Short-term temporal variations of X-ray bright points

Nolte, J. T.; Solodyna, C. V.; Gerassimenko, M.

doi:10.1007/bf00155701

Cited by 32 publications

(20 citation statements)

References 14 publications

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“…The time scales of these variations were as short as the temporal resolution of the observations (5.5 min). Similar variations were found in X-rays (Nolte et al 1979). More recently, Madjarska et al (2003) using SUMER observations with a temporal resolution of 50 s, have confirmed the presence within a BP of small-scale transient brightenings of the order of minutes.…”

Section: Introductionsupporting

confidence: 80%

“…They were first observed and studied in soft X-ray rocket images (Vaiana et al 1970;Nolte et al 1979) where they present an average lifetime of ∼8 h (Golub et al 1974). However, they have also been observed in radio (Marsh et al 1980) and EUV (Habbal & Withbroe 1981) where the emission has an average lifetime of ∼20 h (Zhang et al 2001).…”

Section: Introductionmentioning

confidence: 99%

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Signature of oscillations in coronal bright points

Ugarte-Urra¹,

Doyle²,

Madjarska

et al. 2004

A&A

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Section: Introductionsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Signature of oscillations in coronal bright points

Ugarte-Urra¹,

Doyle²,

Madjarska

et al. 2004

A&A

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“…Microflares in XBPs were already studied by many authors. Nolte et al (1979) observed with Skylab S-054 impulsive brightenings ( < ∼ 5 min) in two XBPs with 90 s time resolution data. They suggested that these intensity variations are the signature of episodic heating superimposed upon continuous input of energy.…”

Section: Discussionmentioning

confidence: 96%

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

Madjarska¹,

Doyle²,

Teriaca

et al. 2003

A&A

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Abstract. This paper presents the formation, evolution and decay of a coronal bright point via a spectroscopic analysis of its transition region counterpart and the evolution of the underlying magnetic bipole during 3 days of almost continuous observations. The data were obtained with various instruments on-board SoHO, including the SUMER spectrograph in the transition region line S  933.40 Å, CDS in the He  584.33, O  629.73 and Mg  368.06 Å lines, plus MDI and EIT. The existence of the coronal feature is strongly correlated with the evolution of the underlying bipolar region. The lifetime of the bright point from the moment when it was first visible in the EIT images until its complete disappearance was ∼18 hrs. Furthermore, the bright point only became visible at coronal temperatures when the two converging opposite magnetic polarities were ∼7000 km apart. As far as the temporal coverage of the data permits, we found that the bright point disappeared at coronal temperatures after a full cancellation of one of the magnetic polarities. The spectroscopic analysis reveals the presence of small-scale (∼6 ) transient brightenings within the bright point with a periodicity of ∼6 min. The Doppler shift in the bright point was found to be in the range of −10 to 10 km s −1 although it is dominated by a red-shifted emission which is associated with regions characterized by stronger "quiet" Sun photospheric magnetic flux. Small-scale brightenings within the bright point show velocity variations in the range 3-6 km s −1 . In general the bright point has a radiance ∼4 times higher than that of the network. No relation was found between the bright point and the UV explosive event phenomena.

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“…MicroÑares in XBPs also were studied by many authors. Nolte, Solodyna, & Gerassimenko (1979) and Sheeley & Golub (1979) observed impulsive X-ray brightenings in XBPs. From observation by the soft X-ray telescope (SXT) aboard Y ohkoh, Strong et al (1992) found that XBPs illustrate their intensity variability over a wide variety of timescales from a few minutes to hours, as well as rapid changes in their morphology.…”

Section: Introductionmentioning

confidence: 98%

Occurrence Rate of Microflares in an X‐Ray–bright Point within an Active Region

Shimojo

Shibata

1999

ApJ

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We examine the occurrence rate of microÑares (transient brightenings) in an X-ray bright point (XBP) during the lifetime of the XBP observed with the Y ohkoh soft X-ray telescope (SXT). The XBP with a size of D30@@ appeared near a preceding spot of NOAA 7270 on 1992 September 1 and disappeared on 1992 September 4. The XBP produced 92 microÑares during the observation time of the SXT. We found that the occurrence rate (number of events per hour) did not change much during the lifetime of the XBP, although the magnetic Ñux of the XBP changed. We also found that the frequency distribution of microÑares as a function of the soft X-ray peak intensity shows a power law with index 1.7^0.4, which is consistent with the previously known index for Ñares and microÑares based on the data for the whole Sun or a whole active region. This result suggests that the power-law distribution of Ñares holds not only for larger areas but also for smaller areas.

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Short-term temporal variations of X-ray bright points

Cited by 32 publications

References 14 publications

Signature of oscillations in coronal bright points

Signature of oscillations in coronal bright points

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

Occurrence Rate of Microflares in an X‐Ray–bright Point within an Active Region

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