Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Solar coronal mass ejections”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Magnetic Reconnection: A Fundamental Process in Space Plasmas

For many years, collisionless magnetic reconnect ion has been recognized as a fundamental process, which facilitates plasma transport and energy release in systems ranging from the astrophysical plasmas to magnetospheres and even laboratory plasma. Beginning with work addressing solar dynamics, it has been understood that reconnection is essential to explain solar eruptions, the interaction of the solar wind with the magnetosphere, and the dynamics of the magnetosphere. Accordingly, the process of magnetic reconnection has been and remains a prime target for space-based and laboratory studies, as well as for theoretical research. Much progress has been made throughout the years, beginning with indirect verifications by studies of processes enabled by reconnection, such as Coronal Mass Ejections, Flux Transfer Events, and Plasmoids. Theoretical advances have accompanied these observations, moving knowledge beyond the Sweet-Parker theory to the recognition that other, collisionless, effects are available and likely to support much faster reconnect ion rates. At the present time we are therefore near a break-through in our understanding of how collisionless reconnect ion works. Theory and modeling have advanced to the point that two competing theories are considered leading candidates for explaining the microphysics of this process. Both theories predict very small spatial and temporal scales. which are. to date, inaccessible to space-based or laboratory measurements. The need to understand magnetic reconnect ion has led NASA to begin the implementation of a tailored mission, Magnetospheric MultiScale (MMS), a four spacecraft cluster equipped to resolve all relevant spatial and temporal scales. In this presentation, we present an overview of current knowledge as well as an outlook towards measurements provided by MMS.

Hesse, Michael↗
NASA NTRS1995

New results on the site of initiation of Cornal Mass Ejections (CMES), and an interpretation of observation of their interaction with streamers

In this paper it is shown that in some months of the phase of minimum solar activity 1985-1987 as many as (80-90)% of a total number of CMEs occur near belts of streamers with neutral line (NL), and only (10-20)% of them appear near belts of streamers without NL. (Streamers without NL separate regions in the corona with the same direction of radial fields of magnetic tubes originating from adjacent coronal holes). With increasing solar activity, the center of gravity of the number of emerging CMEs is shifting toward belts of steamers without NL and reaches over 80% of their total number in some months by the end of 1989. The CME position angle (PA) coincides, on average, with the angle of the portion of NL which straddles the CME. It is quite possible that this condition is satisfied not in the average but rigorously for each CME. The streamer observed on the limb does not disrupt if the CME in transit either only slightly overlaps with the streamer or lies at all outside it. If in the limb plane under consideration the steamer lies inside the CME, then it disrupts after CME passage.

Eselevich, V. G.↗
NASA NTRS1990

The heliospheric current sheet and modulation of Galactic cosmic rays

The posssible effect of the heliospheric current sheet on the modulation of cosmic rays is examined by examining the number and the nature of coronal mass ejections on the basis of data collected on an abrupt onset of cosmic ray modulation observed in May 1987 on earth and in September 1987 by Pioneer 10 and 11 and in a previous study of modulation for the years 1976-1986. The measure used to examine the gradient-drift theory (according to which modulation is associated with solar cycle changes in the current sheet) is the value of the difference in the maximum latitudinal extents for the current sheet in the northern and the southern solar hemispheres. These were obtained from contours of the current sheet produced by extrapolating photospheric magnetic field measurements to a solar wind source surface. The observations are found to be consistent with the predictions of the gradient drift model.

Smith, Edward J.↗
NASA NTRS1997

The solar minimum X2.6/1B flare and CME of 9 July 1996: Solar data - Pt. 1

The solar observations from GOES-8, the Solar and Heliospheric Observatory (SOHO), and the Yohkoh satellite concerning the events of the X-class flare are discussed. The Michelson Doppler imager (MDI) magnetometer shows a new region of magnetic activity in AR 7978. The rapid development and evolution of this region is shown by the MDI and the extreme-ultraviolet Doppler telescope (EDT) data. The coronal mass ejections (CMEs) observed using coronagraphs are presented. The possible association between the CME and the X-flare is considered.

Andrews, M. D.↗
NASA NTRS2009

CME Link to the Geomagnetic Storms

The coronal mass ejection (CME) link to geomagnetic storms stems from the southward component of the interplanetary magnetic field contained in the CME flux ropes and in the sheath between the flux rope and the CME-driven shock. A typical storm-causing CME is characterized by (i) high speed, (ii) large angular width (mostly halos and partial halos), and (iii)solar source location close to the central meridian. For CMEs originating at larger central meridian distances, the storms are mainly caused by the sheath field. Both the magnetic and energy contents of the storm-producing CMEs can be traced to the magnetic structure of active regions and the free energy stored in them.

Gopalswamy, Nat↗
NASA NTRS2017

Predicting the Magnetic Field of Earth-Impacting CMEs

Predicting the impact of coronal mass ejections (CMEs) and the southward component of their magnetic field is one of the key goals of space weather forecasting. We present a new model, the ForeCAT In situ Data Observer (FIDO), for predicting the in situ magnetic field of CMEs. We first simulate a CME using ForeCAT, a model for CME deflection and rotation resulting from the background solar magnetic forces. Using the CME position and orientation from ForeCAT, we then determine the passage of the CME over a simulated spacecraft. We model the CME's magnetic field using a force-free flux rope and we determine the in situ magnetic profile at the synthetic spacecraft. We show that FIDO can reproduce the general behavior of four observed CMEs. FIDO results are very sensitive to the CME's position and orientation, and we show that the uncertainty in a CME's position and orientation from coronagraph images corresponds to a wide range of in situ magnitudes and even polarities. This small range of positions and orientations also includes CMEs that entirely miss the satellite. We show that two derived parameters (the normalized angular distance between the CME nose and satellite position and the angular difference between the CME tilt and the position angle of the satellite with respect to the CME nose) can be used to reliably determine whether an impact or miss occurs. We find that the same criteria separate the impacts and misses for cases representing all four observed CMEs.

Kay, C.↗
NASA NTRS1976

Initial results from the High Altitude Observatory white light coronagraph on Skylab - A progress report

Frequent periodic observations by the white-light coronagraph allow an examination of coronal variations over a broad range of temporal scales. Examples of the slowest and most rapid variations are presented. An example of extremely slow coronal variations is the gradual evolution - to a large equatorial streamer - in association with a marked decrease in solar activity, as the total magnetic flux in one hemisphere decreased. Another example is given of a long-lived quasi-stable coronal streamer, apparently associated with a stable filament channel; comparison of this streamer with coronal potential-magnetic-field computations show little correlation. Some results on coronal transients - the most rapid variations observed - are summarized. Characteristic masses and energies involved in mass-ejection transients, their temporal and spatial distributions, their associations with surface phenomena and possible interplanetary signatures, and their role in coronal evolution are briefly noted.

Macqueen, R. M.↗
NASA NTRS2022

Influence of Large-Scale Interplanetary Structures on the Propagation of Solar Energetic Particles: the Multi-Spacecraft Event on 2021 October 9

An intense solar energetic particle (SEP) event was observed on 2021 October 9 by multiple spacecraft distributed near the ecliptic plane at heliocentric radial distances R ≲ 1 au and within a narrow range of heliolongitudes. A stream interaction region (SIR), sequentially observed by Parker Solar Probe (PSP) at R = 0.76 au and 48° east from Earth (ϕ = E48°), STEREO-A (at R = 0.96 au, ϕ = E39°), Solar Orbiter (SolO; at R = 0.68 au, ϕ = E15°), BepiColombo (at R = 0.33 au, ϕ = W02°), and near-Earth spacecraft, regulated the observed intensity-time profiles and the anisotropic character of the SEP event. PSP, STEREO-A, and SolO detected strong anisotropies at the onset of the SEP event, which resulted from the fact that PSP and STEREO-A were in the declining-speed region of the solar wind stream responsible for the SIR and from the passage of a steady magnetic field structure by SolO during the onset of the event. By contrast, the intensity-time profiles observed near Earth displayed a delayed onset at proton energies ≳13 MeV and an accumulation of ≲5 MeV protons between the SIR and the shock driven by the parent coronal mass ejection (CME). Even though BepiColombo, STEREO-A, and SolO were nominally connected to the same region of the Sun, the intensity-time profiles at BepiColombo resemble those observed near Earth, with the bulk of low-energy ions also confined between the SIR and the CME-driven shock. This event exemplifies the impact that intervening large-scale interplanetary structures, such as corotating SIRs, have in shaping the properties of SEP events.

D. Lario↗
NASA NTRS1982

Coronal holes - Mass loss driven by magnetic reconnection

A nonthermal mechanism for driving coronal hole mass loss is proposed. Three empirical results are noted, namely (1) that polar plumes with short-lived X-ray bright points (XBP) at their base are sites of matter flow sufficient to account for the total solar mass flux, (2) that solar wind densities are positively correlated with the number of XBP in coronal holes, and (3) that XBP are associated with newly emerged magnetic flux. It is noted that since the dynamical development following the onset of nonequilibrium is a hitherto unsolved problem, subsequent features in the scenario described here are relatively speculative. It is proposed that bubbles of matter ejected from magnetic reconnection sites in polar plumes drive the solar wind in coronal holes.

Mullan, D. J.↗
NASA NTRS1993

The origins of planar magnetic structures in the solar wind

It is shown that the solar-wind settings of planar magnetic structures (PMSs) are generally inconsistent with their interpretation by Nakagawa et al. (1989) as magnetic loops or tongues resulting from newly emerging magnetic flux in the photosphere. It is suggested that PMS events have two origins: (1) compression and/or draping of preexisting magnetic structures on the leading edge of high-speed streams, especially ahead of coronal mass ejections; and (2) discontinuities near the heliospheric current sheet.

Neugebauer, M.↗
NASA NTRS2018

The Statistical Properties of Solar Wind Temperature Parameters Near 1 Au

We present a long-duration (approx. 10 yr) statistical analysis of the temperatures, plasma betas, and temperature ratios for the electron, proton, and alpha-particle populations observed by the Wind spacecraft near 1 au. The mean(median) scalar temperatures are T(sub e)(sub tot) = 12.2(11.9) eV, T(sub p)(sub tot) = 12.7(8.6) eV, and T(sub a)(sub tot) = 23.9(10.8) eV. The mean(median) total plasma betas are Beta(sub e)(sub tot) = 2.31(1.09), Beta(sub p)(sub tot) = 1.79(1.05), and Beta(sub a)(sub tot) = 0.17(0.05). The mean(median) temperature ratios are (T(sub e)/T(sub p))(sub tot) = 1.64(1.27), (T(sub e)/T(sub a))(sub tot) = 1.24(0.82), and (T(sub a)/T(sub p))(sub tot) = 2.50(1.94). We also examined these parameters during time intervals that exclude interplanetary (IP) shocks, times within the magnetic obstacles (MOs) of interplanetary coronal mass ejections (ICMEs), and times that exclude MOs. The only times that show significant alterations to any of the parameters examined are those during MOs. In fact, the only parameter that does not show a significant change during MOs is the electron temperature. Although each parameter shows a broad range of values, the vast majority are near the median. We also compute particle–particle collision rates and compare to effective wave–particle collision rates. We find that, for reasonable assumptions of wave amplitude and occurrence rates, the effect of wave–particle interactions on the plasma is equal to or greater than the effect of Coulomb collisions. Thus, wave–particle interactions should not be neglected when modeling the solar wind.

Wilson, Lynn B., III↗
NASA NTRS1993

Sizes and locations of coronal mass ejections - SMM observations from 1980 and 1984-1989

A statistical description of the sizes and locations of 1209 mass ejections observed with the SMM coronagraph/polarimeter in 1980 and 1984-1989 is presented. The average width of the coronal mass ejections detected with this instrument was close to 40 deg in angle for the entire period of SMM observations. No evidence was found for a significant change in mass ejection widths as reported by Howard et al. (1986). There is clear evidence for changes in the latitude distribution of mass ejections over this epoch. Mass ejections occurred over a much wider range of latitudes at the times of high solar activity (1980 and 1989) than at times of low activity (1985-1986).

Hundhausen, A. J.↗
NASA NTRS1997

Problems in the Forecasting of Solar Particle Events for Manned Missions

Manned spaecraft will require a much improved ability to forecast solar particle events. The lead time required will depend on the use to which the forecast is put. Here we discuss problems of forecasting with the lead times of hours to weeks.

forcast problem coronal mass ejections (CMEs) low ↗
NASA NTRS2004

Modeling Interplanetary Coronal Mass Ejections

Heliospheric models of Coronal Mass Ejection (CME) propagation and evolution provide an important insight into the dynamics of CMEa and are a valuable tool for interpreting interplanetary in situ observations. Moreover, they represent a virtual laboratory for exploring conditions and regions of space that are not conveniently or currently accessible by spacecraft. In this review I summarize recent advances in modeling the properties and evolution of CMEs in the solar wind. In particular, I will focus on: (1) the types of ICME models; (2) the boundary conditions that are imposed, (3) the role of the ambient solar wind; (4) predicting new phenomena; and (5) distinguishing between competing CME initiation mechanisms. I will conclude by discussing what topics will likely be important for models to address in the future.

Riley, Pete↗
NASA NTRS2002

RHESSI Observations of Flares During the Storms Period from 14 to 24 April 2002

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observes X-rays and gamma rays from solar flares in the energy range from 3 keV to 17 MeV with a duty cycle of about 50%. The RHESSI observations of the flares during the Storms Workshop period from 14 to 24 April, 2002, will be reviewed. Many Geostationary Operational Environmental Satellites (GOES) C- and M-class flares were observed including the M2.6 flare on 17 April that was followed by a Coronal Mass Ejection (CME). The X1.5 flare on 21 April was particularly well observed with RHESSI in X-rays from its start at 00:40 UT until 01:33 UT on the first orbit, just before the soft X-ray peak. Footpoint emission was detected to energies as high as 200 keV, and a spatially-separated coronal source was identified at energies below about 30 keV. The coronal X-ray source was followed for over 12 more hours on subsequent orbits as it gradually rose to over 130,000 km above the limb. The X-ray images and spectra of this flare will be presented in relation to the Transitional Region and Coronal Explorer (TRACE) images in the 195-angstrom band and the Large Angle and Spectrometric Coronagraph Experiment (LASCO) images of the associated CME.

Rabin, Douglas↗
NASA NTRS2021

A Model for the Coupled Eruption of a Pseudostreamer and Helmet Streamer

A highly important aspect of solar activity is the coupling between eruptions and the surrounding coronal magnetic-field topology, which determines the trajectory and morphology of the event and can even lead to sympathetic eruptions from multiple sources. In this paper, we report on a numerica lsimulation of a new type of coupled eruption, in which a coronal jet initiated by a large pseudostreamer filament eruption triggers a streamer-blowout coronal mass ejection (CME) from the neighboring helmet streamer. Our configuration has a large opposite-polarity region positioned between the polarcoronal hole and a small equatorial coronal hole, forming a pseudostreamer flanked by the coronalholes and the helmet streamer. Further out, the pseudostreamer stalk takes the shape of an extendedarc in the heliosphere. We energize the system by applying photospheric shear along a section of the polarity inversion line within the pseudostreamer. The resulting sheared-arcade filament channel develops a flux rope that eventually erupts as a classic coronal-hole-type jet. However, the enhanced breakout reconnection above the channel as the jet is launched progresses into the neighboring helmet streamer, partially launching the jet along closed helmet streamer field lines and blowing out thestreamer top to produce a classic bubble-like CME. This CME is strongly deflected from the jet’s initial trajectory and contains a mixture of open and closed magnetic field lines. We present the detailed dynamics of this new type of coupled eruption, its underlying mechanisms and the implications of thiswork for the interpretation of in-situ and remote-sensing observations.

P F Wyper↗
NASA NTRS2012

Prior Flaring as a Complement to Free Magnetic Energy for Forecasting Solar Eruptions

From a large database of (1) 40,000 SOHO/MDI line-of-sight magnetograms covering the passage of 1,300 sunspot active regions across the 30 deg radius central disk of the Sun, (2) a proxy of each active region's free magnetic energy measured from each of the active region's central-disk-passage magnetograms, and (3) each active region's full-disk-passage history of production of major flares and fast coronal mass ejections (CMEs), we find new statistical evidence that (1) there are aspects of an active region's magnetic field other than the free energy that are strong determinants of the active region's productivity of major flares and fast CMEs in the coming few days, (2) an active region's recent productivity of major flares, in addition to reflecting the amount of free energy in the active region, also reflects these other determinants of coming productivity of major eruptions, and (3) consequently, the knowledge of whether an active region has recently had a major flare, used in combination with the active region's free-energy proxy measured from a magnetogram, can greatly alter the forecast chance that the active region will have a major eruption in the next few days after the time of the magnetogram. The active-region magnetic conditions that, in addition to the free energy, are reflected by recent major flaring are presumably the complexity and evolution of the field.

Falconer, David A.↗
NASA NTRS2004

Challenges in Modeling the Sun-Earth System

The transfer of mass, energy and momentum through the coupled Sun-Earth system spans a wide range of scales in time and space. While profound advances have been made in modeling isolated regions of the Sun-Earth system, minimal progress has been achieved in modeling the end-to-end system. Currently, end-to-end modeling of the Sun-Earth system is a major goal of the National Space Weather and NASA Living With a Star (LWS) programs. The uncertainty in the underlying physics responsible for coupling contiguous regions of the Sun-Earth system is recognized as a significant barrier to progress. Our limited understanding of the underlying coupling physics is illustrated by the following example questions: how does the propagation of a typical CME/solar flare influence the measured properties of the solar wind at 1 AU? How does the solar wind compel the dynamic response of the Earth's magnetosphere? How is variability in the ionosphere-thermosphere system coupled to magnetospheric variations? Why do these and related important questions remain unanswered? What are the primary problems that need to be resolved to enable significant progress in comprehensive modeling of the Sun-Earth system? Which model/technique improvements are required and what new data coverage is required to enable full model advances? This poster opens the discussion for how these and other important questions can be addressed. A workshop scheduled for October 8-22, 2004 in Huntsville, Alabama, will be a forum for identifying ana exploring promising new directions and approaches for characterizing and understanding the system. To focus the discussion, the workshop will emphasize the genesis, evolution, propagation and interaction of high-speed solar wind streamers or CME/flares with geospace and the subsequent response of geospace from its outer reaches in the magnetosphere to the lower edge of the ionosphere-mesosphere-thermosphere. Particular emphasis will be placed on modeling the coupling aspects of these phenomena across boundaries between regions and on data analysis that guides and constrains model results. Specific topics to be addressed are: Corotating interaction regions, Coronal mass ejections, Energetic particles, System preconditioning, Extreme events and super storms, End-to-End modeling efforts.

Spann, James↗