Large-scale Magnetic Loops Research Articles

Martian dayside magnetic topology and structures of the cross-terminator magnetic loops – multispecies magnetohydrodynamic simulations

ABSTRACTThe interaction between impinging magnetized solar wind and Martian crustal fields produces complexly distributed magnetic topologies in the dayside magnetosphere. This study focused on obtaining the distribution of Martian dayside magnetic topology and the structures of the cross-terminator magnetic loops. A 3D multispecies magnetohydrodynamic model was employed to simulate the interactions between Mars and solar winds, and a 110° spherical harmonic model was used to calculate the crustal fields. We randomly extracted more than 1000 magnetic field lines from the near-Mars region of the model results. These results indicate the existence of large-scale closed fields and high-inclination-angle open fields in the Southern hemisphere, exerting their influence even above the height of the ionopause, resulting in a complex relationship between plasma motion and magnetic topology distribution. In contrast, the plasma motion patterns in the Northern hemisphere are similar to those observed in unmagnetized planets. Furthermore, the model results show two types of cross-terminator magnetic loop. Small-scale cross-terminator magnetic loops connect the local atmosphere on the dayside and nightside, whereas many large-scale magnetic loops cross the centre–tail region and extend more than 2RM downstream of Mars, especially in the Southern hemisphere. Finally, the clock angle distribution shows magnetic field distortion at 1000 km altitude. This study provides a clearer and more detailed description of the Martian dayside magnetic topology and the structures of the cross-terminator magnetic loops.

The Formation Process of the First Halo Coronal Mass Ejection in Solar Cycle 25: Magnetic Cancellation, Bidirectional Jet, and Hot Channel

Abstract To better understand the trigger mechanism of a coronal mass ejection (CME), we present the evolution of a CME source region (active region NOAA 12790) and the formation of a hot channel before the occurrence of the first halo CME in solar cycle 25. Through analyzing the evolution of Solar Dynamics Observatory/Helioseismic and Magnetic Imager line-of-sight magnetograms, it is found that continuous magnetic cancellation occurs at the polarity inversion line (PIL) in this active region. With ongoing magnetic cancellation, several bidirectional jets and unidirectional jets occur along the large-scale arched magnetic loops. A hot channel forms during the first bidirectional jet. After the occurrence of the fourth bidirectional jet, the hot channel immediately erupts and produces a C-class flare, a cusp structure, and a halo CME. It is worth pointing out that the cusp structure only appears in the 131 Å and 94 Å observations (temperature about 10 MK). The obvious contraction of the newly formed loops is observed at the top of the cusp structure. The observations reveal a clear physics process: magnetic cancellation of a bipolar magnetic field at the PIL results in the occurrence of the bidirectional/unidirectional jets and the formation of the hot channel. The axial magnetic flux feeding for the hot channel through the continued magnetic cancellation leads to the hot channel eruption, which results in the formation of the hot cusp structure and the occurrence of the C-class flare and the halo CME.

The Sun at millimeter wavelengths

Context. The Atacama Large Millimeter/submillimeter Array (ALMA) started regular observations of the Sun in 2016, first offering receiver Band 3 at wavelengths near 3 mm (100 GHz) and Band 6 at wavelengths around 1.25 mm (239 GHz). Aims. Here we present an initial study of one of the first ALMA Band 3 observations of the Sun. Our aim is to characterise the diagnostic potential of brightness temperatures measured with ALMA on the Sun. Methods. The observation covers a duration of 48 min at a cadence of 2 s targeting a quiet Sun region at disc-centre. Corresponding time series of brightness temperature maps are constructed with the first version of the Solar ALMA Pipeline and compared to simultaneous observations with the Solar Dynamics Observatory (SDO). Results. The angular resolution of the observations is set by the synthesised beam, an elliptical Gaussian that is approximately 1.4″ × 2.1″ in size. The ALMA maps exhibit network patches, internetwork regions, and elongated thin features that are connected to large-scale magnetic loops, as confirmed by a comparison with SDO maps. The ALMA Band 3 maps correlate best with the SDO/AIA 171 Å, 131 Å, and 304 Å channels in that they exhibit network features and, although very weak in the ALMA maps, imprints of large-scale loops. A group of compact magnetic loops is very clearly visible in ALMA Band 3. The brightness temperatures in the loop tops reach values of about 8000−9000 K and in extreme moments up to 10 000 K. Conclusions. ALMA Band 3 interferometric observations from early observing cycles already reveal temperature differences in the solar chromosphere. The weak imprint of magnetic loops and the correlation with the 171, 131, and 304 SDO channels suggests, however, that the radiation mapped in ALMA Band 3 might have contributions from a wider range of atmospheric heights than previously assumed, but the exact formation height of Band 3 needs to be investigated in more detail. The absolute brightness temperature scale as set by total power measurements remains less certain and must be improved in the future. Despite these complications and the limited angular resolution, ALMA Band 3 observations have a large potential for quantitative studies of the small-scale structure and dynamics of the solar chromosphere.

MHD Instabilities in Accretion Disks and Their Implications in Driving Fast Magnetic Reconnection

Abstract Magnetohydrodynamic instabilities play an important role in accretion disk systems. Besides the well-known effects of magnetorotational instability (MRI), the Parker–Rayleigh–Taylor instability (PRTI) also arises as an important mechanism to help in the formation of the coronal region around an accretion disk and in the production of magnetic reconnection events similar to those occurring in the solar corona. In this work, we have performed three-dimensional magnetohydrodynamical (3D-MHD) shearing-box numerical simulations of accretion disks with an initial stratified density distribution and a strong azimuthal magnetic field with a ratio between the thermal and magnetic pressures of the order of unity. This study aimed at verifying the role of these instabilities in driving fast magnetic reconnection in turbulent accretion disk/corona systems. As we expected, the simulations showed an initial formation of large-scale magnetic loops due to the PRTI followed by the development of a nearly steady-state turbulence driven by both instabilities. In this turbulent environment, we have employed an algorithm to identify the presence of current sheets produced by the encounter of magnetic flux ropes of opposite polarity in the turbulent regions of both the corona and the disk. We computed the magnetic reconnection rates in these locations, obtaining average reconnection velocities in Alfvén speed units of the order of 0.13 ± 0.09 in the accretion disk and 0.17 ± 0.10 in the coronal region (with mean peak values of order 0.2), which are consistent with the predictions of the theory of turbulence-induced fast reconnection.

A Statistical Study to Determine the Origin of Long-duration Gamma-Ray Flares

Abstract Two scenarios have been proposed to account for sustained ≥30 MeV gamma-ray emission in solar flares: (1) prolonged particle acceleration/trapping involving large-scale magnetic loops at the flare site, and (2) precipitation of high-energy (>300 MeV) protons accelerated at coronal/interplanetary shock waves. To determine which of these scenarios is more likely, we examine the associated soft X-ray flares, coronal mass ejections (CMEs), and solar energetic proton events for (a) the long-duration gamma-ray flares (LDGRFs) observed by the Large Area Telescope on Fermi, and (b) delayed and/or spatially extended high-energy gamma-ray flares observed by the Gamma-ray Spectrometer on the Solar Maximum Mission, the Gamma-1 telescope on the Gamma satellite, and the Energetic Gamma-Ray Experiment Telescope on the Compton Gamma-Ray Observatory. For the Fermi data set of 11 LDGRFs with >100 MeV emission lasting for ≥∼2 hr, we search for associations and reverse associations between LDGRFs, X-ray flares, CMEs, and SEPs, i.e., beginning with the gamma-ray flares and also, in turn, with X-class soft X-ray flares, fast (≥1500 km s−1) and wide CMEs, and intense (peak flux ≥2.67 × 10−3 protons cm−2 s−1 sr−1, with peak to background ratio >1.38) >300 MeV SEPs at 1 au. While LDGRFs tend to be associated with bright X-class flares, we find that only one-third of the X-class flares during the time of Fermi monitoring coincide with an LDGRF. However, nearly all fast, wide CMEs are associated with an LDGRF. These preliminary association analyses favor the proton precipitation scenario, although there is a prominent counter-example of a potentially magnetically well-connected solar eruption with >100 MeV emission for ∼10 hr for which the near-Earth >300 MeV proton intensity did not rise above background.

A Study of External Magnetic Reconnection that Triggers a Solar Eruption

Abstract External magnetic reconnection (EMR) is suggested to play an essential role in triggering a solar eruption, but is rarely directly observed. Here, we report on a filament eruption on 2014 October 3 that apparently involves the process of an early EMR. A total of 1.7 × 1020 Mx flux was first canceled along the filament-related polarity inversion line over 12 hr, and then the filament axis started to brighten in extreme ultraviolet (EUV). An impulsive EUV brightening began 30 minutes later, and we attribute this to EMR, as it is located at the center of a bidirectional outflow with a velocity of 60–75 km s−1 along large-scale magnetic loops from active regions NOAA 12178 and 12179, respectively, and over the filament mentioned above. Following the EMR, the filament was activated; then, partial eruption occurred 6 minutes later in the west, in which the decay index above the magnetic flux rope (MFR) reached the critical value of 1.5. The observations are interpreted in terms of underlying magnetic flux cancelation leading to the buildup and eventual formation of the MFR with a filament embedded in it, and the MFR is elevated later. The activated MFR rises and pushes the overlying sheared field and forms a current sheet causing the EMR. The EMR in turn weakens the constraining effect of the overlying field, leading to the arising of the MFR, and subsequently erupting due to torus instability.

M 82 – A radio continuum and polarisation study

The composition and morphology of the interstellar medium in starburst galaxies has been well investigated, but the magnetic field properties are still uncertain. The nearby starburst galaxy M82 provides a unique opportunity to investigate the mechanisms leading to the amplification and reduction of turbulent and regular magnetic fields. Possible scenarios of the contribution of the magnetic field to the star-formation rate are evaluated. Archival data from the VLA and WSRT were combined and re-reduced to cover the wavelength regime between 3cm and 22cm. All observations revealed polarised emission in the inner part of the galaxy, while extended polarised emission up to a distance of 2kpc from the disk was only detected at 18cm and 22cm. The observations hint at a magnetised bar in the inner part of the galaxy. We calculate the mass inflow rate due to magnetic stress of the bar to 7.1 solar masses per year, which can be a significant contribution to the star-formation rate of M82 of approximately 13 solar masses per year. The halo shows polarised emission, which might be the remnant of a regular disk field. Indications for a helical field in the inner part of the outflow cone are provided. The coherence length of the magnetic field in the centre is similar to the size of giant molecular clouds. Using polarisation spectra more evidence for a close coupling of the ionised gas and the magnetic field as well as a two-phase magnetic field topology were found. Electron densities in the halo are similar to the ones found in the Milky Way. The magnetic field morphology is similar to the one in other nearby starburst galaxies with possible large-scale magnetic loops in the halo and a helical magnetic field inside the outflow cones. The special combination of a magnetic bar and a circumnuclear ring are able to significantly raise the star-formation rate in this galaxy by magnetic braking.

Investigating the Origins of Two Extreme Solar Particle Events: Proton Source Profile and Associated Electromagnetic Emissions

Abstract We analyze the high-energy particle emission from the Sun in two extreme solar particle events in which protons are accelerated to relativistic energies and can cause a significant signal even in the ground-based particle detectors. Analysis of a relativistic proton event is based on modeling of the particle transport and interaction, from a near-Sun source through the solar wind and the Earth’s magnetosphere and atmosphere to a detector on the ground. This allows us to deduce the time profile of the proton source at the Sun and compare it with observed electromagnetic emissions. The 1998 May 2 event is associated with a flare and a coronal mass ejection (CME), which were well observed by the Nançay Radioheliograph, thus the images of the radio sources are available. For the 2003 November 2 event, the low corona images of the CME liftoff obtained at the Mauna Loa Solar Observatory are available. Those complementary data sets are analyzed jointly with the broadband dynamic radio spectra, EUV images, and other data available for both events. We find a common scenario for both eruptions, including the flare’s dual impulsive phase, the CME-launch-associated decimetric-continuum burst, and the late, low-frequency type III radio bursts at the time of the relativistic proton injection into the interplanetary medium. The analysis supports the idea that the two considered events start with emission of relativistic protons previously accelerated during the flare and CME launch, then trapped in large-scale magnetic loops and later released by the expanding CME.

HIGH-RESOLUTION OBSERVATIONS OF A LARGE FAN-SHAPED SURGE

ABSTRACT We present high-resolution observations of a large fan-shaped surge, which was observed on 2013 June 5 with the current largest solar telescope, the 1.6 m New Solar Telescope (NST), at the Big Bear Solar Observatory. The observations are made at TiO, Hα, and 10830 Å wavebands with a spatial resolution better than 0 .″ 1 and a full-run cadence of ∼30 s. The fan-shaped surge consists of many small-scale threads with a typical width of 100 km and a length of up to 200 Mm at the maximum. The threads come from material ejections, which start with a velocity of several km s−1, and then accelerate up to 60–80 km s−1 over six to seven minutes with an acceleration of up to 0.2–0.3 km s−2. The threads can be observed in the Hα band and in SDO/AIA 171 Å images as absorbed objects, implying that they are cool material ejections. The surge is ejected along open magnetic field lines in the extrapolated non-linear force-free field, which might actually be a part of a large-scale magnetic loop stretching back to the solar surface. After 10–20 minutes, the ejections gradually decay and the surge eventually vanishes. The total lifetime is about 35 minutes. The Hα brightening at the root of the fan-shaped surge implies that there is heating in the chromosphere, which could be produced by low-atmosphere interchange magnetic reconnection. Our observation provides evidence of the reconnection model for the fan-shaped surges, which was proposed by Jiang et al.

ON THE NATURE OF THE EXTREME-ULTRAVIOLET LATE PHASE OF SOLAR FLARES

The extreme-ultraviolet (EUV) late phase of solar flares is a second peak of warm coronal emissions (e.g., Fe XVI) for many minutes to a few hours after the GOES soft X-ray peak. It was first observed by the EUV Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO). The late phase emission originates from a second set of longer loops (late phase loops) that are higher than the main flaring loops. It is suggested as being caused by either additional heating or long-lasting cooling. In this paper, we study the role of long-lasting cooling and additional heating in producing the EUV late phase using the "enthalpy-based thermal evolution of loops" (EBTEL) model. We find that a long cooling process in late phase loops can well explain the presence of the EUV late phase emission, but we cannot exclude the possibility of additional heating in the decay phase. Moreover, we provide two preliminary methods based on the UV and EUV emissions from the Atmospheric Imaging Assembly (AIA) on board SDO to determine whether an additional heating plays some role or not in the late phase emission. Using nonlinear force-free field modeling, we study the magnetic configuration of the EUV late phase. It is found that the late phase can be generated either in hot spine field lines associated with a magnetic null point or in large-scale magnetic loops of multipolar magnetic fields. In this paper, we also discuss why the EUV late phase is usually observed in warm coronal emissions and why the majority of flares do not exhibit an EUV late phase.

Opening of active region’s large-scale overlying magnetic loops and kinking motion of a magnetic loop triggered by a vicinal small eruption

In this paper, we present a clear case of a small eruption near active region NOAA 10990 leading to opening of active region's large-scale magnetic loops and kinking motion of a magnetic loop in this active region on April 16, 2008. From a sequence of TRACE 171 images, we find that the upper large-scale overlying magnetic loops of the active region expanded upwards from the arcaded configuration to the vertical one accompanying the vicinal small eruption. At the same time, the topology of a magnetic loop inside the active region changed from the inverted "U" shape to the almost vertical one with its two legs intertwining each other. From the temporal analysis of the observations, we find that the opening of the upper large-scale overlying magnetic loops resulted in the instability of the magnetic loop inside the active region. By analyzing the surrounding coronal environment, we suggest that the existence of the lower overlying magnetic loops prevented the magnetic loop from eruption. Generally, the kinking motion of the flux rope is taken as occurrence of kink instability. In this event, the top of the magnetic loop first began the kinking motion and then the two legs intertwined each other. According to our knowledge, the latter process has not been reported. Because there was only one active region on the solar disk on April 16, 2008, it turned out to be a very good candidate for us to investigate the impact of the vicinal eruption on the active region. These findings provide evidence that the active region is very sensitive to the vicinal eruptions.

Mechanical equilibrium of hot, large-scale magnetic loops on T Tauri stars

The most extended, closed magnetic loops inferred on T Tauri stars confine hot, X-ray emitting plasma at distances from the stellar surface beyond the the X-ray bright corona and closed large-scale field, distances comparable to the corotation radius. Mechanical equilibrium models have shown that dense condensations, or "slingshot prominences", can rise to great heights due to their density and temperatures cooler than their environs. On T Tauri stars, however, we detect plasma at temperatures hotter than the ambient coronal temperature. By previous model results, these loops should not reach the inferred heights of tens of stellar radii where they likely no longer have the support of the external field against magnetic tension. In this work, we consider the effects of a stellar wind and show that indeed, hot loops that are negatively buoyant can attain a mechanical equilibrium at heights above the typical extent of the closed corona and the corotation radius.

Solar Flux Emergence Simulations

We simulate the rise through the upper convection zone and emergence through the solar surface of initially uniform, untwisted, horizontal magnetic flux, with the same entropy as the nonmagnetic plasma, that is advected into a domain 48 Mm wide by 20 Mm deep. The magnetic field is advected upward by the diverging upflows and pulled down in the downdrafts, which produces a hierarchy of loop-like structures of increasingly smaller scale as the surface is approached. There are significant differences between the behavior of fields of 10 kG and 20 or 40 kG strength at 20 Mm depth. The 10 kG fields have little effect on the convective flows and show small magnetic-buoyancy effects, reaching the surface in the typical fluid rise time from 20 Mm depth of 32 hours. 20 and 40 kG fields significantly modify the convective flows, leading to long, thin cells of ascending fluid aligned with the magnetic field and their magnetic buoyancy makes them rise to the surface faster than the fluid rise time. The 20 kG field produces a large-scale magnetic loop that as it emerges through the surface leads to the formation of a bipolar, pore-like structure.

Three-dimensional non-linear instability of spontaneous fast magnetic reconnection

Abstract Three-dimensional instability of spontaneous fast magnetic reconnection is studied using MHD (magnetohydro- dynamic) simulation. Previous two-dimensional MHD studies have demonstrated that, if a current-driven anomalous resistivity is assumed, two-dimensional fast magnetic reconnection occurs and two-dimensional largescale magnetic loops, i.e., plasmoids, are ejected from the reconnection region. In most two-dimensional MHD studies, the structure of the current sheet is initially one-dimensinal. On the other hand, in recent space plasma observations, fully three-dimensional magnetic loops frequently appear even in the almost one-dimensional current sheet. This suggests that the classical two-dimensional fast magnetic reconnection may be unstable to any three-dimensional perturbation, resulting in three-dimensional fast magnetic reconnection. In this paper, we show that a three-dimensional resistive perturbation destabilizes two-dimensional fast magnetic reconnection and results in three-dimensional fast magnetic reconnection. The resulting three-dimensional fast reconnection repeatedly ejects three-dimensional magnetic loops downstream. The obtained numerical results are similar to the pulsating downflows observed in solar flares. According to the Fourier analysis of the ejected magnetic loops, the time evolution of this three-dimensional instability is fully non-linear.

Three dimensional computer simulation of magnetic loop associated with magnetic reconnection

The dynamics of large-scale magnetic loop in three dimensions is studied by MHD simulations. The spontaneous fast reconnection model is used in this study. Once a current-driven anomalous resistivity is ignited in a local region in a current sheet, the fast reconnection mechanism spontaneously evolves. As a result, large magnetic loop is developed, and very localized high pressure region appears outside of the magnetic loop. Near the region between magnetic loop and the high pressure region, very large vortex flow appears, and then, the high pressure region more and more localized due to this vortex. On the other hand, we suggest that the spatial size of initial disturbance to the direction of current is very important to evolve of three dimensional fast reconnection processes.

Computer simulations on three-dimensional magnetic loop dynamics by the spontaneous fast reconnection model

Three-dimensional (3D) dynamics of a large-scale magnetic loop is studied by precise magnetohydrodynamic simulations on the basis of the spontaneous fast reconnection model. Once a (current-driven) anomalous resistivity is ignited, the fast reconnection mechanism drastically evolves by the positive feedback between the (3D) global reconnection flow and the anomalous resistivity; on the nonlinear saturation phase, the global reconnection flow has grown so that the reconnection (diffusion) region shrinks to a small extent, and the fast reconnection mechanism involving a pair of standing slow shocks is established in the finite extent. When the 3D plasmoid, formed ahead of the fast reconnection jet, collides with the mirror plane boundary, the reconnected field lines are piled up, leading to formation of a large-scale 3D magnetic loop. Since the resulting 3D fast reconnection jet becomes supersonic, a definite fast shock builds up at the interface between the magnetic loop top and the fast reconnection jet. The 3D fast reconnection jet is limited in a narrow channel between the pair of slow shocks, so that the resulting fast shock is also limited to a small extent ahead of the magnetic loop top. On the other hand, for the uniform resistivity model the 3D fast reconnection mechanism cannot be realized without any vital positive feedback between the reconnection flow and the local magnetic diffusion; hence, such an effective resistivity that can be self-consistently enhanced locally at the X reconnection point by the global reconnection flow is essential for the fast reconnection mechanism to be realized in actual systems.

The influence of gravitational acceleration on the supernova-driven Parker instability

Within a framework of 2D magnetohydrodynamic (MHD) simulations, we explore the dynamical regimes initiated by a supernova explosion in a magnetized stratified interstellar medium (ISM). We concentrate on the formation of large-scale magnetic structures and outflows connected with the Parker instability. For the sake of simplicity we only show models with a fixed explosion energy corresponding to a single supernova (SN) occurring in host galaxies with different fixed values of the gravitational acceleration g and different ratios of specific heats. We show that in general, depending on these two parameters, three different regimes are possible: a slowly growing Parker instability on time-scales much longer than the galactic rotation period for small g; the Parker instability growing at roughly the rotation period, which for ratios of specific heats larger than one is accompanied by an outflow resulting from the explosion for intermediate g; and a rapidly growing instability and a strong blow-out flow for large g. By means of numerical simulations and analytical estimates we show that the explosion energy and gravitational acceleration which separate the three regimes scale as Eg2∼constant in the 2D case. We expect that in the 3D case this scaling law is Eg3∼constant. Our simulations demonstrate furthermore that a single SN explosion can lead to the growth of multiple Parker loops in the disc and large-scale magnetic field loops in the halo, extending over 2–3 kpc horizontally and up to 3 kpc vertically above the mid-plane of the disc.

Physical mechanism of spontaneous fast reconnection evolution

Large dissipative events, such as solar flares and geomagnetic substorms, result from sudden onset of magnetic reconnection, so that it is a long-standing problem to find the physical mechanism that makes magnetic reconnection explosive. As recognized by Petschek, standing slow shocks enable the effective magnetic energy conversion in space plasmas of extremely large magnetic Reynolds number. Hence, a basic question is how the fast reconnection mechanism involving slow shocks can be realized as an eventual solution? We have proposed the spontaneous fast reconnection model, which describes a new type of nonlinear instability that grows by the positive feedback between plasma microphysics (current-driven anomalous resistivity) and macrophysics (global reconnection flow). It is demonstrated that the fast reconnection mechanism explosively grows by the positive feedback in a variety of physical situations; for the larger threshold of anomalous resistivity, the fast reconnection evolves more drastically. Also, distinct plasma processes, such as large-scale plasmoid and magnetic loop dynamics, result directly from the fast reconnection evolution. Even in general asymmetric situations, the spontaneous fast reconnection model effectively works, giving rise to drastic magnetic flux transfer.

Spectropolarimetry of Magnetospheric Accretion on the Classical T Tauri Star BP Tauri

High-resolution (R ≈ 60,000) circular spectropolarimetry of the classical T Tauri star BP Tauri is presented. No net polarization is detected in photospheric absorption lines, placing strong limits (3 σ) on the mean longitudinal magnetic field (±200 G) that is present over the surface of the star. On the other hand, strong circular polarization is measured in the He I λ5876 emission line of BP Tau, indicating a mean longitudinal magnetic field of 2460±120 G in the line formation region. This implies that accretion occurs preferentially along large-scale magnetic loops that occupy a small fraction of the stellar surface. These observations represent the first direct evidence for magnetically controlled accretion onto classical T Tauri stars.

First VLA Observations of Nonthermal Metric Bursts Associated with Coronal Mass Ejections Detected by the [ITAL]Solar and Heliospheric Observatory[/ITAL

We present the first observations of nonthermal decimetric burst emission of the Sun using the new 400 cm (74 MHz) system at the VLA. Our VLA observations were carried out in collaboration with the Large Angle Spectroscopic Coronagraph (LASCO) and the Extreme-Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory spacecraft. Full-disk observations at 400 and 91 cm were used to study the spatial and temporal variations of nonthermal radio bursts during coronal mass ejections (CMEs) detected by LASCO as well as transient extreme-ultraviolet brightenings detected by the EIT. VLA snapshot maps at 400 cm revealed impulsive burst emission in the low corona that began near the estimated start time of the CME activity; that beginning also coincided with a C1.1 GOES X-ray burst and an EIT flarelike brightening. The nonthermal metric bursts then continued sporadically during the next several hours, which included the ejection of spatially separated CME components. The 400 cm bursts are contained within curved, or archlike, sources at a fixed radial distance but with a varying position between two active regions detected by the EIT near the limb, suggesting that they were emitted within large-scale magnetic loops. Our 91 cm observations also show the onset of a long-lasting type I noise storm following the initiation of CME activity, again suggesting an intimate relationship between the production of nonthermal particles and large-scale evolving plasma-magnetic field structures in the corona.