New treatment of gyroresonance and free-free radio emissions from multi-thermal multi-component plasma
by A. Kuznetsov et al.*

2021-07-20 126 views

Thermal plasma in the solar corona is often characterized by a range of temperatures. This plasma can be described by the differential emission measure (DEM), which is a distribution of the thermal electron density square over temperature. The DEM-based treatment is widely used in application to the optically thin EUV and X-ray emissions. However, there has been no corresponding treatment in the radio domain, where optical depth of emission can […]

Radio and X-ray Observations of Short-lived Episodes of Electron Acceleration in a Solar Microflare
by R. Sharma et al.

2021-03-30 156 views

In a solar flare, the plasma is locally heated and particles are accelerated to energies from a few tens of keV to MeVs. X-ray bremsstrahlung emission and radio gyrosynchrotron emission are highly complementary and provide diagnostics of the timing, location and spectral properties of flare-accelerated electrons in a broad energy range. Here we present comprehensive observations of multiple individual bursts during a GOES B1.7-class (back-ground subtracted) microflare observed jointly in […]

Flare SOL2012-07-06: on the origin of the circular polarization reversal between 17 GHz and 34 GHz
by Altyntsev et al.*

2017-10-24 756 views

The new generations of multiwavelength radioheliographs with high spatial resolution will employ microwave imaging spectropolarimetry to recover flare topology and plasma parameters in the flare sources and along the wave propagation paths. The recorded polarization depends on the emission mechanism and emission regime (optically thick or thin), the emitting particle properties, and propagation effects.

Exploring the potential of microwave diagnostics in SEP forecasting
by P. Zucca et al.*

2017-10-03 369 views

Solar energetic particles (SEPs), especially protons and heavy ions, may be a space-weather hazard when they impact spacecraft and the terrestrial atmosphere. Forecasting schemes have been developed, which use earlier signatures of particle acceleration to predict the arrival of solar protons and ions in the space environment of the Earth. The UMASEP (University of MAlaga Solar particle Event Predictor) scheme (Núñez 2011), forecasts the occurrence and the importance of an […]

EUV-invisible reservoir of solar energetic particles
by G. Fleishman et al.*

2017-09-19 558 views

Large-scale magnetic structures, which likely make a “bridge” between the relatively compact particle acceleration site of a flare energy release and the interplanetary medium, are of particular importance because of their potential role as an “escape route” for solar energetic particles (SEPs). Although these escape routes can sometimes be associated with jets visible in extreme ultraviolet (EUV) and/or soft X-rays (SXRs), the jet plasma must be dense enough to be […]

Oscillations in the 45-5000 MHz Radio Spectrum of the 18 April 2014 Flare
by M. Karlicky et al.*

2017-09-05 640 views

Recently, oscillations were recognized in the global X–ray flux detected during the 18 April 2014 M7.3 flare by the Fermi/GBM instrument as well as in the spatially localized UV measurements of the IRIS satellite and the EIS/Hinode instruments (Brosius and Daw, 2015, Brosius, Dawn and Inglis, 2016, and Brannon, Longcope, and Qiu, 2015). Radio observations of this flare were also analyzed by Carley, Vilmer, and Gallagher (2016). The overall radio spectrum […]

Particle acceleration and turbulence during a solar flare
by E.P. Kontar et al.*

2017-06-13 1,790 views

Particle acceleration during solar flares is a highly efficient process, in terms of both the energy (tens of percent of the released magnetic energy can be transferred to the energetic particles) and the particle number (nearly all electrons in the flaring region are accelerated). So-called stochastic acceleration (e.g., Petrosian 2012 for a review) is one of the most popular mechanisms capable of providing these characteristics. In this scenario, the magnetic […]

Multi-Loop Structure of Nonthermal Microwave Sources in a Major Long-Duration Flare
by V. Grechnev et al.*

2017-05-23 596 views

Hard X-ray (HXR) and microwave observations of flares show only a few nonthermal sources. They are simple and compact, especially in impulsive flares, suggesting involvement of one to two loops. Hanaoka (1996) and Nishio et al. (1997) interpreted these observations in terms of double-loop flares. This view was later extended up to long-duration flares (Tzatzakis, Nindos, and Alissandrakis, 2008). A concept of a simple flare loop became dominant. However, observations […]

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