Velocity Of Coronal Mass Ejections Research Articles

Modelling non-radially propagating coronal mass ejections and forecasting the time of their arrival at Earth

We present the study of two solar eruptive events observed on December 7 2020 and October 28 2021. Both events were associated with full halo coronal mass ejections (CMEs) and flares. These events were chosen because they show a strong non-radial direction of propagation in the low corona and their main propagation direction observed in the inner heliosphere is not fully aligned with the Sun-Earth line. This characteristic makes them suitable for our study, which aims to inspect how the non-radial direction of propagation in the low corona affects the time of CMEs' arrival at Earth. We reconstructed the CMEs using SOHO/LASCO and STEREO/COR observations and modelled them with the 3D MHD model EUHFORIA and the cone model for CMEs. In order to compare the accuracy of forecasting the CME and the CME-driven shock arrival time at Earth obtained from different methods, we also used so-called type II bursts, radio signatures of associated shocks, to find the velocities of the CME-driven shocks and forecast the time of their arrival at Earth. Additionally, we estimated the CME arrival time using the 2D CME velocity obtained from the white light images. Our results show that the lowest accuracy of estimated CME Earth arrival times is found when the 2D CME velocity is used (time difference between observed and modelled arrival time, Delta t approx -29 h and -39 h, for the two studied events, respectively). The velocity of the type II radio bursts provides somewhat better — but still not very accurate — results (Delta t approx +21 h and -29 h, for the two studied events, respectively). Employing, as an input to EUHFORIA, the CME parameters obtained from the graduated cylindrical shell (GCS) fittings at consequently increasing heights, results in a strongly improved accuracy of the modelled CME and shock arrival time; Delta t changes from 20 h to 10 min in the case of the first event, and from 12 h to 30 min in the case of the second one. This improvement shows that when we increased the heights of the GCS reconstruction we accounted for the change in the propagation direction of the studied CMEs, which allowed us to accurately model the CME flank encounter at Earth. Our results show the great importance of the change in the direction of propagation of the CME in the low corona when modelling CMEs and estimating the time of their arrival at Earth.

Challenges in Forecasting the Evolution of a Distorted CME Observed During the First Close Solar Orbiter Perihelion

Coronal Mass Ejections (CMEs), drivers of the most severe Space Weather disturbances, are often assumed to evolve self-similarly during their propagation. However, open magnetic field structures in the corona, leading to higher-speed streams in the ambient solar wind, can be source of strong distortions of the CME front. In this paper, we investigate a distorted and Earth-directed CME observed on 2022 March 25 combining three remote sensing with three in situ observatories at different heliocentric distances (from 0.5 to 1 au). Near quadrature observations by Solar Orbiter and the Solar Terrestrial Relations Observatory revealed a distortion of the CME front in both latitude and longitude, with Solar Orbiter observations showing an Earth-directed latitudinal distortion as low as ≈6 R ⊙. Near-Earth extreme-ultraviolet observations indicated the distortion was caused by interaction with faster wind from a nearby equatorial coronal hole. To evaluate the effect of the distortion on the CME's propagation, we adopted a three-point-of-view graduated cylindrical shell (GCS) fitting approach. For the first time, the GCS results are combined with an additional heliospheric single-viewpoint that looks further out in the heliosphere, revealing a deceleration in the CME before reaching ≈100 R ⊙. The CME geometry and velocity determined by this enhanced GCS are used to initialize a drag-based model and a WSA-Enlil MHD model. The estimated times of arrival are compared with in situ data at different heliocentric distances and, despite the complexity of the event, the error in the arrival times at each spacecraft results much lower (≈4 hr error) than the typical errors in literature (≈8–10 hr).

Relationship between solar energetic particle intensity and coronal mass ejections and its associated type II radio bursts

Based on the multiple-vantage observations of STEREO, SOHO, wind and other spacecraft, the fast and wide coronal mass ejections (CME) during the 24th solar cycle from January 2010 to September 2014 are selected in this paper. Using the outputs of Richardson’s (2014) empirical model of solar energetic particle (SEP) intensity under different conditions, the effects of its associations such as CME, pre-CME, and type II radio bursts, on SEP intensity are analyzed, and the relationship between SEP event and these characteristics is also discussed. The main conclusions are as follows. 1) The presence or absence of pre-CME within 13 h before fast CME significantly improves the model prediction effect and has a significant influence on whether fast CME produces SEP event. Compared with the events without pre-CMEs, the events with pre-CMEs have a low proportion of false alarms (FR: 47.7% <i>vs.</i> 70%). However, the number of pre-CMEs does not improve the model output. 2) CMEs with type-II radio bursts have significantly lower FR to generate SEP events than fast CMEs without type-II radio bursts (42% <i>vs.</i> 68%). And selecting type-II radio bursts as a constraint will filter out some small/weak SEP events, the relationship between model predictions and observations especially for large SEP events (e.g. <i>I</i><sub>p</sub> ≥ 0.01 pfu/MeV) will stand out. Moreover, if the type-II radio enhancement is taken into account, FR can be further reduced to 29.4%, and the proportion of hits can be further increased (HR: 48.5%), and the model prediction is significantly improved. 3) The larger the start frequency of type II radio bursts, the smaller the end frequency is, and FR decreases slightly, but at the same time, a large number of SEP events are excluded by this condition, and the results show that the constraints on the start/end frequency of type-II radio bursts do not improve the model predictions distinctly. 4) If the sub-classification of type-II radio bursts is considered as the model constraint, the CMEs associated with multi-band type-II radio bursts have better model predictions than those with single-band events. For example, m-DH-km type-II radio bursts have lower FR (35.4%) and higher HR (48%), and the accuracy of empirical model is higher. In summary, we find that in addition to the velocity and angular width of CME, the associations of pre-CME, type II radio bursts and their enhancement, and multi-band sub-classification are the favorable conditions for CME to generate SEP events. The SEP intensities obtained by the empirical model have better consistency with the observations, and better predictions can be obtained. This investigation indicates that SEP events are more likely generated by fast and wide CMEs accompanied by pre-CMEs, multi-band type II radio bursts and their enhancements, which seem to serve as discriminative signal for SEP-rich and SEP-poor CMEs.

Analysis of signal to noise ratio in coronagraph observations of coronal mass ejections

We establish a baseline signal-to-noise ratio (SNR) requirement for the European Space Agency (ESA)-funded Solar Coronagraph for OPErations (SCOPE) instrument in its field of view of 2.5–30 solar radii based on existing observations by the Solar and Heliospheric Observatory (SOHO). Using automatic detection of coronal mass ejections (CMEs), we anaylse the impacts when SNR deviates significantly from our previously established baseline. For our analysis, SNR values are estimated from observations made by the C3 coronagraph on the Solar and Heliospheric Observatory (SOHO) spacecraft for a number of different CMEs. Additionally, we generate a series of artificial coronagraph images, each consisting of a modelled coronal background and a CME, the latter simulated using the graduated cylindrical shell (GCS) model together with the SCRaytrace code available in the Interactive Data Language (IDL) SolarSoft library. Images are created with CME SNR levels between 0.5 and 10 at the outer edge of the field of view (FOV), generated by adding Poisson noise, and velocities between 700 km s−1 and 2800 km s−1. The images are analysed for the detectability of the CME above the noise with the automatic CME detection tool CACTus. We find in the analysed C3 images that CMEs near the outer edge of the field of view are typically 2% of the total brightness and have an SNR between 1 and 4 at their leading edge. An SNR of 4 is defined as the baseline SNR for SCOPE. The automated detection of CMEs in our simulated images by CACTus succeeded well down to SNR = 1 and for CME velocities up to 1400 km s−1. At lower SNR and higher velocity of ≥ 2100 km s−1 the detection started to break down. For SCOPE, the results from the two approaches confirm that the initial design goal of SNR = 4 would, if achieved, deliver a comparable performance to established data used in operations today, with a more compact instrument design, and a margin in SNR before existing automatic detection produces significant false positives.

Search for the Relationship between the Velocity of a Coronal Mass Ejection and the Decay Rate of the Magnetic Field in the Region of Mass Emission Generation

In this paper, we search for the relationship between the Vlin linear projection velocity and the Vss velocity in the 3D space of coronal mass ejections (CMEs) recorded by LASCO coronagraphs with an “n” decay rate of the transverse component of the Bt magnetic field above the polarity inversion line (PIL) of the photospheric magnetic field in the active region (AR) in which the CME appeared. The Bt decay rate at an altitude h measured from the photosphere was calculated with the formula n(h) = –(h/Bt)(dBt/dh). Three-dimensional calculations of the magnetic field were performed in the potential approximation. The positive trend of the dependences 〈n〉(Vlin) and 〈n〉(Vss), however, does not have sufficient statistical significance: on average, the larger is 〈n〉, the higher are the determined Vlin and Vss CME velocities. Here, 〈n〉 includes the averaging of n over both the altitude and along the extended section of the PIL identified within each studied AR. The relationship between the quality of 〈n〉(Vlin) and 〈n〉(Vss) is shown to depend on the PIL section in the AR within which n is averaged. Based on the example of a fast CME on March 7, 2012, and a slow CME on October 22, 2013, it is shown that the difference in 〈n〉 for CMEs with different velocities is greater if the averaging of n along the PIL is performed within the CME initiation region, not along the entire extended PIL section in the AR.

RELATIONSHIP OF SCR, CME AND CORONAL SHOCK WAVES WITH THE PARAMETERS OF TYPE IV AND II SOLAR RADIO BURSTS

ABSTRACT. This paper presents the results of a comparative analysis of the relationship between solar cosmic rays (SCR), coronal mass ejections (CME), and coronal shock waves (CSW) with the parameters of solar continual type IV radio bursts, as well as with the parame- ters of type II radio bursts. The sample under study con- tains 147 proton events accompanied by type IV continu- um radio bursts in the 25-15400 MHz range, type II radio bursts in the 25-180 MHz range, as well as CME and cor- onal shock waves. For the analysis, we used original rec- ords of solar radio emission at 8 fixed frequencies in the range 245-15400 MHz according to data from RSTN (Ra- dio Solar Telescope Network), original records of dynam- ic spectra from SRS (Solar Radio Spectrograph) in the range of 25-180 MHz, as well as original records intensity of the flux of SCR protons with proton energies in the range> 1-100 MeV according to data from the GOES spacecraft. A comparative analysis showed that the rela- tionship between the intensity of the SCR proton flux and the CME velocity is, on average, much stronger with the parameters of type IV radio bursts than with the parame- ters of type II radio bursts, which indicates the dominant role of the SCR acceleration process in the flare region, rather than shock waves. However, detailed studies of the fine structure of type II radio bursts have shown that there is a fairly strong relationship between the intensity of the flux of mean-relativistic protons I p and the frequency f min,1 at the fundamental harmonic (at the 1-st harmonic) at the time t min corresponding to the minimum relative distance b min between the harmonics of type II radio bursts. De- tailed studies of the fine structure of type II radio bursts have also shown that there is a strong relationship between the intensity of the SCR proton flux I p and parameter V II , which characterizes the displacement of the shock front with time t i in a narrow frequency range of 25-60 MHz.

Kinematics of coronal mass ejections in the LASCO field of view

In this paper we present a statistical study of the kinematics of 28894 coronal mass ejections (CMEs) recorded by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory spacecraft from 1996 until mid-2017. The initial acceleration phase is characterized by a rapid increase in CME velocity just after eruption in the inner corona. This phase is followed by a non-significant residual acceleration (deceleration) characterized by an almost constant speed of CMEs. We demonstrate that the initial acceleration is in the range 0.24–2616 m s−2 with median (average) value of 57 m s−2 (34 m s−2) and it takes place up to a distance of about 28 RSUN with median (average) value of 7.8 RSUN (6 RSUN). Additionally, the initial acceleration is significant in the case of fast CMEs (V > 900 km s−1), where the median (average) values are about 295 m s−2 (251 m s−2), respectively, and much weaker in the case of slow CMEs (V < 250 km s−1), where the median (average) values are about 18 m s−2 (17 m s−2), respectively. We note that the significant driving force (Lorentz force) can operate up to a distance of 6 RSUN from the Sun during the first 2 hours of propagation. We found a significant anti-correlation between the initial acceleration magnitude and the acceleration duration, whereas the residual acceleration covers a range from −1224 to 0 m s−2 with a median (average) value of −34 m s−2 (−17 m s−2). One intriguing finding is that the residual acceleration is much smaller during the 24th cycle in comparison to the 23rd cycle of solar activity. Our study has also revealed that the considered parameters, initial acceleration (ACCINI), residual acceleration (ACCRES), maximum velocity (VMAX), and time at maximum velocity (TimeMAX) mostly follow solar cycles and the intensities of the individual cycle.

New ionospheric index for Space Weather services

Modern society replies on the ionosphere for technology such as radio navigation and telecommunications. However, this is not a static environment and its characteristics can be affected by solar phenomena such as coronal mass ejections (CMEs) and high-speed solar winds. In this paper we present a set of space weather parameters (e.g. type and velocity of CMEs, X-ray flux, the velocity of high-speed solar wind) that allow to identify the dominant physical connections between ionospheric dynamics and these two solar phenomena. The study uses vertical and oblique sounding data of the ionosphere obtained during several space weather events occurring in solar cycle 21, 22 and 24. We propose and discuss the advantage of a new ionospheric index for defining how CMEs and high speed solar streams, as global events of solar activity, influence the values of the parameters used to characterize the ionosphere.

3D numerical experiment for EUV waves caused by flux rope eruption

ABSTRACTWe present a 3D magnetohydrodynamic numerical experiment of an eruptive magnetic flux rope (MFR) and the various types of disturbances it creates, and employ forward modelling of extreme ultraviolet (EUV) observables to directly compare numerical results and observations. In the beginning, the MFR erupts and a fast shock appears as an expanding 3D dome. Under the MFR, a current sheet grows, in which magnetic field lines reconnect to form closed field lines, which become the outermost part of an expanding coronal mass ejection (CME) bubble. In our synthetic SDO/AIA images, we can observe the bright fast shock dome and the hot MFR in the early stages. Between the MFR and the fast shock, a dimming region appears. Later, the MFR expands so its brightness decays and it becomes difficult to identify the boundary of the CME bubble and distinguish it from the bright MFR in synthetic images. Our synthetic images for EUV disturbances observed at the limb support the bimodality interpretation for coronal disturbances. However, images for disturbances propagating on-disc do not support this interpretation because the morphology of the bright MFR does not lead to circular features in the EUV disturbances. At the flanks of the CME bubble, slow shocks, velocity vortices and shock echoes can also be recognized in the velocity distribution. The slow shocks at the flanks of the bubble are associated with a 3D velocity separatrix. These features are found in our high-resolution simulation, but may be hard to observe as shown in the synthetic images.

CME Productive and Non-productive Recurring Jets Near an Active Region AR11176

We study the recurring jets near AR11176 during the period 2011 March 31 17:00 UT to April 1 05:00 UT using observations from the Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO). Mini-filaments (mini-filament1 & 2) are found at the base of these recurring jets where mini-filament1 shows the partial signature of eruption in case of Jet1-3. However, the mini-filament2 shows a complete eruption driving a full blow-out jet (Jet4). The eruption of mini-filament2 triggers C-class flare and Jet4 eruption. The eruption of Jet4 triggers a coronal mass ejection (CME). The plane-of-sky velocity of recurring jets (Jet1-4) results in 160 km/s, 106 km/s, 151 km/s and 369 km/s. The estimated velocity of CME is 636 km/s. The continuous magnetic flux cancellation is observed at the base of the jet productive region which could be the cause of the eruption of mini-filaments and recurring jets. In the former case, the mini-filament1 shows partial eruption and first three jets (Jet1-3) are produced, but the rate of cancellation was rather low. However, in the latter case, mini-filament2 fully erupts (perhaps because of a higher cancellation rate), and this triggers a C-class flare and a CME-productive jet. At the base of first three jets (Jet1-3), the mini-filament1 causes to push the overlying dynamic complex thin loops resulting in the reconnection and drives the jet (Jet1-3) eruptions. The formation of the plasma blobs are observed during the eruption of the first jet (Jet1).

Особенности развития длительных потоков высокоэнергичного гамма-излучения на разных стадиях солнечных вспышек

We have studied properties of sustained gamma fluxes having quantum energies of >100 MeV at different stages of flares with 1-min temporal resolution (Fermi/LAT). 
 The most probable process of emergence of high-energy gamma-quanta during the impulsive phase of flares (6 events) has been confirmed. Acceleration of particles, produced by flare energy release (at dissipation of current sheet), occurs when they interact with a shock front of a coronal mass ejection (CME), which develops in the same active region at the same time. Nuclear interactions of accelerated protons (>500 MeV) with plasma ions lead further to the emergence of high-energy gamma-quanta. We have established that the interaction between a flare flux and a high-speed CME during the flare impulsive phase occurs within fairly limited periods — from 2 to 16 min. In the events considered, we have found a direct connection between maximum gamma flux F max (γ > 100 MeV) and CME velocity.
 High maximum values of gamma fluxes are typical of the flare impulsive phase: 3.5·10⁻⁴ cm⁻²s⁻¹ ≤ F max (γ > 100 MeV) ≤ 1.3·10⁻² cm⁻² s⁻¹. At the same time, the value F max (γ > 100 MeV) = 0.013 cm⁻²s⁻¹ was the highest for the events observed by Fermi/LAT from 2008 to 2017.
 During the development of CMEs moving with a supersonic speed, shock waves are formed which are the major power source of accelerated particles during the main phase of gradual flares. In some cases, however, the impact of shock waves on particle acceleration is the greatest in the short impulsive phase.
 To reveal parameters most effectively influencing the generation of high-energy gamma-ray emission, we have compared 17 flare events. The most significant parameter proved to be the time interval of joint action of flare process and CME shocks.
 We have established that during simultaneous development of flare process and CME attendant on the flare, the most efficient particle acceleration occurs which gives rise to maximum fluxes of high-energy gamma-quanta.

Features of development of sustained fluxes of high-energy gamma-ray emission at different stages of solar flares

We have studied properties of sustained gamma fluxes having quantum energies of >100 MeV at different stages of flares with 1-min temporal resolution (Fermi/LAT). 
 The most probable process of emergence of high-energy gamma-quanta during the impulsive phase of flares (6 events) has been confirmed. Acceleration of particles, produced by flare energy release (at dissipation of current sheet), occurs when they interact with a shock front of a coronal mass ejection (CME), which develops in the same active region at the same time. Nuclear interactions of accelerated protons (>500 MeV) with plasma ions lead further to the emergence of high-energy gamma-quanta. We have established that the interaction between a flare flux and a high-speed CME during the flare impulsive phase occurs within fairly limited periods — from 2 to 16 min. In the events considered, we have found a direct connection between maximum gamma flux F max (γ > 100 MeV) and CME velocity.
 High maximum values of gamma fluxes are typical of the flare impulsive phase: 3.5·10⁻⁴ cm⁻²s⁻¹ ≤ F max (γ > 100 MeV) ≤ 1.3·10⁻² cm⁻² s⁻¹. At the same time, the value F max (γ > 100 MeV) = 0.013 cm⁻²s⁻¹ was the highest for the events observed by Fermi/LAT from 2008 to 2017.
 During the development of CMEs moving with a supersonic speed, shock waves are formed which are the major power source of accelerated particles during the main phase of gradual flares. In some cases, however, the impact of shock waves on particle acceleration is the greatest in the short impulsive phase.
 To reveal parameters most effectively influencing the generation of high-energy gamma-ray emission, we have compared 17 flare events. The most significant parameter proved to be the time interval of joint action of flare process and CME shocks.
 We have established that during simultaneous development of flare process and CME attendant on the flare, the most efficient particle acceleration occurs which gives rise to maximum fluxes of high-energy gamma-quanta.

The Stellar CME–Flare Relation: What Do Historic Observations Reveal?

Abstract Solar coronal mass ejections (CMEs) and flares have a statistically well-defined relationship, with more energetic X-ray flares corresponding to faster and more massive CMEs. How this relationship extends to more magnetically active stars is a subject of open research. Here we study the most probable stellar CME candidates associated with flares captured in the literature to date, all of which were observed on magnetically active stars. We use a simple CME model to derive masses and kinetic energies from observed quantities and transform associated flare data to the Geostationary Operational Environmental Satellite 1–8 Å band. Derived CME masses range from ∼1015 to 1022 g. Associated flare X-ray energies range from 1031 to 1037 erg. Stellar CME masses as a function of associated flare energy generally lie along or below the extrapolated mean for solar events. In contrast, CME kinetic energies lie below the analogous solar extrapolation by roughly 2 orders of magnitude, indicating approximate parity between flare X-ray and CME kinetic energies. These results suggest that the CMEs associated with very energetic flares on active stars are more limited in terms of the ejecta velocity than the ejecta mass, possibly because of the restraining influence of strong overlying magnetic fields and stellar wind drag. Lower CME kinetic energies and velocities present a more optimistic scenario for the effects of CME impacts on exoplanets in close proximity to active stellar hosts.

A statistical study of CME-associated flare during the solar cycle 24

We investigate on the relationship between flares and coronal mass ejections (CMEs) in which a flare started before and after the CME events which differ in their physical properties, indicating potentially different initiation mechanisms. The physical properties of two types flare-correlated CME remain an interesting and important question in space weather. We study the relationship between flares and CMEs using a different approach requiring both temporal and spatial constraints during the period from December 1, 2008 to April 30, 2017 in which the CMEs data were acquired by SOHO/LASCO (Solar and Heliospheric Observatory/Large Angle Spectrometric Coronagraph) over the solar cycle 24. The soft X-ray flare flux data, such as flare class, location, onset time and integrated flux, are collected from Geostationary Environmental satellite (GOES) and XRT Flare catalogs. We selected 307 CMEs-flares pairs applying simultaneously temporal and spatial constraints in all events for the distinguish between two associated CME-flare types. We study the correlated properties of coincident flares and CMEs during this period, specifically separating the sample into two types: flares that precede a CME and flares that follow a CME. We found an opposite correlation relationship between the acceleration and velocity of CMEs in the After- and Before-CMEs events. We found a log-log relation between the width and mass of CMEs in the two associated types. The CMEs and flares properties show that there were significant differences in all physical parameters such as (mass, angular width, kinetic energy, speed and acceleration) between two flare-associated CME types.

THE RELATIONSHIP OF THE SCR WITH PARAMETERS OF RADIO BURSTS AND CME

The relationship the intensity of the proton flux Ip of solar cosmic rays (SCR) with the parameters of continual radio bursts of the IV type, with the speed of coronal mass ejections (CME) of VCME, as well as with the parameters of slowly drifting radio bursts of type II is investigated. Comparative analysis showed that for the vast majority of proton events a strong correlation of the intensity of the proton flux Ip with the integral flux ∫Fμdt of microwave bursts and the CME velocity VCME is observed, where the correlation coefficient r between the investigated parameters is 0.80 and 0.72, respectively. Earlier, the author reported on a strong connection between the integral flux ∫Fμdt of the microwave bursts and the CME velocity VCME, where the correlation coefficient r between the investigated quantities is about 0.80. The strong connection between the intensity of the proton flux Ip and the integral flux ∫Fμdt of microwave bursts and the speed of the CME, as well as the strong connection between the integral flux ∫Fμdt of the microwave bursts and the CME velocity VCME, attests about the common origin of SCRs and CMEs during proton flares. In this paper it is also shown that there is a strong relationship between the intensity of the proton flux Ip and the parameter of type II burst VII, which characterizes the shock front displacement velocity. Moreover, the relationship between the intensity of the proton flux Ip and the parameter VII depends to a large extent on the frequency f2 of the maximum of the type II radio burst on the second harmonic at a given time t and on the energy of the protons Ep. The maximum correlation between the proton flux Ip and parameter VII is observed for protons with an energy Ep>30 MeV and for the upper frequency f2 in the range 25-60 MHz.

Dependence of Coronal Mass Ejection Properties on Their Solar Source Active Region Characteristics and Associated Flare Reconnection Flux

Abstract The near-Sun kinematics of coronal mass ejections (CMEs) determine the severity and arrival time of associated geomagnetic storms. We investigate the relationship between the deprojected speed and kinetic energy of CMEs and magnetic measures of their solar sources, reconnection flux of associated eruptive events, and intrinsic flux-rope characteristics. Our data covers the period 2010–2014 in solar cycle 24. Using vector magnetograms of source active regions, we estimate the size and nonpotentiality. We compute the total magnetic reconnection flux at the source regions of CMEs using the post-eruption arcade method. By forward modeling the CMEs, we find their deprojected geometric parameters and constrain their kinematics and magnetic properties. Based on an analysis of this database, we report that the correlation between CME speed and their source active region size and global nonpotentiality is weak, but not negligible. We find the near-Sun velocity and kinetic energy of CMEs to be well correlated with the associated magnetic reconnection flux. We establish a statistically significant empirical relationship between the CME speed and reconnection flux that may be utilized for prediction purposes. Furthermore, we find CME kinematics to be related with the axial magnetic field intensity and relative magnetic helicity of their intrinsic flux ropes. The amount of coronal magnetic helicity shed by CMEs is found to be well correlated with their near-Sun speeds. The kinetic energy of CMEs is well correlated with their intrinsic magnetic energy density. Our results constrain processes related to the origin and propagation of CMEs and may lead to better empirical forecasting of their arrival and geoeffectiveness.

Determination of projection effects of CMEs using quadrature observations with the two STEREO spacecraft

Since 1995 coronal mass ejections (CMEs) have been routinely observed thanks to the sensitive Large Angle and Spectrometric Coronagraphs (LASCO) on board the Solar and Heliospheric Observatory (SOHO) mission. Their observed characteristics are stored, among other, in the SOHO/LASCO catalog. These parameters are commonly used in scientific studies. Unfortunately, coronagraphic observations of CMEs are subject to projection effects. This makes it practically impossible to determine the true properties of CMEs and therefore makes it more difficult to forecast their geoeffectiveness. In this study, using quadrature observations with the two Solar Terrestrial Relations Observatory (STEREO) spacecrafts, we estimate the projection effect affecting velocity of CMEs included in the SOHO/LASCO catalog. It was demonstrated that this effect depends significantly on width and source location of CMEs. It can be very significant for narrow events and originating from the disk center. The effect diminishes with increasing width and absolute longitude of source location of CMEs. For very wide (width ⩾ 250°) or limb events (|longitude ⩾ 70°) projection effects completely disappears.

New Parameter in the Description of Solar Cosmic Ray Events—Energy of Balance between Solar and Galactic Protons

Solar proton events possess a wide variety of features that reflect the conditions of solar proton acceleration and propagation. Relevant investigations rely on statistical methods that make it possible to classify events with the aim of obtaining deeper insight into physical processes leading to the generation of solar cosmic rays. In classifying events in power, the intensity of particles with energy above 10MeV at the maximum of the event time profile or the fluence of particles throughout the event time is usually used. A new parameter, Eqm, that characterizes the proton event power and which is some kind of approximation of the maximum energy of accelerated particles is analyzed in the present study. Correlations of Eqm with properties of x-ray flares on the Sun and with the velocity of coronal mass ejections are examined.

MICROWAVE EMISSION OF SOLAR FLARES: CORONAL MASS EJECTIONS AND SHOCK WAVES

Coronal mass ejections (CMEs) mostly affect the geomagnetic field. These structures are observed and studied with coronagraphic images therefore we don’t see the corona in the plane of the sky and the measurements of the propagation speed for solar disk events are not accessible to coronagraphic observations. This suggests that microwave emission of solar flares that can be attributed to the gyrosynchrotron mechanism of mildly relativistic electrons can be used. In turn, the relationship between coronal shock waves and CMEs also remains unclear. The data set that we use in this study is based on microwave (μ) observations of spectral fluxes Fμ at 8.8 GHz obtained with the Radio Solar Telescope Network for the 124 proton solar events . The correlation coefficient r between the CME velocities VCME and integral fluxes of microwave emission ∫Fμdt achieves of about 0.8 while it does not exceed 0.36 between VCME and the shock wave velocities. It has been found the quite strong correlation between the growth rate of microwave emission and the deceleration of frequency drift in the frequency range of 25-180 GHz (r ≈ 0.66). The obtained results suggest that microwave observation can be used to predict VCME and the shock wave generation occurs in the region of flare energy release.

Predicting Flares and Solar Energetic Particle Events: The FORSPEF Tool

A novel integrated prediction system for solar flares (SFs) and solar energetic particle (SEP) events is presented here. The tool called forecasting solar particle events and flares (FORSPEF) provides forecasts of solar eruptive events, such as SFs with a projection to occurrence and velocity of coronal mass ejections (CMEs), and the likelihood of occurrence of an SEP event. In addition, the tool provides nowcasting of SEP events based on actual SF and CME near real-time data, as well as the SEP characteristics (e.g. peak flux, fluence, rise time, and duration) per parent solar event. The prediction of SFs relies on the effective connected magnetic field strength ( $B_{\mathrm{eff}}$ ) metric, which is based on an assessment of potentially flaring active-region (AR) magnetic configurations, and it uses a sophisticated statistical analysis of a large number of AR magnetograms. For the prediction of SEP events, new statistical methods have been developed for the likelihood of the SEP occurrence and the expected SEP characteristics. The prediction window in the forecasting scheme is 24 hours with a refresh rate of 3 hours, while the respective prediction time for the nowcasting scheme depends on the availability of the near real-time data and ranges between 15 – 20 minutes for solar flares and 6 hours for CMEs. We present the modules of the FORSPEF system, their interconnection, and the operational setup. Finally, we demonstrate the validation of the modules of the FORSPEF tool using categorical scores constructed on archived data, and we also discuss independent case studies.