scholarly journals The source and engine of coronal mass ejections

2019 ◽  
Vol 377 (2148) ◽  
pp. 20180094 ◽  
Author(s):  
Manolis K. Georgoulis ◽  
Alexander Nindos ◽  
Hongqi Zhang
Keyword(s):  
Space Weather ◽  
Coronal Mass Ejections ◽  
Large Scale ◽  
Magnetic Energy ◽  
Active Regions ◽  
Magnetic Polarity ◽  
X Rays ◽  
Polarity Inversion ◽  
Magnetic Flux Ropes ◽  
Causal Sequence

Coronal mass ejections (CMEs) are large-scale expulsions of coronal plasma and magnetic field propagating through the heliosphere. Because CMEs are observed by white-light coronagraphs which, by design, occult the solar disc, supporting disc observations (e.g. in EUV, soft X-rays, Halpha and radio) must be employed for the study of their source regions and early development phases. We review the key properties of CME sources and highlight a certain causal sequence of effects that may occur whenever a strong (flux-massive and sheared) magnetic polarity inversion line develops in the coronal base of eruptive active regions (ARs). Storing non-potential magnetic energy and helicity in a much more efficient way than ARs lacking strong polarity inversion lines, eruptive regions engage in an irreversible course, making eruptions inevitable and triggered when certain thresholds of free energy and helicity are crossed. This evolution favours the formation of pre-eruption magnetic flux ropes. We describe the steps of this plausible path to sketch a picture of the pre-eruptive phase of CMEs that may apply to most events, particularly the ones populating the high end of the energy/helicity distribution, that also tend to have the strongest space-weather implications. This article is part of the theme issue ‘Solar eruptions and their space weather impact’.

scholarly journals Beyond sunspots: Studies using the McIntosh Archive of global solar magnetic field patterns

2016 ◽  
Vol 12 (S328) ◽  
pp. 93-100 ◽  
Author(s):  
Sarah E. Gibson ◽  
David Webb ◽  
Ian M. Hewins ◽  
Robert H. McFadden ◽  
Barbara A. Emery ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Coronal Holes ◽  
Magnetic Polarity ◽  
Solar Cycles ◽  
Polarity Inversion ◽  
Magnetic Structures ◽  
Field Patterns ◽  
Global Evolution

AbstractIn 1964 (Solar Cycle 20; SC 20), Patrick McIntosh began creating hand-drawn synoptic maps of solar magnetic features, based on Hα images. These synoptic maps were unique in that they traced magnetic polarity inversion lines, and connected widely separated filaments, fibril patterns, and plage corridors to reveal the large-scale organization of the solar magnetic field. Coronal hole boundaries were later added to the maps, which were produced, more or less continuously, into 2009 (i.e., the start of SC 24). The result was a record of ~45 years (~570 Carrington rotations), or nearly four complete solar cycles of synoptic maps. We are currently scanning, digitizing and archiving these maps, with the final, searchable versions publicly available at NOAA's National Centers for Environmental Information. In this paper we present preliminary scientific studies using the archived maps from SC 23. We show the global evolution of closed magnetic structures (e.g., sunspots, plage, and filaments) in relation to open magnetic structures (e.g., coronal holes), and examine how both relate to the shifting patterns of large-scale positive and negative polarity regions.

scholarly journals Degree of electric current neutralization and the activity in solar active regions

2019 ◽  
Vol 486 (4) ◽  
pp. 4936-4946 ◽  
Author(s):  
P Vemareddy
Keyword(s):  
Current Density ◽  
Active Regions ◽  
Magnetic Polarity ◽  
Vector Magnetic Field ◽  
Polarity Inversion ◽  
Source Regions ◽  
Solar Active Regions ◽  
The Difference ◽  
Emergence Phase ◽  
Local Nature

Abstract Using time-sequence vector magnetic field observation from Helioseismic and Magnetic Imager, we examined the connection of non-neutralized currents and the observed activity in 20 solar active regions (ARs). The net current in a given magnetic polarity is algebraic sum of direct current (DC) and return current (RC) and the ratio |DC/RC| is a measure of degree of net current neutralization (NCN). In the emerging ARs, the non-neutrality of these currents builds with the onset of flux emergence, following the relaxation to neutrality during the separation motion of bipolar regions. Accordingly, some emerging ARs are source regions of CMEs occurring at the time of higher level non-neutrality. ARs in the post-emergence phase can be CME productive provided they have interacting bipolar regions with converging and shearing motions. In these cases, the net current evolves with higher level (>1.3) of non-neutrality. Differently, the |DC/RC| in flaring and quiet ARs vary near unity. In all the AR samples, the |DC/RC| is higher for chiral current density than that for vertical current density. Owing to the fact that the non-neutralized currents arise in the vicinity of sheared polarity-inversion-lines (SPILs), the profiles of the total length of SPIL segments and the degree of NCN follow each other with a positive correlation. We find that the SPIL is localized as small segments in flaring-ARs, whereas it is long continuous in CME-producing ARs. These observations demonstrate the dividing line between the CMEs and flares with the difference being in global or local nature of magnetic shear in the AR that reflected in non-neutralized currents.

scholarly journals Forecasting Solar Energetic Particle (SEP) events with Flare X-ray peak ratios

2018 ◽  
Vol 8 ◽  
pp. A47 ◽  
Author(s):  
Stephen W. Kahler ◽  
Alan. G. Ling
Keyword(s):  
Solar Flare ◽  
Space Weather ◽  
Coronal Mass Ejections ◽  
Energetic Particle ◽  
Solar Energetic Particle ◽  
Western Hemisphere ◽  
X Rays ◽  
X Ray ◽  
Forecasting Methods ◽  
Versus Peak

Solar flare X-ray peak fluxes and fluences in the 0.1–0.8 nm band are often used in models to forecast solar energetic particle (SEP) events. Garcia (2004) [Forecasting methods for occurrence and magnitude of proton storms with solar soft X rays, Space Weather, 2, S02002, 2004] used ratios of the 0.05–0.4 and 0.1–0.8 nm bands of the X-ray instrument on the GOES spacecraft to plot inferred peak flare temperatures versus peak 0.1–0.8 nm fluxes for flares from 1988 to 2002. Flares associated with E > 10 MeV SEP events of >10 proton flux units (pfu) had statistically lower peak temperatures than those without SEP events and therefore offered a possible empirical forecasting tool for SEP events. We review the soft and hard X-ray flare spectral variations as SEP event forecast tools and repeat Garcia’s work for the period 1998–2016, comparing both the peak ratios and the ratios of the preceding 0.05–0.4 nm peak fluxes to the later 0.1–0.8 nm peak fluxes of flares >M3 to the occurrence of associated SEP events. We divide the events into eastern and western hemisphere sources and compare both small (1.2–10 pfu) and large (≥300 pfu) SEP events with those of >10 pfu. In the western hemisphere X-ray peak ratios are statistically lower for >10 pfu SEP events than for non-SEP events and are even lower for the large (>300 pfu) events. The small SEP events, however, are not distinguished from the non-SEP events. We discuss the possible connections between the flare X-ray peak ratios and associated coronal mass ejections that are presumed to be the sources of the SEPs.

scholarly journals Signatures of ubiquitous magnetic reconnection in the deep atmosphere of sunspot penumbrae

2021 ◽  
Vol 648 ◽  
pp. A54
Author(s):  
Luc H. M. Rouppe van der Voort ◽  
Jayant Joshi ◽  
Vasco M. J. Henriques ◽  
Souvik Bose
Keyword(s):  
Magnetic Reconnection ◽  
Spatial Resolution ◽  
Magnetic Energy ◽  
Continuous Process ◽  
Dynamical Evolution ◽  
Active Regions ◽  
Magnetic Polarity ◽  
Balmer Line ◽  
Large Numbers ◽  
Ellerman Bombs

Context. Ellerman bombs are regions with enhanced Balmer line wing emission and mark magnetic reconnection in the deep solar atmosphere in active regions and the quiet Sun. They are often found in regions where opposite magnetic polarities are in close proximity. Recent high-resolution observations suggest that Ellerman bombs are more prevalent than previously thought. Aims. We aim to determine the occurrence of Ellerman bombs in the penumbra of sunspots. Methods. We analyzed high spatial resolution observations of sunspots in the Balmer Hα and Hβ lines as well as auxiliary continuum channels obtained with the Swedish 1-m Solar Telescope and applied the k-means clustering technique to systematically detect and characterize Ellerman Bombs. Results. Features with all the defining characteristics of Ellerman bombs are found in large numbers over the entire penumbra. The true prevalence of these events is only fully appreciated in the Hβ line due to the highest spatial resolution and lower chromospheric opacity. We find that the penumbra hosts some of the highest Ellerman bomb densities, surpassed only by the moat in the immediate surroundings of the sunspot. Some penumbral Ellerman bombs show flame morphology and rapid dynamical evolution. Many penumbral Ellerman bombs are fast moving with typical speed of 3.7 km s−1 and sometimes more than 10 km s−1. Many penumbral Ellerman bombs migrate from the inner to the outer penumbra over hundreds of km, and some continue moving beyond the outer penumbral boundary into the moat. Many penumbral Ellerman bombs are found in the vicinity of regions with opposite magnetic polarity. Conclusions. We conclude that reconnection is a near continuous process in the low atmosphere of the penumbra of sunspots that manifest in the form of penumbral Ellerman bombs. These are so prevalent that they may be a major sink of sunspot magnetic energy.

scholarly journals Evolution of Plasma Composition in an Eruptive Flux Rope

2022 ◽  
Vol 924 (1) ◽  
pp. 17
Author(s):  
D. Baker ◽  
L. M. Green ◽  
D. H. Brooks ◽  
P. Démoulin ◽  
L. van Driel-Gesztelyi ◽  
...  
Keyword(s):  
Magnetic Energy ◽  
Flux Rope ◽  
Plasma Composition ◽  
Imaging Spectrometer ◽  
Polarity Inversion ◽  
Magnetic Flux Ropes ◽  
Flux Ropes ◽  
Free Magnetic Energy ◽  
Polarity Inversion Line ◽  
Euv Imaging

Abstract Magnetic flux ropes are bundles of twisted magnetic field enveloping a central axis. They harbor free magnetic energy and can be progenitors of coronal mass ejections (CMEs). However, identifying flux ropes on the Sun can be challenging. One of the key coronal observables that has been shown to indicate the presence of a flux rope is a peculiar bright coronal structure called a sigmoid. In this work, we show Hinode EUV Imaging Spectrometer observations of sigmoidal active region (AR) 10977. We analyze the coronal plasma composition in the AR and its evolution as a sigmoid (flux rope) forms and erupts as a CME. Plasma with photospheric composition was observed in coronal loops close to the main polarity inversion line during episodes of significant flux cancellation, suggestive of the injection of photospheric plasma into these loops driven by photospheric flux cancellation. Concurrently, the increasingly sheared core field contained plasma with coronal composition. As flux cancellation decreased and a sigmoid/flux rope formed, the plasma evolved to an intermediate composition in between photospheric and typical AR coronal compositions. Finally, the flux rope contained predominantly photospheric plasma during and after a failed eruption preceding the CME. Hence, plasma composition observations of AR 10977 strongly support models of flux rope formation by photospheric flux cancellation forcing magnetic reconnection first at the photospheric level then at the coronal level.

scholarly journals Difference of source regions between fast and slow coronal mass ejections

2019 ◽  
Vol 36 ◽  
Author(s):  
B. Filippov
Keyword(s):  
Magnetic Field ◽  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
Source Regions ◽  
Free Magnetic Energy ◽  
The Difference ◽  
Sunspot Groups

Abstract Coronal mass ejections (CMEs) are tightly related to filament eruptions and usually are their continuation in the upper solar corona. It is common practice to divide all observed CMEs into fast and slow ones. Fast CMEs usually follow eruptive events in active regions near big sunspot groups and associated with major solar flares. Slow CMEs are more related to eruptions of quiescent prominences located far from active regions. We analyse 10 eruptive events with particular attention to the events on 2013 September 29 and on 2016 January 26, one of which was associated with a fast CME, while another was followed by a slow CME. We estimated the initial store of free magnetic energy in the two regions and show the resemblance of pre-eruptive situations. The difference of late behaviour of the two eruptive prominences is a consequence of the different structure of magnetic field above the filaments. We estimated this structure on the basis of potential magnetic field calculations. Analysis of other eight events confirmed that all fast CMEs originate in regions with rapidly changing with height value and direction of coronal magnetic field.

scholarly journals Investigation of two coronal mass ejections from circular ribbon source region:Origin, Sun-Earth propagation and Geoeffectiveness

2022 ◽  
Vol 21 (12) ◽  
pp. 318
Author(s):  
Syed Ibrahim ◽  
Wahab Uddin ◽  
Bhuwan Joshi ◽  
Ramesh Chandra ◽  
Arun Kumar Awasthi
Keyword(s):  
Geomagnetic Storm ◽  
Coronal Mass Ejections ◽  
Large Scale ◽  
Source Region ◽  
Large Angle ◽  
Flux Rope ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
Field Configuration ◽  
Solar Dynamics Observatory

Abstract In this article, we compare the properties of two coronal mass ejections (CMEs) that show similar source region characteristics but different evolutionary behaviors in the later phases. We discuss the two events in terms of their near-Sun characteristics, interplanetary evolution and geoeffectiveness. We carefully analyzed the initiation and propagation parameters of these events to establish the precise CME-interplanetary CME (ICME) connection and their near-Earth consequences. The first event is associated with poor geomagnetic storm disturbance index (Dst ≈-20 nT) while the second event is associated with an intense geomagnetic storm of DST ≈-119 nT. The configuration of the sunspots in the active regions and their evolution are observed by Helioseismic and Magnetic Imager (HMI). For source region imaging, we rely on data obtained from Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO) and Hα filtergrams from the Solar Tower Telescope at Aryabhatta Research Institute of Observational Sciences (ARIES). For both the CMEs, flux rope eruptions from the source region triggered flares of similar intensities (≈M1). At the solar source region of the eruptions,we observed a circular ribbon flare (CRF) for both cases, suggesting fan-spine magnetic configuration in the active region corona. The multi-channel SDO observations confirm that the eruptive flares and subsequent CMEs were intimately related to the filament eruption. Within the Large Angle and Spectrometric Coronograph (LASCO) field of view (FOV) thetwo CMEs propagated with linear speeds of 671 and 631 km s−1, respectively. These CMEs were tracked up to the Earth by Solar Terrestrial Relations Observatory (STEREO) instruments. We find that the source region evolution of CMEs, guided by the large-scale coronal magnetic field configuration, along with near-Sun propagation characteristics, such as CME-CME interactions, played important roles in deciding the evolution of CMEs in the interplanetary medium and subsequently their geoeffectiveness.

scholarly journals Impulsive coronal heating during the interaction of surface magnetic fields in the lower solar atmosphere

2020 ◽  
Vol 644 ◽  
pp. A130
Author(s):  
L. P. Chitta ◽  
H. Peter ◽  
E. R. Priest ◽  
S. K. Solanki
Keyword(s):  
Solar Surface ◽  
Magnetic Energy ◽  
Active Regions ◽  
Opposite Polarity ◽  
Space Mission ◽  
Magnetic Polarity ◽  
Coronal Heating ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Solar Dynamics

Coronal plasma in the cores of solar active regions is impulsively heated to more than 5 MK. The nature and location of the magnetic energy source responsible for such impulsive heating is poorly understood. Using observations of seven active regions from the Solar Dynamics Observatory, we found that a majority of coronal loops hosting hot plasma have at least one footpoint rooted in regions of interacting mixed magnetic polarity at the solar surface. In cases when co-temporal observations from the Interface Region Imaging Spectrograph space mission are available, we found spectroscopic evidence for magnetic reconnection at the base of the hot coronal loops. Our analysis suggests that interactions of magnetic patches of opposite polarity at the solar surface and the associated energy release during reconnection are key to impulsive coronal heating.

scholarly journals ANALISIS PREKURSOR PERISTIWA FLARE/PELONTARAN MASSA KORONA DALAM RANGKA PERINGATAN DINI CUACA ANTARIKSA

2016 ◽  
Vol 13 (2) ◽  
pp. 97
Author(s):  
Agustinus Gunawan Admiranto ◽  
Nanang Widodo ◽  
Iyus Edi Rusnadi ◽  
Heri Sutastio ◽  
. Dasimun
Keyword(s):  
Energy Conversion ◽  
Coronal Mass Ejection ◽  
Coronal Mass Ejections ◽  
Magnetic Energy ◽  
Active Regions ◽  
Mass Ejection

Based on active regions dynamics we analyzed the precursors of flare/coronal mass ejections. From the assumption that the energy of coronal mass ejection/flare are from magnetic energy conversion that can be deducted from the changes of sunspots area we analyzed some active regions which produced flare/CME to identify the area changes before the occurrence of the event. We found that in general the sunspots area decreased before the flare/CME occurred, so it is concluded that the decrease of sunspots area can be used as precursors of flare/CME. Abstrak Dengan melihat dinamika daerah aktif dilakukan analisis prekursor fenomena flare/ pelontaran massa korona (CME). Dengan asumsi bahwa energi pelontaran massa korona berasal dari konversi energi magnet yang dilihat dari perubahan luas harian bintik Matahari maka dilakukan analisis perubahan luas harian bintik Matahari pada beberapa daerah aktif yang menghasilkan flare dan atau CME untuk melihat bagaimana luas daerah-daerah tersebut berubah menjelang terjadinya fenomena flare/CME. Didapat bahwa secara umum luas bintik Matahari mengalami penurunan beberapa saat sebelum peristiwa flare/CME ini terjadi. Dari sini dapat disimpulkan bahwa penurunan luas Harian bintik Matahari bisa dijadikan precursor atau indikasi akan adanya peristiwa flare/CME.

Energetic electrons in solar flares: observational support for acceleration processes linked to magnetic reconnection

2021 ◽  
Author(s):  
Nicole Vilmer ◽  
Sophie Musset
Keyword(s):  
Solar Flares ◽  
Magnetic Energy ◽  
Imaging Spectroscopy ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
High Energy ◽  
X Rays ◽  
Energetic Electrons ◽  
Radio Imaging ◽  
Gyrosynchrotron Emission

<p>Efficient electron (and ion) acceleration is produced in association with solar flares. Energetic particles play a major role in the active Sun since they contain a large amount of the magnetic energy released during flares. Energetic electrons (and ions) interact with the solar atmosphere and produce high-energy X-rays and γ-rays. Energetic electrons also produce radio emission in a large frequency band through gyrosynchrotron emission processes in the magnetic fields of flaring active regions and conversion of plasma waves when e.g. propagating to the high corona towards the interplanetary medium. It is currently admitted that solar flares are powered by magnetic energy previously stored in the coronal magnetic field and that magnetic energy release is likely to occur on coronal currents sheets along regions of strong gradient of magnetic connectivity. However, understanding the connection between particle acceleration processes and the topology of the complex magnetic structures present in the corona is still a challenging issue. In this talk, we shall review some recent results derived from X-ray and radio imaging spectroscopy of solar flares bringing some new observational constraints on the localization of HXR/radio sources with respect to current sheets, termination shocks in the corona derived from EUV observations.</p>

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