An EUV Bright Point as seen by SUMER, CDS, MDI and EIT on-board SoHO

Madjarska, M. S.; Doyle, J. G.; Teriaca, L.; Banerjee, D.

doi:10.1051/0004-6361:20021732

Cited by 77 publications

(84 citation statements)

References 31 publications

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“…6. Similar small-scale/short-duration brightenings are also seen in bright points (Doyle et al 1998;Madjarska et al 2003).…”

Section: Intensity Variationssupporting

confidence: 68%

Simultaneous observations of solar transition region blinkers and explosive events by SUMER, CDS and BBSO

Madjarska¹,

Doyle²

2003

A&A

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Abstract. The SoHO discovery of the new "blinker" phenomena focused our study on the search of its relation to already known phenomena such as explosive events and spicules. The study was performed using a specially planned joint observing program involving the Coronal Diagnostic Spectrometer (CDS), Solar Ultraviolet Measurements of Emitted Radiation spectrograph (SUMER) and Big Bear Solar Observatory (BBSO) magnetograph. Within each blinker, the SUMER data reveal the presence of small-scale (3 -5 ), short-lived (2-3 min) bright features not seen in the CDS data which has sometimes being interpreted as oscillations in SUMER data. With this data we have clearly identified UV explosive events in CDS data. The explosive events show a size close to the small-scale brightenings forming the blinker core. However, they appear in the SUMER data with their typical strong blue and red wings while the blinker shows at best only a small increase in the emission of the blue and red wings and in most instances the typical transition region red-shift in the center of the line. In all cases the explosive events cover one pixel in CDS corresponding to a size of 4 × 4 −6 . All identified explosive events were located at the border of the bright network i.e. the blinker, in the network or even in the internetwork. From this data, we believe that blinkers and explosive events are two separate phenomena not directly related or triggering each other. In this study, the Doppler shift was derived in a blinker phenomenon for the first time. It ranges from -5 to 25 km s −1 and is predominantly red-shifted. The observed magnetic flux increase during the blinker phenomena seems to play a crucial role in the development of this event. We suggest that "blinkers" maybe the on-disk signature of spicules.

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“…6. Similar small-scale/short-duration brightenings are also seen in bright points (Doyle et al 1998;Madjarska et al 2003).…”

Section: Intensity Variationssupporting

confidence: 68%

Simultaneous observations of solar transition region blinkers and explosive events by SUMER, CDS and BBSO

Madjarska¹,

Doyle²

2003

A&A

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“…We know so far that 88% of X-ray BPs are associated with converging magnetic polarities (Webb et al 1993) and most of the BPs are related to cancelling magnetic features. Usually, one of the magnetic polarities involved is stronger than the other (Madjarska et al 2003) and after the full cancellation of the weaker polarity, the remnant one either joins the CH dominant polarity (if it is of the same sign), expanding the CH surface, or forms a new connection (closed magnetic field lines) which triggers contraction of the CH boundaries. This scenario will be tested by applying magnetic field extrapolation on Michelson Doppler Imager data in high-resolution mode for CH2 as well as new forthcoming data from SOT/Hinode.…”

Section: Discussionmentioning

confidence: 99%

“…Kahler & Moses (1990) studied Skylab X-ray images of a single EECH with a time resolution of 90 min to look for discrete changes of the CH boundaries. They found that X-ray bright points (BPs, small-scale loops in the quiet Sun and CHs, for details see Madjarska et al 2003) play an important role in both the expansion and contraction of the CH. For this study, a single coronal hole observed during the decreasing phase of the solar cycle activity was used.…”

Section: Introductionmentioning

confidence: 99%

Coronal hole boundaries evolution at small scales

Madjarska

Wiegelmann

2009

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Aims. We aim to study the small-scale evolution at the boundaries of an equatorial coronal hole connected with a channel of open magnetic flux to the polar region and an "isolated" one in the extreme-ultraviolet spectral range. We determine the spatial and temporal scale of these changes.Methods. Imager data from TRACE in the Fe ix/x 171 Å passband and EIT on-board Solar and Heliospheric Observatory in the Fe xii 195 Å passband were analysed.Results. We found that small-scale loops known as bright points play an essential role in coronal hole boundary evolution at small scales. Their emergence and disappearance continuously expand or contract coronal holes. The changes appear to be random on a time scale comparable to the lifetime of the loops seen at these temperatures. No signature was found for a major energy release during the evolution of the loops. Conclusions. Although coronal holes seem to maintain their general shape during a few solar rotations, a closer look at their dayby-day and even hour-by-hour evolution demonstrates significant dynamics. The small-scale loops (10 −40 and smaller) which are abundant along coronal hole boundaries contribute to the small-scale evolution of coronal holes. Continuous magnetic reconnection of the open magnetic field lines of the coronal hole and the closed field lines of the loops in the quiet Sun is more likely to take place.

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“…A&A 526, A134 (2011) Habbal & Withbroe (1981), on the other hand, found evidence of variations of EUV emission in chromospheric, transition region and coronal lines, on timescales as short as 5.5 min (the cadence of their Skylab observations). Some work based on SOHO/CDS and SUMER spectroscopic observations to study XBPs at transition region temperatures followed (see e.g., Madjarska et al 2003;Ugarte-Urra 2004;Ugarte-Urra et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Hinode observations and 3D magnetic structure of an X-ray bright point

Alexander

Zanna

Maclean

2011

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Aims. We present complete Hinode Solar Optical Telescope (SOT), X-Ray Telescope (XRT)and EUV Imaging Spectrometer (EIS) observations of an X-ray bright point (XBP) observed on the 10, 11 of October 2007 over its entire lifetime (∼12 h). We aim to show how the measured plasma parameters of the XBP change over time and also what kind of similarities the X-ray emission has to a potential magnetic field model. Methods. Information from all three instruments on-board Hinode was used to study its entire evolution. XRT data was used to investigate the structure of the bright point and to measure the X-ray emission. The EIS instrument was used to measure various plasma parameters over the entire lifetime of the XBP. Lastly, the SOT was used to measure the magnetic field strength and provide a basis for potential field extrapolations of the photospheric fields to be made. These were performed and then compared to the observed coronal features. Results. The XBP measured ∼15 in size and was found to be formed directly above an area of merging and cancelling magnetic flux on the photosphere. A good correlation between the rate of X-ray emission and decrease in total magnetic flux was found. The magnetic fragments of the XBP were found to vary on very short timescales (minutes), however the global quasi-bipolar structure remained throughout the lifetime of the XBP. The potential field extrapolations were a good visual fit to the observed coronal loops in most cases, meaning that the magnetic field was not too far from a potential state. Electron density measurements were obtained using a line ratio of Fe xii and the average density was found to be 4.95 × 10 9 cm −3 with the volumetric plasma filling factor calculated to have an average value of 0.04. Emission measure loci plots were then used to infer a steady temperature of log T e [K] ∼ 6.1. The calculated Fe xii Doppler shifts show velocity changes in and around the bright point of ±15 km s −1 which are observed to change on a timescale of less than 30 min.

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An EUV Bright Point as seen by SUMER, CDS, MDI and EIT on-board SoHO

Cited by 77 publications

References 31 publications

Simultaneous observations of solar transition region blinkers and explosive events by SUMER, CDS and BBSO

Simultaneous observations of solar transition region blinkers and explosive events by SUMER, CDS and BBSO

Coronal hole boundaries evolution at small scales

Hinode observations and 3D magnetic structure of an X-ray bright point

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