Using SDO’s AIA to investigate energy transport from a flare’s energy release site to the chromosphere

Brosius, J. W.; Holman, Gordon D.

doi:10.1051/0004-6361/201118144

Cited by 27 publications

(31 citation statements)

References 42 publications

(50 reference statements)

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“…From the movies, it appeared to start from a region in the corona above the flare, and did not coincide with any strong photospheric flux concentrations. The ejection was seen in all AIA EUV channels which may be because the plasma was rapidly heated (Fletcher et al 2013) or it could be due to intense emission from chromospheric lines in all the channels (Brosius & Holman 2012). In the 131 and 94Å movies the ejected plasma rises upwards, driving a front of hot plasma along the loop ahead of it.…”

Section: Excitation Mechanismmentioning

confidence: 93%

SOLAR DYNAMICS OBSERVATORY/ATMOSPHERIC IMAGING ASSEMBLY OBSERVATIONS OF A REFLECTING LONGITUDINAL WAVE IN A CORONAL LOOP

Kumar

Innes

Inhester

2013

ApJ

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We report high resolution observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) of intensity oscillations in a hot, T ∼8-10 MK, loop. The AIA images show a large coronal loop that was rapidly heated following plasma ejection from one of the loop's footpoints. A wave-like intensity enhancement, seen very clearly in the 131 and 94Å channel images, propagated ahead of the ejecta along the loop, and was reflected at the opposite footpoint. The wave reflected four times before fading. It was only seen in the hot, 131 and 94Å channels. The characteristic period and the decay time of the oscillation was ∼630 and ∼440 s, respectively. The phase speed was about 460-510 km s −1 which roughly matches the sound speed of the loop (430-480 km s −1 ). The observed properties of the oscillation are consistent with the observations of Doppler shift oscillations discovered by the Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation (SUMER) and with their interpretation as slow magnetoacoustic waves. We suggest that the impulsive injection of plasma, following reconnection at one of the loop footpoints, led to rapid heating and the propagation of a longitudinal compressive wave along the loop. The wave bounces back and forth a couple of times before fading.

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Section: Excitation Mechanismmentioning

confidence: 93%

SOLAR DYNAMICS OBSERVATORY/ATMOSPHERIC IMAGING ASSEMBLY OBSERVATIONS OF A REFLECTING LONGITUDINAL WAVE IN A CORONAL LOOP

Kumar

Innes

Inhester

2013

ApJ

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“…Since, this region simultaneously brightened in all AIA channels and was associated with Fe xxi blueshifts, we attribute the lower-than-average Fe xxi to additional Fe viii due to a recent injection of cool plasma into the loop. In the brighter 131 flare kernels (>600 DN s −1 ), the 131 EM is about 20−60% more than the IRIS Fe xxi suggesting that there is a contribution of up to 52% from cool plasma emission (Brosius & Holman 2012). A small-scale kernel structure results in a broad range of 131/Fe xxi EM ratios and sharp gradients in IRIS Fe xxi emission at sites of molecular and transition region emission.…”

Section: Conclusion and Discussionmentioning

confidence: 98%

“…Observations of the kernels show simultaneous brightening in all Atmospheric Imaging Assembly (AIA) extreme ultraviolet (EUV) channels (Brosius & Holman 2012;Fletcher et al 2013;Young et al 2013). The analysis by Brosius & Holman (2012) that compared AIA images with Coronal Diagnostic Spectrometer (CDS) spectra showed that in a small GOES B4.8 flare a significant fraction of the hot channel 94 Å and 131 Å emission could be attributed to the brightening of the transition region and lower coronal lines.…”

Section: Introductionmentioning

confidence: 99%

“…The analysis by Brosius & Holman (2012) that compared AIA images with Coronal Diagnostic Spectrometer (CDS) spectra showed that in a small GOES B4.8 flare a significant fraction of the hot channel 94 Å and 131 Å emission could be attributed to the brightening of the transition region and lower coronal lines. On the other hand, Fletcher et al (2013) attributed all the 131 Å brightening in an M1.0 flare to plasma with temperatures greater than 10 MK.…”

Section: Introductionmentioning

confidence: 99%

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Observations of solar flares with IRIS and SDO

Innes

Ning

2016

A&A

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Flare kernels brighten simultaneously in all Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) channels making it difficult to determine their temperature structure. The Interface Region Imaging Spectrograph (IRIS) is able to spectrally resolve Fe xxi emission from cold chromospheric brightenings, so it can be used to infer the amount of Fe xxi emission in the 131 Å AIA channel. We use observations of two small solar flares seen by IRIS and SDO to compare the emission measures (EMs) deduced from the IRIS Fe xxi line and the AIA 131 Å channel to determine the fraction of Fe xxi emission in flare kernels in the 131 Å channel of AIA. Cotemporal and cospatial pseudo-raster AIA images are compared with the IRIS results. We use multi-Gaussian line fitting to separate the blending chromospheric emission so as to derive Fe xxi intensities and Doppler shifts in IRIS spectra. We define loop and kernel regions based on the brightness of the 131 Å and 1600 Å intensities. In the loop regions the Fe xxi EMs are typically 80% of the 131 Å values, and range from 67% to 92%. Much of the scatter is due to small misalignments, but the largest site with low Fe xxi contributions was probably affected by a recent injection of cool plasma into the loop. In flare kernels the contribution of Fe xxi increases from less than 10% at the low-intensity 131 Å sites to 40−80% in the brighter kernels. Here the Fe xxi is superimposed on bright chromospheric emission and the Fe xxi line shows blueshifts, sometimes extending up to the edge of the spectral window, 200 km s −1 . The AIA 131 Å emission in flare loops is due to Fe xxi emission with a 10−20% contribution from continuum, Fe xxiii, and cooler background plasma emission. In bright flare kernels up to 52% of the 131 Å is from cooler plasma. The wide range seen in the kernels is caused by significant structure in the kernels, which is seen as sharp gradients in Fe xxi EM at sites of molecular and transition region emission.

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“…Moreover, in several cases, large flares consist of an avalanche of several microflares (Berghmans et al 2001). First observed in EUV by Skylab as transients, microflares were systematically studied in X-rays with later missions, such as the Solar Maximum Mission (SMM), the Soft X-ray Telescope (SXT) on the Yohkoh satellite, and, more recently, with the Extreme ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO), the Transition Region And Coronal Explorer (TRACE), the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), Hinode (Hannah et al 2008), and the Atmospheric Imaging Assembly (AIA) on the Solar Dynamic Observatory (SDO; Brosius & Holman 2012). They are characterized by a duration of one to ten minutes, a size of 6 Mm 2 to 300 Mm 2 , and radiative losses of 10 24 ergs to 10 26 ergs (Berghmans & Clette 1999).…”

Section: Introductionmentioning

confidence: 99%

Spectral diagnostic of a microflare. Evidences of resonant scattering in C IV 1548 Å, 1550 Å lines

Gontikakis

Winebarger

Patsourakos

2013

A&A

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Aims. We study a microflare, classified as a GOES-A1 after background subtraction, which was observed in active region NOAA 8541 on May 15, 1999. Methods. We used TRACE filtergrams to study the morphology and time evolution. SUMER spectral lines were used to diagnose the chromospheric plasma (Si ii 1533 Å), transition region plasma (C iv 1548, 1550 Å), and coronal plasma (Ne viii 770 Å).Results. In the 171 Å and 195 Å filtergrams, we measure apparent mass motions along two small loops that compose the microflare from the eastern toward the western footpoints. In SUMER, the microflare is detected as a small (47 Mm 2 ), bright area at the western footpoints of the TRACE loops. The spectral profiles recorded over the bright area are complex. The Si ii 1533 Å line is self-reversed owing to opacity, and the coronal Ne viii line profile is composed of two Gaussian components, one of them systematically redshifted. The C iv 1548 Å and 1550 Å profiles are badly distorted because of the temporary depression of the detector local gain caused by the very high count rates reached in the flaring region and we can only confirm the presence of strong blueshifts of -200 km s −1 .Few, unaffected C iv profiles show two spectral components. In the northern part of the bright area, all SUMER spectral lines have at least one blueshifted spectral component. In the southern region of the bright area the spectral lines are redshifted. Adjacent to the microflare we measure, for the first time on the solar disk, an intensity ratio of the 1548 Å line to 1550 Å line with values of three to four, indicating that resonance scattering prevails in the lines formation. Moreover, the scattering region is found to be cospatial to a solar pore. Conclusions. The blueshifts in the footpoints of the microflare and the apparent mass motions observed with TRACE can be explained by a gentle chromospheric evaporation triggered by the microflare. The redshifted spectral components can be explained as cooling material that is falling back on the solar surface. The presence of resonant scattering can be explained by the low electron density expected in the transition region of a solar pore, combined with the high photon flux coming from the nearby microflare. We estimate that the lower limit of the electron density in the pore lies in the range 10 8 cm −3 to 10 9 cm −3 .

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Using SDO’s AIA to investigate energy transport from a flare’s energy release site to the chromosphere

Cited by 27 publications

References 42 publications

SOLAR DYNAMICS OBSERVATORY/ATMOSPHERIC IMAGING ASSEMBLY OBSERVATIONS OF A REFLECTING LONGITUDINAL WAVE IN A CORONAL LOOP

SOLAR DYNAMICS OBSERVATORY/ATMOSPHERIC IMAGING ASSEMBLY OBSERVATIONS OF A REFLECTING LONGITUDINAL WAVE IN A CORONAL LOOP

Observations of solar flares with IRIS and SDO

Spectral diagnostic of a microflare. Evidences of resonant scattering in C IV 1548 Å, 1550 Å lines

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