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1.
Based on energetic particle observations made at \({\approx}\,1\) AU, we present a catalogue of 46 wide-longitude (\({>}\,45^{\circ}\)) solar energetic particle (SEP) events detected at multiple locations during 2009?–?2016. The particle kinetic energies of interest were chosen as \({>}\,55\) MeV for protons and 0.18?–?0.31 MeV for electrons. We make use of proton data from the Solar and Heliospheric Observatory/Energetic and Relativistic Nuclei and Electron Experiment (SOHO/ERNE) and the Solar Terrestrial Relations Observatory/High Energy Telescopes (STEREO/HET), together with electron data from the Advanced Composition Explorer/Electron, Proton, and Alpha Monitor (ACE/EPAM) and the STEREO/Solar Electron and Proton Telescopes (SEPT). We consider soft X-ray data from the Geostationary Operational Environmental Satellites (GOES) and coronal mass ejection (CME) observations made with the SOHO/Large Angle and Spectrometric Coronagraph (LASCO) and STEREO/Coronagraphs 1 and 2 (COR1, COR2) to establish the probable associations between SEP events and the related solar phenomena. Event onset times and peak intensities are determined; velocity dispersion analysis (VDA) and time-shifting analysis (TSA) are performed for protons; TSA is performed for electrons. In our event sample, there is a tendency for the highest peak intensities to occur when the observer is magnetically connected to solar regions west of the flare. Our estimates for the mean event width, derived as the standard deviation of a Gaussian curve modelling the SEP intensities (protons \({\approx}\,44^{\circ}\), electrons \({\approx}\,50^{\circ}\)), largely agree with previous results for lower-energy SEPs. SEP release times with respect to event flares, as well as the event rise times, show no simple dependence on the observer’s connection angle, suggesting that the source region extent and dominant particle acceleration and transport mechanisms are important in defining these characteristics of an event. There is no marked difference between the speed distributions of the CMEs related to wide events and the CMEs related to all near-Earth SEP events of similar energy range from the same time period.  相似文献   

2.
The dynamics of the boundary of the penetration of solar energetic particles (electrons and protons) to Earth’s magnetosphere during solar flares and related geomagnetic disturbances in November 2001 and October–November 2003 is analyzed using CORONAS-F data. The relationship between the penetration boundary, the geomagnetic activity indices, and the local magnetic time is investigated. The correlation coefficient between the invariant latitude of the penetration boundary and the K p and D st indices for electrons with energies ranging from 0.3 to 0.6 MeV in the dayside sector is demonstrated to be higher than that in the nightside sector. The correlation coefficient for protons with energies from 1 to 5 MeV is higher in the nightside sector as compared to the dayside sector. For protons with energies from 50 to 90 MeV, the correlation is high at all MLT.  相似文献   

3.
We consider the modulation of nonthermal gyrosynchrotron emission from solar flares by the ballooning and radial oscillations of coronal loops. The damping mechanisms for fast magnetoacoustic modes are analyzed. We suggest a method for diagnosing the plasma of flare loops that allows their main parameters to be estimated from peculiarities of the microwave pulsations. Based on observational data obtained with the Nobeyama Radioheliograph (17 GHz) and using a technique developed for the event of May 8, 1998, we determined the particle density n≈3.7×1010 cm?3, the temperature T≈4×107 K, and the magnetic field strength B≈220 G in the region of flare energy release. A wavelet analysis for the solar flare of August 28, 1999, has revealed two main types of microwave oscillations with periods P1≈7, 14 s and P2≈2.4 s, which we attribute to the ballooning and radial oscillations of compact and extended flare loops, respectively. An analysis of the time profile for microwave emission shows evidence of coronal loop interaction. We determined flare plasma parameters for the compact (T≈5.3×107 K, n≈4.8≈1010 cm?3, B≈280 G) and extended (T≈2.1≈107 K, n≈1.2≈1010 cm?3, B≈160 G) loops. The results of the soft X-ray observations are consistent with the adopted model.  相似文献   

4.
The results of an experimental study of the variations in the intensity of the fluxes of the Earth radiation belt (ERB) particles in 0.3–6 and 1–50 MeV energy intervals for electrons and protons, respectively, are reported. ERBs were studied during strong magnetic storms from August 2001 through November 2003. The results of the CORONAS-F mission obtained during the magnetic storms of November 6 (D st = ?257 nT) and November 24, 2001 (D st = ?221 nT), October 29–30 (D st = ?400 nT) and November 20, 2003 (D st = ?465 nT) are analyzed. The electron flux is found to decrease abruptly in the outer radiation belt during the main phase of the magnetic storms under consideration. During the recovery phase, the outer radiation belt is found to recover much closer to Earth, near the boundary of the penetration of solar electrons during the main phase of the magnetic storm. We associate the decrease in the electron flux with the abrupt decrease of the size of the magnetosphere during the main phase of the storm. Note that, in all cases studied, the Earth radiation belts exhibited rather long (several days) variations. In those cases where solar cosmic-ray fluxes were observed during the storm, protons with energies 1–5 MeV could be trapped to form an additional maximum of protons with such energies at L >2.  相似文献   

5.
The 5 July 2012 solar flare SOL2012-07-05T11:44 (11:39?–?11:49 UT) with an increasing millimeter spectrum between 93 and 140 GHz is considered. We use space and ground-based observations in X-ray, extreme ultraviolet, microwave, and millimeter wave ranges obtained with the Reuven Ramaty High-Energy Solar Spectroscopic Imager, Solar Dynamics Observatory (SDO), Geostationary Operational Environmental Satellite, Radio Solar Telescope Network, and Bauman Moscow State Technical University millimeter radio telescope RT-7.5. The main parameters of thermal and accelerated electrons were determined through X-ray spectral fitting assuming the homogeneous thermal source and thick-target model. From the data of the Atmospheric Imaging Assembly/SDO and differential-emission-measure calculations it is shown that the thermal coronal plasma gives a negligible contribution to the millimeter flare emission. Model calculations suggest that the observed increase of millimeter spectral flux with frequency is determined by gyrosynchrotron emission of high-energy (\(\gtrsim 300\) keV) electrons in the chromosphere. The consequences of the results are discussed in the light of the flare-energy-release mechanisms.  相似文献   

6.
In this article, we present a multi-wavelength and multi-instrument investigation of a halo coronal mass ejection (CME) from active region NOAA 12371 on 21 June 2015 that led to a major geomagnetic storm of minimum \(\mathrm{Dst} = -204\) nT. The observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory in the hot EUV channel of 94 Å confirm the CME to be associated with a coronal sigmoid that displayed an intense emission (\(T \sim6\) MK) from its core before the onset of the eruption. Multi-wavelength observations of the source active region suggest tether-cutting reconnection to be the primary triggering mechanism of the flux rope eruption. Interestingly, the flux rope eruption exhibited a two-phase evolution during which the “standard” large-scale flare reconnection process originated two composite M-class flares. The eruption of the flux rope is followed by the coronagraphic observation of a fast, halo CME with linear projected speed of 1366 km?s?1. The dynamic radio spectrum in the decameter-hectometer frequency range reveals multiple continuum-like enhancements in type II radio emission which imply the interaction of the CME with other preceding slow speed CMEs in the corona within \(\approx10\)?–?\(90~\mbox{R} _{\odot}\). The scenario of CME–CME interaction in the corona and interplanetary medium is further confirmed by the height–time plots of the CMEs occurring during 19?–?21 June. In situ measurements of solar wind magnetic field and plasma parameters at 1 AU exhibit two distinct magnetic clouds, separated by a magnetic hole. Synthesis of near-Sun observations, interplanetary radio emissions, and in situ measurements at 1 AU reveal complex processes of CME–CME interactions right from the source active region to the corona and interplanetary medium that have played a crucial role towards the large enhancement of the geoeffectiveness of the halo CME on 21 June 2015.  相似文献   

7.
Based on an analogy between stellar and solar flares, we investigate the ten-second oscillations detected in the U and B bands on the star EV Lac. The emission pulsations are associated with fast magnetoacoustic oscillations in coronal loops. We have estimated the magnetic field, B ≈ 320 G; the temperature, T ≈ 3.7 × 107 K; and the plasma density, n ≈ 1.6 × 1011 cm?3, in the region of energy release. We provide evidence suggesting that the optical emission source is localized at the loop footpoints.  相似文献   

8.
Isotropization mechanisms for a beam of low-energy (10–100 keV) protons in the Hα formation region are considered. An increase in the magnetic field strength is shown to have no significant effect on the pitch-angle distribution of the accelerated particles in the solar chromosphere. The excitation of small-scale Alfvén waves by protons can lead to their effective scattering. The results obtained are used to interpret peculiarities of the impact polarization of the Hα emission.  相似文献   

9.
It is generally accepted that densities of quiet-Sun and active region plasma are sufficiently low to justify the optically thin approximation, and this is commonly used in the analysis of line emissions from plasma in the solar corona. However, the densities of solar flare loops are substantially higher, compromising the optically thin approximation. This study begins with a radiative transfer model that uses typical solar flare densities and geometries to show that hot coronal emission lines are not generally optically thin. Furthermore, the model demonstrates that the observed line intensity should exhibit center-to-limb variability (CTLV), with flares observed near the limb being dimmer than those occurring near disk center. The model predictions are validated with an analysis of over 200 flares observed by the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO), which uses six lines, with peak formation temperatures between 8.9 and 15.8 MK, to show that limb flares are systematically dimmer than disk-center flares. The data are then used to show that the electron column density along the line of sight typically increases by \(1.76 \times 10^{19}~\mbox{cm}^{-2}\) for limb flares over the disk-center flare value. It is shown that the CTLV of hot coronal emissions reduces the amount of ionizing radiation propagating into the solar system, and it changes the relative intensities of lines and bands commonly used for spectral analysis.  相似文献   

10.
Solar eruptions are the most spectacular events in our solar system and are associated with many different signatures of energy release including solar flares, coronal mass ejections, global waves, radio emission and accelerated particles. Here, we apply the Coronal Pulse Identification and Tracking Algorithm (CorPITA) to the high-cadence synoptic data provided by the Solar Dynamics Observatory (SDO) to identify and track global waves observed by SDO. 164 of the 362 solar flare events studied (45%) were found to have associated global waves with no waves found for the remaining 198 (55%). A clear linear relationship was found between the median initial velocity and the acceleration of the waves, with faster waves exhibiting a stronger deceleration (consistent with previous results). No clear relationship was found between global waves and type II radio bursts, electrons or protons detected in situ near Earth. While no relationship was found between the wave properties and the associated flare size (with waves produced by flares from B to X-class), more than a quarter of the active regions studied were found to produce more than one wave event. These results suggest that the presence of a global wave in a solar eruption is most likely determined by the structure and connectivity of the erupting active region and the surrounding quiet solar corona rather than by the amount of free energy available within the active region.  相似文献   

11.
The spatial-distribution dynamics of the hot coronal plasma with T ～ 10 MK during a period of high solar activity is studied. We analyze images of the NOAA 9830 active region and its surroundings obtained during the second half of February 2002 with the SPIRIT spectroheliograph in the Mg XII 8.42-Å line and simultaneously on the SOHO satellite with the EIT instrument and on the TRACE satellite in the 195-Å channel. As shown by a multiwavelength analysis, a high-temperature plasma is concentrated in the corona near the apices of magnetic loops, it has long lifetimes (up to several days), and its dynamics is complex and bears no direct relation to flare activity. During the flares, conspicuous increases are observed in the X-ray flux and the emission measure for temperatures of ～5–15 MK. Our analyses of the time variations in emission during a flare suggest that hot plasma is heated by fluxes of accelerated electrons.  相似文献   

12.
We present the results of five-year observations of the southern seasonal cap of Mars based on neutron spectroscopy of the surface fulfilled by the Russian HEND instrument onboard the NASA 2001 Mars Odyssey spacecraft. The numerical modeling of the observational data allowed us to reconstruct the curves of the variations of the total mass of the southern seasonal cap of Mars for different years (three Martian years) and to find the year-to-year variations of the seasonal cycle.  相似文献   

13.
The peculiar development of solar activity in the current cycle resulted in an asynchronous reversal of the Sun’s polar fields. The asymmetry is also observed in the formation of polar coronal holes. A stable coronal hole was first formed at the South Pole, despite the later polar-field reversal there. The aim of this study is to understand the processes making this situation possible. Synoptic magnetic maps from the Global Oscillation Network Group and corresponding coronal-hole maps from the Extreme ultraviolet Imaging Telescope onboard the Solar and Heliospheric Observatory and the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory are analyzed here to study the causal relationship between the decay of activity complexes, evolution of large-scale magnetic fields, and formation of coronal holes. Ensembles of coronal holes associated with decaying active regions and activity complexes are presented. These ensembles take part in global rearrangements of the Sun’s open magnetic flux. In particular, the south polar coronal hole was formed from an ensemble of coronal holes that came into existence after the decay of multiple activity complexes observed during 2014.  相似文献   

14.
We study the formation of solar-wind streams in the years of maximum solar activity 2000–2002. We use observations of the scattering of radio emission by solar-wind streams at distances of ～4–60RS from the Sun, data on the magnetic field structure and strength in the source region (R ～ 2.5RS), and observations with the LASCO coronagraph onboard the SOHO spacecraft. Analysis of these data allowed us to investigate the changes in the structure of circumsolar plasma streams during the solar maximum. We constructed radio maps of the solar-wind transition, transonic region in which the heliolatitudinal stream structure is compared with the structure of the white-light corona. We show that the heliolatitudinal structure of the white-light corona largely determines the structure of the solar-wind transition region. We analyze the correlation between the location of the inner boundary of the transition region Rin and the magnetic field strength on the source surface |BR|. We discuss the peculiarities of the Rin = F(|BR|) correlation diagrams that distinguish them from similar diagrams at previous phases of the solar cycle.  相似文献   

15.
We present a study of the complex event consisting of several solar wind transients detected by the Advanced Composition Explorer (ACE) on 4?–?7 August 2011, which caused a geomagnetic storm with \(\mathit{Dst}=-110~\mbox{nT}\). The supposed coronal sources, three flares and coronal mass ejections (CMEs), occurred on 2?–?4 August 2011 in active region (AR) 11261. To investigate the solar origin and formation of these transients, we study the kinematic and thermodynamic properties of the expanding coronal structures using the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) EUV images and differential emission measure (DEM) diagnostics. The Helioseismic and Magnetic Imager (HMI) magnetic field maps were used as the input data for the 3D magnetohydrodynamic (MHD) model to describe the flux rope ejection (Pagano, Mackay, and Poedts, 2013b). We characterize the early phase of the flux rope ejection in the corona, where the usual three-component CME structure formed. The flux rope was ejected with a speed of about \(200~\mbox{km}\,\mbox{s}^{-1}\) to the height of \(0.25~\mbox{R}_{\odot}\). The kinematics of the modeled CME front agrees well with the Solar Terrestrial Relations Observatory (STEREO) EUV measurements. Using the results of the plasma diagnostics and MHD modeling, we calculate the ion charge ratios of carbon and oxygen as well as the mean charge state of iron ions of the 2 August 2011 CME, taking into account the processes of heating, cooling, expansion, ionization, and recombination of the moving plasma in the corona up to the frozen-in region. We estimate a probable heating rate of the CME plasma in the low corona by matching the calculated ion composition parameters of the CME with those measured in situ for the solar wind transients. We also consider the similarities and discrepancies between the results of the MHD simulation and the observations.  相似文献   

16.
EUV and Magnetic Activities Associated with Type-I Solar Radio Bursts   总被引：1，自引：0，他引：1  
Type-I bursts (i.e. noise storms) are the earliest-known type of solar radio emission at the meter wavelength. They are believed to be excited by non-thermal energetic electrons accelerated in the corona. The underlying dynamic process and exact emission mechanism still remain unresolved. Here, with a combined analysis of extreme ultraviolet (EUV), radio and photospheric magnetic field data of unprecedented quality recorded during a type-I storm on 30 July 2011, we identify a good correlation between the radio bursts and the co-spatial EUV and magnetic activities. The EUV activities manifest themselves as three major brightening stripes above a region adjacent to a compact sunspot, while the magnetic field there presents multiple moving magnetic features (MMFs) with persistent coalescence or cancelation and a morphologically similar three-part distribution. We find that the type-I intensities are correlated with those of the EUV emissions at various wavelengths with a correlation coefficient of 0.7?–?0.8. In addition, in the region between the brightening EUV stripes and the radio sources there appear consistent dynamic motions with a series of bi-directional flows, suggesting ongoing small-scale reconnection there. Mainly based on the induced connection between the magnetic motion at the photosphere and the EUV and radio activities in the corona, we suggest that the observed type-I noise storms and the EUV brightening activities are the consequence of small-scale magnetic reconnection driven by MMFs. This is in support of the original proposal made by Bentley et al. (Solar Phys. 193, 227, 2000).  相似文献   

17.
The Sun is an effective particle accelerator that produces solar energetic particle (SEP) events, during which particles of up to several GeVs can be observed. These events, when they are observed at Earth with the neutron monitor network, are called ground-level enhancements (GLEs). Although these events with their high-energy component have been investigated for several decades, a clear relation between the spectral shape of the SEPs outside the Earth’s magnetosphere and the increase in neutron monitor count rate has yet to be established. Hence, an analysis of these events is of interest for the space weather and for the solar event community.In this article, SEP events with protons accelerated to above 500 MeV were identified using data obtained with the Electron Proton Helium Instrument (EPHIN) onboard the Solar and Heliospheric Observatory (SOHO) between 1995 and 2015. For a statistical analysis, onset times were determined for the events and the proton energy spectra were derived and fitted with a power law.As a result, we present a list of 42 SEP events with protons accelerated to above 500 MeV measured with the EPHIN instrument onboard SOHO. The statistical analysis based on the fitted spectral slopes and absolute intensities is discussed, with special emphasis on whether an event has been observed as a GLE. Furthermore, we are able to determine that the derived intensity at 500 MeV and the observed increase in neutron monitor count rate are correlated for a subset of events.  相似文献   

18.
The eclipse observations were performed at the Laboratory of Radio Astronomy of the CrAO in Katsiveli with stationary instrumentation of the Solar Patrol at wavelengths of 10.5 and 12.0 cm. The data obtained were used to determine the brightness temperature of the undisturbed Sun at solar activity minimum between 11-year cycles 23 and 24: T d10.5 = (43.7 ± 0.5) × 103 K at 10.5 cm and T d12.0 = (51.8 ± 0.5) × 103 K at 12.0 cm. The radio brightness distribution above the limb group of sunspots NOAA 0866 was calculated. It shows that at both wavelengths the source consisted of a compact bright nucleus about 50 × 103 km in size with temperatures T b10.5 = 0.94 × 106 K and T b12.0 = 2.15 × 106 K located, respectively, at heights h 10.5 = 33.5 × 103 km and h 12.0 = 43.3 × 103 km above the sunspot and an extended halo with a temperature T b = (230–300) × 103 K stretching to a height of 157 × 103 km above the photosphere. The revealed spatial structure of the local source is consistent with the universally accepted assumption that the radiation from the bright part of the source is generated by electrons in the sunspot magnetic fields at the second-third cyclotron frequency harmonics and that the halo is the bremsstrahlung of thermal electrons in the coronal condensation forming an active region. According to the eclipse results, the electron density near the upper boundary of the condensation was N e ≈ 2.3 × 108 cm?3, while the optical depth was τ ≈ 0.1 at an electron temperature T e ≈ 106 K. Thus, the observations of the March 29, 2006 eclipse have allowed the height of the coronal condensation at solar activity minimum to be experimentally determined and the physical parameters of the plasma near its upper boundary to be estimated.  相似文献   

19.
The SOL2001-12-26 moderate solar eruptive event (GOES importance M7.1, microwaves up to 4000 sfu at 9.4 GHz, coronal mass ejection (CME) speed 1446 km?s?1) produced strong fluxes of solar energetic particles and ground-level enhancement (GLE) of cosmic-ray intensity (GLE63). To find a possible reason for the atypically high proton outcome of this event, we study multi-wavelength images and dynamic radio spectra and quantitatively reconcile the findings with each other. An additional eruption probably occurred in the same active region about half an hour before the main eruption. The latter produced two blast-wave-like shocks during the impulsive phase. The two shock waves eventually merged around the radial direction into a single shock traced up to \(25~\mathrm{R}_{\odot}\) as a halo ahead of the expanding CME body, in agreement with an interplanetary Type II event recorded by the Radio and Plasma Wave Investigation (WAVES) experiment on the Wind spacecraft. The shape and kinematics of the halo indicate an intermediate regime of the shock between the blast wave and bow shock at these distances. The results show that i) the shock wave appeared during the flare rise and could accelerate particles earlier than usually assumed; ii) the particle event could be amplified by the preceding eruption, which stretched closed structures above the developing CME, facilitated its lift-off and escape of flare-accelerated particles, enabled a higher CME speed and stronger shock ahead; iii) escape of flare-accelerated particles could be additionally facilitated by reconnection of the flux rope, where they were trapped, with a large coronal hole; and iv) the first eruption supplied a rich seed population accelerated by a trailing shock wave.  相似文献   

20.
Based on observational data obtained with the RT-22 Crimean Astrophysical Observatory radio telescope at frequencies of 8.6 and 15.4 GHz, we investigate the quasi-periodic variations of microwave emission from solar active regions with periods Tp<10 min. As follows from our wavelet analysis, the oscillations with periods of 3–5 min and 10–40 s have the largest amplitudes in the dynamic power spectra, while there are virtually no oscillations with Tp<10 s. Our analysis shows that acoustic modes with Tp?1 min strongly dissipate in the lower solar corona due to thermal conduction losses. The oscillations with Tp=10–40 s are associated with Alfvén disturbances. We analyze the influence of acoustic and Alfvén oscillations on the thermal mechanisms of microwave emission in terms of the homogeneous model. We discuss the probable coronal heating sources.  相似文献   

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