Localized sources of propagating acoustic waves in the solar photosphere

Brown, Timothy M.; Bogdan, Thomas J.; Lites, B. W.; Thomas, John H.

doi:10.1086/186473

Cited by 94 publications

(107 citation statements)

References 0 publications

Supporting

Mentioning

101

Contrasting

Order By: Relevance

“…If the profile of w 2 (x) were to be plotted along an isopycnic (i.e., curve of constant density), then for the incident p-modes, enhanced levels of w 2 (x) and reduced levels of u 2 (x) would be present within the magnetic slab compared to their characteristic values on the fore side of the flux slab. For the incident f-mode, on the other hand, the contrary is found to apply in better agreement with the observed suppression of 5 minute oscillations within sunspots (Lites et al 1997) and plage (Brown et al 1992;Hindman 1997). …”

Section: Resultssupporting

confidence: 76%

Simulation of [CLC][ITAL]f[/ITAL][/CLC]- and [CLC][ITAL]p[/ITAL][/CLC]-Mode Interactions with a Stratified Magnetic Field Concentration

Cally

Bogdan

1997

The Astrophysical Journal

View full text Add to dashboard Cite

The interaction of f-and p-modes with a slab of vertical magnetic field of sunspot strength is simulated numerically in two spatial dimensions. Both f-modes and p-modes are partially converted to slow magnetoatmospheric gravity (MAG) waves within the magnetic slab because of the strong gravitational stratification of the plasma along the magnetic lines of force. The slow MAG waves propagate away from the conversion layer guided by the magnetic field lines, and the energy they extract from the incident f-and p-modes results in a reduced amplitude for these modes as they exit from the back side of the slab. In addition, the incident p-modes are partially mixed into f-modes of comparable frequency, and therefore larger spherical harmonic degree, when they exit the magnetic flux concentration. These findings have important implications for the interpretation of observations of p-mode absorption by sunspots, both in terms of the successes and failures of this simple numerical simulation viewed in the sunspot seismology context.

show abstract

Section: Resultssupporting

confidence: 76%

Simulation of [CLC][ITAL]f[/ITAL][/CLC]- and [CLC][ITAL]p[/ITAL][/CLC]-Mode Interactions with a Stratified Magnetic Field Concentration

Cally

Bogdan

1997

The Astrophysical Journal

View full text Add to dashboard Cite

show abstract

“…There have been several different explanations of power halos in the literature: (i) the enhancement of acoustic emission by some unknown source (Braun et al 1992;Brown et al 1992;Jain & Haber 2002); (ii) incompressible oscillations, such as Alfvén waves or transverse kink waves, in magnetic tubes (Hindman & Brown 1998); (iii) the interaction of acoustic waves with the overlying magnetic canopy (Muglach et al 2005;Kuridze et al 2008); and (iv) a change of the spatial-temporal spectrum of the turbulent convection in the magnetic field (Jacoutot et al 2008). However, observations show a lack of power halos in the intensity maps (Hindman & Brown 1998;Jain & Haber 2002;Muglach et al 2005;Nagashima et al 2007), which needs an adequate explanation.…”

Section: Discussionmentioning

confidence: 99%

“…The observed velocity power maps are sometimes referred to as "photospheric power halos" (Braun et al 1992;Brown et al 1992;Hindman & Brown 1998;Jain & Haber 2002;Muglach et al 2005;Moretti et al 2007;Nagashima et al 2007;Hanasoge 2008). The power enhancement is only observed in the Doppler velocity power maps and not in continuum intensity (Hindman & Brown 1998;Jain & Haber 2002;Muglach et al 2005;Nagashima et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Acoustic oscillations in the field-free, gravitationally stratified cavities under solar bipolar magnetic canopies

Kuridze

Zaqarashvili

Shergelashvili

et al. 2009

A&A

View full text Add to dashboard Cite

Aims. The main goal here is to study the dynamics of the gravitationally stratified, field-free cavities in the solar atmosphere, located under small-scale, cylindrical magnetic canopies, in response to explosive events in the lower-lying regions (due to granulation, smallscale magnetic reconnection, etc.). Methods. We derive the two-dimensional Klein-Gordon equation for isothermal density perturbations in cylindrical coordinates. The equation is first solved by a standard normal mode analysis to obtain the free oscillation spectrum of the cavity. Then, the equation is solved in the case of impulsive forcing associated to a pressure pulse specified in the lower lying regions. Results. The normal mode analysis shows that the entire cylindrical cavity of granular dimensions tends to oscillate with frequencies of 5-8 mHz and also with the atmospheric cut-off frequency. Furthermore, the passage of a pressure pulse, excited in the convection zone, sets up a wake in the cavity oscillating with the same cut-off frequency. The wake oscillations can resonate with the free oscillation modes, which leads to an enhanced observed oscillation power. Conclusions. The resonant oscillations of these cavities explain the observed power halos near magnetic network cores and active regions.

show abstract

“…It has been found, from time series studies of photospheric Doppler velocities obtained with the Michelson Doppler Imager (MDI) and of intensities obtained in the chromospheric Ca ii K line, that there is an enhancement of the oscillatory power at the period of 2-3 min in the surroundings of active regions (e.g. Braun et al 1992;Brown et al 1992;Hindman & Braun 1998Thomas & Stanchfield 2000;Muglach et al 2005). It is called power halo and is associated, but it is not co-spatial, with magnetic field concentrations.…”

Section: Introductionmentioning

confidence: 99%

Power halo and magnetic shadow in a solar quiet region observed in the Hαline

Kontogiannis

Tsiropoula

Tziotziou

2010

A&A

View full text Add to dashboard Cite

Context. We investigate the oscillatory behavior of the quiet solar chromosphere and its discrete components in terms of oscillation properties, i.e. network and internetwork. For this purpose, we use a time series of high resolution filtergrams at five wavelengths along the Hα profile, obtained by the Dutch Open Telescope. Aims. We aim to gain insight on the distribution of power in different period bands and its variation between network and internetwork. Our spectral resolution provides information on the vertical distribution of power, since the Hα line has both photospheric and chromospheric components. We investigate the effect of Hα mottles on chromospheric oscillations, since they are the most prominent feature of the Hα chromosphere and outline inclined magnetic fields. Methods. We use wavelet and phase difference analyses of Hα intensities and Doppler signals. Two-dimensional power maps in the 3, 5 and 7 min period bands as well as coherence and phase difference maps were constructed. Results. At photospheric heights, where the Hα ± 0.7 Å wing is formed, the 3 and 5 min power is enhanced around the network, and forms power halos. Higher in the chromosphere these areas are replaced by magnetic shadows, i.e. places of power suppression. Interestingly, the power maps show a filamentary structure in the network which correlates very well with mottles. These areas show positive phase differences at the 3 min period band. At the 5 min and 7 min period bands both positive and negative phase differences are obtained with an increased number of pixels with high coherence, indicating the existence of both upward and downward propagating waves. Conclusions. We attribute our findings to the interaction between acoustic oscillations and the magnetic fields that constitute the magnetic network. The network flux tubes diverge at chromospheric levels and obtain a significant horizontal component, which is betrayed by the presence of mottles. The variation of power reveals the discrete role of the magnetic field at different heights, which guides or suppresses the oscillations, depending on its inclination. Spectral resolution in Hα provides useful information on the coupling between the acoustic sub-canopy atmosphere and the magnetized chromosphere.

show abstract

Localized sources of propagating acoustic waves in the solar photosphere

Cited by 94 publications

References 0 publications

Simulation of [CLC][ITAL]f[/ITAL][/CLC]- and [CLC][ITAL]p[/ITAL][/CLC]-Mode Interactions with a Stratified Magnetic Field Concentration

Simulation of [CLC][ITAL]f[/ITAL][/CLC]- and [CLC][ITAL]p[/ITAL][/CLC]-Mode Interactions with a Stratified Magnetic Field Concentration

Acoustic oscillations in the field-free, gravitationally stratified cavities under solar bipolar magnetic canopies

Power halo and magnetic shadow in a solar quiet region observed in the Hαline

Contact Info

Product

Resources

About