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NASA NTRS2003

Spatial Relationship of Signatures of Interplanetary Coronal Mass Ejections

Interplanetary coronal mass ejections (ICMEs) are characterized by a number of signatures. In particular, we examine the relationship between Fe charge states and other signatures during ICMEs in solar cycle 23. Though enhanced Fe charge states characterize many ICMEs, average charge states vary from event to event, are more likely to be enhanced in faster or flare-related ICMEs, and do not appear to depend on whether the ICME is a magnetic cloud.

Richardson, I. G.↗
NASA NTRS2023

Partially Erupted Prominence Material as a Diagnostic of Coronal Mass Ejection Trajectory

Coronal mass ejections (CMEs) are energetic releases of large-scale magnetic structures from the Sun. CMEs can have impacts on spacecraft and at Earth. This trajectory is typically assumed to be radial, but often the CME moves outward with some spatial off set from the source region where the eruption initially occurred. A CME is frequently accompanied by a prominence eruption, a movement of cool, dense material up into the corona that can be ejected or fall back down. We investigate eruptions in which some portion of the prominence material falls back to the Sun along field lines which have reconfigured in the eruption, rather than draining back to the source or escaping with the CME. Using a method called persistence mapping, 304 ˚A images from the Solar Dynamics Observatory (SDO), and coronagraph images from the Solar and Heliospheric Observatory (SOHO), we measure and compare the offsets in latitude of 20 CMEs and their respective prominences with respect to the source region. The 20 events were chosen to sample over the first 10 years of the SDO mission. We find that the offsets are correlated. We find no difference between eruptions offset towards the equator or the poles, suggesting that the offset is a result of local changes in the eruptive field, rather than of the Sun’s global magnetic field structure. These findings help us contextualize individual eruptions and highlight changes in the local magnetic field associated with the prominence eruption.

B A Hovis-Afflerbach↗
NASA NTRS2023

Global Ozone Loss Following Extreme Solar Proton Storms Based on the July 2012 Coronal Mass Ejection

Large solar coronal mass ejections pose a threat in the near-Earth space. As a cause of extreme periods of space weather, they can damage satellite-based communications and create geomagnetically induced currents in power and energy grids. Further, the solar wind energetic particles can reduce the protecting layer of atmospheric ozone and pose a threat to life on Earth. The large coronal mass ejection (CME) of July 2012, although directed away from the Earth, is often highlighted as a prime example of a potentially devastating super storm. Here we show, based on proton fluxes recorded by the instruments aboard the STEREO-A satellite, that the atmospheric response to the July 2012 event would have been comparable to those of the largest solar proton events of the satellite era. Significant impact on total ozone outside polar regions would require a much larger event, similar to those recorded in historical proxy data sets. Such an extreme event would cause long-term ozone reduction all the way to the equator and increase the size, duration, and depth of the Antarctic ozone hole. The impact would be comparable to predicted drastic and sudden ozone reduction from major volcanic eruptions, regional nuclear conflicts, or long-term stratospheric geoengineering.

ozone depletion↗
NASA NTRS2004

In-Situ Solar Wind and Magnetic Field Signatures of Interplanetary Coronal Mass Ejections

The heliospheric counterparts of coronal mass ejections (CMEs) at the Sun, interplanetary coronal mass ejections (ICMEs), can be identified in-situ based on a number of magnetic field, plasma, compositional and energetic particle signatures, as well as combinations thereof. Although many of these signatures have been recognized since the early space era, recent observations from improved instrumentation on spacecraft such as Ulysses, Wind, and ACE, in conjunction with solar observations from SOHO, have advanced our understanding of the characteristics of ICMEs and their solar counterparts. We summarize these signatures and their implications for understanding the nature of these structures and the physical properties of coronal mass ejections. We conclude that our understanding of ICMEs is far from complete, and formulate several challenges that, if addressed, would substantially improve our knowledge of the relationship between CMEs at the Sun and in the heliosphere.

Zurbuchen, Thomas H.↗
NASA NTRS2023

A Data-driven, Physics-based Transport Model of Solar Energetic Particles Accelerated by Coronal Mass Ejection Shocks Propagating through the Solar Coronal and Heliospheric Magnetic Fields

In an effort to develop computational tools for predicting radiation hazards from solar energetic particles (SEPs), we have created a data-driven physics-based particle transport model to calculate the injection, acceleration, and propagation of SEPs from coronal mass ejection (CME) shocks traversing through the solar corona and interplanetary magnetic fields. The model runs on an input of corona and heliospheric plasma and magnetic field configuration from a magnetohydrodynamic model driven by solar photospheric magnetic field measurements superposed with observed CME shocks determined from coronagraph images. SEP source particles are injected at the shock using the result of diffusive shock acceleration formulation from a characteristic obliquity-dependent injection from a heated solar wind thermal tail population. With several advanced computation techniques involving stochastic simulation and integration, the model obtains the particle intensity at any location in interplanetary space through the rigorous solution to the time-dependent 5D focus transport equation in the phase space that includes perpendicular diffusion. We apply the model to the 2011 November 3 CME event. The calculation results reproduce multispacecraft SEP observations at Earth and STEREO-B reasonably well without normalization of particle flux. The observations at STEREO-A can be reproduced by rescaling particle energy or modified energy dependence of particle diffusion coefficients. This circumsolar SEP event seen by spacecraft at Earth, STEREO-A, and STEREO-B at widely separated longitudes can be explained by diffusive shock acceleration by a single CME shock with a moderate speed.

Solar energetic particles↗
NASA NTRS2007

A Survey of Interplanetary Coronal Mass Ejections During 1996 - 2007

Interplanetary coronal mass ejections, the interplanetary counterparts of coronal mass ejections at the Sun, are the major drivers of interplanetary shocks in the heliosphere, and are associated with modulations of the galactic cosmic ray intensity, both short term (Forbush decreases caused by the passage of the shock, post-shock sheath, and ICME) and possibly with longer term modulation. Using several in-situ signatures of ICMEs, including plasma temperature, and composition, magnetic fields, and cosmic ray modulations, made by near-Earth spacecraft, we have compiled a "comprehensive" list of ICMEs passing the Earth since 1996, encompassing solar cycle 23. We summarize the properties of these ICMEs, such as their occurrence rate, speeds, association with solar energetic particle events, shocks and cosmic ray decreases.

Richardson, Ian↗
NASA NTRS2007

Interplanetary Coronal Mass Ejections During 1996 - 2007

Interplanetary coronal mass ejections, the interplanetary counterparts of coronal mass ejections at the Sun, are the major drivers of interplanetary shocks in the heliosphere, and are associated with modulations of the galactic cosmic ray intensity, both short term (Forbush decreases caused by the passage of the shock, post-shock sheath, and ICME), and possibly with longer term modulation. Using several in-situ signatures of ICMEs, including plasma temperature, and composition, magnetic fields, and cosmic ray modulations, made by near-Earth spacecraft, we have compiled a "comprehensive" list of ICMEs passing the Earth since 1996, encompassing solar cycle 23. We summarize the properties of these ICMEs, such as their occurrence rate, speeds and other parameters, the fraction of ICMEs that are classic magnetic clouds, and their association with solar energetic particle events, halo CMEs, interplanetary shocks, geomagnetic storms, shocks and cosmic ray decreases.

Richardson, I. G.↗
NASA NTRS2016

Relationship of EUV Irradiance Coronal Dimming Slope and Depth to Coronal Mass Ejection Speed and Mass

Extreme ultraviolet (EUV) coronal dimmings are often observed in response to solar eruptive events. These phenomena can be generated via several different physical processes. For space weather, the most important of these is the temporary void left behind by a coronal mass ejection (CME). Massive, fast CMEs tend to leave behind a darker void that also usually corresponds to minimum irradiance for the cooler coronal emissions. If the dimming is associated with a solar are, as is often the case, the are component of the irradiance light curve in the cooler coronal emission can be isolated and removed using simultaneous measurements of warmer coronal lines. We apply this technique to 37dimming events identified during two separate two-week periods in 2011, plus an event on 2010 August 7 analyzed in a previous paper, to parameterize dimming in terms of depth and slope. We provide statistics on which combination of wavelengths worked best for the flare-removal method, describe the fitting methods applied to the dimming light curves, and compare the dimming parameters with corresponding CME parameters of mass and speed. The best linear relationships found are nu(sub CME) [km/s] approx. equals 2.36 x 10 6 [km/%] x s(sub dim) [%/s] m(sub CME) [g] approx. equals 2.59 x 10(exp.15 [g/%] x the square root of d(sub dim) [%].These relationships could be used for space weather operations of estimating CME mass and speed using near-real-time irradiance dimming measurements.

Mason, James Paul↗
NASA NTRS1995

Relationship of coronal mass ejections with solar flares, prominences and coronal holes

We have investigated more than 450 coronal mass ejections (CME's) observed between 1979-1985 (by SOLWIND) having speed more than 500 km/s. To carry out the study we have used the method of time and spatial correlations. From the study we have found the following: (1) About 50% CMEs are related with coronal holes; (2) About 15% CMEs are related with solar flares; (3) About 25% CMEs are associated with eruptive prominence; and (4) About 10% CMEs are not related with any solar phenomena. The relationship of CMEs and solar radio bursts are also studied. In the light of above, we are of the view that there may be two types of CMEs. The origin of one of them may be related with coronal holes and that for other may be solar flares and prominences.

Verma, V. K.↗
NASA NTRS1986

Do we understand coronal mass ejections yet?

Though many more coronal mass ejections (CMEs) were observed, and though much more has been learned about them during the Solar Maximum Analysis period, they are not yet fully understood. A few recent observational results are reviewed; conclusions and implications drawn from these observations are presented. An emerging picture of the magnetic character of CMEs is sketched; the variations of CMEs' frequency and latitudes over most of a solar cycle are shown. A strong caution about the present lack of concensus on the definition of CMEs is illustrated with examples of the consequences of using different definitions. Finally, some remaining questions about coronal mass ejections are posed.

Hildner, Ernest↗
NASA NTRS1990

MHD intermediate shocks in coronal mass ejections

A simplified model of coronal mass ejections is considered in which at least a portion of the interaction with the background corona involves a shock wave, and the allowable shock solutions and their compressive signatures are examined. The MHD shock-jump equations have a maximum of three possible types of solutions with an entropy rise for fixed values of the physical variables (slow, intermediate, and fast shocks). However, one of the three solution classes (the intermediate shock) is widely believed to not occur in nature and is regarded as nonevolutionary or extraneous. Without the intermediate shock, there is no multiplicity of solutions in that only one shock (or none) can occur for given physical values. All three potential shock types are considered, and it is shown solely on the basis of the shock-jump equations, that intermediate shocks must exist along some segment of the shock front for certain parametric regimes and for conditions that probably occur in some coronal mass ejections.

Steinolfson, R. S.↗
NASA NTRS1997

The evolution of a rapidly-expanding active region loop into a trans-equatorial coronal mass ejection

On 23 February 1997, a coronal mass ejection erupted off the NE limb of the sun from a coronal loop system which had earlier been visible soft X-rays and Fe XIV. The ejection coincided with the onset of a small soft X-ray event, and it left the corona at a position angle of around 60 deg at around 880 km s(exp -1). This ejection then merged with a much larger event which spanned the equator and became indistinguishable, in projection, with the primary event. The soft X-ray images indicate that the highest temperature plasma was associated with the loop system near the original erupting loop. A large loop system became visible south of the equator as the coronal mass ejection developed. It appears that there are high closed coronal magnetic loops linking the northern region to that in the south.

Simnett, G. M.↗
NASA NTRS1988

The driver in flares and coronal mass ejections: Magnetic expansion

Chromospheric filaments, and hence the sheared magnetic fields that they trace, are observed to erupt in flares and coronal mass ejections. In the eruption, the filament-traced field is seen to expand in volume. For frozen-in magnetic field and isotropic expansion, the magnetic energy in a flux tube decreases as the flux tube expands. The amount of expansion of the magnetic field and the corresponding decrease in magnetic energy in a filament-eruption flare and/or coronal mass ejection can be estimated to order of magnitude from the observed expansion of the erupting filament. This evaluation for filament-eruption events in which the filament expansion is clearly displayed gives decreases in magnetic energy of the order of the total energy of the accompanying flare and/or coronal mass ejection. This simple expanding flux tube model can also fit the observed acceleration of coronal mass ejections, if it is assumed that the increase in mechanical energy of the mass ejection comes from the magnetic energy decrease in the expansion. These results encourage the view that magnetic expansion such as seen in filament eruptions drives both the plasma particle energization in flares and the bulk mass motion in coronal mass ejections.

Moore, Ronald L.↗
NASA NTRS1988

Evidence that coronal mass ejections are magnetically self-propelled

The observed embedment of erupting filaments in coronal mass ejections, the work of Kahler et al. (1988) on the dynamics of erupting filaments and Moore's (1988) empirical estimates of the magnetic energy released in filament eruptions are examined. It is found that these studies provide evidence that coronal mass ejections are low-beta, magnetically self-propelled plasmoids. It is suggested that erupting filaments become the cores of coronal mass ejections, are not driven by plasma pressure, trace expansion and untwisting of the magnetic field, and mark decreases of magnetic energy great enough to drive coronal mass ejections.

Moore, Ronald L.↗
NASA NTRS1987

The coronal mass ejection of July 6, 1980 - A candidate for interpretation as a coronal shock wave

The July 6, 1980 looplike coronal mass ejection observed with the Solar Maximum Mission coronagraph is described and analyzed. Two observations are given special consideration: (1) the sides of the loop moved laterally while they were visible and did not form stationary bright columns, or 'legs', in the late stage, and (2) raylike features initially outside the mass ejection loop were not pushed aside or bent until the laterally moving loop sides passed over them. These observations, as well as the results of quantitative analysis of the motion of the bright loop, are consistent with the identification of the bright loop as a shock front. The loop top moved outward faster (at about 1000 km/s) than most mass ejections studied previously, and possibly faster than the Alfven speed in the corona, while the loop sides moved laterally at a speed of about 800 km/s and showed no evidence of deceleration. The excess mass in the bright loop is estimated to be less than about 2 x 10 to the 14th g, well below the value found to be typical of coronal mass ejections.

Sime, D. G.↗
NASA NTRS1983

Evidence linking coronal mass ejections with interplanetary magnetic clouds

Using proxy data for the occurrence of those mass ejections from the solar corona which are directed earthward, we investigate the association between the post-1970 interplanetary magnetic clouds of Klein and Burlaga and coronal mass ejections. The evidence linking magnetic clouds following shocks with coronal mass ejections is striking; six of nine clouds observed at Earth were preceded an appropriate time earlier by meter-wave type II radio bursts indicative of coronal shock waves and coronal mass ejections occurring near central meridian. During the selected periods when no clouds were detected near Earth, the only type II bursts reported were associated with solar activity near the limbs. Where the proxy solar data to be sought are not so clearly suggested, that is, for clouds preceding interaction regions and clouds within cold magnetic enhancements, the evidence linking the clouds and coronal mass ejections is not as clear; proxy data usually suggest many candidate mass-ejection events for each cloud. Overall, the data are consistent with and support the hypothesis suggested by Klein and Burlaga that magnetic clouds observed with spacecraft at 1 AU are manifestations of solar coronal mass ejection transients.

Wilson, R. M.↗
NASA NTRS2011

From SOHO to STEREO: Understanding Propagation of Coronal Mass Ejections

Direct comparison between coronal mass ejections (CMEs) from near the Sun and their solar wind counterparts became possible roughly a decade after the discovery of CMEs (Lindsay et aL 1999). This comparison revealed that fast CMEs decelerate and slow CMEs accelerate due to the interaction with the solar wind. Gopalswamy et al (2000) quantified this interaction as an interplanetary acceleration which is useful in predicting the arrival time and speed of CMEs at 1 AU. The interplanetary acceleration is essentially due to the aerodynamic drag between the CME and the solar wind because the propelling force and the solar gravity are effective only near the Sun. Combined remote-sensing and in situ observations from SOHO and Wind/ACE have helped us estimate the influence of the solar wind on the propagation of CMEs. However, these measurements have severe limitations because the remote sensed and in-situ observations correspond to different portions of the CME. Furthermore, the true speeds of Earth-directed CMEs cannot be measured accurately from a spacecraft located along the Sun-Earth line. There have been attempts to model the CME as a cone and get the space speed of the CME, which did improve the travel time predictions. Instruments on board the Solar Terrestrial Relations Observatory (STEREO) mission were able to provide observations of Earth-arriving CMEs without projection effects, while the same CMEs were observed at Sun-Earth L1 by Wind and ACE spacecraft. The quadrature between STEREO and L1 spacecraft presented an ideal situation to study the interplanetary evolution of CMEs and test earlier model results. The quadrature observations did improve the CME travel time predictions, but additional factors such as the unusually slow solar wind, CME cannibalism, and coronal-hole deflection need to be considered to reconcile the difference between observed and predicted travel times. This point is illustrated using the 2011 February 15 CME

Gopalswamy, Natchimuthuk↗
NASA NTRS1986

Solwind observations of coronal mass ejections during 1979-1985

Coronal observations have been processed for parts of each year during the interval 1979-1985. Around sunspot maximum, coronal mass ejections (CMEs) occurred at the rate of approximately 2 per day, and had a wide range of physical and morphological properties. During the recent years of relatively low sunspot number, CMEs occurred at the rate of only 0.2 per day, and were dominated by the class of so-called streamer blowout. These special CMEs maintained a nearly constant occurrence rate of roughly 0.1 per day during the entire interval.

Sheeley, N. R., Jr.↗