We studied chromospheric oscillations using Atacama Large millimeter and sub-millimeter Array (ALMA) time-series of interferometric observations of the quiet Sun obtained at 3 mm with a 2-s cadence and a spatial resolution of a few arcsec. The same analysis, over the same fields of view and for the same intervals, was performed for simultaneous Atmospheric Imaging Assembly (AIA) image sequences in 1600 A. Spatially-resolved chromospheric oscillations at 3 mm, with frequencies of $ 4.2 +- 1.7$ mHz are observed in the quiet Sun, in both cell and network. The coherence length-scale of the oscillations is commensurate with the spatial resolution of our ALMA observations. Brightness-temperature fluctuations in individual pixels could reach up to a few hundred K, while the spatially averaged power spectral densities yield rms in the range ~ 55-75 K, i.e., up to ~ 1 % of the averaged brightness temperatures and exhibit a moderate increase towards the limb. For AIA 1600 A, the oscillation frequency is 3.7 +- 1.7 mHz. The relative rms is up to 6 % of the background intensity, with a weak increase towards disk center (cell, average). ALMA 3 mm time-series lag AIA 1600 A by ~ 100 s, which corresponds to a formation-height difference of ~ 1200 km. The ALMA oscillations that we detected exhibit higher amplitudes than those derived from the lower (~ 10 arcsec) resolution observations at 3.5 mm by White et al. (2006). Chromospheric oscillations are, therefore, not fully resolved at the length-scale of the chromospheric network, and possibly not even at the spatial resolution of our ALMA observations. Any study of transient brightenings in the mm-domain should take into account the oscillations.
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of a quiet-Sun region at a wavelength of 3 mm, obtained during the first solar ALMA cycle on April 27, 2017, and compare them with available chromospheric observations in the UV and visible as well as with photospheric magnetograms. ALMA images clearly reveal the presence of distinct particularly dark/cool areas in the millimeter maps having temperatures as low as 60% of the normal quiet Sun at 3 mm, which are not seen in the other data. We speculate that ALMA is sensing cool chromospheric gas, whose presence had earli…
We propose and employ a novel empirical method for determining chromospheric plage regions, which seems to better isolate plage from its surrounding regions compared to other methods commonly used. We caution that isolating plage from its immediate surroundings must be done with care in order to successfully mitigate statistical biases that, for instance, can impact quantitative comparisons between different chromospheric observables. Using this methodology, our analysis suggests that 1.25 mm wavelength free-free emission in plage regions observed with ALMA/Band6 may not form in the low chromo…
We present the first high-resolution, simultaneous observations of the solar chromosphere in the optical and millimeter wavelength ranges, obtained with ALMA and the IBIS instrument at the Dunn Solar Telescope. In this paper we concentrate on the comparison between the brightness temperature observed in ALMA Band 3 (3 mm; 100 GHz) and the core width of the H$α$ 656.3 nm line, previously identified as a possible diagnostic of the chromospheric temperature. We find that in the area of plage, network and fibrils covered by our FOV the two diagnostics are well correlated, with similar spatial stru…
We report detection of oscillations in brightness temperature, size, and horizontal velocity of three small bright features in the chromosphere of a plage/enhanced-network region. The observations, which were taken with high temporal resolution (i.e., 2-sec cadence) with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 3 (centred at 3 mm; 100 GHz), exhibit three small-scale features with oscillatory behaviour with different, but overlapping, distributions of period on the order of, on average, $90 \pm 22$ s, $110 \pm 12$ s and $66 \pm 23$ s, respectively. We find anti-correlatio…
We present observations of the solar chromosphere obtained simultaneously with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Interface Region Imaging Spectrograph (IRIS). The observatories targeted a chromospheric plage region of which the spatial distribution (split between strongly and weakly magnetized regions) allowed the study of linear-like structures in isolation, free of contamination from background emission. Using these observations in conjunction with a radiative magnetohydrodynamic 2.5D model covering the upper convection zone all the way to the corona that consid…
We study chromospheric oscillations including umbral flashes and running penumbral waves in a sunspot of active region (AR) using scanning spectroscopy in H-alpha and Ca II 8542A, with the Fast Imaging Solar Spectrograph (FISS) at the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. A bisector method is applied to spectral observations to construct chromospheric Doppler velocity maps. Temporal sequence analysis of these shows enhanced high-frequency oscillations inside the sunspot umbra in both lines. Their peak frequency gradually decreases outward from the umbra. The oscillation …
We analyse the chromospheric Doppler velocity oscillations in a sunspot using the high resolution spectral observations obtained from the Fast Imaging Solar Spectrograph(FISS) of the New Solar Telescope at the Big Bear Solar Observatory. The Doppler velocity maps are constructed from the bisectors of the spectral observations. The time series analysis of Doppler velocity maps show enhanced power in the sunspot umbra at higher frequencies and in the penumbra at lower frequencies. We find that the peak power frequency decreases gradually from the umbra to outward.
Chromospheric inferences rely on the interpretation of spectral lines that are formed under Non-Local Thermodynamic Equilibrium (NLTE) conditions. In the presence of oscillations, changes in the opacity impact the response height of the spectral lines and hinder the determination of the real properties of the fluctuations. We aim to explore the relationship between the chromospheric oscillations inferred by NLTE inversion codes and the waves' intrinsic fluctuations in velocity and temperature. Numerical simulations of wave propagation in an umbra have been computed with the code MANCHA. The NL…
We developed an efficient algorithm integrated in our 3D modeling tool, GX Simulator (Nita et al. 2015), allowing quick computation of the synthetic intensity and polarization maps of solar active regions (AR) in the ALMA spectral range. The algorithm analyzes the photospheric input (white light and magnetogram) to classify a given photospheric pixel to belong to a given photospheric structure. Then, a 1D chromospheric model (Fontenla et al. 2009) is added on top of each pixel, which forms a chromospheric model of the AR. Next step is computation of the mm and sub-mm emission produced from thi…
An analysis of line-of-sight velocity oscillation in nine solar faculae was undertaken with the aim of studying of phase relations between chromosphere (He i 10830 A line) and photosphere (Si i 10827 A line) five-minute oscillations. We found that time lag of the chromospheric signal relative to photospheric one varies from -12 to 100 seconds and is about 50 seconds on average.We assume that the small observed lag can have three possible explanations: i) convergence of formation levels of He i 10830 A and Si i 10827 A in faculae; ii) significant increase of five-minute oscillation propagation …
The precise mechanisms that provide the non-radiative energy for heating the chromosphere and the corona of the Sun and other stars are at the focus of intense contemporary research. Observations at submm/mm wavelengths are particularly useful to obtain information about the run of the temperature in the upper atmosphere of Sun-like stars. We used ALMA to study the chromospheric emission of the aCen binary system in all six available frequency bands during Cycle2 in 2014/15. Since ALMA is an interferometer, the multi-telescope array is particularly suited for the observation of point sources. …
Sunspot umbrae show a change in the dominant period of their oscillations from five minutes in the photosphere to three minutes in the chromosphere. In this paper, we explore the two most popular models proposed to explain the three-minute oscillations: the chromospheric acoustic resonator and the propagation of waves with frequency above the cutoff value directly from lower layers. We employ numerical simulations of wave propagation from the solar interior to the corona. Waves are driven by a piston at the bottom boundary. We have performed a parametric study of the measured chromospheric pow…
In this investigation oscillation periods in Mg II k line intensity, brightness temperature, and Doppler velocity obtained above Magnetic Bright Points (MBPs) are investigated. For that purpose, data from the Interface Region Imaging Spectrometer (IRIS) observing the higher chromosphere and transition region (TR) were analysed together with imaging and magnetogram data obtained by Solar Dynamics Observatory (SDO). The MBPs were identified in combining Si IV 1403 A Slit Jaw Images (SJIs) with the magnetogram information from the Heliospheric and Magnetic Imager (HMI). A time-slice analysis foll…
We present a statistical analysis of power distribution of oscillations in a plage region in active region NOAA AR12651, observed jointly with ALMA (Atacama Large Millimeter/Submillimeter Array), IRIS (Interface Region Imaging Spectrograph), and SDO (Solar Dynamics Observatory). We employ coordinated ALMA Band-6 (1.25 mm) brightness temperature maps, IRIS Slit-Jaw Images in 2796 Å passband, and observations in six passbands (1600 Å, 304 Å, 131 Å, 171 Å, 193 Å and 211 Å) of AIA (Atmospheric Imaging Assembly) onboard SDO. We perform Lomb-Scargle transforms to study the distribution of oscillatio…
Sunspots host a large variety of oscillatory phenomena, whose properties depend on the nature of the wave modes and the magnetic and thermodynamic structure of the spot. Umbral chromospheric oscillations exhibit significant differences compared to their photospheric counterparts. They show an enhanced power and a shorter dominant period, from waves with an amplitude of a few hundred meters per second in the five-minute band at the photosphere, to amplitudes of several kilometers per second in the three-minute band at the chromosphere. Various models have been proposed to explain this behaviour…
Aims. We use advanced 3D NLTE radiative magnetohydrodynamic simulations of the solar atmosphere to carry out detailed tests of chromospheric diagnostics at millimeter and submillimeter wavelengths. Methods. We focused on the diagnostics of the thermal structure of the chromosphere in the wavelength bands from 0.4 mm up to 9.6 mm that can be accessed with the Atacama Large Millimeter/Submillimeter Array (ALMA) and investigated how these diagnostics are affected by the instrumental resolution. Results. We find that the formation height range of the millimeter radiation depends on the location in…
A number of recent investigations have revealed that transverse waves are ubiquitous in the solar chromosphere. The vast majority of these have been reported in limb spicules and active region fibrils. We investigate long-lived, quiet Sun, on-disk features such as chromospheric mottles (jet-like features located at the boundaries of supergranular cells) and their transverse motions. The observations were obtained with the Rapid Oscillations in the Solar Atmosphere (ROSA) instrument at the Dunn Solar Telescope. The dataset comprises simultaneous imaging in the H$α$ core, Ca II K, and G band of …
The strongest known correspondence between ALMA 3mm emission and other solar observations is between the H-alpha line width and 3 mm brightness temperature, while the typical 3-5min p-mode oscillations found in many chromospheric diagnostics are often lacking from ALMA Band 3 and 6 observations. We study these issues using a publicly available data set of weak network flux near disk center at time SOL2017-03-17T15:42-16:45 that includes IBIS H-alpha and ALMA 3 mm data series. We confirm the correlation between the H-alpha line width and the 3 mm temperature, but find a different slope between …
Solar observations at sub-mm, mm and cm wavelengths offer a straightforward diagnostic of physical conditions in the solar atmosphere because they yield measurement of brightness temperature which, for optically thick features, equals intrinsic temperature - much unlike solar diagnostics in other spectral ranges. The Atacama Large Millimeter and sub-millimeter Array (ALMA) has therefore opened a new, hitherto underexplored, spectral window for studying the enigmatic solar chromosphere. In this review we discuss initial ALMA studies of the quiet chromosphere that used both single-dish and compa…
In this Letter we report the detection of chromospheric 3-minute oscillations in disk-integrated EUV irradiance observations during a solar flare. A wavelet analysis of detrended Lyman-alpha (from GOES/EUVS) and Lyman continuum (from SDO/EVE) emission from the 2011 February 15 X-class flare (SOL2011-02-15T01:56) revealed a $\sim$3-minute period present during the flare's main phase. The formation temperature of this emission locates this radiation to the flare's chromospheric footpoints, and similar behaviour is found in the SDO/AIA 1600Å and 1700Å channels, which are dominated by chromospheri…
Helioseismic Signature of Chromospheric Downflows in Acoustic Travel-Time Measurements from Hinode
我们报告的一个签名的色球下降流在两个新兴的通量地区检测的时间距离日震学分析。我们使用Hinode/SOT获得的Ca II H线的色球强度振荡数据和Fe I 557.6nm线的光球多普勒数据进行分析。通过互相关的钙II振荡信号，我们已经检测到了一个旅行时间异常的plage地区，向外旅行时间比向内旅行时间短0.5-1分钟。然而，这样的异常是不存在的Fe I数据。这些结果可以解释为低色球层下行流的证据。下降速度估计低于10 km/s。这一结果表明，一个新的可能性研究色球流的时距分析。
Using data obtained by the high temporal and spatial resolution Rapid Oscillations in the Solar Atmosphere (ROSA) instrument on the Dunn Solar Telescope, we investigate at an unprecedented level of detail transverse oscillations in chromospheric fine structures near the solar disk center. The oscillations are interpreted in terms of propagating and standing magnetohydrodynamic kink waves. Wave characteristics including the maximum transverse velocity amplitude and the phase speed are measured as a function of distance along the structure's length. Solar magneto-seismology is applied to these m…
Waves and oscillations are important solar phenomena, not only because they can propagate and dissipate energy in the chromosphere, but also because they carry information about the structure of the atmosphere in which they propagate. The nature of the three-minute oscillations observed in the umbral region of sunspots is considered to be an effect of propagation of magnetohydrodynamic (MHD) waves upward from below the photosphere. We present a study of sunspot oscillations and wave propagation in NOAA AR 12470 using an approximately one-hour long data set acquired on 2015 December 17 by the A…
This study aims to provide further evidence for the potential influence of the global solar magnetic field on localised chromospheric jets, the macrospicules (MS). To find a connection between the long-term variation of properties of MS and other solar activity proxies, including e.g. the temporal variation of the frequency shift of solar global oscillations, sunspot area, etc., a database overarching seven years of observations was built up. This database contains 362 MS, based on observations at the 30.4 nm of the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SD…
ALMA will open a new chapter in the study of the Sun by providing a leap in spatial resolution and sensitivity compared to currently available mm wave- length observations. In preparation of ALMA, we have carried out a large number of observational tests and state-of-the-art radiation MHD simulations. Here we review the best available observations of the Sun at millimeter wavelengths.Using state of the art radiation MHD simulations of the solar atmosphere we demonstrate the huge potential of ALMA observations for uncovering the nature of the solar chromosphere. We show that ALMA will not only …
The Atacama Large Millimeter/submillimeter Array offers an unprecedented view of our Sun at sub-/millimeter wavelengths. The high spatial, temporal, and spectral resolution facilitates the measurement of gas temperatures and magnetic fields in the solar chromosphere with high precision. The anticipated results will revolutionize our understanding of the solar atmosphere and may in particular result in major steps towards solving the coronal heating problem. Based on state-of-the-art 3D radiation magnetohydrodynamic simulations, we calculate the emergent continuum intensity (and thus brightness…
Chromospheric wave activity around flares and filaments has been a research focus for years, and could provide indirect measurements of local conditions that are not otherwise accessible. One interesting observed phenomenon is oscillations in filaments, activated by distant flares and the large-scale waves they produce. Characteristics of these oscillations, such as periods, amplitudes, and lifetimes, can provide unique information about the filament. We measure oscillation properties in flares and filaments from H-alpha chromospheric data using a new method that provides important spatial and…
Oscillations in the solar atmosphere have long been observed in quiet conditions, and increasingly also in data taken during solar flares. The chromosphere is known for its 3-minute signals, which are particularly strong over sunspot umbrae. These signals are thought to be driven by photospheric disturbances and their periods determined by the chromosphere's acoustic cut-off frequency. A small number of observations have shown the chromospheric 3-minute signals to be affected by energetic events such as solar flares, however the link between flare activity and these oscillatory signals remains…
A study of the propagation of magnetoacoustic waves in small-scale magnetic fields using solar photospheric and chromospheric Dopplergrams: HMI/SDO and MAST observations
We studied oscillations related to flare SOL2012-09-21T02:19 in the transition region and chromosphere based on Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Solar Dynamics Observatory (SDO) data, as well as data from a ground-based observatory. We found that 2-minute oscillations triggered by the flare first appeared in the RHESSI channels then subsequently showed up in the SDO 171 Å and 304 Å channels and after that in the chromospheric He I 10830 Å line. The delay of the chromospheric signal compared to the RHESSI signal is 7 minutes, which indicates that the wave pertur…
Oscillations in sunspot umbrae exhibit remarkable differences between the photosphere and chromosphere. We evaluate two competing scenarios proposed for explaining those observations: a chromospheric resonant cavity and waves traveling from the photosphere to upper atmospheric layers. We have employed numerical simulations to analyze the oscillations in both models. They have been compared with observations in the low (Na I D2) and high (He I 10830 Å) chromosphere. The nodes of the resonant cavity can be detected as phase jumps or power dips, although the identification of the latter is not su…
We have analyzed H-alpha intensity images obtained at a 1 minute cadence with the Global Oscillation Network Group (GONG) system to investigate the properties of oscillations in the 0-8 mHz frequency band at the location and time of strong M- and X-class flares. For each of three sub-regions within two flaring active regions, we extracted time series from multiple distinct positions, including the flare core and quieter surrounding areas. The time series were analyzed with a moving power map analysis to examine power as a function of frequency and time. We find that, in the flare core of all t…
In the past few years, the ALMA radio telescope has become available for solar observations. ALMA diagnostics of the solar atmosphere are of high interest because of the theoretically expected linear relationship between the brightness temperature at mm wavelengths and the local gas temperature in the solar atmosphere. Key for the interpretation of solar ALMA observations is understanding where in the solar atmosphere the ALMA emission originates. Recent theoretical studies have suggested that ALMA bands at 1.2 (band 6) and 3 mm (band 3) form in the middle and upper chromosphere at significant…
Using high resolution off-band \ha\ data from the New Solar Telescope and Morlet wavelet analysis technique, we analyzed transverse motions of type II spicules observed near the North Pole of the Sun. Our new findings are that i) some of the observed type II spicules display kink or an inverse "Y" features, suggesting that their origin may be due to magnetic reconnection, and ii) type II spicules tend to display coherent transverse motions/oscillations. Also, the wavelet analysis detected significant presence of high frequency oscillations in type II spicules, ranging from 30 to 180 s with the…
We use state-of-the-art, three-dimensional non-local thermodynamic equilibrium (non-LTE) radiative magnetohydrodynamic simulations of the quiet solar atmosphere to carry out detailed tests of chromospheric magnetic field diagnostics from free-free radiation at millimeter and submillimeter wavelengths (mm/submm). The vertical component of the magnetic field was deduced from the mm/submm brightness spectra and the degree of circular polarization synthesized at millimeter frequencies. We used the frequency bands observed by the Atacama Large Millimeter/Submillimeter Array (ALMA) as a convenient r…
By direct measurements of the gas temperature, the Atacama Large Millimeter/sub-millimeter Array (ALMA) has yielded a new diagnostic tool to study the solar chromosphere. Here we present an overview of the brightness-temperature fluctuations from several high-quality and high-temporal-resolution (i.e., 1 and 2 sec cadence) time series of images obtained during the first two years of solar observations with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz) and 1.25 mm (239 GHz), respectively. The various datasets represent solar regions with different levels of magnetic flux. We perf…
We present an overview of high resolution quiet Sun observations, from disk center to the limb, obtained with the Atacama Large mm and sub-mm Array (ALMA) at 3 mm. Seven quiet Sun regions were observed with resolution of up to 2.5" by 4.5". We produced both average and snapshot images by self-calibrating the ALMA visibilities and combining the interferometric images with full disk solar images. The images show well the chromospheric network, which, based on the unique segregation method we used, is brighter than the average over the fields of view of the observed regions by $\sim 305$ K while …
We present the first high-resolution Atacama Large Millimeter/Submillimeter Array (ALMA) observations of a sunspot at wavelengths of 1.3 mm and 3 mm, obtained during the solar ALMA Science Verification campaign in 2015, and compare them with the predictions of semi-empirical sunspot umbral/penumbral atmosphere models. For the first time millimeter observations of sunspots have resolved umbral/penumbral brightness structure at the chromospheric heights, where the emission at these wavelengths is formed. We find that the sunspot umbra exhibits a radically different appearance at 1.3 mm and 3 mm,…
A magnetohydrodynamic model that includes a complete electrical conductivity tensor is used to estimate conditions for photospherically driven, linear, non-plane Alfvenic oscillations extending from the photosphere to the lower corona to drive a chromospheric heating rate due to Pedersen current dissipation that is comparable to the net chromospheric net radiative loss of $\sim 10^7$ ergs-cm$^{-2}$-sec$^{-1}$. The heating rates due to electron current dissipation in the photosphere and corona are also computed. The wave amplitudes are computed self-consistently as functions of an inhomogeneous…
Images of the Sun at millimeter wavelengths obtained by ALMA show a significant correspondence with the magnetograms. In this paper, we investigate this correspondence by comparing ALMA full-disk solar image taken at 1.2 mm with a SDO/HMI magnetogram and analyze their correlation. It is found that chromospheric network and active regions show a positive correlation where brightness temperature is increasing with the line-of-sight magnetic field strength, while sunspots have a negative correlation. Quiet Sun regions do not show any dependence of the brightness temperature with the magnetic fiel…
On September 21, 2012, we carried out spectral observations of a solar facula in the Si I 10827 Å, He I 10830 Å, and Hα spectral lines. Later, in the process of analyzing the data, we found a small-scale flare in the middle of the time series. Due to an anomalous increase in the absorption of the He I 10830 Å line, we identified this flare as a negative flare. The aim of this paper is to study the influence of the negative flare on the oscillation characteristics in the facular photosphere and chromosphere. We measured line-of-sight (LOS) velocity and intensity of all the three lines as well a…
The Atacama Large Millimeter/sub-millimeter Array (ALMA) has provided us with an excellent diagnostic tool for studies of the dynamics of the Solar chromosphere, albeit through a single receiver band at one time presently. Each ALMA band consists of four sub-bands that are comprised of several spectral channels. To date, however, the spectral domain has been neglected in favour of ensuring optimal imaging, so that time-series observations have been mostly limited to full-band data products, thereby limiting studies to a single chromospheric layer. Here, we report the first observations of a dy…
The data of ground-based telescopes of Global Oscillation Network Group (GONG) obtained in the H-alpha line provide an opportunity to study the long-period oscillations of chromospheric filaments (quiescent prominence). For the first time, on the base of time-series of 5 days duration, combined from the observations of three observatories of the GONG, a new ultra-low mode, with period between 20 and 30 hours, was reliably detected in oscillations of a long-lived dark filament on the solar disc.
We report the discovery of a brightness enhancement in the center of a large sunspot umbra at a wavelength of 3 mm using the Atacama Large Millimeter/sub-millimeter Array (ALMA). Sunspots are amongst the most prominent features on the solar surface, but many of their aspects are surprisingly poorly understood. We analyzed a λ=3 mm (100 GHz) mosaic image obtained by ALMA, which includes a large sunspot within the active region AR12470 on December 16, 2015. The 3 mm map has a field-of-view and spatial resolution, which is the highest spatial-resolution map of an entire sunspot in this frequency …
Polar brightening of the Sun at radio frequencies has been studied for almost fifty years and yet a disagreement persists between solar atmospheric models and observations. Some observations reported brightening values much smaller than the expected values obtained from the models, with discrepancies being particularly large at millimeter wavelengths. New clues to calibrate the atmospheric models can be obtained with the advent of the Atacama Large Millimeter/submillimeter Array (ALMA) radio interferometer. In this work, we analyzed the lower limit of the polar brightening observed at 100 and …
Solar chromospheric observations of sunspot umbrae offer an exceptional view of magneto-hydrodynamic wave phenomena. In recent years, a wealth of wave signatures related to propagating magneto-acoustic modes have been presented, which demonstrate complex spatial and temporal structuring of the wave components. Theoretical modelling has demonstrated how these ubiquitous waves are consistent with an m=0 slow magneto-acoustic mode, which are excited by trapped sub-photospheric acoustic (p-mode) waves. However, the spectrum of umbral waves is broad, suggesting that the observed signatures represen…
We present observational constraints on the solar chromospheric heating contribution from acoustic waves with frequencies between 5 and 50 mHz. We utilize observations from the Dunn Solar Telescope in New Mexico complemented with observations from the Atacama Large Millimeter Array collected on 2017 April 23. The properties of the power spectra of the various quantities are derived from the spectral lines of Ca II 854.2 nm, H I 656.3 nm, and the millimeter continuum at 1.25 mm and 3 mm. At the observed frequencies the diagnostics almost all show a power law behavior, whose particulars (slope, …
Using Atacama Large Millimeter/submillimeter Array (ALMA) observations of the quiet Sun at 1.26 and 3 mm, we study spatially resolved oscillations and transient brightenings, i.e. small, weak events of energy release. Both phenomena may have a bearing on the heating of the chromosphere. At 1.26 mm, in addition to power spectra of the original data, we degraded the images to the spatial resolution of the 3 mm images and used fields of view of equal area for both data sets. The detection of transient brightenings was made after the oscillations were removed. At both frequencies we detected p-mod…
3-minute oscillations in the chromosphere are attributed to both slow magnetoacoustic waves propagating from the photosphere, and to oscillations generated within the chromosphere itself at its natural frequency as a response to a disturbance. Here we present an investigation of the spatial and temporal behavior of the chromospheric 3-minute oscillations before, during, and after the SOL2011-02-15T01:56 X2.2 flare. Observations in ultraviolet emission centered on 1600 and 1700 Angstroms obtained at 24- second cadence from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory…
We analyse sunspot oscillations using Interface Region Imaging Spectrograph (IRIS) slit-jaw and spectral data and narrow-band chromospheric images from the New Solar Telescope (NST) for the main sunspot in NOAA AR 11836. We report that the difference between the shock arrival times as measured the Mg II k 2796.35Å and Si IV 1393.76Å line formation levels changes during the observed period and peak-to-peak delays may range from 40~s to zero. The intensity of chromospheric shocks also displays a long term (about 20~min) variations. NST's high spatial resolution \ha\ data allowed us to conclude t…
Quiescent filaments appear as absorption features on the solar disk when observed in chromospheric lines and at continuum wavelengths in the millimeter (mm) range. Active region (AR) filaments are their small-scale, low-altitude analogues, but they could not be resolved in previous mm observations. This spectral diagnostic can provide insight into the details of the formation and physical properties of their fine threads, which are still not fully understood. Here, we shed light on the thermal structure of an AR filament using high-resolution brightness temperature ($T_{\rm b}$) maps taken wit…
We present both coronal and chromospheric observations of large-scale disturbances associated with a major solar eruption on 2005 September 7. In GOES/SXI, arclike coronal brightenings are recorded propagating in the southern hemisphere. The SXI front shows an initially constant speed of 730 km s$^{-1}$ and decelerates later on, and its center is near the central position angle of the associated coronal mass ejection (CME) but away from flare site. Chromospheric signatures of the disturbances are observed in both MLSO/PICS H$α$ and MLSO/CHIP He I 10830 Å, and can be divided into two parts. The…
The Atacama Large Millimeter/submillimeter Array (ALMA) offers new diagnostic possibilities that complement other commonly used diagnostics for the study of our Sun. In particular, ALMA's ability to serve as an essentially linear thermometer of the chromospheric gas at unprecedented spatial resolution at millimetre wavelengths and future polarisation measurements have great diagnostic potential. Solar ALMA observations are therefore expected to contribute significantly to answering long-standing questions about the structure, dynamics and energy balance of the outer layers of the solar atmosph…
