Microflares in the solar magnetic network

Porter, J. G.; Moore, Ronald L.; Reichmann, E. J.; Engvold, O.; Harvey, K. L.

doi:10.1086/165835

Cited by 151 publications

(53 citation statements)

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“…High resolution UV spectra taken by the High Resolution Telescope and Spectrograph (Brueckner & Bartoe 1983;Dere et al 1989) revealed very small spatial regions in the solar atmosphere of sudden enhancements in the emission line intensities, associated with strongly broadened non-Gaussian, Doppler shifted line profiles in regions of 2 arcsec or less in size. Similar observations in mid-transition region lines of SMM UVSP (see, e.g., Porter et al 1987) and more recently by SUMER (Innes et al 1997;Perez et al 1998Perez et al , 1999Erdélyi et al 1997Erdélyi et al , 1998 and by TRACE (Erdélyi et al , 2001) have confirmed these very localized high-speed events.…”

Section: Introductionsupporting

confidence: 78%

Modelling of explosive events in the solar transition region in a 2D environment

Roussev¹,

Galsgaard²,

Erdélyi

et al. 2001

A&A

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Abstract. The aim of the present study is to investigate the reconnection jets formed during the process of magnetic flux cancellation in the physical environment of the solar transition region. The emission properties of these jets are then computed for two resonance transition region lines, C iv 1548.2Å and O vi 1031.9Å, under the assumption of non-equilibrium ionization. The numerical modelling involves 2-dimensional (2D) dissipative, radiative, nonlinear magnetohydrodynamics. The nonlinear anisotropic thermal conduction, radiative losses, and volumetric heating are taken into account in order to assess their role in the physical situation examined. This work is a continuation of previous related simulations where small-scale energy depositions were modelled in 1D radiative hydrodynamics. Having an X-point reconnection in the mid-transition region gives blue-shifts of the order of ∼100 km s −1 , however, the red-shift can be up to one order of magnitude less.

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Section: Introductionsupporting

confidence: 78%

Modelling of explosive events in the solar transition region in a 2D environment

Roussev¹,

Galsgaard²,

Erdélyi

et al. 2001

A&A

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“…Thus, the swaying of flux tube bundles might explain temporary brightness enhancements when the buffeting of granules pushes the flux tubes, which are normally pointing 50 degrees away from the observer, towards them. However, due to the sharp rise in intensity and the corresponding decay pattern, we deem these intensity fluctuations to be characteristic of microflare activity with similar energetics and durations observed by Porter et al (1987).…”

Section: Resultsmentioning

confidence: 75%

Twisting flux tubes as a cause of micro-flaring activity

Jess

McAteer

Mathioudakis³

et al. 2007

A&A

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High-cadence optical observations of an H-α blue-wing bright point near solar AR NOAA 10794 are presented. The data were obtained with the Dunn Solar Telescope at the National Solar Observatory/Sacramento Peak using a newly developed camera system, the rapid dual imager. Wavelet analysis is undertaken to search for intensity-related oscillatory signatures, and periodicities ranging from 15 to 370 s are found with significance levels exceeding 95%. During two separate microflaring events, oscillation sites surrounding the bright point are observed to twist. We relate the twisting of the oscillation sites to the twisting of physical flux tubes, thus giving rise to reconnection phenomena. We derive an average twist velocity of 8.1 km s −1 and detect a peak in the emitted flux between twist angles of 180• and 230• .

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“…In addition, it is possible that blinkers are in fact composed of many shortduration small-scale unit brightenings (a few arcseconds in size and a few minutes in duration) that show distorted characteristics when averaged together by CDS observations made using lower spatial or temporal resolutions (Chae et al 2000;Bewsher et al 2002). Intensity enhancements had previously been observed in transition region lines using data sets from older missions (see, e.g., Vernazza et al 1975;Porter et al 1987), but these observations had several limitations (e.g., ambiguities in separating spatial and spectral information and limited temperature coverage), so many questions about the properties of the brightenings remained unanswered.…”

Section: Introductionmentioning

confidence: 99%

Short‐Duration Active Region Brightenings Observed in the Extreme Ultraviolet and Hα by theSolar and Heliospheric ObservatoryCoronal Diagnostic Spectrometer and Hida Domeless Solar Telescope

Brooks

Kurokawa

Kamio

et al. 2004

ApJ

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We present the first detection of an H counterpart to the EUV blinker. The observations come from a coordinated campaign between the Hida Observatory Domeless Solar Telescope (DST) and the Solar and Heliospheric Observatory Coronal Diagnostic Spectrometer (CDS) conducted in 2002 July and August. Utilizing studies designed for high-cadence observations, many short-duration brightenings (<3 minutes) were identified in the He i k584.334 and O v k629.732 spectral lines in CDS data of active region NOAA 10039/10044. These brightenings show similar characteristics (increases in intensity, size) to longer duration EUV blinkers previously reported in active regions and the quiet Sun. Focusing on two events that show pronounced emission in the upper chromosphere (He i), we have been able to identify cospatial bright points in the lower chromosphere (H center, AE 0.5 Å ) that show enhanced emission during the EUV blinker. These bright features have lifetimes similar to those of their EUV counterparts, and their peak intensities occur nearly simultaneously with the peak blinker intensities in the He i and O v lines. In both cases the He i and O v lines show excess line broadening at the peak of the event (>15 km s À1 ). Our high-cadence observations also enabled us to examine the dimensions and lifetimes of short-duration active region blinkers in detail. We find that the instrumental spatial and temporal resolution can combine to distort their characteristics: even short-duration blinkers appear to be composed of elementary brightening events. The optical brightenings also appear to closely follow the behavior of the elementary brightenings. The spatial and temporal relationships between the brightenings indicate a causal link between the EUV and H blinkers.

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Microflares in the solar magnetic network

Cited by 151 publications

References 0 publications

Modelling of explosive events in the solar transition region in a 2D environment

Modelling of explosive events in the solar transition region in a 2D environment

Twisting flux tubes as a cause of micro-flaring activity

Short‐Duration Active Region Brightenings Observed in the Extreme Ultraviolet and Hα by theSolar and Heliospheric ObservatoryCoronal Diagnostic Spectrometer and Hida Domeless Solar Telescope

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