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We present a study of the M6.6 flare that occurred on 13 February 2011 in AR 11158. The flare was accompanied by a CME and EUV waves. We use multiwavelength observations from the ground: H-alpha Solar Telescope for Argentina (HASTA), and space: Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA), both onboard the Solar and Dynamic Observatory (SDO).

International audience; We study an extreme ultraviolet (EUV) confined ejection observed on 9 May 2012 in Active Region (AR) NOAA 11476. For the analysis we use observations in multiple wavelengths (EUV, X-rays, Hα, and magnetograms) from a variety of ground- and space-based instruments. The magnetic configuration showed two rotating bipoles within the following polarity of the AR. This evolution was present some tens of hours before the studied event and continued thereafter. During this period, the magnetic flux of both bipoles continuously decreased. A mini-filament with a length of ≈30′′ lay along the photospheric inversion line of the largest bipole. The mini-filament was observed to erupt, accompanied by an M4.7 flare (SOL20120509T12:23:00). This injected dense material as well as twist along closed loops in the form of a very broad ejection whose morphology resembled that of typical Hα surges. We conclude that the flare and eruption can be explained as due to two reconnection processes, one occurring below the erupting mini-filament, and another above it. This second process injects the mini-filament plasma within the reconnected closed loops linking the main AR polarities. By analyzing the magnetic topology using a force-free model of the coronal field, we identify the location of quasi-separatix layers, where reconnection is prone to occur, and present a detailed interpretation of the chromospheric and coronal eruption observations. In particular, this event, in contrast to what has been proposed in several models explaining surges and/or jets, is not produced by magnetic flux emergence, but by magnetic flux cancellation accompanied by the rotation of the bipoles. In fact, the conjunction of these two processes, flux cancellation and bipole rotations, is at the origin of a series of events, homologous to the event we analyze in this article, which occurred in AR 11476 from 8 to 10 May 2012.

The recent discovery of impulsive solar burst emission in the 30 THz band is raising new interpretation challenges. One event associated with a GOES M2 class flare has been observed simultaneously in microwaves, H-alpha, EUV, and soft X-ray bands. Although these new observations confirm some features found in the two prior known events, they exhibit time profile structure discrepancies between 30 THz, microwaves, and hard X-rays (as inferred from the Neupert effect). These results suggest a more complex relationship between 30 THz emission and radiation produced at other wavelength ranges. The multiple frequency emissions in the impulsive phase are likely to be produced at a common flaring site lower in the chromosphere. The 30 THz burst emission may be either part of a nonthermal radiation mechanism or due to the rapid thermal response to a beam of high-energy particles bombarding the dense solar atmosphere., Comment: accepted to Astronomy and Astrophysics

Solar observations in the infrared domain can bring important clues on the response of the low solar atmosphere to primary energy released during flares. At present the infrared continuum has been detected at 30 THz (10 $\mu$m) in only a few flares. SOL2012-03-13 , which is one of these flares, has been presented and discussed in Kaufmann et al. (2013). No firm conclusions were drawn on the origin of the mid-infrared radiation. In this work we present a detailed multi-frequency analysis of the SOL2012-03-13 event, including observations at radio millimeter and sub--millimeter wavelengths, in hard X-rays (HXR), gamma-rays (GR), H$\alpha$, and white-light. HXR/GR spectral analysis shows that \so\ is a GR line flare and allows estimating the numbers of and energy contents in electrons, protons and $\alpha$ particles produced during the flare. The energy spectrum of the electrons producing the HXR/GR continuum is consistent with a broken power-law with an energy break at $\sim$ 800 keV. It is shown that the high-energy part (above $\sim$ 800 keV) of this distribution is responsible for the high-frequency radio emission ($>$ 20 GHz) detected during the flare. By comparing the 30 THz emission expected from semi-empirical and time-independent models of the quiet and flare atmospheres, we find that most ($\sim$80\%) of the observed 30 THz radiation can be attributed to thermal free--free emission of an optically-thin source. Using the F2 flare atmospheric model this thin source is found to be at temperatures T $\sim$ 8000 K and is located well above the minimum temperature region. We argue that the chromospheric heating, which results in 80 \% of the 30 THz excess radiation, can be due to energy deposition by non-thermal flare accelerated electrons, protons and $\alpha$ particles. The remaining 20\% of the 30 THz excess emission is found to be radiated from an optically-thick atmospheric layer at T $\sim$ 5000 K, below the temperature minimum region, where direct heating by non-thermal particles is insufficient to account for the observed infrared radiation.

It is well known that chromospheric observations in the hydrogen alpha line give relevant information about solar flares, plages and protuberances, among other typical features of the Sun. From 1998 to 2006, the HAlpha Solar Telescope of Argentina (HASTA) has provided solar images to the scientific community with the technological resources available at that time. Starting in 2007, major improvements have been incorporated, like a new CCD camera with enhanced spatial and temporal resolution, filter replacement, the automatic focusing system, and a new flat-fielding procedure. The hardware changes also called for software improvements, and a new solar-flare classification routine was implemented. At present, the Félix Aguilar Observatory (OAFA) of the University of San Juan (UNSJ) has a permanent staff of observers which now permits continuous solar monitoring. We expect that all these advances will allow to analyze chromospheric solar activity, especially solar flares, in more detail.

Solar flares observed in the 200-400 GHz radio domain may exhibit a slowly varying and time-extended component which follows a short (few minutes) impulsive phase and which lasts for a few tens of minutes to more than one hour. The few examples discussed in the literature indicate that such long-lasting submillimeter emission is most likely thermal bremsstrahlung. We present a detailed analysis of the time-extended phase of the 2003 October 27 (M6.7) flare, combining 1-345 GHz total-flux radio measurements with X-ray, EUV, and H{\alpha} observations. We find that the time-extended radio emission is, as expected, radiated by thermal bremsstrahlung. Up to 230 GHz, it is entirely produced in the corona by hot and cool materials at 7-16 MK and 1-3 MK, respectively. At 345 GHz, there is an additional contribution from chromospheric material at a few 10^4 K. These results, which may also apply to other millimeter-submillimeter radio events, are not consistent with the expectations from standard semi-empirical models of the chromosphere and transition region during flares, which predict observable radio emission from the chromosphere at all frequencies where the corona is transparent., Comment: 27 pages, 7 figures

Solar flares observed in the 200 – 400 GHz radio domain may exhibit a slowly varying and time-extended component which follows a short (few minutes) impulsive phase and can last for a few tens of minutes to more than one hour. The few examples discussed in the literature indicate that such long-lasting submillimeter emission is most likely thermal bremsstrahlung. We present a detailed analysis of the time-extended phase of the 27 October 2003 (M6.7) flare, combining 1 – 345 GHz total-flux radio measurements with X-ray, EUV, and Hα observations. We find that the time-extended radio emission is, as expected, radiated by thermal bremsstrahlung. Up to 230 GHz, it is entirely produced in the corona by hot and cool materials at 7 – 16 MK and 1 – 3 MK, respectively. At 345 GHz, there is an additional contribution from chromospheric material at a few 104 K. These results, which may also apply to other millimeter–submillimeter radio events, are not consistent with the expectations from standard semiempirical models of the chromosphere and transition region during flares, which predict observable radio emission from the chromosphere at all frequencies where the corona is transparent.

Magnetic helicity (MH) has been recognized as a useful tool to study the link between active regions (ARs) and magnetic clouds (MCs). In this work, we compare the MH and flux of the MC of October 18–19, 1995, and its associated AR. We compute both quantities and we find that the AR flux is one order of magnitude larger than in the MC, while the coronal MH is lower after an ejection linked to a long duration event and comparable to the MC helicity. We conclude that the MH in the interplanetary flux rope comes from the coronal one.