Return Current Instability in Flares

Return to Work in COVID-19: Review of Current Guidelines

Background and aims: Coronavirus Disease 2019 (COVID-19) is mainly a respiratory disease which is caused by the SARS-CoV-2 Virus. The outbreak first began in Wuhan, China, in December 2019 and then expanded globally. COVID-19 can result in illness ranging from mild to severe. However, some of the affected individuals might be asymptomatic. Symptoms of the disease may appear in as few as 2 days...

Balmer line formation in solar flares affected by return currents

Aims. We investigate the effect of the electric return currents in solar flares on the profiles of hydrogen Balmer lines. We consider the monoenergetic approximation for the primary beam and runaway model of the neutralizing return current. Methods. Propagation of the 10 keV electron beam from a coronal reconnection site is considered for the semiempirical chromosphere model F1. We estimate the...

Electron Firehose instability and acceleration of electrons in solar flares

An electron distribution with a temperature anisotropy T‖/T⊥ > 1 can lead to the Electron Firehose instability (Here ‖ and ⊥ denote directions relative to the background magnetic field B0). Since possible particle acceleration mechanisms in solar flares exhibit a preference of energizing particles in parallel direction, such an anisotropy is expected during the impulsive phase of a flare. The p...

Current concepts review. Carpal instability.

Alternating current driven instability in magnetic junctions.

An effect is considered of alternating (high-frequency) current on the spin-valve-type magnetic junction configuration. The stability with respect to small fluctuations is investigated in the macrospin approximation. When the current frequency is close to the eigenfrequency (precession frequency) of the free layer, parametric resonance occurs. Both collinear configurations, antiparallel and par...