow blobs not only along the outer spine but also along the fan surface. The blobs appear at a higher frequency than previously observed with an average velocity of about 80 km s^-1 and life-times of about 40 s. The null-point reconnection also occurs explosively but only for 4 minutes, its coupling with a mini-filament eruption generates a spiral jet. These results suggest that magnetic reconnection, at previously unresolved scales, proceeds continually in a gentle and/or explosive way to persistently transfer mass and energy to the overlying corona.

Fast plasmoid-mediated reconnection in a solar flare

Magnetic reconnection is a multi-faceted process of energy conversion in astrophysical, space and laboratory plasmas that operates at microscopic scales but has macroscopic drivers and consequences. Solar flares present a key laboratory for its study, leaving imprints of the microscopic physics in radiation spectra and allowing the macroscopic evolution to be imaged, yet a full observational characterization remains elusive. Here we combine high resolution imaging and spectral observations of a confined solar flare at multiple wavelengths with data-constrained magnetohydrodynamic modeling to study the dynamics of the flare plasma from the current sheet to the plasmoid scale. The analysis suggests that the flare resulted from the interaction of a twisted magnetic flux rope surrounding a filament with nearby magnetic loops whose feet are anchored in chromospheric fibrils. Bright cusp-shaped structures represent the region around a reconnecting separator or quasi-separator (hyperbolic flux tube). The fast reconnection, which is relevant for other astrophysical environments, revealed plasmoids in the current sheet and separatrices and associated unresolved turbulent motions.

Solar flares provide wide range of observational details about fundamental processes involved. Here, the authors show evidence for magnetic reconnection in a strong confined solar flare displaying all four reconnection flows with plasmoids in the current sheet and the separatrices.

Flux Rope Formation Due to Shearing and Zipper Reconnection

Zipper reconnection has been proposed as a mechanism for creating most of the twist in the flux tubes that are present prior to eruptive flares and coronal mass ejections. We have conducted a first numerical experiment on this new regime of reconnection, where two initially untwisted parallel flux tubes are sheared and reconnected to form a large flux rope. We describe the properties of this experiment, including the linkage of magnetic flux between concentrated flux sources at the base of the simulation, the twist of the newly formed flux rope, and the conversion of mutual magnetic helicity in the sheared pre-reconnection state into the self-helicity of the newly formed flux rope.

Flux-Rope Twist in Eruptive Flares and CMEs: Due to Zipper and Main-Phase Reconnection

The nature of three-dimensional reconnection when a twisted flux tube erupts during an eruptive flare or coronal mass ejection is considered. The reconnection has two phases: first of all, 3D "zipper reconnection" propagates along the initial coronal arcade, parallel to the polarity inversion line (PIL); then subsequent quasi-2D "main-phase reconnection" in the low corona around a flux rope during its eruption produces coronal loops and chromospheric ribbons that propagate away from the PIL in a direction normal to it. One scenario starts with a sheared arcade: the zipper reconnection creates a twisted flux rope of roughly one turn ( 2 π radians of twist), and then main-phase reconnection builds up the bulk of the erupting flux rope with a relatively uniform twist of a few turns. A second scenario starts with a pre-existing flux rope under the arcade. Here the zipper phase can create a core with many turns that depend on the ratio of the magnetic fluxes in the newly formed flare ribbons and the new flux rope. Main phase reconnection then adds a layer of roughly uniform twist to the twisted central core. Both phases and scenarios are modeled in a simple way that assumes the initial magnetic flux is fragmented along the PIL. The model uses conservation of magnetic helicity and flux, together with equipartition of magnetic helicity, to deduce the twist of the erupting flux rope in terms the geometry of the initial configuration. Interplanetary observations show some flux ropes have a fairly uniform twist, which could be produced when the zipper phase and any pre-existing flux rope possess small or moderate twist (up to one or two turns). Other interplanetary flux ropes have highly twisted cores (up to five turns), which could be produced when there is a pre-existing flux rope and an active zipper phase that creates substantial extra twist.

Extreme ultraviolet imaging of three-dimensional magnetic reconnection in a solar eruption

Magnetic reconnection, a change of magnetic field connectivity, is a fundamental physical process in which magnetic energy is released explosively, and it is responsible for various eruptive phenomena in the universe. However, this process is difficult to observe directly. Here, the magnetic topology associated with a solar reconnection event is studied in three dimensions using the combined perspectives of two spacecraft. The sequence of extreme ultraviolet images clearly shows that two groups of oppositely directed and non-coplanar magnetic loops gradually approach each other, forming a separator or quasi-separator and then reconnecting. The plasma near the reconnection site is subsequently heated from ∼1 to ≥5 MK. Shortly afterwards, warm flare loops (∼3 MK) appear underneath the hot plasma. Other observational signatures of reconnection, including plasma inflows and downflows, are unambiguously revealed and quantitatively measured. These observations provide direct evidence of magnetic reconnection in a three-dimensional configuration and reveal its origin.

Magnetic reconnection is a fundamental energy release process taking place in various astrophysical environments, but it is difficult to observe it directly. Here, the authors provide evidence of three-dimensional magnetic reconnection in a solar eruption using combined perspectives of two spacecraft.

A phase I study of subcutaneous recombinant interleukin-2 and interferon alfa-2a

BACKGROUND

Both recombinant interferon alfa and interleukin-2 (IL-2) have been shown to have some activity as single agents in metastatic renal cell cancer (RCC), although their activity is minimal in more common solid tumors. Recent preclinical studies have suggested that the combination of these two agents is especially promising.

METHODS

Subcutaneous recombinant interferon alfa-2a and IL-2 were administered at one of five dose levels to 33 patients with refractory solid tumors, including 21 patients with RCC. A constant ratio of 5:1 of interferon alfa-2a to IL-2 was used. Interferon alfa-2a and IL-2 were administered three and five times weekly, respectively, for a total of 4 weeks, followed by a rest of 1-3 weeks between cycles.

RESULTS

The dose-limiting toxic effects included hypotension, nephrotoxicity, and fatigue. At the recommended Phase II dose of 7.5 million units (MU)/m2 of interferon alfa-2a and 1.5 MU/m2 of IL-2, 12 patients were treated. Ten of 12 completed the 4-week cycle without modification. Four patients at that dose level had Grade 3-4 toxic effects. Partial responses were observed in 4 of 16 assessable patients with RCC.

CONCLUSIONS

Subcutaneous interferon alfa-2a and IL-2 can be self-administered safely on an outpatient basis. At tolerable doses, responses can be achieved in metastatic RCC.

Spontaneous regression of histologically proved pulmonary metastases from renal cell carcinoma: a case with 5-year followup

Spontaneous regression of biopsy proved metastatic renal cell carcinoma is rare. We describe a 39-year-old man who had histologically proved metastatic disease to the lungs after nephrectomy. The lesions had spontaneously regressed 3 months later. The patient remained without evidence of recurrence 5 years after diagnosis.

Medical staff privileges for ethics consultants: an institutional model

On January 1, 1991, the Joint Commission required hospitals to be equipped for resolving moral dilemmas that arise in the care of a patient. Regulation of those professing expertise in clinical ethics is new and untested yet must be evaluated and further developed to protect patients from practitioners who lack expertise in clinical ethics but may promote themselves as qualified. The authors report the development of standard criteria for clinical ethics consultation privileges as one model to protect patients. An institutional medical staff model utilizing approved credentialing mechanisms is a generous umbrella under which patients may be protected, qualified clinical ethicists may practice, and continuous quality improvement may be sought.

Optimal drug therapy in the treatment of testicular cancer

Although testes cancer is the most common malignancy affecting young men, dramatic survival rates are now possible with the development of optimal individualised drug therapy. Human chorionic gonadotropin and alpha-fetoprotein are important tumour markers associated with testes cancer, and can provide essential information about prognosis and treatment efficacy. For treatment purposes, testicular germ-cell malignancies are broadly classified as seminomatous or non-seminomatous. Early stage seminomas are treated with radiotherapy, while more advanced disease requires systemic chemotherapy. Stage I nonseminoma patients can now be offered the option of retroperitoneal lymph node dissection (RPLND) or close clinical observation, while patients with stage II or III nonseminoma should generally be treated with chemotherapy. The dramatic survival rates now apparent with chemotherapy are due in large part to the introduction of cisplatin (cisplatinum II)-based chemotherapy and to the optimisation of therapy based on pretreatment risk analysis. The most common chemotherapeutic regimen for standard risk patients includes cisplatin and etoposide (VP 16213) and long term disease-free survival rates exceed 80%. A subset of poor risk patients with significantly reduced survival can be defined. These patients, and patients with relapsed or refractory disease, should receive more aggressive regimens, and ifosfamide (isophosphamide) is proving to be a particularly promising new agent in this regard. High-dose carboplatin with autologous bone marrow rescue is another encouraging alternative currently being investigated for these patients. Chemotherapy, despite substantial effectiveness, is not without toxicity, which consists primarily of myelosuppression, nausea and emesis, and renal toxicity. With careful monitoring and prophylaxis, however, these toxicities can generally be ameliorated or avoided.