21 research outputs found
Particle Acceleration and Their Escape into the Heliosphere in Solar Flares with Open Magnetic Field
© 2023, The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Energetic particle populations in the solar corona and in the heliosphere appear to have different characteristics even when produced in the same solar flare. It is not clear what causes this difference: properties of the acceleration region, the large-scale magnetic field configuration in the flare, or particle transport effects, such as scattering. In this study, we use a combination of magnetohydrodynamic and test-particle approaches to investigate magnetic reconnection, particle acceleration, and transport in two solar flares: an M-class flare on 2013 June 19, and an X-class flare on 2011 September 6. We show that in both events, the same regions are responsible for the acceleration of particles remaining in the coronal and being ejected toward the heliosphere. However, the magnetic field structure around the acceleration region acts as a filter, resulting in different characteristics (such as energy spectra) acquired by these two populations. We argue that this effect is an intrinsic property of particle acceleration in the current layers created by the interchange reconnection, and therefore, may be ubiquitous, particularly, in noneruptive solar flares with substantial particle emission into the heliosphere.Peer reviewe
Solar and Heliospheric Physics with the Square Kilometre Array
The fields of solar radiophysics and solar system radio physics, or radio
heliophysics, will benefit immensely from an instrument with the capabilities
projected for SKA. Potential applications include interplanetary scintillation
(IPS), radio-burst tracking, and solar spectral radio imaging with a superior
sensitivity. These will provide breakthrough new insights and results in topics
of fundamental importance, such as the physics of impulsive energy releases,
magnetohydrodynamic oscillations and turbulence, the dynamics of post-eruptive
processes, energetic particle acceleration, the structure of the solar wind and
the development and evolution of solar wind transients at distances up to and
beyond the orbit of the Earth. The combination of the high spectral, time and
spatial resolution and the unprecedented sensitivity of the SKA will radically
advance our understanding of basic physical processes operating in solar and
heliospheric plasmas and provide a solid foundation for the forecasting of
space weather events.Comment: 15 pages, Proceedings of Advancing Astrophysics with the Square
Kilometre Array (AASKA14). 9 -13 June, 2014. Giardini Naxos, Italy. Online at
http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=215, id.16
Anisotropic Radio-Wave Scattering and the Interpretation of Solar Radio Emission Observations
The observed properties (i.e., source size, source position, time duration, decay time) of solar radio emission produced through plasma processes near the local plasma frequency, and hence the interpretation of solar radio bursts, are strongly influenced by propagation effects in the inhomogeneous turbulent solar corona. In this work, a 3D stochastic description of the propagation process is presented, based on the Fokker-Planck and Langevin equations of radio-wave transport in a medium containing anisotropic electron density fluctuations. Using a numerical treatment based on this model, we investigate the characteristic source sizes and burst decay times for Type III solar radio bursts. Comparison of the simulations with the observations of solar radio bursts shows that predominantly perpendicular density fluctuations in the solar corona are required, with an anisotropy factor ~0.3 for sources observed at around 30 MHz. The simulations also demonstrate that the photons are isotropized near the region of primary emission, but the waves are then focused by large-scale refraction, leading to plasma radio emission directivity that is characterized by a half-width-half-maximum of about 40 degrees near 30 MHz. The results are applicable to various solar radio bursts produced via plasma emission
Untersuchung zur Lernkultur in Online-Kursen
Ausgehend von einer veränderten, durch Lern- und Kompetenzorientierung geprägten Lernkultur analysieren die Autorinnen zwölf mehrwöchige Online-Kurse mit insgesamt 130 Teilnehmer/innen. Die Autorinnen nehmen ein Klima der hohen Wertschätzung unter den Lernenden wahr sowie gegenseitiges Feedback in den Reflexions- und Diskussionsprozessen, welches das Lernen verstärkt. Die Hypothese, dass in rein virtuellen, mehrwöchigen Weiterbildungskursen eine veränderte Lernkultur gefördert und gelebt wird, wird mittels halbstrukturierter Interviews sowie qualitativer Inhaltsanalyse der Beiträge in den Diskussionsforen untersucht. (DIPF/ Orig.
Pulsations of microwave emission from a solar flare in a twisted loop caused by intrinsic MHD oscillations
We present results revealing microwave pulsations produced in a model of a
flaring twisted solar coronal loop, without any external oscillatory driver.
Two types of oscillations are identified: slowly-decaying oscillations with a
period of about 70-75s and amplitude of about 5-10% seen in loops both with and
without energetic electrons, and oscillations with period of about 40s and
amplitude of a few tens of percent observed only in loops with energetic
electrons for about 100s after onset of fast energy release. We interpret the
longer-period oscillations as the result of a standing kink mode modulating the
average magnetic field strength in the loop, whilst the short-period
intermittent oscillations associated with energetic electrons are likely to be
produced by fast variations of the electric field which produces energetic
electrons in this scenario. The slowly-decaying oscillations can explain the
quasi-periodic pulsations often observed in the flaring corona.Comment: To be published in MNRA
Accelerated particles and their observational signatures from confined solar flares in twisted coronal loops
International audienc