Multiwavelength Studies of MHD Waves in the Solar Chromosphere

Jess, D. B.; Morton, R. J.; Verth, G.; Fedun, V.; Grant, S. D. T.; Giagkiozis, Ioannis

doi:10.1007/s11214-015-0141-3

Cited by 179 publications

(172 citation statements)

References 407 publications

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“…Table 2 summarizes properties of transverse oscillations (and waves) for various fibrillar structures observed in different chromospheric passbands reported in the literature, along with our results for the SCFs (see Jess et al 2015 for a detailed overview).…”

Section: Discussionmentioning

confidence: 98%

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Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI

Jafarzadeh

Solanki

Gafeira

et al. 2017

ApJS

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We present observations of transverse oscillations in slender Ca IIH fibrils (SCFs) in the lower solar chromosphere. We use a 1 hr long time series of high-(spatial and temporal-) resolutionseeing-free observations in a 1.1 Å wide passband covering the line core of Ca IIH 3969 Å from the second flight of the SUNRISE balloon-borne solar observatory. The entire field of view, spanning the polarity inversion line of an active region close to the solar disk center, is covered with bright, thin, and very dynamic fine structures. Our analysis reveals the prevalence of transverse waves in SCFs with median amplitudes and periods on the order of 2.4±0.8 km s −1 and 83±29 s, respectively (with standard deviations given as uncertainties). We find that the transverse waves often propagate along (parts of) the SCFs with median phase speeds of 9±14 km s −1. While the propagation is only in one direction along the axis in some of the SCFs, propagating waves in both directions, as well as standing waves are also observed. The transverse oscillations are likely Alfvénic and are thought to be representative of magnetohydrodynamic kink waves. The wave propagation suggests that the rapidhigh-frequency transverse waves,often produced in the lower photosphere, can penetrate into the chromospherewith an estimated energy flux of ≈15 kW m −2. Characteristics of these waves differ from those reported for other fibrillar structures, which, however, were observed mainly in the upper solar chromosphere.

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Section: Discussionmentioning

confidence: 98%

“…In the vigorously dynamic Sun even individual lines may obtain a contribution from a large range of heights (Rutten 2007). Hence,the lines used in the various observations may be affected by different local plasma properties, leading to subtle variations in the determined wave parameters (Jess et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI

Jafarzadeh

Solanki

Gafeira

et al. 2017

ApJS

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“…They have different physical nature and causes, and their periods vary from a fraction of second up to several years, and even to centuries. Some examples of the oscillatory processes responsible for the periodicities are the 11 yr solar cycle, the so-called quasi-biennial oscillations, the helioseismic variations (see Hathaway 2010;Bazilevskaya et al 2014;Christensen-Dalsgaard 2002, and references therein for recent comprehensive reviews), magnetohydrodynamic waves and oscillations in different plasma structures of the solar atmosphere (see De Moortel & Nakariakov 2012;Liu & Ofman 2014;Jess et al 2015), and various quasi-periodic pulsations (QPP) appearing in solar flare light curves (Nakariakov & Melnikov 2009;Kupriyanova et al 2010;Simões et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Empirical mode decomposition analysis of random processes in the solar atmosphere

Kolotkov

Anfinogentov

Nakariakov

2016

A&A

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Context. Coloured noisy components with a power law spectral energy distribution are often shown to appear in solar signals of various types. Such a frequency-dependent noise may indicate the operation of various randomly distributed dynamical processes in the solar atmosphere. Aims. We develop a recipe for the correct usage of the empirical mode decomposition (EMD) technique in the presence of coloured noise, allowing for clear distinguishing between quasi-periodic oscillatory phenomena in the solar atmosphere and superimposed random background processes. For illustration, we statistically investigate extreme ultraviolet (EUV) emission intensity variations observed with SDO/AIA in the coronal (171 Å), chromospheric (304 Å), and upper photospheric (1600 Å) layers of the solar atmosphere, from a quiet sun and a sunspot umbrae region. Methods. EMD has been used for analysis because of its adaptive nature and essential applicability to the processing non-stationary and amplitude-modulated time series. For the comparison of the results obtained with EMD, we use the Fourier transform technique as an etalon. Results. We empirically revealed statistical properties of synthetic coloured noises in EMD, and suggested a scheme that allows for the detection of noisy components among the intrinsic modes obtained with EMD in real signals. Application of the method to the solar EUV signals showed that they indeed behave randomly and could be represented as a combination of different coloured noises characterised by a specific value of the power law indices in their spectral energy distributions. On the other hand, 3-min oscillations in the analysed sunspot were detected to have energies significantly above the corresponding noise level. Conclusions. The correct accounting for the background frequency-dependent random processes is essential when using EMD for analysis of oscillations in the solar atmosphere. For the quiet sun region the power law index was found to increase with height above the photosphere, indicating that the higher frequency processes are trapped deeper in the quiet sun atmosphere. In contrast, lower levels of the sunspot umbrae were found to be characterised by higher values of the power law index, meaning the domination of lower frequencies deep inside the sunspot atmosphere. Comparison of the EMD results with those obtained with the Fourier transform showed good consistency, justifying the applicability of EMD.

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“…A similar spiky behavior, characterized by a timescale of a couple of minutes, can also be seen in the other two ribbons, concerning more clearly the total UV intensity. However, this can be in some measure due to variations in the seeing or to oscillations in the chromosphere (e.g., Jess et al 2015) as it partially affects the background emission measured in the rectangular box of Figure 14.…”

Section: Late Gradual Phasementioning

confidence: 99%

A MULTI-INSTRUMENT ANALYSIS OF a C4.1 FLARE OCCURRING IN a Δ SUNSPOT

Guglielmino¹,

Zuccarello²,

Romano

et al. 2016

ApJ

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We present an analysis of multi-instrument space-and ground-based observations relevant to a C4.1 solar flare that occurred in the active region (AR) NOAA 11267 on 2011 August 6. Solar Dynamics Observatoryobservations indicate that at the flare's beginning, it was localized in the preceding sunspot of the AR, which exhibits a δ configuration. Along the polarity inversion line between its opposite polarities we find a large shear angle of about 80°. The helicity accumulation shows that the AR does not obey the general hemispheric helicity rule. At the flare peak, unique observations taken with the X-Ray Telescope aboard Hinode reveal that the bulk of the X-ray emission takes place in the δ-spot region, where the plasma heats up to 1.9 10 7 · » K. During the gradual phase, we observe the development of a Y-shaped structure in the corona and in the high chromosphere. An extruding structure forms, being directed from the emitting region above the δ spot toward the following sunspot. This structure cools down in a few tens of minutes while moving eastward along a direction opposite to the flare ribbon expansion. Finally, remote brightenings are found at the easternmost footpoint of this structure, appearing as a third flare ribbon in the chromosphere. After some minutes, RHESSI measurements show that the X-ray emission is localized in the region close to the crossing point of the coronal Y-shaped structure. Simultaneously, highresolution (0 15) observations performed at the Swedish 1 m Solar Telescope indicate a decreasing trend of the Ca II H intensity in the flare ribbons with some transient enhancements. All these findings suggest that this event is a manifestation of magnetic reconnection, likely induced by an asymmetric magnetic configuration in a highly sheared region.

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Multiwavelength Studies of MHD Waves in the Solar Chromosphere

Cited by 179 publications

References 407 publications

Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI

Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI

Empirical mode decomposition analysis of random processes in the solar atmosphere

A MULTI-INSTRUMENT ANALYSIS OF a C4.1 FLARE OCCURRING IN a Δ SUNSPOT

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