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NASA NTRS1987

Coronal mass ejections: The long-term variation of their occurrence rate and the solar wind mass flux

Solar Coronal Mass Ejections (CMEs) from the Sun are an important aspect of coronal physics, and a potentially important contributor to the solar wind mass flux. However, despite significant progress in studies of CMEs since their discovery in the early 70's, questions remain about their effects on the interplanetary medium. A study is done of the long-term variations of the occurrence rates of CMEs, of activity tracers related to CMEs, and of the solar wind particle flux. CMEs are most directly detected by scattered electron radiation in white light. To estimate their long-term occurrence frequency and their contributions to the in-ecliptic solar wind mass flux, observed CME rates must be corrected for instrumental duty cycles, detection efficiency out of the plane of the sky, mass detection thresholds, and geometrical considerations. These corrections are evaluated using data on solar CMEs from the spaceborne Skylab, SMM, and SOLWIND coronagraphs and on interplanetary plasma clouds from the HELIOS white light photometers. Variations in the CME rate and the contribution of CMEs to the solar wind mass flux are traced over nearly a complete solar activity cycle.

Webb, David F.↗
NASA NTRS1994

Coronal mass ejections and major solar flares: The great active center of March 1989

The solar flare and coronal mass ejection (CME) events associated with the large and complex March 1989 active region are discussed. This active region gave us a chance to study the relation of CME with truly major solar flares. The work concentrates on questions of the relation of CMEs and flares to one another and to other types of activity on the Sun. As expected, some major (X-3B class) flares had associated CMEs. However, an unexpected finding is that others did not. In fact, there is strong evidence that the X4-4B flare of March 9th had no CME. This lack of a CME for such an outstanding flare event has important implications to theories of CME causation.Apparently, not all major flares cause CMEs or are caused by CMEs. The relations between CMEs and other types of solar activity are also discussed. No filament disappearances are reported for major CMEs studied here. Comparing these results with other studies, CMEs occur in association with flares and with erupting prominences, but neither are required for a CME. The relation between solar structures showing flaring without filament eruptions and structures showing filament eruptions without flares becomes important. The evolutionary relation between an active flaring sunspot region and extensive filaments without sunspots is reviewed, and the concept of an 'evolving magnetic structure' (EMS) is introduced. It is suggested that all CMEs arise in EMSs and that CMEs provide a major path through which azimuthal magnetic fields escape form the Sun during the solar cycle.

Feynman, Joan↗
NASA NTRS2023

Type II Radio Bursts and Their Association With Coronal Mass Ejections in Solar Cycles 23 and 24

Context. Meter-wavelength type II solar radio bursts are thought to be the signatures of shock-accelerated electrons in the corona. Studying these bursts can give information about the initial kinematics, dynamics, and energetics of coronal mass ejections (CMEs) in the absence of white-light observations. Aims. We investigate the occurrence of type II bursts in solar cycles 23 and 24 and their association with CMEs. We also explore whether type II bursts might occur in the absence of a CME. Methods. We performed a statistical analysis of type II bursts that occurred between 200 and 25 MHz in solar cycles 23 and 24 and determined the temporal association of these radio bursts with CMEs. We categorized the CMEs based on their linear speed and angular width and studied the distribution of type II bursts with fast (≥500 km s−1 ), slow (<500 km s−1), wide (≥60◦), and narrow (<60◦) CMEs. We explored the dependence of type II bursts occurrence on the phases of the solar cycle. Results. Our analysis shows that during solar cycles 23 and 24, 768 and 435 type II bursts occurred, respectively. Of these, 79% were associated with CMEs in solar cycle 23, and 95% were associated with CMEs in solar cycle 24. However, only 4% and 3% of the total number of CMEs were accompanied by type II bursts in solar cycle 23 and 24, respectively. Most of the type II bursts in both cycles were related to fast and wide CMEs (48%). We also determined the typical drift rate and duration for type II bursts, which is 0.06 MHz s−1 and 9 min. Our results suggest that type II bursts dominate at heights ≈1.7−2.3±0.3 R . A clear majority have an onset height around 1.7 ± 0.3 R assuming the four-fold Newkirk model. Conclusions. The results indicate that most of the type II bursts had a white-light CME counterpart, but a few type II bursts lacked a clear CME association. There were more CMEs in cycle 24 than in cycle 23. However, cycle 24 contained fewer type II radio bursts than cycle 23. The onset heights of type II bursts and their association with wide CMEs reported in this study indicate that the early lateral expansion of CMEs may play a key role in the generation of these radio bursts.

Sun: activity↗
NASA NTRS1994

A coronal mass ejection model for the 1992 July 15 flare on AU Microscopii observed by the extreme ultraviolet explorer

The dM1e flare star AU Microscopii (AU Mic) was observed by the EUVE Deep Survey Instrument on 1992 July 14-18. A large flare was detected in the Deep Survey Lexan/Boron (DS Lex/B)(65-190 A) band and the SW (70-190 A) and MW (140-380 A) spectrometers. The flare consisted of a sharp impulsive peak lasting approximately 2 hours followed by a decaying tail lasting about a day. We present a simple, single temperature, dynamic model for the flare decay which is consistent with the DS Lex/B light curve and reproduces the strongest, high-temperature spectral lines in the released EUVE spectra. In this model, we assume the long decay time is due to an ejected, magnetically confined, low beta plasmoid expanding self similarly in the ambient medium in a manner reminiscent of solar coronal mass ejections. We demonstrate that the long tail of the DS Lex/B light curve can be explained by rapid expansion, causing the plasma to become tenuous sufficiently quickly that it avoids catastrophic radiative cooling. From this model, we estimate the mass of the plasmoid to be approximately = 10(exp 20) g and the total energy of the event to be approximately = 10(exp 36) ergs. These values are approximately 10(exp 4) times as large as those seen during the largest solar coronal mass ejection (CME) events. We argue that the results of our model are consistent with other measurements of stellar flare parameters. We also estimate a mass-loss rate of a few times 10(exp -13) Solar mass/yr and discuss the role of mass loss from dMe stars in the mass balance of the interstellar medium. We estimate the rotational braking timescale from these events to be less than 500 million years and suggest that CME's may be an important source of angular momentum loss from late-type stars.

Cully, Scott L.↗
DOE OSTI2024

Coupled Experimental/Computational Investigation of the Dynamics of Interacting Magnetized Plasmas

The interaction, or interpenetration, of magnetized plasmas of different density and/or pressure occurs in a wide variety of natural and man-made systems. Such systems include extragalactic jets propagating into the intergalactic medium, solar coronal mass ejections into background solar wind, compact toroid (CT) fueling of magnetic fusion plasmas, and jets of capsule shell impurities into DT fusion fuel, which can lead to enhanced impurity mix in inertial fusion implosions. These plasmas may take the form of jets, with open, helical magnetic structure, or plasma “bubbles” with closed magnetic fields (B-fields), such as spheromaks or CT’s. Such structures, both open and closed B-field cases, can transport heat, particles and magnetic flux or magnetic helicity into background plasma regions. For example, the origin of extragalactic magnetic fields may be due, at least in part, to transport by astrophysical jets. The goal of this proposed work was to elucidate the detailed plasma and magnetic field dynamics of high-density plasma jets (open B-field) and bubbles (closed B-field) propagating into lower density background magnetized plasma through controlled laboratory experiments and closely coupled nonlinear MHD modeling. These experiments were conducted in the HelCat (Helicon-Cathode) linear plasma device at the University of New Mexico (UNM). Plasma jets and bubbles were launched via an existing compact coaxial plasma gun, mounted on the HelCat device. This gun produced plasmas tens of cm in scale and lasting tens of microseconds, thereby allowing detailed multipoint, space- and time-resolved measurements to be made routinely. The experiments were directly modeled using the extended magnetohydrodynamic (XMHD) PERSEUS code, developed at Cornell University [23,24]. Both experimental and numerical modeling work are ongoing. The main results to date are reported here. Additional supplemental funding for one year (8/1/2019 – 7/31/2020) supported numerical investigation of photoionization processes important in many low temperature plasmas, including the HelCat device. Initial results of this modeling work is also reported.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1979

The association of coronal mass ejection transients with other forms of solar activity

Coronal mass-ejection transients observed with the white-light coronagraph on Skylab are found to be associated with several other forms of solar activity. There is a strong correlation between such mass-ejection transients and chromospheric H-alpha activity, with three-quarters of the transients apparently originating in or near active regions. It is inferred that 40% of transients are associated with flares, 50% are associated with eruptive prominences solely (without flares), and more than 70% are associated with eruptive prominences or filament disappearances (with or without flares). Nine of ten flares that displayed apparent mass ejections of H-alpha-emitting material from the flare site could be associated with coronal transients. Within each class of activity, the more energetic events are more likely to be associated with an observable mass ejection.

Munro, R. H.↗
NASA NTRS1994

The speeds of coronal mass ejections in the solar wind at mid heliographic latitudes: Ulysses

Six CMEs (coronal mass ejections) have been detected in the Ulysses plasma observations poleward of S31 deg. The most striking aspect of these mid-latitude CMEs was their high speeds; the overall average speed of these CMEs was approximately 740 km/s, which was comparable to that of the rest of the solar wind at these latitudes. This average CME speed is much higher than average CME speeds observed in the solar wind in the ecliptic or in the corona close to the Sun. The evidence indicates that the CMEs were not pushed up to high speeds in interplanetary space by interaction with trailing high-speed plasma. Rather, they simply seem to have received the same basic acceleration as the rest of the solar wind at these mid-latitudes. Our results suggest that the basic acceleration process for many CMEs at all latitudes is essentially the same as for the normal solar wind. Frequently most of this acceleration must occur well beyond 6 solar radii from Sun center.

Gosling, J. T.↗
NASA NTRS2016

History and Development of Coronal Mass Ejections as a Key Player in Solar Terrestrial Relationship

Coronal mass ejections (CMEs) are relatively a recently discovered phenomenon in 1971, some 15 years into the Space Era. It took another two decades to realize that CMEs are the most important players in solar terrestrial relationship as the root cause of severe weather in Earths space environment. CMEs are now counted among the major natural hazards because they cause large solar energetic particle (SEP) events and major geomagnetic storms, both of which pose danger to humans and their technology in space and ground. Geomagnetic storms discovered in the 1700s, solar flares discovered in the 1800s, and SEP events discovered in the 1900s are all now found to be closely related to CMEs via various physical processes occurring at various locations in and around CMEs, when they interact with the ambient medium. This article identifies a number of key developments that preceded the discovery of white-light CMEs suggesting that CMEs were waiting to be discovered. The last two decades witnessed an explosion of CME research following the launch of the Solar and Heliospheric Observatory mission in 1995, resulting in the establishment of a full picture of CMEs.

Gopalswamy, N.↗
NASA NTRS1994

Coronal mass ejections in the solar wind at high solar latitudes: An overview

Ulysses provided the first direct measurements of coronal mass ejections (CME's) in the solar wind at high heliographic latitudes. An overview of new results from the plasma experiment on Ulysses and magnetic field measurements, during the spacecraft's first excursion to high solar latitudes are summarized. A striking aspect of the high-latitude CME's observed is that they all had high speeds, with the overall average speed being 730 km/sec. A new class of forward-reverse shock pairs, associated with expansion of CME's was discovered at high latitudes. Of six certain CME's observed at high latitudes, three have associated shock pairs of this nature. Combined Ulysses and Yohkoh observations suggest that the flux rope topology characteristic of some CME's results from reconnection within the legs of neighboring magnetic loops embedded within the escaping CME's.

Gosling, Jack T.↗
NASA NTRS2019

Are Solar Energetic Particle Events and Type II Bursts Associated with Fast and Narrow Coronal Mass Ejections?

Gradual solar energetic ( E>10 MeV ) particle (SEP) events and metric through kilometric wavelength type II radio bursts are usually associated with shocks driven by fast ( V > 900 kms-1 ) and wide ( W>60deg ) coronal mass ejections (FW CMEs). This criterion was established empirically by several studies from solar cycle 23. The characteristic Alfven speed in the corona, which ranges over 500-1500 kms-1 at heights > 2 Ro, provides the minimum V requirement for a CME to drive a shock, but the general absence of SEP events or type II bursts with fast and narrow ( W<60deg ) CMEs has not been explained. We review and confirm the earlier studies with a more comprehensive comparison of SEP events and type II bursts with fast and narrow (FN) CMEs. We offer an explanation for the lack of SEP event and type II burst associations with FN CMEs in terms of recent heuristic arguments and modeling that show that the response of a magnetized plasma to the propagation of a CME depends on the CME geometry as well as on its speed. A clear distinction is made between a projectile that propagates through the medium to produce a bow shock, and a 3D piston that everywhere accumulates material to produce a broad shock and sheath. The bow shock is unfavorable for producing SEP events and type II bursts, but the 60 deg cut-off is not explained.

Kahler, S.W.↗
NASA NTRS1999

Investigation of the Large Scale Evolution and Topology of Coronal Mass Ejections in the Solar Wind

This investigation is concerned with the large-scale evolution and topology of Coronal Mass Ejections (CMEs) in the solar wind. During this reporting period we have analyzed a series of low density intervals in the ACE (Advanced Composition Explorer) plasma data set that bear many similarities to CMEs. We have begun a series of 3D, MHD (Magnetohydrodynamics) coronal models to probe potential causes of these events. We also edited two manuscripts concerning the properties of CMEs in the solar wind. One was re-submitted to the Journal of Geophysical Research.

Riley, Peter↗
NASA NTRS2000

An Investigation of the Large Scale Evolution and Topology of Coronal Mass Ejections in the Solar Wind

This investigation is concerned with the large-scale evolution and topology of coronal mass ejections (CMEs) in the solar wind. During this reporting period we have focused on several aspects of CME properties, their identification and their evolution in the solar wind. The work included both analysis of Ulysses and ACE observations as well as fluid and magnetohydrodynamic simulations. In addition, we analyzed a series of "density holes" observed in the solar wind, that bear many similarities with CMEs. Finally, this work was communicated to the scientific community at three meetings and has led to three scientific papers that are in various stages of review.

Riley, Peter↗
NASA NTRS2001

Investigation of the Large Scale Evolution and Topology of Coronal Mass Ejections in the Solar Wind

This investigation is concerned with the large-scale evolution and topology of coronal mass ejections (CMEs) in the solar wind. During the course of this three-year investigation, we have undertaken a number of studies that are discussed in more detail in this report. For example, we conducted an analysis of all CMEs observed by the Ulysses spacecraft during its in-ecliptic phase between 1 and 5 AU. In addition to studying the properties of the ejecta, we also analyzed the shocks that could be unambiguously associated with the fast CMEs. We also analyzed a series of 'density holes' observed in the solar wind that bear many similarities with CMEs. To complement this analysis, we conducted a series of 1-D and 2 1/2-D fluid, MHD, and hybrid simulations to address a number of specific issues related to CME evolution in the solar wind. For example, we used fluid simulations to address the interpretation of negative electron temperature-density relationships often observed within CME/cloud intervals. As part of this investigation, a number of fruitful international collaborations were forged. Finally, the results of this work were presented at nine scientific meetings and communicated in eight scientific, refereed papers.

Riley, Pete↗
NASA NTRS2023

Solar Energetic-Particle-Associated Coronal Mass Ejections Observed by the Mauna Loa Solar Observatory Mk3 and Mk4 Coronameters

We report on the first comprehensive study of the coronal mass ejections (CMEs) associated with ~25 MeV solar energetic-proton (SEP) events in 1980 – 2013 observed in the low/inner corona by the Mauna Loa Solar Observatory (MLSO) Mk3 and Mk4 coronameters. Where possible, these observations are combined with space-based observations from the Solar Maximum Mission C/P, P78-1 SOLWIND, or SOHO/LASCO coronagraphs. The aim of the study is to understand directly measured (rather than inferred from proxies) CME motions in the low to midcorona and their association with SEP acceleration, and hence attempt to identify early signatures that are characteristic of SEP acceleration in ground-based CME observations that may be used to warn of impending SEP events. Although we find that SEP events are associated with CMEs that are on average faster and wider than typical CMEs observed by MLSO, a major challenge turns out to be determining reliable estimates of the CME dynamics in the low corona from the 3-min cadence Mk3/4 observations since different analysis techniques can produce inconsistent results. This complicates the assessment of what early information on a possible SEP event is available from these low-coronal observations.

I. G. Richardson↗
NASA NTRS1985

Characteristics of coronal mass ejections associated with solar frontside and backside metric Type II bursts

Fast velocities of 500 km/s or greater coronal mass ejections (CME's) are compared with reported metric type II bursts to study the properties of CME's associated with coronal shocks. An earlier report of fast frontside CME's with no associated metric type II bursts is confirmed, and it is calculated that 33 + or - 15 percent of all fast frontside CME's are not associated with such bursts. Faster CME's are more likely to be associated with type II bursts, as expected from the hypothesis of piston-driven shocks. However, CME brightness and associated peak 3-cm burst intensity are also important factors, as might be inferred from the Wagner and MacQueen (1983) view of type II shocks decoupled from associated CME's. The equal visibility of solar frontside and backside CME's is used to deduce the observability of backside type II bursts. It is calculated that 23 + or - 7 percent of all backside type II bursts associated with fast CME's can be observed at the earth and that 13 + or - 4 percent of all type II bursts originate in backside flares. CME speed again is the most important factor in the obervability of backside type II bursts.

Kahler, S. W.↗
NASA NTRS2004

Understanding the Global Structure and Evolution of Coronal Mass Ejections in the Solar Wind

This report summarizes the technical progress made during the first six months of the second year of the NASA Living with a Star program contract Understanding the global structure and evolution of coronal mass ejections in the solar wind, between NASA and Science Applications International Corporation, and covers the period November 18, 2003 - May 17,2004. Under this contract SAIC has conducted numerical and data analysis related to fundamental issues concerning the origin, intrinsic properties, global structure, and evolution of coronal mass ejections in the solar wind. During this working period we have focused on a quantitative assessment of 5 flux rope fitting techniques. In the following sections we summarize the main aspects of this work and our proposed investigation plan for the next reporting period. Thus far, our investigation has resulted in 6 refereed scientific publications and we have presented the results at a number of scientific meetings and workshops.

Riley, Pete↗
NASA NTRS2001

Laboratory for Extraterrestrial Physics

The NASA Goddard Space Flight Center (GSFC) Laboratory for Extraterrestrial Physics (LEP) performs experimental and theoretical research on the heliosphere, the interstellar medium, and the magnetospheres and upper atmospheres of the planets, including Earth. LEP space scientists investigate the structure and dynamics of the magnetospheres of the planets including Earth. Their research programs encompass the magnetic fields intrinsic to many planetary bodies as well as their charged-particle environments and plasma-wave emissions. The LEP also conducts research into the nature of planetary ionospheres and their coupling to both the upper atmospheres and their magnetospheres. Finally, the LEP carries out a broad-based research program in heliospheric physics covering the origins of the solar wind, its propagation outward through the solar system all the way to its termination where it encounters the local interstellar medium. Special emphasis is placed on the study of solar coronal mass ejections (CME's), shock waves, and the structure and properties of the fast and slow solar wind. LEP planetary scientists study the chemistry and physics of planetary stratospheres and tropospheres and of solar system bodies including meteorites, asteroids, comets, and planets. The LEP conducts a focused program in astronomy, particularly in the infrared and in short as well as very long radio wavelengths. We also perform an extensive program of laboratory research, including spectroscopy and physical chemistry related to astronomical objects. The Laboratory proposes, develops, fabricates, and integrates experiments on Earth-orbiting, planetary, and heliospheric spacecraft to measure the characteristics of planetary atmospheres and magnetic fields, and electromagnetic fields and plasmas in space. We design and develop spectrometric instrumentation for continuum and spectral line observations in the x-ray, gamma-ray, infrared, and radio regimes; these are flown on spacecraft to study the interplanetary medium, asteroids, comets, and planets. Suborbital sounding rockets and groundbased observing platforms form an integral part of these research activities. This report covers the period from approximately October 1999 through September 2000.

Vondrak, Richard R.↗
NASA NTRS2023

Spacecraft Floating Potential Measurements for the Wind Spacecraft

Analysis of 8,804,545 electron velocity distribution functions, observed by the Wind spacecraft near 1 au between 2005 January 1 and 2022 January 1, was performed to determine the spacecraft floating potential, ∅ sc . Wind was designed to be electrostatically clean, which helps keep the magnitude of ∅ sc small (i.e., ∼5–9 eV for nearly all intervals) and the potential distribution more uniform. We observed spectral enhancements of ∅ sc at frequencies corresponding to the inverse synodic Carrington rotation period with at least three harmonics. The two-dimensional histogram of ∅ sc versus time also shows at least two strong peaks, with a potential third, much weaker peak. These peaks vary in time, with the intensity correlated with solar maximum. Thus, the spectral peaks and histogram peaks are likely due to macroscopic phenomena like coronal mass ejections (solar cycle dependence) and stream interaction regions (Carrington rotation dependence). The values of ∅ sc are summarized herein and the resulting data set is discussed.

Lynn B Wilson III↗