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Full list of authors: Harra, Louise; Andretta, Vincenzo; Appourchaux, Thierry; Baudin, Frédéric; Bellot-Rubio, Luis; Birch, Aaron C.; Boumier, Patrick; Cameron, Robert H.; Carlsson, Matts; Corbard, Thierry; Davies, Jackie; Fazakerley, Andrew; Fineschi, Silvano; Finsterle, Wolfgang; Gizon, Laurent; Harrison, Richard; Hassler, Donald M.; Leibacher, John; Liewer, Paulett; Macdonald, Malcolm; Maksimovic, Milan; Murphy, Neil; Naletto, Giampiero; Nigro, Giuseppina; Owen, Christopher; Martínez-Pillet, Valentín; Rochus, Pierre; Romoli, Marco; Sekii, Takashi; Spadaro, Daniele; Veronig, Astrid; Schmutz, W.--This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/., A mission to view the solar poles from high helio-latitudes (above 60°) will build on the experience of Solar Orbiter as well as a long heritage of successful solar missions and instrumentation (e.g. SOHO Domingo et al. (Solar Phys. 162(1-2), 1–37 1995), STEREO Howard et al. (Space Sci. Rev. 136(1-4), 67–115 2008), Hinode Kosugi et al. (Solar Phys. 243(1), 3–17 2007), Pesnell et al. Solar Phys. 275(1–2), 3–15 2012), but will focus for the first time on the solar poles, enabling scientific investigations that cannot be done by any other mission. One of the major mysteries of the Sun is the solar cycle. The activity cycle of the Sun drives the structure and behaviour of the heliosphere and of course, the driver of space weather. In addition, solar activity and variability provides fluctuating input into the Earth climate models, and these same physical processes are applicable to stellar systems hosting exoplanets. One of the main obstructions to understanding the solar cycle, and hence all solar activity, is our current lack of understanding of the polar regions. In this White Paper, submitted to the European Space Agency in response to the Voyage 2050 call, we describe a mission concept that aims to address this fundamental issue. In parallel, we recognise that viewing the Sun from above the polar regions enables further scientific advantages, beyond those related to the solar cycle, such as unique and powerful studies of coronal mass ejection processes, from a global perspective, and studies of coronal structure and activity in polar regions. Not only will these provide important scientific advances for fundamental stellar physics research, they will feed into our understanding of impacts on the Earth and other planets’ space environment. © The Author(s) 2021., Open Access funding provided by ETH Zurich., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

This article summarises the results of an analysis of solar radio bursts (SRBs) detected by the Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometer hosted by the University of Rwanda. The data analysed were detected during the first year (2014–2015) of the instrument operation. Using quick plots provided by the e-CALLISTO website, a total of 201 intense and well-separated solar radio bursts detected by the CALLISTO station located in Rwanda, are found consisting of 4 type II, 175 type III and 22 type IV radio bursts. It is found that all analysed type II and ∼ 37 % of type III bursts are associated with impulsive solar flares, while the minority (∼ 13 %) of type IV radio bursts are associated with solar flares. Furthermore, all type II radio bursts are associated with coronal mass ejections (CMEs), ∼ 44 % of type III bursts are associated with CMEs, and the majority (∼ 82 %) of type IV bursts were accompanied by CMEs. With aid of the atmospheric imaging assembly (AIA) images on board the Solar Dynamics Observatory (SDO), the location of open magnetic field lines of non-flare-associated type III radio bursts are shown. The same images are used to show the magnetic loops in the solar corona for type IV radio bursts observed in the absence of solar flares and/or CMEs. Findings from this study indicate that analysis of SRBs that are observed from the ground can provide a significant contribution to the early diagnosis of solar transients phenomena, such as solar flares and CMEs, which are major drivers of potential space weather hazards.

Type-II radio emission often accompanies events in solar cosmic rays and is an indicator of the propagation of a shock wave in the solar corona. Conversely, the shock wave associated with coronal mass ejections plays an important role in the acceleration of solar protons. Both of these phenomena can occur unaccompanied by solar cosmic rays, while not all solar cosmic ray events are accompanied by type-II radio emission. The statistical relationships between these phenomena are considered based on the catalogs of solar proton events for the 23rd and 24th solar-activity cycles. It is shown that the events of solar cosmic rays accompanied by type-II radio emissions are among the most powerful in terms of both particle characteristics and source characteristics.

Most hot Jupiters have extended envelopes of gas that spread beyond their Roche lobes. A typical envelope is weakly gravitationally bound to the planet and, therefore, its structure and properties are strongly affected by stellar wind disturbances, for example, coronal mass ejections. Earlier, we performed gas-dynamic modeling of the interaction of a narrow coronal mass ejection (CME) with the envelope of the hot Jupiter HD 209458b. In this study, we investigate the influence of the planet’s magnetic field and stellar wind on the structure and dynamics of the HD 209458b envelope exposed to a similar CME. For this, an MHD model of the CME interaction with the envelope was developed. It was assumed that the field of the planet had a generally accepted value and corresponded to 1/10 of the magnetic moment of Jupiter. The field of the star was assumed to be weak (10–3 G), which ensured the super-Alfven flow of the stellar wind around the planet. The comparison of the MHD simulation with gas-dynamic calculations shows that, for the adopted values of the fields of the planet and the star, the effect of the magnetic field on the envelope is not decisive and the qualitative picture of the flow does not change. At the same time, taking magnetic fields into account leads to a change in the quantitative characteristics of the envelope and the mass loss rate, which can be important in determining the evolutionary status of the exoplanet.

A technique is proposed for determining the moment of 10–100 MeV proton injection in solar proton events with similarity of scale (scaling). It is possible to determine the moment of injection in such events according to their time profile. Using a series of events, it is shown that protons are injected during the propagation of a coronal mass ejection when it reaches a distance of 1–1.5 solar radii.

The present paper reports magnetospheric-thermospheric-ionospheric interactions, observed during geomagnetically disturbed periods in 2015–2016 from mid-latitude stations located in the US-Pacific longitudes (~120°W geographic). These interactions have been analyzed for a series of Coronal Mass Ejection (CME) and High Speed Solar Wind (HSSW) driven geomagnetic storms during the moderate solar activity periods. The geomagnetically disturbed periods under consideration in this paper have an interesting feature of the occurrences of one or more HSSW events following an intense CME driven intense geomagnetic storm. Correlations were observed between the solar and geomagnetic parameters, hemispherically integrated Joule heating, changes in O/N2 ratio, corresponding changes in neutral wind velocities and mid-latitude Vertical Total Electron Content (VTEC) in most of the cases. Prolonged effects of neutral wind driven equatorward plasma transport process were noticed during the period of the summer solstice (June 23–26, 2015) which was correlated with the hemispherically integrated Joule heating and ionospheric conductivities. The effects of storm onset were observed during March 17–18, 2015. The influences of the ‘super-fountain effect’ in terms of Prompt Penetration Electric Field (PPEF) were seen during the main phases of the geomagnetic storms from these mid-latitude stations. This is correlated with the strength of Equatorial Electrojet (EEJ).

The activity of stars such as the Sun varies over timescales ranging from the very short to the very long—stellar and planetary evolutionary timescales. Experience from our solar system indicates that short-term, transient events such as stellar flares and coronal mass ejections create hazardous space environmental conditions that impact Earth-orbiting satellites and planetary atmospheres. Extreme events such as stellar superflares may play a role in atmospheric mass loss and create conditions unsuitable for life. Slower, long-term evolutions of the activity of Sun-like stars over millennia to billions of years result in variations in stellar wind properties, radiation flux, cosmic ray flux, and frequency of magnetic storms. This coupled evolution of star-planet systems eventually determines planetary and exoplanetary habitability. The Solar Evolution and Extrema (SEE) initiative of the Variability of the Sun and Its Terrestrial Impact (VarSITI) program of the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) aimed to facilitate and build capacity in this interdisciplinary subject of broad interest in astronomy and astrophysics. In this review, we highlight progress in the major themes that were the focus of this interdisciplinary program, namely, reconstructing and understanding past solar activity including grand minima and maxima, facilitating physical dynamo-model-based predictions of future solar activity, understanding the evolution of solar activity over Earth’s history including the faint young Sun paradox, and exploring solar-stellar connections with the goal of illuminating the extreme range of activity that our parent star—the Sun—may have displayed in the past, or may be capable of unleashing in the future.

The Earth’s magnetosphere is region that is carved out by the solar wind as it flows past and interacts with the terrestrial magnetic field. The inner magnetosphere is the region that contains the plasmasphere, ring current, and the radiation belts all co-located within about 6.6 Re, nominally taken to be bounding this region. This region is highly dynamic and is home to a variety of plasma waves and particle populations ranging in energy from a few eV to relativistic and ultra-relativistic electrons and ions. The interplanetary magnetic field (IMF) embedded in the solar wind via the process of magnetic reconnection at the sub-solar point sets up plasma convection and creates the magnetotail. Magnetic reconnection also occurs in the tail and is responsible for explosive phenomena known as substorms. Substorms inject low-energy particles into the inner magnetosphere and help generate and sustain plasma waves. Transients in the solar wind such as coronal mass ejections (CMEs), co-rotating interaction regions (CIRs), and interplanetary shocks compress the magnetosphere resulting in geomagnetic storms, energization, and loss of energetic electrons in the outer radiation belt nad enhance the ring current, thereby driving the geomagnetic dynamics. The Specification and Prediction of the Coupled Inner-Magnetospheric Environment (SPeCIMEN) is one of the four elements of VarSITI (Variability of the Sun and Its Terrestrial Impact) program which seeks to quantitatively predict and specify the inner magnetospheric environment based on Sun/solar wind driving inputs. During the past 4 years, the SPeCIMEN project has brought together scientists and researchers from across the world and facilitated their efforts to achieve the project goal. This review provides an overview of some of the significant scientific advances in understanding the dynamical processes and their interconnectedness during the VarSITI era. Major space missions, with instrument suites providing in situ measurements, ground-based programs, progress in theory, and modeling are briefly discussed. Open outstanding questions and future directions of inner magnetospheric research are explored.

The results of the forecasting of quasi-stationary and transient solar wind streams velocity for a period from May to December 2010 are presented. The velocity of quasi-stationary solar wind streams on the near-Earth orbit was calculated with the empiric model based on an analysis of solar images obtained in the extreme ultraviolet. The velocity and arrival time of the interplanetary coronal mass ejections were predicted with the Drag-Based Model. The results of the forecast of the velocity of quasi-stationary solar wind streams were used as a parameter of the interplanetary medium through which the transient streams propagate and with which they interact. For the period of May–December 2010, 94 coronal mass ejections were selected from the databases, which were updated in near-real time. Analysis of the forecast results has shown that 67% of the selected interplanetary coronal mass ejections had a predicted velocity of less than 400 km/s, and 96% of them are associated with a quiet geomagnetic conditions (Dst > –30 nT). The forecast of quasi-stationary solar wind streams is improved by the addition of the prediction of interplanetary coronal mass ejections. For the period from May to December 2010, the standard deviation between the solar wind stream velocities measured on the ACE spacecraft and the predicted values, which take into account both quasi-stationary and transient streams, is 82 km/s, and the correlation coefficient is 0.6.

An analysis is performed of the statistical relationship between coronal mass ejections and solar flares to establish the sequence of these events. Periods of delay in the occurrence of coronal mass ejections relative to the associated flare-like manifestations of solar activity are determined. It is found that situations in which flares occur several hours ahead of coronal ejections predominate.

This paper provides a brief description individual elements that can be included in the Solntse–Terahertz scientific apparatus that was designed for the first time to carry out an extra-atmospheric experiment onboard the International Space Station. Its purpose is to measure terahertz electromagnetic radiation both from the quiet Sun and during active processes on the Sun (solar flares, coronal mass ejections, etc.), which is necessary to establish the physical nature of solar activity and solar flares. The possibility is discussed of using optoacoustic converters (Golay cells) as receivers of terahertz radiation, the sensitivity, stability, and response time of which were determined in the course of preliminary laboratory studies under terrestrial conditions.

This is the second paper in a series of two, which analyze the position of the Barents Sea ice-edge (BIE) based on a 442-year long dataset to understand its time variations. The data have been collected from ship-logs, polar expeditions, and hunters in addition to airplanes and satellites in recent times. Our main result is that the BIE position alternates between a southern and a northern position followed by Gulf Stream Beats (GSBs) at the occurrence of deep solar minima. We decompose the low frequency BIE position variations in cycles composed of dominant periods which are related to the Jose period of 179 years, indicating planetary forcings. We propose that the mechanism transferring planetary signals into changes in BIE position is the solar wind (SW), which provides magnetic shielding of the Earth in addition to geomagnetic disturbances. Increase in the solar wind produces pressure which decelerates the Earth’s rotation. It also transfers electrical energy to the ring current in the earth’s magnetosphere. This current magnetizes the earth’s solid core and makes it rotate faster. To conserve angular momentum the earth’s outer fluid mantle rotates slower with a delay of about 100 years. In addition will geomagnetic storms, initiated by solar coronal mass ejections (CMEs) penetrate deep in the Earth’s atmosphere and change pressure pattern in the Arctic. This effect is larger during solar minima since the magnetic shielding then is reduced. The Arctic may then experience local warming. The transition of solar activities to a possibly deep and long minimum in the present century may indicate Arctic cooling and the BIE moving south this century. For the North Atlantic region, effects of the BIE expanding southward will have noticeable consequences for the ocean bio-production from about 2040.

The technique of coronal mass ejection (CME) mass estimates from the energy of stellar flares has been applied to the data on the flare activity of late-type stars. In this study we use the data from catalogs on stellar flares obtained from the results of observations with the Kepler Space Telescope and present the relations between CME mass and effective temperature for objects from these catalogs. We have established that, in this case, the range of CME masses is $${\sim}10^{19}{-}10^{22}$$ g, with an increase in the CME mass being observed as we pass to hotter (more massive) stars. We consider the data for several well-studied active stars that characterize the possible range of CME properties for cool dwarfs. Our results are compared with the data found by an independent method of estimates of CME characteristics from spectroscopic observations. The CME masses estimated from the empirical relations for flare energies exceed the CME masses found from the asymmetry of Balmer hydrogen line profiles.

The Advanced Space-based Solar Observatory (ASO-S) is the China's first comprehensive solar dedicated satellite, scheduled to be launched around 2022. The Lyman-alpha (Ly α ) Solar Telescope (LST) is one of the payloads of the ASO-S, consisting of three scientific instruments and two Guide Telescopes (GTs). The scientific instruments include a Solar Disk Imager (SDI), a White-light Solar Telescope (WST), and a Solar Corona Imager (SCI), which are aimed to observe the whole evolving process of two types of violent eruptions on the Sun, i.e., solar flares and coronal mass ejections, in multiwavelengths with high temporal and spatial resolutions. To achieve this goal, all LST instruments have included an observation mode (event mode) dedicated to event observations. In this mode, all instruments take images at a higher cadence (the SCI takes full-frame coronal images while SDI and WST take only partial frame images around the eruption region). The time and location information of the eruption events can be effectively obtained by monitoring the local brightness enhancement of the onboard images processed with median filtering and pixel rebinning. The obtained information will provide an important electronic input for the automatic switching between different observation modes of LST.

We have analyzed the fast coronal mass ejection (CME) that occurred on February 25, 2014. The analysis is based on images taken in the 131, 211, 304, and 1700 Å UV channels of the SDO/AIA instrument and from observations obtained in the Hα line (6562.8 Å) with the telescopes of the Teide and Big Bear Observatories. The February 25, 2014 CME is associated with the ejection and subsequent explosive expansion of the magnetic flux rope, which appeared near the solar surface presumably due to the tether-cutting magnetic reconnection. The impulse of full pressure (thermal plus magnetic) resulting from such an “explosion” acts on the overlying coronal arcades, causing them to merge and form an accelerated moving frontal structure of the CME. This pressure impulse also generates a blast collisional shock wave ahead of the CME, whose velocity decreases rapidly with distance. At large distances R>7R₀ (R₀ is the solar radius) from the center of the Sun in front of the CME, a shock wave of another type is formed — a “piston” collisional shock wave whose velocity varies little with distance. At R≥15R₀, there is a transition from a collisional to a collisionless shock wave.

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.

We present the model calculation results of the atomic oxygen loss rate from the Martian atmosphere induced by precipitation of high-energy protons and hydrogen atoms (H/H+) from the solar wind plasma. Penetration of energetic protons and hydrogen atoms from the solar wind plasma to the upper atmosphere of Mars at altitudes of 100−250 km is accompanied by the momentum and energy transfer in collisions with the main component, atomic oxygen. This process is considered as atmospheric gas sputtering during proton auroral events, which is accompanied by formation of the suprathermal hydrogen and oxygen atom fluxes escaping from the atmosphere. When calculating the formation rate of suprathermal atoms, the modified Monto Carlo kinetic model was used. This model was earlier developed to analyze the data of the Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) and the Solar Wind Ion Analyzer (SWIA) onboard the Mars Express (MEX) and the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, respectively. We study the processes of kinetics and transport of hot oxygen atoms in the transition zone (from the thermosphere to the exosphere) of Mars’ upper atmosphere. The kinetic energy distribution functions for suprathermal oxygen atoms were calculated. It has been shown that, during proton auroral events on Mars, the exosphere is populated with a significant number of suprathermal oxygen atoms, the kinetic energy of which reaches the escape energy, 2 eV. In addition to photochemical sources, a hot fraction is formed in the oxygen corona; and a nonthermal flux of atomic oxygen escaping from the Martian atmosphere is produced during proton aurora events. Proton aurorae are sporadic auroral events. Consequently, according to the estimates obtained from the recent MAVEN observations the magnitude of the precipitation-induced escaping flux of hot oxygen atoms may become prevailing over the photochemical sources under conditions of the extreme solar events such as solar flares and coronal mass ejections.

The interplanetary magnetic field magnitude Bo, proton density Np and solar wind speed Vsw data from Ulysses spacecraft during its interplanetary cruise interval from Earth to Jupiter, from 18 November 1990 to 31 January 1992, are analyzed in this study. Statistical and wavelet techniques are employed to characterize some properties from the solar wind parameters near the ecliptic plane and their dependence with radial distance. The results from kurtosis analysis showed that the three solar wind parameters (Bo, Np and Vsw) presented a decrease of this statistical quantity with the increase of scales, indicating that these variables are intermittent in short time scales. Further, the kurtosis parameter presented an increase in all scales around 2–3 AU distance range that corresponds to a solar wind regime transition. It was noted that the interplanetary medium was dominated by solar transients (interplanetary coronal mass ejections) until the middle of 1991. Afterwards a more stable pattern of corotating interaction regions arose. Furthermore, the probability distribution functions presented a spreading shape due to the occurrence of intermittence. In order to study the temporal variability of the solar wind parameters, the wavelet approach was used. The following major periodicities were found for the three solar wind variables studied: ~13, ~26, and ~83–88 days. It was noted that the ~13 day periods presented strong spectral power in the 2 to 4 AU range, where the solar wind was dominated by ICME transients. On the other hand, the 26 day period shows higher spectral power for distances higher than 4 AU, where the interplanetary space is more dominated by CIRs. Thus, it was found in this paper a significant dependence of solar wind parameters on radial heliocentric distance which can be accounted by the dynamical evolution of solar wind structures with distance.

Major geomagnetic storms are caused by unusually intense solar wind southward magnetic fields that impinge upon the Earth's magnetosphere (Dungey, 1961). How can we predict the occurrence of future interplanetary events? Do we currently know enough of the underlying physics and do we have sufficient observations of solar wind phenomena that will impinge upon the Earth's magnetosphere? We view this as the most important challenge in space weather. We discuss the case for magnetic clouds (MCs), interplanetary sheaths upstream of interplanetary coronal mass ejections (ICMEs), corotating interaction regions (CIRs) and solar wind high-speed streams (HSSs). The sheath- and CIR-related magnetic storms will be difficult to predict and will require better knowledge of the slow solar wind and modeling to solve. For interplanetary space weather, there are challenges for understanding the fluences and spectra of solar energetic particles (SEPs). This will require better knowledge of interplanetary shock properties as they propagate and evolve going from the Sun to 1 AU (and beyond), the upstream slow solar wind and energetic “seed” particles. Dayside aurora, triggering of nightside substorms, and formation of new radiation belts can all be caused by shock and interplanetary ram pressure impingements onto the Earth's magnetosphere. The acceleration and loss of relativistic magnetospheric “killer” electrons and prompt penetrating electric fields in terms of causing positive and negative ionospheric storms are reasonably well understood, but refinements are still needed. The forecasting of extreme events (extreme shocks, extreme solar energetic particle events, and extreme geomagnetic storms (Carrington events or greater)) are also discussed. Energetic particle precipitation into the atmosphere and ozone destruction are briefly discussed. For many of the studies, the Parker Solar Probe, Solar Orbiter, Magnetospheric Multiscale Mission (MMS), Arase, and SWARM data will be useful.

Coronal Mass Ejections (CMEs) may have major importance for planetary and stellar evolution. Stellar CME parameters, such as mass and velocity, have yet not been determined statistically. So far only a handful of stellar CMEs has been detected mainly on dMe stars using spectroscopic observations. We therefore aim for a statistical determination of CMEs of solar-like stars by using spectroscopic data from the ESO phase 3 and Polarbase archives. To identify stellar CMEs we use the Doppler signal in optical spectral lines being a signature of erupting filaments which are closely correlated to CMEs. We investigate more than 3700 hours of on-source time of in total 425 dF-dK stars. We find no signatures of CMEs and only few flares. To explain this low level of activity we derive upper limits for the non detections of CMEs and compare those with empirically modelled CME rates. To explain the low number of detected flares we adapt a flare power law derived from EUV data to the H{\alpha} regime, yielding more realistic results for H{\alpha} observations. In addition we examine the detectability of flares from the stars by extracting Sun-as-a-star H{\alpha} light curves. The extrapolated maximum numbers of observable CMEs are below the observationally determined upper limits, which indicates that the on-source times were mostly too short to detect stellar CMEs in H{\alpha}. We conclude that these non detections are related to observational biases in conjunction with a low level of activity of the investigated dF-dK stars., Comment: MNRAS accepted

—Currently, hot Jupiters have extended gaseous (ionospheric) envelopes extending far beyond the Roche lobe. The envelopes are loosely bound to the planet and are subject to a strong influence by stellar wind fluctuations. Since hot Jupiters are close to the parent star, the magnetic field of the stellar wind is an important factor which defines the structure of their magnetospheres. For a typical hot Jupiter, the velocity of stellar wind plasma flowing around the atmosphere is close to the Alfven velocity. Thus, fluctuations of the stellar wind parameters (density, velocity, magnetic field) can affect conditions for the formation of the bow shock around a hot Jupiter, such as transforming the flow from sub-Alfven to super-Alfven regime and back. The study results of three-dimensional numerical MHD simulations confirm that, in a hot Jupiter’s envelope located near the Alfven point of the stellar wind, both the disappearance and appearance of a detached shock can occur under the influence of a coronal mass ejection. The study also shows that this process can affect the observational manifestations of a hot Jupiter, including the radiation flux in the spectrum’s hard region.

This paper gives an overview of the terms space weather, coronal mass ejections (CMEs), galactic cosmic rays (GCRs) and their impact on satellites. To detect a CME and its counterpart interplanetary coronal mass ejection (ICME), coronagraph and instruments for measuring interplanetary plasma properties are needed, respectively. Plasma measurements used in this paper are taken from SWE and MAG instruments on the spacecraft Wind. In addition, the coronagraphs on board SOHO and STEREO-A and -B spacecraft are used to provide stereoscopic image of CMEs. This paper will explain how CMEs impact GCRs and telecommunications and will provide the interpretation of CME measurements from an event that happened on 16/06/2010.

Kollhoff, A., et al., Context. On 2020 November 29, the first widespread solar energetic particle (SEP) event of solar cycle 25 was observed at four widely separated locations in the inner (≲ 1 AU) heliosphere. Relativistic electrons as well as protons with energies > 50 MeV were observed by Solar Orbiter (SolO), Parker Solar Probe, the Solar Terrestrial Relations Observatory (STEREO)-A and multiple near-Earth spacecraft. The SEP event was associated with an M4.4 class X-ray flare and accompanied by a coronal mass ejection and an extreme ultraviolet (EUV) wave as well as a type II radio burst and multiple type III radio bursts. Aims. We present multi-spacecraft particle observations and place them in context with source observations from remote sensing instruments and discuss how such observations may further our understanding of particle acceleration and transport in this widespread event. Methods. Velocity dispersion analysis (VDA) and time shift analysis (TSA) were used to infer the particle release times at the Sun. Solar wind plasma and magnetic field measurements were examined to identify structures that influence the properties of the energetic particles such as their intensity. Pitch angle distributions and first-order anisotropies were analyzed in order to characterize the particle propagation in the interplanetary medium. Results. We find that during the 2020 November 29 SEP event, particles spread over more than 230° in longitude close to 1 AU. The particle onset delays observed at the different spacecraft are larger as the flare-footpoint angle increases and are consistent with those from previous STEREO observations. Comparing the timing when the EUV wave intersects the estimated magnetic footpoints of each spacecraft with particle release times from TSA and VDA, we conclude that a simple scenario where the particle release is only determined by the EUV wave propagation is unlikely for this event. Observations of anisotropic particle distributions at SolO, Wind, and STEREO-A do not rule out that particles are injected over a wide longitudinal range close to the Sun. However, the low values of the first-order anisotropy observed by near-Earth spacecraft suggest that diffusive propagation processes are likely involved., The CAU Kiel team acknowledges support from the German Federal Ministry for Economic Affairs and Energy, the German Space Agency (Deutsches Zentrum für Luft- und Raumfahrt e.V., DLR) under grants 50OT0901, 50OT1202, 50OT1702, and 50OT2002. A.K. acknowledges financial support from the ANR COROSHOCK project (ANR-17-CE31-0006-01). D.L. acknowledges support from NASA-HGI grant NNX16AF73G and the NASA Program NNH17ZDA001N-LWS. This study has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101004159 (SERPENTINE). The U. Turku team acknowledges funding by the Academy of Finland (Grant No. 336809). The UAH team acknowledges financial support by the Spanish Ministerio de Ciencia, Innovación y Universidades FEDER/MCIU/AEI Projects ESP2017-88436-R and PID2019-104863RB-I00/AEI/10.13039/501100011033. [...] The Swedish National Space Agency, ESA-PRODEX and all the participating institutes. I.G.R. acknowledges support from NASA programs NNH19ZDA001N-HSR and NNH19ZDA001N-LWS, and the STEREO mission. IRFU team acknowledges support from the Swedish National Space Agency grant 20/136. A.A. acknowledges the support of the Spanish Ministerio de Ciencia e Innovación (MICINN) under grant PID2019- 105510GB-C31 and through the ‘Center of Excellence María de Maeztu 2020-2023’ award to the ICCUB (CEX2019-000918- M). F.C. acknowledges the financial support by the Spanish MINECO-FPI-2016 predoctoral grant with FSE. E.A. would like to acknowledge the financial support by the Academy of Finland (Postdoctoral Grant No 322455). V.K. acknowledges the support by NASA under grants 18-2HSWO218_2-0010 and 19-HSR-19_2-0143. Solar Orbiter magnetometer operations are funded by the UK Space Agency (grant ST/T001062/1). T.S.H. is supported by STFC grant ST/S000364/1. T.L. and S.D. acknowledge support from the UK Science and Technology Facilities Council (STFC; grant ST/R000425/1).

High-energy stellar irradiation can photoevaporate planetary atmospheres, which can be observed in spectroscopic transits of hydrogen lines. For the exoplanet HD189733b, multiple observations in the Ly-$\alpha$ line have shown that atmospheric evaporation is variable, going from undetected to enhanced evaporation in a $1.5$-year interval. Coincidentally or not, when HD189733b was observed to be evaporating, a stellar flare had just occurred 8h prior to the observation. This led to the question of whether this temporal variation in evaporation occurred due to the flare, an unseen associated coronal mass ejection (CME), or even the effect of both simultaneously. In this work, we investigate the impact of flares (radiation), winds, and CMEs (particles) on the atmosphere of HD189733b using 3D radiation hydrodynamic simulations of atmospheric evaporation that self-consistently include stellar photon heating. We study four cases: first- the quiescent phase of the star including stellar wind, second- a flare, third- a CME, and fourth- a flare that is followed by a CME. Compared to the quiescent case, we find that the flare alone increases the evaporation rate by only 25%, while the CME leads to a factor of 4 increase in escape rate. We calculate Ly-$\alpha$ synthetic transits and find that the flare alone cannot explain the observed high blueshifted velocities seen in the Ly-$\alpha$ observation. The CME, however, leads to an increase in the velocity of the escaping atmosphere, enhancing the transit depth at high blueshifted velocities. While the effects of CMEs show a promising potential to explain the blueshifted line feature, our models are not able to fully explain the blueshifted transit depths, indicating that they might require additional physical mechanisms., Comment: Accepted for publication in MNRAS, 14 pages, 9 figures

Solar wind dynamic pressure pulses (DPPs) are small-scale plasma structures with abrupt and large-amplitude plasma dynamic pressure changes on timescales of seconds to several minutes. Overwhelming majority of DPP events (around 79.13%) reside in large-scale solar wind transients, i.e., coronal mass ejections, stream interaction regions, and complex ejecta. In this study, the intermittency, which is a typical feature of solar wind turbulence, is determined and compared during the time intervals in the undisturbed solar wind and in large-scale solar wind transients with clustered DPP events, respectively, as well as in the undisturbed solar wind without DPPs. The probability distribution functions (PDFs) of the fluctuations of proton density increments normalized to the standard deviation at different time lags in the three types of distinct regions are calculated. The PDFs in the undisturbed solar wind without DPPs are near-Gaussian distributions. However, the PDFs in the solar wind with clustered DPPs are obviously non-Gaussian distributions, and the intermittency is much stronger in the large-scale solar wind transients than that in the undisturbed solar wind. The major components of the DPPs are tangential discontinuities (TDs) and rotational discontinuities (RDs), which are suggested to be formed by compressive magnetohydrodynamic (MHD) turbulence. There are far more TD-type DPPs than RD-type DPPs both in the undisturbed solar wind and large-scale solar wind transients. The results imply that the formation of solar wind DPPs could be associated with solar wind turbulence, and much stronger intermittency may be responsible for the high occurrence rate of DPPs in the large-scale solar wind transients.

Coronal mass ejections (CMEs) are huge expulsions of magnetized matter from the Sun and stars, traversing space with speeds of millions of kilometers per hour. Solar CMEs can cause severe space weather disturbances and consumer power outages on Earth, whereas stellar CMEs may even pose a hazard to the habitability of exoplanets. While CMEs ejected by our Sun can be directly imaged by white-light coronagraphs, for stars this is not possible. So far, only a few candidates for stellar CME detections are reported. Here we demonstrate a different approach, based on sudden dimmings in the extreme-ultraviolet (EUV) and X-ray emission caused by the CME mass loss. We report dimming detections associated with flares on cool stars, indicative of stellar CMEs and benchmarked by Sun-as-a-star EUV measurements. This study paves the way for comprehensive detections and characterizations of CMEs on stars, important for planetary habitability and stellar evolution.

Observations of the dynamics of solar coronal structures are necessary to investigate space weather phenomena and global heating of the corona. The profiles of high temperature lines emitted by the hot plasma are usually integrated by narrow band filters or recorded by classical spectroscopy. We present in this paper details of a new transportable instrument (under construction) for imaging spectroscopy: the Solar Line Emission Dopplerometer (SLED). It uses the Multi-channel Subtractive Double Pass (MSDP) technique, which combines the advantages of both filters and narrow slit spectrographs, i.e. high temporal, spatial and spectral resolutions. The SLED will measure at high cadence (1 Hz) the line-of-sight velocities (Doppler shifts) of hot coronal loops, in the forbidden lines of FeX 637. nm and FeXIV 530.3 nm. It will follow the dynamics of fast evolving events of solar activity such as flares or Coronal Mass Ejections (CMEs), and also study coronal heating by short period waves. Observations will be performed with the coronagraph at the Lomnicky Stit Observatory (LSO, in Slovakia) or during total eclipses. The SLED will also observe the dynamics of solar prominences in Halpha 656.3 nm or HeD3 587.6 nm lines when mounted on the Bialkow coronagraph (near Wroclaw, Poland). It is fully compatible with polarimetric measurements by various techniques., 15 figures

Investigations of the dynamics of the hot coronal plasma are crucial for understanding various space weather phenomena and making in-depth analyzes of the global heating of the solar corona. We present here numerical simulations of observations of siphon flows along loops (simple semi-circular flux ropes) to demonstrate the capabilities of the Solar Line Emission Dopplerometer (SLED), a new instrument under construction for imaging spectroscopy. It is based on the Multi-channel Subtractive Double Pass (MSDP) technique, which combines the advantages of filters and slit spectrographs. SLED will observe coronal structures in the forbidden lines of FeX 637.4 nm and FeXIV 530.3 nm, and will measure Doppler shifts up to 150 km/s at high precision (50 m/s) and cadence (1 Hz). It is optimized for studies of the dynamics of fast evolving events such as flares or Coronal Mass Ejections (CMEs), as well as for the detection of high-frequency waves. Observations will be performed with the coronagraph at Lomnicky Stit Observatory (LSO), and will also occur during total solar eclipses as SLED is a portable instrument., 9 pages, 8 figures

The magnetopause marks the outer edge of the Earth's magnetosphere and a distinct boundary between solar wind and magnetospheric plasma populations. In this letter, we use global magnetohydrodynamic simulations to examine the response of the terrestrial magnetopause to fast-forward interplanetary shocks of various strengths and compare to theoretical predictions. The theory and simulations indicate the magnetopause response can be characterised by three distinct phases; an initial acceleration as inertial forces are overcome, a rapid compressive phase comprising the majority of the distance travelled, and large-scale damped oscillations with amplitudes of the order of an Earth radius. The two approaches agree in predicting subsolar magnetopause oscillations with frequencies 2-13 mHz but the simulations notably predict larger amplitudes and weaker damping rates. This phenomenon is of high relevance to space weather forecasting and provides a possible explanation for magnetopause oscillations observed following the large interplanetary shocks of August 1972 and March 1991., 9 pages, 3 figures, 1 table. Accepted as a Geophysical Research Letter on 09 July 2021

Both coronal holes and active regions are source regions of the solar wind. The distribution of these coronal structures across both space and time is well known, but it is unclear how much each source contributes to the solar wind. In this study we use photospheric magnetic field maps observed over the past four solar cycles to estimate what fraction of magnetic open solar flux is rooted in active regions, a proxy for the fraction of all solar wind originating in active regions. We find that the fractional contribution of active regions to the solar wind varies between 30% to 80% at any one time during solar maximum and is negligible at solar minimum, showing a strong correlation with sunspot number. While active regions are typically confined to latitudes $\pm$30$^{\circ}$ in the corona, the solar wind they produce can reach latitudes up to $\pm$60$^{\circ}$. Their fractional contribution to the solar wind also correlates with coronal mass ejection rate, and is highly variable, changing by $\pm$20% on monthly timescales within individual solar maxima. We speculate that these variations could be driven by coronal mass ejections causing reconfigurations of the coronal magnetic field on sub-monthly timescales., Comment: 18 pages, 7 figures. Published in Solar Physics

Solar Energetic Particles (SEPs) are known to be accelerated at Coronal Mass Ejection (CME)-driven interplanetary shocks. Traditionally their propagation has been described via focussed transport approaches, limited to 1 or 2 spatial dimensions. We use 3D test particle simulations, which naturally incorporate the effect of drifts, to simulate the propagation of SEPs from a moving shock-like source. We investigate the effect of an expanding shock-like source propagating through interplanetary space, as opposed to an SEP source within the corona, on the observable properties of SEPs at 1 au and at locations nearer the Sun. We derive intensity profiles, anisotropies and longitudinal and latitudinal distribution of SEPs, with the aim of supporting observations from Solar Orbiter and Parker Solar Probe.

Importance of search for neutrinos generated during solar flares has been discussed for last 60~years, however, neutrinos associated with solar flares~(solar flare neutrinos) have not been obserbed yet. Since neutrinos are not affected by interplanetary magnetic field, solar flare neutrinos would provide us with information about a particle acceleration mechanism in solar flares. According to some theoretical predictions, flux of the solar flare neutrino would depend on the releasing energy and the location where solar flares ocurr on the Sun surface. Typical predicted probability of detection by Super-Kamiokande (SK) detector is $8.5 \times 10^{-1}$ event/flare for a solar flare which occurs on the opposite side of Sun surface from the earth (invisible side). On the other hands, $1.36 \times 10^{-4}$ event/flare would be predicted for the other side (visible side). To minimize background for the solar flare neutrino searches, data of solar satellites (GOES, RHESSI, and Geotail) were analyzed and time windows for solar flare neutrino searches on the visible side were defined. Coronal Mass Ejection event catalogs were used to determine the search windows for solar flare neutrinos on the invisible side of the Sun. SK is the world's largest underground water Cherenkov detector. The SK experiment has been started the measurement of neutrinos since 1996. The results of solar flare neutrino searches using data sets from SK-I to SK-IV are presented.

The Drag-based Model (DBM) is a 2D analytical model for heliospheric propagation of Coronal Mass Ejections (CMEs) in ecliptic plane predicting the CME arrival time and speed at Earth or any other given target in the solar system. It is based on the equation of motion and depends on initial CME parameters, background solar wind speed, $w$ and the drag parameter $\gamma $ . A very short computational time of DBM (< 0.01 s) allowed us to develop the Drag-Based Ensemble Model (DBEM) that takes into account the variability of model input parameters by making an ensemble of n different input parameters to calculate the distribution and significance of the DBM results. Thus the DBEM is able to calculate the most likely CME arrival times and speeds, quantify the prediction uncertainties and determine the confidence intervals. A new DBEMv3 version is described in detail and evaluated for the first time determining the DBEMv3 performance and errors by using various CME–ICME lists and it is compared with previous DBEM versions, ICME being a short-hand for interplanetary CME. The analysis to find the optimal drag parameter $\gamma $ and ambient solar wind speed $w$ showed that somewhat higher values ( $\gamma \approx 0.3 \times 10^{-7}$ km−1, $w \approx $ 425 km s−1) for both of these DBEM input parameters should be used for the evaluation than the previously employed ones. Based on the evaluation performed for 146 CME–ICME pairs, the DBEMv3 performance with mean error (ME) of −11.3 h, mean absolute error (MAE) of 17.3 h was obtained. There is a clear bias towards the negative prediction errors where the fast CMEs are predicted to arrive too early, probably due to the model physical limitations and input errors (e.g. CME launch speed). This can be partially reduced by using larger values for $\gamma $ resulting in smaller prediction errors ( $\mathrm{ME} =-3.9$ h, MAE = 14.5 h) but at the cost of larger prediction errors for single fast CMEs as well as larger CME arrival speed prediction errors. DBEMv3 showed also slight improvement in the performance for all calculated output parameters compared to the previous DBEM versions.

We provide analysis of a coronal mass ejection (CME) that passed over Parker Solar Probe (PSP) on January 20, 2020 when the spacecraft was at just 0.32 AU. The Integrated Science Investigation of the Sun instrument suite measures energetic particle populations associated with the CME before, during, and after its passage over the spacecraft. We observe a complex evolution of energetic particles, including a brief ~2 h period where the energetic particle fluxes are enhanced and the nominal orientation of the energetic particle streaming outward from the Sun (from 30 to 100 keV nuc−1 ) abruptly reverses inward toward the Sun. This transient and punctuated evolution highlights the importance of magnetic field structures that connect the spacecraft to different acceleration sites, one of which is likely more distant from the Sun than PSP during the evolution of the CME. We discuss these characteristics and what they tell us about the source of the energetic particles. During this period, PSP was radially aligned with the Solar Terrestrial Relations Observatory A (STEREO-A), which measured the same CME when it passed 1 AU. The magnetic field measurements at both spacecraft are remarkably similar, indicating that the spacecraft are likely encountering the same portion of the magnetic structure that has not evolved significantly in transit. The energetic particle observations on the other hand, are quite different at STEREO-A, showing how transport effects have acted on the energetic particle populations and obscured the detailed properties present earlier in the development of the CME. This event provides a unique case study in how energetic particle populations evolve as CMEs propagate through the heliosphere.

Context. Solar Orbiter, the new-generation mission dedicated to solar and heliospheric exploration, was successfully launched on February 10, 2020, 04:03 UTC from Cape Canaveral. During its first perihelion passage in June 2020, two successive interplanetary coronal mass ejections (ICMEs), propagating along the heliospheric current sheet (HCS), impacted the spacecraft. Aims. This paper addresses the investigation of the ICMEs encountered by Solar Orbiter on June 7−8, 2020, from both an observational and a modeling perspective. The aim is to provide a full description of those events, their mutual interaction, and their coupling with the ambient solar wind and the HCS. Methods. Data acquired by the MAG magnetometer, the Energetic Particle Detector suite, and the Radio and Plasma Waves instrument are used to provide information on the ICMEs’ magnetic topology configuration, their magnetic connectivity to the Sun, and insights into the heliospheric plasma environment where they travel, respectively. On the modeling side, the Heliospheric Upwind eXtrapolation model, the 3D COronal Rope Ejection technique, and the EUropean Heliospheric FORecasting Information Asset (EUHFORIA) tool are used to complement Solar Orbiter observations of the ambient solar wind and ICMEs, and to simulate the evolution and interaction of the ejecta in the inner heliosphere, respectively. Results. Both data analysis and numerical simulations indicate that the passage of two distinct, dynamically and magnetically interacting (via magnetic reconnection processes) ICMEs at Solar Orbiter is a possible scenario, supported by the numerous similarities between EUHFORIA time series at Solar Orbiter and Solar Orbiter data. Conclusions. The combination of in situ measurements and numerical simulations (together with remote sensing observations of the corona and inner heliosphere) will significantly lead to a deeper understanding of the physical processes occurring during the CME-CME interaction.

Magnetic clouds (MCs) are transient structures containing large-scale magnetic flux ropes from solar eruptions. The twist of magnetic field lines around the rope axis reveals information about flux rope formation processes and geoeffectivity. During propagation, MC flux ropes may erode via reconnection with the ambient solar wind. Any erosion reduces the magnetic flux and helicity of the ropes, and changes their cross-sectional twist profiles. This study relates twist profiles in MC flux ropes observed at 1 AU to the amount of erosion undergone by the MCs in interplanetary space. The twist profiles of two well-identified MC flux ropes associated with the clear appearance of post eruption arcades in the solar corona are analysed. To infer the amount of erosion, the magnetic flux content of the ropes in the solar atmosphere is estimated, and compared to estimates at 1 AU. The first MC shows a monotonically decreasing twist from the axis to periphery, while the second displays high twist at the axis, rising twist near the edges, and lower twist in between. The first MC displays a larger reduction in magnetic flux between the Sun and 1 AU, suggesting more erosion, than that seen in the second MC. In the second cloud, rising twist at the rope edges may have been due to an envelope of overlying coronal field lines with relatively high twist, formed by reconnection beneath the erupting flux rope in the low corona. This high-twist envelope remained almost intact from the Sun to 1 AU due to the low erosion levels. In contrast, the high-twist envelope of the first cloud may have been entirely peeled away via erosion by the time it reaches 1 AU., 10 pages, 5 figures, 1 table

In-situ measurements carried out by spacecraft in radial alignment are critical to advance our knowledge on the evolutionary behavior of coronal mass ejections (CMEs) and their magnetic structures during propagation through interplanetary space. Yet, the scarcity of radially aligned CME crossings restricts investigations on the evolution of CME magnetic structures to a few case studies, preventing a comprehensive understanding of CME complexity changes during propagation. In this paper, we perform numerical simulations of CMEs interacting with different solar wind streams using the linear force-free spheromak CME model incorporated into the EUropean Heliospheric FORecasting Information Asset (EUHFORIA) model. The novelty of our approach lies in the investigation of the evolution of CME complexity using a swarm of radially aligned, simulated spacecraft. Our scope is to determine under which conditions, and to what extent, CMEs exhibit variations of their magnetic structure and complexity during propagation, as measured by spacecraft that are radially aligned. Results indicate that the interaction with large-scale solar wind structures, and particularly with stream interaction regions, doubles the probability to detect an increase of the CME magnetic complexity between two spacecraft in radial alignment, compared to cases without such interactions. This work represents the first attempt to quantify the probability of detecting complexity changes in CME magnetic structures by spacecraft in radial alignment using numerical simulations, and it provides support to the interpretation of multi-point CME observations involving past, current (such as Parker Solar Probe and Solar Orbiter), and future missions. ispartof: Astrophysical Journal Letters vol:916 issue:2 pages:1-14 status: published

The flare-associated stellar coronal mass ejection (CME) in solar-like and late type stars is quite essential for the habitability of an exoplanet. In this paper, we report detection of flare-associated CMEs in two M-dwarfs, thanks to the high cadence survey carried out by the Ground Wide-angle Camera system and the fast photometric and spectroscopic follow-ups. The flare energy in $R-$band is determined to be $1.6\times10^{35}\ \mathrm{erg}$ and $8.1\times10^{33}\ \mathrm{erg}$ based on the modeling of their light curves. The time-resolved spectroscopyic observations start at about 20 and 40 minutes after the trigger in both cases. The large projected maximum velocity of $\sim500-700\ \mathrm{km\ s^{-1}}$ suggests that the high velocity wing of their H$\alpha$ emission lines are most likely resulted from a CME event in both stars, after excluding the possibility of chromospheric evaporation and coronal rain. The masses of the CMEs are estimated to be $1.5-4.5\times10^{19}\ \mathrm{g}$ and $7.1\times10^{18}\ \mathrm{g}$., Comment: 15 pages, 10 figures and 5 tables, accepted by ApJ

The Wind spacecraft, launched on November 1, 1994, is a critical element in NASA’s Heliophysics System Observatory (HSO) – a fleet of spacecraft created to understand the dynamics of the sun‐Earth system. The combination of its longevity ( > 25 years in service), its diverse complement of instrumentation, and high resolution and accurate measurements has led to it becoming the “standard candle” of solar wind measurements. Wind has over 55 selectable public data products with over ∼1100 total data variables (including OMNI data products) on SPDF/CDAWeb alone. These data have led to paradigm shifting results in studies of statistical solar wind trends, magnetic reconnection, large‐scale solar wind structures, kinetic physics, electromagnetic turbulence, the Van Allen radiation belts, coronal mass ejection topology, interplanetary and interstellar dust, the lunar wake, solar radio bursts, solar energetic particles, and extreme astrophysical phenomena such as gamma‐ray bursts. This review introduces the mission and instrument suites then discusses examples of the contributions by Wind to these scientific topics that emphasize its importance to both the fields of heliophysics and astrophysics.

The features of daytime high latitude geomagnetic disturbances and geomagnetic pulsations during the recent strong magnetic storm on August 25–26, 2018, which occurred at the end of the decline phase of the 24th solar activity cycle with a very low level of solar flare activity, are considered. As a rule, during this phase of the solar activity cycle, magnetic storms are caused by high-speed solar wind flows from coronal holes; however, the magnetic storms during the decay of the 24th cycle were caused by coronal mass ejections (CMEs). It was shown that, despite very weak disturbances on the Sun and a low solar wind speed, a rather strong magnetic storm occurred in the Earth’s magnetosphere in August 2018 (Dst = –171 nT). The storm SC with a slight (~25 nT) jump in the Dst index caused quite intense daytime geomagnetic pulsations ipcl at the latitudes of the possible position of the daytime polar cusp. A feature of the recovery phase of this storm was the development of a magnetosphere substorm on a global scale, i.e., the appearance of a negative magnetic bay recorded simultaneously in the auroral night sector and in the polar latitudes of the day sector. A possible interpretation is considered.

Cosmic plasma represents a natural laboratory for studying turbulence in a wide range of scales. Rapid measurements of the ion flux by the Bright Monitor of the Solar Wind (BMSW) instrument on the Spektr-R satellite make it possible to investigate the characteristics of the plasma turbulence in the solar wind and the magnetosheath at ion and sub-ion scales. This study analyzes the question, in what manner do turbulent cascade characteristics, at these scales in the magnetosheath, depend on the characteristics of the solar wind’s plasma turbulence in front of Earth’s bow shock (BS). Several crosses of Earth’s BS by the Spektr-R satellite are analyzed. A comparison of the shapes of the spectra of ion flux fluctuations and exponents of power-law functions, which describe the spectra at kinetic and magnetohydrodynamic scales in front of and behind Earth’s BS is carried out. It is shown that, directly behind Earth’s BS on magnetohydrodynamic scales, the spectra deviate from the form predicted by the developed turbulence theories and observed in the solar wind. This feature of the spectra indicates the redistribution of energy in the turbulent cascade immediately behind the near-Earth shock wave. At kinetic scales, steeper spectra are usually observed behind the near-Earth shock wave front than in the solar wind, but their slope is determined by the properties of the turbulent cascade in the incident flow. It is shown that the strongest difference between turbulence characteristics in front of and behind Earth’s BS is observed during solar wind flow periods associated with the regions of compression before interplanetary manifestations of coronal mass ejections.

We propose a method for determining location and orientation of extended solar sources of magnetic clouds, using coronagraph data and SOHO EIT/MDI images of the photosphere. To estimate the probability of formation of magnetic clouds, we use a simple cylindrical force-free model. We have established that more extended sources and those having a slight inclination to the solar equator and located on the solar limb as compared to those that are nonextended and strongly inclined can generate expanding clouds, which with high probability can reach the magnetosphere like clouds from a source near the zero meridian and low latitudes. We determine the relationship between extreme values of substorm activity and parameters of solar sources under study during the impact of magnetic clouds on Earth’s magnetosphere from the AL index. We note that there are no substorms associated with extended sources outside the heliolatitude range ~5–20°. The established relationship between solar source coordinates and geomagnetic activity of the magnetic cloud sheath and body are consistent with the most probable distribution of magnetoactive regions over the solar disk.

Coronal mass ejections are the largest-scale eruptive phenomenon in the solar system. Their drastic effect on space weather is a reason for the significant interest in observing, simulating, and forecasting these events. We describe the main features of mass ejections from the solar atmosphere, their physical parameters and frequency, and its dependence on the solar cycle phase. We consider potential sources of ejections in the solar atmosphere and magnetic field configurations wherein the energy needed for sudden explosive acceleration of large masses of matter can be stored. The main instabilities of coronal structures that lead to the triggering and development of eruptive processes are analyzed. We show that coronal mass ejections are related to other manifestations of solar activity, while the eruptive processes observed using various techniques in various layer of the solar atmosphere and interplanetary space are the same phenomenon. We discuss indicators of the Sun’s pre-eruptive regions approaching a catastrophe and the options to use them to forecast eruptions and space weather disturbances.

Automatic detection of solar events, especially uncommon events such as coronal dimming (CD) and coronal wave (CW), is very important in solar physics research. The CD and CW are not only related to the detection of coronal mass ejections (CMEs) but also affect space weather. In this paper, we have studied methods for automatically detecting them. In addition, we have collected and processed a dataset that includes the solar images and event records, where the solar images come from the Atmospheric Imaging Assembly (AIA) of Solar Dynamics Observatory (SDO) and the event records come from Heliophysics Event Knowledgebase (HEK). Different from the methods used before, we introduce the idea of deep learning. We train single-wavelength and multiwavelength models based on Faster R-CNN. In terms of accuracy, the single-wavelength model performs better. The multiwavelength model has a better detection performance on multiple solar events than the single-wavelength model.

The Sun is the celestial body in the sky with the closest relationship with the Earth. The violent eruptive activities happening on the Sun can greatly impact the human living environment and lead to disastrous consequences. It is well accepted that solar eruptions including the solar flare, prominence eruption and coronal mass ejection are the different manifestations of a single physical process powered by the magnetic free energy gradually stored in the corona prior to eruptions. Therefore, mapping the three-dimensional structure of coronal magnetic field is a prerequisite to understand the initiation mechanism of solar eruptions. Due to the technological and methodological difficulties, routine observations of the coronal magnetic field are still unavailable. Therefore, a number of methods have been developed to reconstruct the coronal magnetic field. This paper mainly reviews the applications of various reconstruction methods to the studies of the solar eruptions in the recent ten years.

The Pioneer Venus and Venus Express missions, and the Mars Express and MAVEN missions, along with numerous Earth orbiters carrying space physics and aeronomy instruments, have utilized the increasing availability of space weather observations to provide better insight into the impacts of present-day solar activity on the atmospheres of terrestrial planets. Of most interest among these are the responses leading to escape of either ion or neutral constituents, potentially altering both the total atmospheric reservoirs and their composition. While debates continue regarding the role(s) of a planetary magnetic field in either decreasing or increasing these escape rates, observations have shown that enhancements can occur in both situations in response to solar activity-related changes. These generally involve increased energy inputs to the upper atmospheres, increases in ion production, and/or increases in escape channels, e.g. via interplanetary field penetration or planetary field ‘opening’. Problems arise when extrapolations of former loss rates are needed. While it is probably safe to suggest lower limits based simply on planet age multiplied by currently measured ion and neutral escape rates, the evolution of the Sun, including its activity, must be folded into these estimations. Poor knowledge of the history of solar activity, especially in terms of coronal mass ejections and solar wind properties, greatly compounds the uncertainties in related planetary atmosphere evolution calculations. Prospects for constraining their influences will depend on our ability to do a better job of solar activity history reconstruction.

Solar coronal dimmings have been observed extensively in the past two decades and are believed to have close association with coronal mass ejections (CMEs). Recent study found that coronal dimming is the only signature that could differentiate powerful ares that have CMEs from those that do not. Therefore, dimming might be one of the best candidates to observe the stellar CMEs on distant Sun-like stars. In this study, we investigate the possibility of using coronal dimming as a proxy to diagnose stellar CMEs. By simulating a realistic solar CME event and corresponding coronal dimming using a global magnetohydrodynamics model (AWSoM: Alfven-wave Solar Model), we first demonstrate the capability of the model to reproduce solar observations. We then extend the model for simulating stellar CMEs by modifying the input magnetic flux density as well as the initial magnetic energy of the CME flux rope. Our result suggests that with improved instrument sensitivity, it is possible to detect the coronal dimming signals induced by the stellar CMEs., 8 pages, 4 figures, to appear in the Proceedings of IAU Symposium No. 354 - Solar and Stellar Magnetic Fields: Origins and Manifestations

The passage of a hot Jupiter with a quasi-closed extended envelope through a short coronal mass ejection (CME) with a small opening angle is considered. The results of three-dimensional gasdynamical simulations are used to determine the characteristics of the flow in the planet’s envelope as it intersects the CME, and to infer possible observational manifestations of such an event. Two options are considered—entry of the planet into the CME at the beginning of the CME and a tangential interaction with the leading edge of the CME. The mass lost by the planet as a result of its interaction with the CME is estimated.

The event on January 27, 2012 is an example of the features of the dynamics of formation of a shock, excited by a fast coronal mass ejection (CME) at a velocity higher than 2000 km/s, are investigated. The following data were used: (a) images of the Sun in the UV channel of 13.1 nm from the AIA instrument at distances of 1.0–1.4 solar radii from the Sun’s center, (b) the images of the white corona from the LASCO C2 and C3 coronographs at R ≈ 2.1–30 solar radii. Investigations indicated the validity of regularities, established earlier for the cases of relatively slow CMEs (at velocities

Enhancements of the dayside Lyman-α emission by as much as ∼50% have been observed between 120 and 130 km in the lower Martian thermosphere from the Mars Express and MAVEN satellites, usually following solar events such as coronal mass ejections and corotating interaction regions. They have been assumed to be optical signatures of proton aurora related to an increase in the solar wind proton flux hitting Mars’ bow shock. We present model simulations of the Lyman-α line profiles at different altitudes. These are partly guided by in situ measurements of the energy spectrum of protons in the magnetosheath region by the SWIA instrument on board the MAVEN spacecraft. We show that the auroral Lyman-α line profile is significantly broader than the hydrogen core of the planetary thermal H atom. Consequently, most of the auroral emission is produced outside the optically thick hydrogen core and creates the observed intensity enhancement. Simulations with incident energetic hydrogen atoms (H ENAs) produce a somewhat broader line profile. Monte Carlo calculations are made separately for incident solar wind protons and H ENAs produced by charge exchange in the hydrogen corona. Absorption by CO2 along the line of sight significantly affects the intensity distribution in the lower thermosphere. The calculated altitude of the peak emission for both types of incident particles is consistent with the observed characteristics of the proton aurora. We show that the presence of a horizontal induced magnetic field somewhat increases the line width and decreases the altitude of the emission peak as a consequence of the magnetic barrier effect on proton precipitation. The brightness of the Lyman-α emission also drops as a result of increased magnetic shielding of the protons.