We present the second part of a project on the global energetics of solar flares and CMEs that includes about 400 M- and X-class flares observed with AIA/SDO during the first 3.5 years of its mission. In this Paper II we compute the differential emission measure (DEM) distribution functions and associated multi-thermal energies, using a spatially-synthesized Gaussian DEM forward-fitting method. The multi-thermal DEM function yields a significantly higher (by an average factor of $\approx 14$), but more comprehensive (multi-)thermal energy than an isothermal energy estimate from the same AIA data. We find a statistical energy ratio of $E_{th}/E_{diss} \approx 2\%-40\%$ between the multi-thermal energy $E_{th}$ and the magnetically dissipated energy $E_{diss}$, which is an order of magnitude higher than the estimates of Emslie et al.~2012. For the analyzed set of M and X-class flares we find the following physical parameter ranges: $L=10^{8.2}-10^{9.7}$ cm for the length scale of the flare areas, $T_p=10^{5.7}-10^{7.4}$ K for the DEM peak temperature, $T_w=10^{6.8}-10^{7.6}$ K for the emission measure-weighted temperature, $n_p=10^{10.3}-10^{11.8}$ cm$^{-3}$ for the average electron density, $EM_p=10^{47.3}-10^{50.3}$ cm$^{-3}$ for the DEM peak emission measure, and $E_{th}=10^{26.8}-10^{32.0}$ erg for the multi-thermal energies. The deduced multi-thermal energies are consistent with the RTV scaling law $E_{th,RTV} = 7.3 \times 10^{-10} \ T_p^3 L_p^2$, which predicts extremal values of $E_{th,max} \approx 1.5 \times 10^{33}$ erg for the largest flare and $E_{th,min} \approx 1 \times 10^{24}$ erg for the smallest coronal nanoflare. The size distributions of the spatial parameters exhibit powerlaw tails that are consistent with the predictions of the fractal-diffusive self-organized criticality model combined with the RTV scaling law.
MQ Dra is a strongly magnetic Cataclysmic Variable whose white dwarf accretes material from its secondary star through a stellar wind at a low rate. TESS observations were made of MQ Dra in four sectors in Cycle 2 and show a short duration, high energy flare (~10^35 erg) which has a profile characteristic of a flare from the M5V secondary star. This is one of the few occasions where an energetic flare has been seen from a Polar. We find no evidence that the flare caused a change in the light curve following the event and consider whether a coronal mass ejection was associated with the flare. W…
We report the observation of non-stationary Quasi-Periodic Pulsations (QPPs) in high-energy particles during the impulsive phase of an X4.8 flare on 2002 July 23 (SOL2002-07-23T00:35). The X4.8 flare was simultaneously measured by the Reuven Ramaty High Energy Solar Spectroscopic Imager, Nobeyama Radio Polarimeters, and Nobeyama Radioheliograph. The quasi-period of about 50 s, determined by the wavelet transform, is detected in the Gamma-ray line emission. Using the same method, a quasi-period of about 90 s is found in Gamma-ray continuum, hard X-ray (HXR) and radio emissions during almost the…
Solar energetic particles (SEPs), including protons and heavy ions, are believed to be accelerated either by CME shock or by magnetic reconnection. The latter also produces solar flares, in which the white light flares (WLFs) are among the most energetic ones. Magnetic reconnections occur in the corona and the accelerated particles propagate both downward and upward along the magnetic loops. The former is the source of flare emission and the latter is thought to be SEPs. Therefore, a comparison between flare emission and SEP events provides valuable constraint in determining the acceleration s…
White-light (WL) flares have been observed and studied more than a century since the first discovery. However, some fundamental physics behind the brilliant emission remains highly controversial. One of the important facts in addressing the flare energetics is the spatialtemporal correlation between the white-light emission and the hard X-ray radiation, presumably suggesting that the energetic electrons are the energy sources. In this study, we present a statistical analysis of 25 strong flares (?greater than or equal to M5) observed simultaneously by the Helioseismic and Magnetic Imager (HMI)…
In this article, we measure the mean magnetic shear from the morphological evolution of flare ribbons, and examine the evolution of flare thermal and non-thermal X-ray emissions during the progress of flare reconnection. We analyze three eruptive flares and three confined flares ranging from GOES class C8.0 to M7.0. They exhibit well-defined two ribbons along the magnetic polarity inversion line (PIL), and have been observed by the Atmospheric Imaging Assembly and the Ramaty High Energy Solar Spectroscopic Imager from the onset of the flare throughout the impulsive phase. The analysis confirms…
In this study we determine scaling relationships of observed solar flares that can be used to predict upper limits of the GOES-class magnitude of solar flares. The flare prediction scheme is based on the scaling of the slowly-varying potential energy $E_p(t)$, which is extrapolated in time over an interval of $Δt \le$ 24 hrs. The observed scaling of the dissipated energy $E_{diss}$ scales with the potential field energy as $E_{diss} \propto E_p^{1.32}$. In addition, the observed scaling relationship of the flare volume, $V \propto E_{diss}^{1.17}$, the multi-thermal energy, $E_{th} \propto V^{…
This study entails the fourth part of a global flare energetics project, in which the mass $m_{\mathrm{cme}}$, kinetic energy $E_{\mathrm{kin}}$, and the gravitational potential energy $E_{\mathrm{grav}}$ of coronal mass ejections (CMEs) is measured in 399 M and X-class flare events observed during the first 3.5 yrs of the Solar Dynamics Observatory (SDO) mission, using a new method based on the EUV dimming effect. The EUV dimming is modeled in terms of a radial adiabatic expansion process, which is fitted to the observed evolution of the total emission measure of the CME source region. The mo…
Revealing Flare Energetics and Dynamics with SDO EVE Solar Extreme Ultraviolet Spectral Irradiance Observations
Laboratory for Atmospheric and Space Physics, University of Colorado（科罗拉多大学大气与空间物理实验室）；Johns Hopkins University, Applied Physics Laboratory（约翰斯·霍普金斯大学应用物理实验室）；High Altitude Observatory, National Center for Atmospheric Research（美国国家大气研究中心高空观测站）；Naval Research Laboratory（海军研究实验室）
One of the key problems in solar flare physics is the determination of the low-energy cut-off; the value that determines the energy of nonthermal electrons and hence flare energetics. We discuss different approaches to determine the low-energy cut-off in the spectrum of accelerated electrons: (i) the total electron number model, (ii) the time-of-flight model (based on the equivalence of the time-of-flight and the collisional deflection time); (iii) the warm target model of Kontar et al.~(2015), and (iv) the model of the spectral cross-over between thermal and nonthermal components. We find tha…
In this study we refine a CME model presented in an earlier study on the global energetics of solar flares and associated CMEs, and apply it to all (860) GOES M- and X-class flare events observed during the first 7 years (2010-2016) of the Solar Dynamics Observatory (SDO) mission, which doubles the statistics of the earlier study. The model refinements include: (1) the CME geometry in terms of a 3D sphere undergoing self-similar adiabatic expansion; (2) the inclusion of solar gravitational deceleration during the acceleration and propagation of the CME, which discriminates eruptive and confine…
M dwarf stars are known for their vigorous flaring. This flaring could impact the climate of orbiting planets, making it important to characterize M dwarf flares at the short wavelengths that drive atmospheric chemistry and escape. We conducted a far-ultraviolet flare survey of 6 M dwarfs from the recent MUSCLES (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems) observations, as well as 4 highly-active M dwarfs with archival data. When comparing absolute flare energies, we found the active-M-star flares to be about 10$\times$ more energetic than inactiv…
In this study we synthesize the results of four previous studies on the global energetics of solar flares and associated coronal mass ejections (CMEs), which include magnetic, thermal, nonthermal, and CME energies in 399 solar M and X-class flare events observed during the first 3.5 years of the Solar Dynamics Observatory (SDO) mission. Our findings are: (1) The sum of the mean nonthermal energy of flare-accelerated particles ($E_{\mathrm{nt}}$), the energy of direct heating ($E_{\mathrm{dir}}$), and the energy in coronal mass ejections ($E_{\mathrm{CME}}$), which are the primary energy dissip…
The aim of this study is to generate maps of the hard X-ray emission produced by energetic electrons in a solar flare and compare them with observations. The ultimate goal is to test the viability of the combined MHD/test-particle approach for data-driven modelling of active events in the solar corona and their impact on the heliosphere. Based on an MHD model of X-class solar flare observed on the 8th of September 2017, we calculate trajectories of a large number of electrons and protons using the relativistic guiding-centre approach. Using the obtained particle trajectories, we deduce the spa…
Energetics and Emission in a Simulated Solar Flare Initialised by a Non-Force Free Magnetic Field
University of Hertfordshire（赫特福德大学）；Statkraft AS（斯塔特勒克公司）；University of Oslo（奥斯陆大学）；Université Paris-Saclay（巴黎萨克雷大学）；Université Paris Cité（巴黎西岱大学）；CEA（法国原子能和替代能源委员会）；CNRS（法国国家科学研究中心）；University of Manchester（曼彻斯特大学）；New Jersey Institute of Technology（新泽理工学院）
Typical solar flares display two quasi-parallel, bright ribbons on the chromosphere. In between is the polarity inversion line (PIL) separating concentrated magnetic fluxes of opposite polarity in active regions (ARs). Intriguingly a series of flares exhibiting X-shaped ribbons occurred at the similar location on the outskirts of NOAA AR 11967, where magnetic fluxes were scattered, yet three of them were alarmingly energetic. The X shape, whose center coincided with hard X-ray emission, was similar in UV/EUV, which cannot be accommodated in the standard flare model. Mapping out magnetic connec…
A new estimation of the total number and energy of the non-thermal electrons produced in the giant ($>\text{X}17$) solar flare on 2003 October 28 is presented based on the analysis of the observations of the hard X-ray (HXR) emission by the High Energy Neutron Detector (HEND) onboard the Mars Odyssey spacecraft orbiting Mars. Previous estimations of the non-thermal electron energy based on the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) data were incomplete since RHESSI missed the peak of the flare impulsive phase. In contrast, HEND observed the whole flare. We used two model…
This paper is an attempt to understand the physical processes occurring in different layers of solar atmosphere during a solar flare. For a complete understanding of the flare we must analyze multi-wavelength datasets, as emission at different wavelength originates from different layers of the solar atmosphere. Also, flares are transient and localized events observed to occur at all longitudes. With these considerations, we have carried out multi-wavelength analysis of two representative flare events. One event occurred close to the centre of the solar disk and other occurred close to the limb…
In this study we test 30 variants of 5 physical scaling laws that describe different aspects of solar flares. We express scaling laws in terms of the magnetic potential field energy $E_p$, the mean potential field strength $B_p$, the free energy $E_{free}$, the dissipated magnetic flare energy $E_{diss}$, the mean loop length scale $L$, the mean helically twisted flux tube radius $R$, the sunspot radius $r$, the emission measure-weighted flare temperature $T_w$, the electron density $n_e$, and the total emission measure $EM$, measured from a data set of $\lapprox 400$ GOES M- and X-class flare…
We investigate physical scaling laws for magnetic energy dissipation in solar flares, in the framework of the Sweet-Parker model and the Petschek model. We find that the total dissipated magnetic energy $E_{diss}$ in a flare depends on the mean magnetic field component $B_f$ associated with the free energy $E_f$, the length scale $L$ of the magnetic area, the hydrostatic density scale height $λ$ of the solar corona, the Alfvén Mach number $M_A=v_1/v_A$ (the ratio of the inflow speed $v_1$ to the Alfvénic outflow speed $v_A$), and the flare duration $τ_f$, i.e., $E_{diss} = (1/4π) B_f^2\ L\ λ v…
We examine the production of energetic neutral atoms (ENAs) in solar flares and CME-driven shocks and their subsequent propagation to 1 au. Time profiles and fluence spectra of solar ENAs at 1 au are computed for two scenarios: 1) ENAs are produced downstream at CME-driven shocks, and 2) ENAs are produced at large-scale post-flare loops in solar flares. Both the time profiles and fluence spectra for these two scenarios are vastly different. Our calculations indicate that we can use solar ENAs as a new probe to examine the underlying acceleration process of solar energetic particles (SEPs) and …
A more accurate analytical solution of the {\sl vertical-current approximation nonlinear force-free field (VCA3-NLFFF)} model is presented that includes besides the radial $(B_r)$ and the azimuthal $(B_φ)$ magnetic field components a poloidal component $(B_θ \neq 0)$ also. This new analytical solution is of second-order accuracy in the divergence-freeness condition, and of third-order accuracy in the force-freeness condition. We re-analyze the sample of 173 GOES M- and X-class flares observed with the {\sl Atmospheric Imaging Assembly (AIA)} and {\sl Helioseismic and Magnetic Imager (HMI)} onb…
The free energy that is dissipated in a magnetic reconnection process of a solar flare, generally accompanied by a coronal mass ejection (CME), has been considered as the ultimate energy source of the global energy budget of solar flares in previous statistical studies. Here we explore the effects of the aerodynamic drag force on CMEs, which supplies additional energy from the slow solar wind to a CME event, besides the magnetic energy supply. For this purpose we fit the analytical aerodynamic drag model of Cargill (2004) and Vrsnak et al.~{\bf (2013)} to the height-time profiles $r(t)$ of LAS…
Magnetic field-line reconnection is a universal plasma process responsible for the conversion of magnetic field energy to the plasma heating and charged particle acceleration. Solar flares and Earth's magnetospheric substorms are two most investigated dynamical systems where magnetic reconnection is believed to be responsible for global magnetic field reconfiguration and energization of plasma populations. Such a reconfiguration includes formation of a long-living current systems connecting the primary energy release region and cold dense conductive plasma of photosphere/ionosphere. In both fl…
We present results revealing microwave pulsations produced in a model of a flaring twisted solar coronal loop, without any external oscillatory driver. Two types of oscillations are identified: slowly-decaying oscillations with a period of about 70-75s and amplitude of about 5-10% seen in loops both with and without energetic electrons, and oscillations with period of about 40s and amplitude of a few tens of percent observed only in loops with energetic electrons for about 100s after onset of fast energy release. We interpret the longer-period oscillations as the result of a standing kink mode…
Particle acceleration in stellar flares is ubiquitous in the Universe, however, our Sun is the only astrophysical object where energetic particles and their source flares can both be observed. The acceleration mechanism in solar flares, tremendously enhancing (up to a factor of ten thousand) rare elements like 3He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we present some of the most intense 3He- and Fe-rich solar energetic particle events ever reported. The events were accompanied by non-relativistic electron events and type III radio bursts. The corresponding high-re…
Context. The remote observations of solar flare ion acceleration are rather limited. There are theoretical predictions for signatures of ion acceleration in EUV line profiles. Previous tests involve observations of flares with no evidence for energetic ions. Aims. We aim to examine a source flare of impulsive (or 3He-rich) solar energetic particle events with EUV line spectroscopy. Methods. We inspect all (90+) reported 3He-rich flares of previous solar cycle 23 and find only four (recurrent) jets in the field of view of SOHO CDS. The jet with the most suitable spatial and temporal coverage is…
This study entails the third part of a global flare energetics project, in which Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) data of 191 M and X-class flare events from the first 3.5 yrs of the Solar Dynamics Observatory (SDO) mission are analyzed. We fit a thermal and a nonthermal component to RHESSI spectra, yielding the temperature of the differential emission measure (DEM) tail, the nonthermal power law slope and flux, and the thermal/nonthermal cross-over energy $e_{\mathrm{co}}$. From these parameters we calculate the total nonthermal energy $E_{\mathrm{nt}}$ in electrons with…
What powers the most energetic flares in the Kepler field? Revisiting the superflaring star KIC 2852961
Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，匈牙利研究与教育网络天文学与地球科学研究中心）；HUN-REN CSFK, MTA Centre of Excellence（匈牙利研究与教育网络科学院研究所，马塔卓越中心）；Eötvös Loránd University（厄特沃什·罗兰大学）；Institute of Physics/IGAM, University of Graz（格拉茨大学物理研究所/IGAM）
Solar energetic particle (SEP) events are known to occur following solar flares and coronal mass ejections (CMEs). However some high-energy solar events do not result in SEPs being detected at Earth, and it is these types of event which may be termed "false alarms". We define two simple SEP forecasting algorithms based upon the occurrence of a magnetically well-connected CME with a speed in excess of 1500 km/s ("a fast CME") or a well-connected X-class flare and analyse them with respect to historical data sets. We compare the parameters of those solar events which produced an enhancement of >…
Solar-type stars exhibit their highest levels of magnetic activity during their early convective pre-main sequence (PMS) phase of evolution. The most powerful PMS flares, super-flares and mega-flares, have peak X-ray luminosities of $\log(L_X)=30.5-34.0$~erg~s$^{-1}$ and total energies $\log(E_X)=34-38$~erg. Among $>24,000$ X-ray selected young ($t<5$~Myr) members of 40 nearby star-forming regions from our earlier $Chandra$ MYStIX and SFiNCs surveys, we identify and analyze a well-defined sample of 1,086 X-ray super-flares and mega-flares, the largest sample ever studied. Most are considerably…
High Resolution Spectroscopic Analysis of Chromospheric Line Evolution during an Energetic Flare on AD Leo
Seoul National University（首尔大学）；SNU Astronomy Research Center, Astronomy Program, Department of Physics and Astronomy, Seoul National University（首尔大学天体物理与天文系天文研究中心）；Korea Astronomy and Space Science Institute（韩国天文与空间科学研究院）；University of Science and Technology（科学技术大学）
利用高分辨率光谱分析AD Leo超耀斑的色球谱线演化，发现Hα辐射能量8.8×10^30 erg，总能量约10^33 erg，Ca II H&K和红外三重线延迟发射符合Neupert效应，表明累积加热主导缓变相。
In this work we provide an updated description of the Vertical Current Approximation Nonlinear Force-Free Field (VCA-NLFFF) code, which is designed to measure the evolution of the potential, nonpotential, free energies, and the dissipated magnetic energies during solar flares. This code provides a complementary and alternative method to existing traditional NLFFF codes. The chief advantages of the VCA-NLFFF code over traditional NLFFF codes are the circumvention of the unrealistic assumption of a force-free photosphere in the magnetic field extrapolation method, the capability to minimize the …
In solar flares, energy is released impulsively and is partly converted into thermal energy of hot plasmas and kinetic energy of accelerated nonthermal particles. Despite numerous efforts, no consensus on quantifying this energy balance has yet been reached. We aim to understand the reasons for the contradicting results on energy partition obtained by various recent studies. We considered five recent studies that address the thermal-nonthermal energy partition in solar flares. Their results are reviewed, and their methods are compared and discussed in detail. The main uncertainties in deriving…
Sunquakes are enhanced seismic waves excited in some energetic solar flares. Up to now, their origin has still been controversial. In this Letter, we select and study 20 strong flares in Solar Cycle 24, whose impulse phase is fully captured by the \emph{Reuven Ramaty High Energy Solar Spectroscopic Imager} (\emph{RHESSI}). For 11 out of 12 sunquake-active flares in our sample, the hard X-ray (HXR) emission shows a good temporal and spatial correlation with the white-light (WL) enhancement and the sunquake. Spectral analysis also reveals a harder photon spectrum that extends to several hundred …
The scattering of electrons by heat-flux-driven whistler waves is explored with a particle-in-cell (PIC) simulation relevant to the transport of energetic electrons in flares. The simulation is initiated with a large heat flux that is produced using a kappa distribution of electrons with positive velocity and a cold return current beam. This system represents energetic electrons escaping from a reconnection-driven energy release site. This heat flux system drives large amplitude oblique whistler waves propagating both along and against the heat flux, as well as electron acoustic waves. While t…
Our major aim is a height-time model $r(t)$ of the propagation of {\sl Coronal Mass Ejections (CMEs)}, where the lower corona is self-consistently connected to the heliospheric path. We accomplish this task by using the Neupert effect to derive the peak time, duration, and rate of the CME acceleration phase, as obtained from the time derivative of the {\sl soft X-ray (SXR)} light curve. This novel approach offers the advantage to obtain the kinematics of the CME height-time profile $r(t)$, the CME velocity profile $v(t)=dr(t)/dt$, and the CME acceleration profile $a(t)=dv(t)/dt$ from {\sl Geos…
