Small-scale magnetic field concentrations (magnetic elements) in the quiet Sun are believed to contribute to the energy budget of the upper layers of the Suns atmosphere, as they are observed to support a large number of MHD modes. In recent years, k
ink waves in magnetic elements were observed at different heights in the solar atmosphere, from the photosphere to the corona. However, the propagation of these waves has not been fully evaluated. Our aim is to investigate the propagation of kink waves in small magnetic elements in the solar atmosphere. We analysed spectropolarimetric data of high-quality and long duration of a photospheric quiet Sun region observed near the disk center with the spectropolarimeter CRISP at the Swedish Solar Telescope (SST), and complemented by simultaneous and co-spatial broad-band chromospheric observations of the same region. Our findings reveal a clear upward propagation of kink waves with frequency above $~2.6$ mHz. Moreover, the signature of a non-linear propagation process is also observed. By comparing photospheric to chromospheric power spectra, no signature of an energy dissipation is found at least at the atmospheric heights at which the data analysed originate. This implies that most of the energy carried by the kink waves (within the frequency range under study $< 17$ mHz) flows to upper layers in the Suns atmosphere.
The role of diffuse photospheric magnetic elements in the energy budget of the upper layers of the Suns atmosphere has been the recent subject of many studies. This was made possible by the availability of high temporal and spatial resolution observa
tions of the solar photosphere, allowing large numbers of magnetic elements to be tracked to study their dynamics. In this work we exploit a long temporal series of seeing-free magnetograms of the solar photosphere to study the effect of the turbulent convection in the excitation of kink oscillations in magnetic elements. We make use of the empirical mode decomposition technique (EMD) in order to study the transverse oscillations of several magnetic flux tubes. This technique permits the analysis of non-stationary time series like those associated to the horizontal velocities of these flux tubes which are continuously advected and dispersed by granular flows. Our primary findings reveal the excitation of low frequency modes of kink oscillations, which are sub-harmonics of a fundamental mode with a $7.6 pm 0.2$ minute periodicity. These results constitute a strong case for observational proof of the excitation of kink waves by the buffeting of the convection cells in the solar photosphere, and are discussed in light of their possible role in the energy budget of the upper Suns atmosphere.
Small scale magnetic fields (magnetic elements) are ubiquitous in the solar photosphere. Their interaction can provide energy to the upper atmospheric layers, and contribute to heat the solar corona. In this work, the dynamic properties of magnetic e
lements in the quiet Sun are investigated. The high number of magnetic elements detected in a supegranular cell allowed us to compute their displacement spectrum $langle(Delta r)^2rangleproptotau^gamma$ (being $gamma>0$, and $tau$ the time since the first detection), separating the contribution of the network (NW) and the internetwork (IN) regions. In particular, we found $gamma=1.27pm0.05$ and $gamma=1.08pm0.11$ in NW (at smaller and larger scales, respectively), and $gamma=1.44pm0.08$ in IN. These results are discussed in light of the literature on the topic, as well as the implications for the build up of the magnetic network.
A recent study carried out on high sensitivity SUNRISE/IMAX data has reported about the existence of areas of limited flux emergence in the quiet Sun. By exploiting an independent and longer (4 hours) data set acquired by HINODE/SOT, we further inves
tigate these regions by analysing their spatial distribution and relation with the supergranular flow. Our findings, while confirming the presence of these calm areas, also show that the rate of emergence of small magnetic elements is largely suppressed at the locations where the divergence of the supergranular plasma flows is positive. This means that the dead calm areas previously reported in literature are not randomly distributed over the solar photosphere but they are linked to the supergranular cells themselves. These results are discussed in the framework of the recent literature.
Recently, the availability of new high-spatial and -temporal resolution observations of the solar photosphere has allowed the study of the oscillations in small magnetic elements. Small magnetic elements have been found to host a rich variety of osci
llations detectable as intensity, longitudinal or transverse velocity fluctuations which have been interpreted as MHD waves. Small magnetic elements, at or below the current spatial resolution achieved by modern solar telescopes, are though to play a relevant role in the energy budget of the upper layers of the Suns atmosphere, as they are found to cover a significant fraction of the solar photosphere. Unfortunately, the limited temporal length and/or cadence of the data sets, or the presence of seeing-induced effects have prevented, so far, the estimation of the power spectra of kink-like oscillations in small magnetic elements with good accuracy. Motivated by this, we studied kink-like oscillations in small magnetic elements, by exploiting very long duration and high-cadence data acquired with the Solar Optical Telescope on board the Hinode satellite. In this work we present the results of this analysis, by studying the power spectral density of kink-like oscillations on a statistical basis. We found that small magnetic elements exhibit a large number of spectral features in the range 1-12 mHz. More interestingly, most of these spectral features are not shared among magnetic elements but represent a unique signature of each magnetic element itself.
The velocity field in the lower solar atmosphere undergoes strong interactions with magnetic fields. Many authors have pointed out that power is reduced by a factor between two and three within magnetic regions, depending on frequency, depth, the rad
ius and the magnetic strength of the flux tube. Many mechanisms have been proposed to explain the observations. In this work, SDO dopplergrams and magnetograms of 12 bipolar active regions ($beta$ARs) at a 45 second cadence, are used to investigate the relation between velocity fluctuations and magnetic fields. We show that there is an asymmetry within $beta$ARs, with the velocity oscillation amplitude being more suppressed in the leading polarities compared to the trailing polarities. Also, the strongest magnetic fields do not completely suppress the five-minute oscillation amplitude, neither in the spot innermost umbrae.
