Internal gravity waves have been observed in the Earth's atmosphere and oceans, on Mars and Jupiter, and in the Sun's atmosphere. Despite ample evidence for the existence of propagating gravity waves in the Sun's atmosphere, we still do not have a full understanding of their characteristics and overall role for the dynamics and energetics of the solar atmosphere. Here we present a new approach to study the propagation of gravity waves in the solar atmosphere. It is based on calculating the three-dimensional cross-correlation function between the vertical velocities measured at different heights. We apply this new method to a time series of co-spatial and co-temporal Doppler images obtained by SOHO/MDI and Hinode/SOT as well as to simulations of upward propagating gravity wave packets. We show some preliminary results and outline future developments.
Northumbria University（诺森比亚大学）；University College London, Mullard Space Science Laboratory（伦敦大学学院穆拉德空间科学实验室）；Donostia International Physics Center（圣塞巴斯蒂安国际物理中心）
The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares I: Modeling the Brightest NUV Footpoints in the X1 Solar Flare of 2014 March 29
Current post-processing techniques for the correction of atmospheric seeing in solar observations -- such as Speckle interferometry and Phase Diversity methods -- have limitations when it comes to their reconstructive capabilities of solar flare observations. This, combined with the sporadic nature of flares meaning observers cannot wait until seeing conditions are optimal before taking measurements, means that many ground-based solar flare observations are marred with bad seeing. To combat this, we propose a method for dedicated flare seeing correction based on training a deep neural network …
The Sun and sun-like stars commonly host the multi-million-Kelvin coronae and the 10,000-Kelvin chromospheres. These extremely hot gases generate X-ray and Extreme Ultraviolet emissions that may impact the erosion and chemistry of (exo)planetary atmospheres, influencing the climate and conditions of habitability. However, the mechanism of coronal and chromospheric heating is still poorly understood. While the magnetic field most probably plays a key role in driving and transporting energy from the stellar surface upwards, it is not clear if the atmospheric heating mechanisms of the Sun and act…
Large-scale Coronal Propagating Fronts in Solar Eruptions as Observed by the Atmospheric Imaging Assembly on Board the Solar Dynamics Observatory\,--\,An Ensemble Study
The formation of extremely hot outer atmospheres is one of the most prominent manifestations of magnetic activity common to the late-type dwarf stars, including the Sun. It is widely believed that these atmospheric layers, the corona, transition region, and chromosphere, are heated by the dissipation of energy transported upwards from the stellar surface by the magnetic field. This is signified by the spectral line fluxes at various wavelengths, scaled with power-law relationships against the surface magnetic flux over a wide range of formation temperatures, which are universal to the Sun and …
Pulse-beam heating of deep atmospheric layers triggering their oscillations and upwards moving shocks that can modulate the reconnection in solar flares
The Mg I b triplet and the 4571 Å line as diagnostics of stellar chromospheric activity
上下文在文献中，Mg I 4571三线态和b三线态被认为是太阳和恒星活动的诊断，因为它们是在低色球层形成的。目的。研究这四条谱线作为类太阳恒星色球活动诊断的潜力，通过改变大气模型和恒星参数，研究这些谱线的强度与当地大气变化的关系。方法.从Next-Gen光球模型出发，建立了包括光球、色球和过渡区的大气模型网格，求解了辐射转移，得到了合成轮廓，并与主序星、类太阳恒星（有效温度在4800-6400 K之间）、太阳重力和太阳金属丰度的观测光谱进行了比较。结果我们发现，Mg I 4571的线是显着敏感的局部变化，在大气模式周围的最低温度。相反，b三重态的谱线对当地大气结构的变化没有明显的响应。
Coronal loops form the basic building blocks of the magnetically closed solar corona yet much is still to be determined concerning their possible fine-scale structuring and the rate of heat deposition within them. Using an improved multi-stranded loop model to better approximate the numerically challenging transition region, this paper examines synthetic NASA Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) emission simulated in response to a series of prescribed spatially and temporally random, impulsive and localised heating events across numerous sub-loop elements with …
Analysis of Solar Activity and Atmospheric Pressure Competition Effects on Cosmic Radiation Events
本文基于一个监测次级宇宙线强度的地基μ子探测器系统Hierarchy（The High School Project on Astro Physics Research with宇宙射线），分析了太阳活动特征参数以及太阳活动和大气压力的竞争效应对宇宙辐射记录的影响。我们收集的数据来自位于荷兰阿姆斯特丹科学园Nikhef的No.501 Hierarchy站（52.3558963°N，4.9509827°E，海拔56.18 m）。通过比较太阳耀斑数、太阳黑子相对数和探测器计数率，证实了太阳活动与近地宇宙线强度之间的普遍关系。气压效应被认为是对事件数量的修正。此外，还提出了宇宙线强度与太阳黑子群的数量、面积和纬度等太阳活动特征参数之间关系的新的经验公式。对于太阳活动和大气压力的竞争效应，我们发现探测器对太阳黑子数的灵敏度存在一个阈值。在阈值以上，探测器对大气压力比对太阳活动更敏感。揭示了太阳活动和大气压力竞争对事件率的影响，为实时监测空间天气提供了一种新的途径，也为太阳活动短期预报的研究提供了新的思路。
The suitability of solar pores as magnetic wave guides has been a key topic of discussion in recent years. Here we present observational evidence of propagating magnetohydrodynamic wave activity in a group of five photospheric solar pores. Employing data obtained by the Facility Infrared Spectropolarimeter at the Dunn Solar Telescope, oscillations with periods on the order of 5 minutes were detected at varying atmospheric heights by examining Si I 10827 Å line bisector velocities. Spectropolarimetric inversions, coupled with the spatially resolved root mean square bisector velocities, allowed …
Spicules are rapidly evolving fine-scale jets of magnetized plasma in the solar chromosphere. It remains unclear how these prevalent jets originate from the solar surface and what role they play in heating the solar atmosphere. Using the Goode Solar Telescope at the Big Bear Solar Observatory, we observed spicules emerging within minutes of the appearance of opposite-polarity magnetic flux around dominant-polarity magnetic field concentrations. Data from the Solar Dynamics Observatory showed subsequent heating of the adjacent corona. The dynamic interaction of magnetic fields (likely due to ma…
Red-shifted components of chromospheric emission lines in the hard X-ray impulsive phase of solar flares have recently been studied through their 30 s evolution with the high resolution of IRIS. Radiative-hydrodynamic flare models show that these redshifts are generally reproduced by electron-beam generated chromospheric condensations. The models produce large ambient electron densities, and the pressure broadening of hydrogen Balmer series should be readily detected in observations. To accurately interpret upcoming spectral data of flares with the DKIST, we incorporate non-ideal, non-adiabati…
An isolated, isothermal, and wide magnetic flux tube embedded either in the solar chromosphere or in the lower solar corona is considered, and the propagation of linear torsional Alfv'en waves is investigated. It is shown that the wideness of the tube leads to a new cutoff frequency, which is a local quantity that gives the conditions for the wave propagation at different atmospheric heights. The cutoff is used to establish the ranges of frequencies for the propagating and reflected waves in the solar chromosphere and lower solar corona. The obtained results are compared to those previously ob…
Context: In the context of the solar coronal heating problem, one possible explanation for the high coronal temperature is the release of energy by magnetohydrodynamic (MHD) waves. The energy transfer is believed to be possible, among others, by the development of the Kelvin-Helmholtz instability (KHI) in coronal loops. Aims: Our aim is to determine if standing slow waves in solar atmospheric structures such as coronal loops, and also prominence threads, sunspots, and pores, can trigger the KHI due to the oscillating shear flow at the structure's boundary. Methods: We used linearized nonstatio…
Stellar models often use relations between the temperature $T$ and optical depth $τ$ to evaluate the structure of their optically-thin outer layers. We fit a novel analytic function to the Hopf function $q(τ)$ of a radiation-coupled hydrodynamics simulation of near-surface convection with solar parameters by Trampedach et al. (2014). The fit is accurate to within 0.82 per cent for the solar simulation and to within 13 per cent for all the simulations that are not on either the low-temperature or low-gravity edges of the grid of simulations.
A diagnosis of the Ar densities measured by the Neutral Gas and Ion Mass Spectrometer aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) and the temperatures derived from these densities shows that solar activity, solar insolation, and the lower atmospheric dust are the dominant forcings of the Martian thermosphere. A methodology, based on multiple linear regression analysis, is developed to quantify the contributions of the dominant forcings to the densities and temperatures. The results of the present study show that a 100 sfu (solar flux units) change in the solar activity results in…
Thermal Diagnostics with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory: A Validated Method for Differential Emission Measure Inversions
Determining accurate velocity measurements from observations of the Sun is of vital importance to solar physicists who are studying the wave dynamics in the solar atmosphere. Weak chromospheric absorption lines, due to dynamic events in the solar atmosphere, often consist of multiple spectral components. Isolating these components allows for the velocity field of the dynamic and quiescent regimes to be studied independently. However, isolating such components is particularly challenging due to the wide variety of spectral shapes present in the same dataset. MCALF provides a novel method and in…
Discussion on the vanishment of solar atmospheric structures during magnetic reconnection
School of Physics, Anhui University（安徽大学物理学院）；School of Materials Science and Engineering, Anhui University（安徽大学材料科学与工程学院）；School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory for Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education（教育部现代天文学与天体物理学重点实验室（南京大学））
The Matuyama-Brunhes reversal of Earth's magnetic dipole field took place 0.78 Ma ago, and detailed temporally resolved paleomagnetic data are available for this period. A geomagnetic reversal is expected to impact the cosmic ray flux, which in turn might impact atmospheric ionization rates. In this study a model that yields atmospheric ionization for the entire globe based on an input magnetic field is presented. Taking the time dependent paleomagnetic data as input, a 3D time series of the atmospheric ionization rates during the reversal is produced. We show, that as the dipole field weakens…
