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Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.

doi:10.1023/a:1016238317702

Cited by 60 publications

(48 citation statements)

References 31 publications

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“…For all driver amplitudes we have found that the simulated waves experience strong stratification driven growth to a local maximum at the transition region, which is in good agreement with the results of various observational studies of three minute sunspot oscillations, which have found that the observed oscillation amplitude of such waves above sunspots peaks at transition region temperatures (Brynildsen et al 2002;Fludra 2001;Marsh & Walsh 2006;O'Shea et al 2002).…”

Section: Discussionsupporting

confidence: 89%

Leakage of photospheric acoustic waves into non-magnetic solar atmosphere

Erdélyi

Malins

Tóth³

et al. 2007

A&A

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Aims. This paper aims to look at the propagation of synthetic photospheric oscillations from a point source into a two-dimensional non-magnetic solar atmosphere. It takes a particular interest in the leakage of 5-min global oscillations into the atmosphere, and aims to complement efforts on the driving of chromospheric dynamics (e.g. spicules and waves) by 5-min oscillations. Methods. A model solar atmosphere is constructed based on realistic temperature and gravitational stratification. The response of this atmosphere to a wide range of adiabatic periodic velocity drivers is numerically investigated in the hydrodynamic approximation. Results. The findings of this modelling are threefold. Firstly, high-frequency waves are shown to propagate from the lower atmosphere across the transition region experiencing relatively low reflection and transmitting energy into the corona. Secondly, it is demonstrated that driving the upper solar photosphere with a harmonic piston driver at around the 5 min period may generate three separate standing modes with similar periods in the chromosphere and transition region. In the cavity formed by the chromosphere and bounded by regions of low cut-off period at the photospheric temperature minimum and the transition region this is caused by reflection, while at either end of this region in the lower chromosphere and transition region the standing modes are caused by resonant excitation. Finally, the transition region becomes a guide for horizontally propagating surface waves for a wide range of driver periods, and in particular at those periods which support chromospheric standing waves. Crucially, these findings are the results of a combination of a chromospheric cavity and resonant excitation in the lower atmosphere and transition region.

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Section: Discussionsupporting

confidence: 89%

Leakage of photospheric acoustic waves into non-magnetic solar atmosphere

Erdélyi

Malins

Tóth³

et al. 2007

A&A

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“…Multi-wavelength observations with EIT and TRACE confirmed that the diverging fan structures consist of multiple loop threads with different temperatures and corresponding sound speeds (Robbrecht et al 2001;King et al 2003). Time periods of P = 172 ± 32 s were reported for loops rooted near sunspots (our region 2 and 3), which coincide with the 3-min p-mode oscillations detected in sunspots (Brynildsen et al 2002(Brynildsen et al , 2000Fludra 2001;Maltby et al 2001;Banerjee et al 2002), while waves that start further away from sunspots (active region plages, our region 4) have periods of P = 321 ± 74 s, which coincide with the global 5-min p-mode oscillations. O'Shea et al (2002) found the presence of oscillations in a wide range of temperatures (from the temperature minimum of the solar atmosphere to the temperature of the upper corona) and time delays between the low-and hightemperature oscillations.…”

Section: Discussionsupporting

confidence: 56%

“…Maltby et al (1999) found 3-min oscillations in coronal loops that are rooted in the umbra. By examining TRACE and CDS data, Brynildsen et al (2002) found that the 3-min oscillations of transition region lines are present in the whole umbral region but the 3-min oscillations of coronal lines tend to localize in small regions that coincide with the endpoints of coronal loops. In their study, the 3-min oscillations were not observed with CDS at coronal temperatures within the spots, but were seen in the TRACE 171 Å band.…”

Section: Introductionmentioning

confidence: 99%

The extent of 3-min oscillations in regions other than sunspot plumes

Lin¹,

Banerjee

Doyle³

et al. 2005

A&A

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The active region, AR0554, was observed with NIS/CDS on board SoHO to examine the extent and range of oscillations from a range of features. Among all the NIS spectral lines analysed, significant oscillations were found in Si xii 520 Å, Mg x 625 Å, O v 629 Å, and He i 522 Å. The periods of the strongest oscillations in these lines were ≈10−20 min. After the dominant 10−20 min oscillations were filtered out from these lines, only O v 629 Å showed significant (i.e. above the 95% significance level) shorter-period oscillations. Specifically, we found that weak but significant 3-min oscillations are not confined to the umbra/plume but can be seen in many bright locations. The duration of these non-umbral 3-min oscillations is mostly ≈20 min. In contrast, the 3-min oscillations within the umbra are strong and stable for longer than 50 min. The duration could be related to the size of the oscillating source region, rather than the lifetime of the oscillation. To find the possible sources of these 3-min oscillations outside of the umbra, we compared the oscillations of single pixels in different regions. The results of our comparison indicate a possible connection between the magnetic fields and the oscillations. Therefore, we suggest that 3-min oscillations may exist in many magnetic structures, but are often too weak to be seen in an unfiltered signal.

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“…The measured propagation speeds suggest that the observed oscillations are slow magneto-acoustic waves propagating from the footpoints along the magnetic field lines. From a joint SOHO and TRACE observing campaign, Brynildsen et al (2002) also found evidence for a 3 min period oscillation above a sunspot umbra. The oscillation amplitudes are found to increase with increasing temperature, reaching a maximum at about 1−2 × 10 5 K and then decreasing again in the higher temperature lines.…”

Section: Introductionmentioning

confidence: 92%

The damping of slow MHD waves in solar coronal magnetic fields

Moortel

Hood

2003

A&A

167

134

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Abstract.A theoretical description of slow MHD wave propagation in the solar corona is presented. Two different damping mechanisms, namely thermal conduction and compressive viscosity, are included and discussed in detail. We revise the properties of the "thermal" mode, which is excited when thermal conduction is included. The thermal mode is purely decaying in the case of standing waves, but is oscillatory and decaying in the case of driven waves. When thermal conduction is dominant, the waves propagate largely undamped, at the slower, isothermal sound speed. This implies that there is a minimum damping time (or length) that can be obtained by thermal conduction alone. The results of numerical simulations are compared with TRACE observations of propagating waves, driven by boundary motions, and standing waves observed by SUMER/SOHO, excited by an initial impulse. For typical coronal conditions, thermal conduction appears to be the dominant damping mechanism.

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Cited by 60 publications

References 31 publications

Leakage of photospheric acoustic waves into non-magnetic solar atmosphere

Leakage of photospheric acoustic waves into non-magnetic solar atmosphere

The extent of 3-min oscillations in regions other than sunspot plumes

The damping of slow MHD waves in solar coronal magnetic fields

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