Recent Parker Solar Probe (PSP) observations of several small SEP events show highly variable helium to hydrogen ratios over a factor of ~50 and evidence of variable ion compositions in other species. We use numerical simulations for calculating SEP propagation in a turbulent interplanetary magnetic field with a Kolmogorov power spectrum from large scale down to the gyration scale of energetic...
We used H$\alpha$, Ca II 8542, Ca II K line and Ca II K continuum point observations of an X9.3 flare on Sept 6th 2017 from the Swedish Solar Telescope and, where possible, hard X-ray maps from RHESSI to describe the morphology and evolution of a flare ribbon. This highlighted systematic variations of the line profiles over photospheric features including granulation, light bridges, penumbral,...
Solar flares are very efficient particle accelerators on a short timescale. The X-ray and type III radio emission emitted during a flare are direct signatures of the accelerated electrons. Hard X-rays are emitted from the accelerated electrons through bremsstrahlung radiation primarily in the dense atmosphere, while type III emissions are caused by the accelerated electrons propagating through...
Solar type III radio bursts are generated by beams of energetic electrons that travel outward along open magnetic field lines through the corona and the interplanetary space. Here we report a type III burst event observed jointly by the Expanded Owens Valley Solar Array (EOVSA) and the Parker Solar Probe (PSP) shortly after its second perihelion in April 2019. This type III burst event is...
Helioseismic response to solar flares ("sunquakes") occurs due to localized force or/and momentum impacts observed during the flare impulsive phase in the lower atmosphere. Such impacts may be caused by precipitation of high-energy particles, downward shocks, or magnetic Lorentz force. However, the current theories of solar flares are unable to explain the origin of sunquakes. Our statistical...
Type III radio bursts are usually associated with energetic electrons that are accelerated by solar flares and propagate out from the corona. The standard theoretical paradigm links these emissions to a conversion of electrostatic Langmuir oscillations excited by the bump-on-tail instability into electromagnetic waves. Since the electron beams are observed to propagate to large heliospheric...
We report on the Atmospheric Imaging Assembly observations of plasma outflows from a coronal dimming during the 2015 April 28 filament eruption. After the filament started to erupt, two flare ribbons formed, one of which developed a well-visible hook enclosing a core dimming region. Along multiple funnels located inside this dimming region, outward-directed motions of plasma started to be...
The computational model kglobal was developed to explore energetic
particle production via magnetic reconnection in macroscale systems.
It is based on the observation that the production of energetic
particles during reconnection is controlled by Fermi reflection in
large-scale magnetic fields and not by parallel electric fields
localized in kinetic scale boundary layers. Earlier work...
Observations of impulsive solar energetic particle events occasionally show enhancements of helium-3 up to ~104 greater than coronal abundances. Fisk (1978) and Temerin and Roth (1992) proposed that these enhancements could be caused by ion cyclotron waves and that helium-3 would be preferentially heated due to its unique cyclotron frequency. In order to test this theory, we have run kinetic...
In this talk I will demonstrate with time-dependent Fokker-Planck calculations that steady injection of energetic electron beams into loop legs is compensated by returning electrons scattered the precipitating beams combined with the accelerated electrons from the ambient plasma. We evaluate the time for establishing the electric circuit of precipitating and returning electrons. We also...
During solar flares, a large flux of energetic electrons propagate from the tops of reconnecting magnetic flux tubes toward the lower atmosphere. Over the course of the electrons' transport, a co-spatial counter-streaming return current is induced, thereby balancing the current density. In response to the return current electric field, a fraction of the ambient electrons will be accelerated...
The role of whistler waves in scattering energetic electrons as they undergo acceleration during magnetic energy release in solar flares is explored with particle-in-cell (PIC) simulations and in an analytic model. Energetic electrons accelerated in flares reach relativistic velocities. The transit time of these energetic electrons across the energy release region in flares (< 0.1s) is much...
Radio zebras are detected in radio observations from Sun, Jupiter, and also from the Crab pulsar. They are Type IV radio fine structures and can diagnose the local density, magnetic field, and velocity distribution of the particles released into the magnetic loops during the solar flares. The double plasma resonance model of solar radio zebra assumes the dense and cold background isotropic...
$^3$He-rich solar energetic particles (SEPs) are believed to be accelerated in solar flares or jets by a mechanism that depends on the ion charge-to-mass ($Q/M$) ratio. It implies that the flare plasma characteristics (e.g., temperature) may be effective in determining the elemental abundances of $^3$He-rich SEPs. This study examines the relationship between the suprathermal ($<$0.2 MeV...
Active Region 12673 produced an X8.2 flare on September 10, 2017 at around 16:00 UT when it was rotating to the West limb of the Sun. The flare was partially occult to ground telescopes, therefore a significant fraction of the photospheric and part of the chromospheric emission may have not been observed from Earth. The Solar Submillimeter Telescope (SST) registered intense radiation at 212...
