An upgrade of nobeyama radioheliograph to a dual-frequency (17 and 34 GHz) system

Takano, Toshiaki; Nakajima, Hiroshi; Énomé, Shinzo; Shibasaki, Κ.; Nishio, Makoto; Hanaoka, Yoichiro; Shiomi, Y.; Sekiguchi, H.; Kawashima, Susumu; Bushimata, Takeshi; Shinohara, N.; Torii, Chikayoshi; Fujiki, K.; Irimajiri, Yoshihisa

doi:10.1007/bfb0106457

Cited by 19 publications

(6 citation statements)

References 3 publications

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“…We also used 17 GHz radio maps obtained routinely by NoRH with resolution of 10-18 arcsec in intensity and circular polarization (Nakajima et al, 1994) and intensity maps at 34 GHz with 5-10″ spatial resolution (Takano et al, 1997). We used a 17 GHz map observed at 02:44 UT and available in 512 × 512 pixels 2 format (4.91" resolution), rotated longitudinally by 7.31 °with respect to the HMI magnetogram.…”

Section: Radio Mapsmentioning

confidence: 99%

A Genetic Algorithm to Model Solar Radio Active Regions From 3D Magnetic Field Extrapolations

Silva

Selhorst

Costa

et al. 2022

Front. Astron. Space Sci.

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In recent decades our understanding of solar active regions (ARs) has improved substantially due to observations made with better angular resolution and wider spectral coverage. While prior AR observations have shown that these structures were always brighter than the quiet Sun at centimeter wavelengths, recent observations at millimeter and submillimeter wavelengths have shown ARs with well defined dark umbrae. Given this new information, it is now necessary to update our understanding and models of the solar atmosphere in active regions. In this work, we present a data-constrained model of the AR solar atmosphere, in which we use brightness temperature measurements of NOAA 12470 at three radio frequencies: 17, 100 and 230 GHz. The observations at 17 GHz were made by the Nobeyama Radioheliograph (NoRH), while the observations at 100 and 230 GHz were obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Based on our model, which assumes that the radio emission originates from thermal free-free and gyroresonance processes, we calculate radio brightness temperature maps that can be compared with the observations. The magnetic field at distinct atmospheric heights was determined in our modelling process by force-free field extrapolation using photospheric magnetograms taken by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). In order to determine the best plasma temperature and density height profiles necessary to match the observations, the model uses a genetic algorithm that modifies a standard quiet Sun atmospheric model. Our results show that the height of the transition region (TR) of the modelled atmosphere varies with the type of region being modelled: for umbrae the TR is located at 1080 ± 20 km above the solar surface; for penumbrae, the TR is located at 1800 ± 50 km; and for bright regions outside sunspots, the TR is located at 2000 ± 100 km. With these results, we find good agreement with the observed AR brightness temperature maps. Our modelled AR can be used to estimate the emission at frequencies without observational coverage.

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Section: Radio Mapsmentioning

confidence: 99%

A Genetic Algorithm to Model Solar Radio Active Regions From 3D Magnetic Field Extrapolations

Silva

Selhorst

Costa

et al. 2022

Front. Astron. Space Sci.

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“…As has been discussed, one primary reason for observers to look for candidate FSMs by examining this particular timescale is the persistence of Feature 4 for ER83-like equilibria, namely the existence of cutoff wavenumbers (see Equation 5). Resolving this short periodicity is readily achievable with radio instruments like NoRH (Takano et al 1997), but is only marginally possible in (E)UV even with high-cadence instruments like IRIS (Tian et al 2016). High-cadence measurements in white light and coronal forbidden lines are available with ground-based instruments like the Solar Eclipse Corona Imaging System (SE-CIS, Williams et al 2001), but were exclusively performed at total eclipses.…”

Section: Seismologymentioning

confidence: 99%

Magnetohydrodynamic Fast Sausage Waves in the Solar Corona

Antolin

Guo

et al. 2020

Space Sci Rev

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Characterized by cyclic axisymmetric perturbations to both the magnetic and fluid parameters, magnetohydrodynamic fast sausage modes (FSMs) have proven useful for solar coronal seismology given their strong dispersion. This review starts by summarizing the dispersive properties of the FSMs in the canonical configuration where the equilibrium quantities are transversely structured in a step fashion. With this preparation we then review the recent theoretical studies on coronal FSMs, showing that the canonical dispersion features have been better understood physically, and further exploited seismologically. In addition, we show that departures from the canonical equilibrium configuration have led to qualitatively different dispersion features, thereby substantially broadening the range of observations that FSMs can be invoked to account for. We also summarize the advances in forward modeling studies, emphasizing the intricacies in interpreting observed oscillatory signals in terms of FSMs. All these advances notwithstanding,

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“…Solar radio observations have been available for a number of years in different frequencies for quiet full sun (Takano et al 1997;Oberoi et al 2011;Mohan & Oberoi 2017) and flaring conditions (e.g. Kundu et al 2009;Kochanov et al 2013;Chen et al 2015).…”

Section: Observational Test At High Frequencymentioning

confidence: 99%

Synthetic Radio Imaging for Quiescent and CME-flare Scenarios

Moschou

Соколов

Cohen

et al. 2018

ApJ

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Radio observations grant access to a wide range of physical processes through different emission mechanisms. These processes range from thermal and quiescent to eruptive phenomena, such as shock waves and particle beams. We present a new synthetic radio imaging tool that calculates and visualizes the Bremsstrahlung radio emission. This tool works concurrently with state-ofthe-art Magnetohydrodynamic (MHD) simulations of the solar corona using the code BATS-R-US. Our model produces results that are in good agreement with both high and low frequency observations of the solar disk. In this study, a ray-tracing algorithm is used and the radio intensity is computed along the actual curved ray trajectories. We illustrate the importance of refraction in locating the radio emitting source by comparison of the radio imaging illustrations when the line-of-sight instead of the refracted paths are considered. We are planning to incorporate non-thermal radio emission mechanisms in a future version of the radio imaging tool.

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An upgrade of nobeyama radioheliograph to a dual-frequency (17 and 34 GHz) system

Cited by 19 publications

References 3 publications

A Genetic Algorithm to Model Solar Radio Active Regions From 3D Magnetic Field Extrapolations

A Genetic Algorithm to Model Solar Radio Active Regions From 3D Magnetic Field Extrapolations

Magnetohydrodynamic Fast Sausage Waves in the Solar Corona

Synthetic Radio Imaging for Quiescent and CME-flare Scenarios

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