Passage Of Coronal Mass Ejection Research Articles

Detecting the Oscillation and Propagation of the Nascent Dynamic Solar Wind Structure at 2.6 Solar Radii Using Very Long Baseline Interferometry Radio Telescopes

Probing the solar corona is crucial to study the coronal heating and solar wind acceleration. However, the transient and inhomogeneous solar wind flows carry large-amplitude inherent Alfvén waves and turbulence, which make detection more difficult. We report the oscillation and propagation of the solar wind at 2.6 solar radii (Rs) by observation of China’s Tianwen and ESA’s Mars Express with radio telescopes. The observations were carried out on 2021 October 9, when one coronal mass ejection (CME) passed across the ray paths of the telescope beams. We obtain the frequency fluctuations (FFs) of the spacecraft signals from each individual telescope. First, we visually identify the drift of the frequency spikes at a high spatial resolution of thousands of kilometers along the projected baselines. They are used as traces to estimate the solar wind velocity. Then we perform the cross-correlation analysis on the time series of FF from different telescopes. The velocity variations of solar wind structure along radial and tangential directions during the CME passage are obtained. The oscillation of tangential velocity confirms the detection of a streamer wave. Moreover, at the tail of the CME, we detect the propagation of an accelerating fast field-aligned density structure indicating the presence of magnetohydrodynamic waves. This study confirms that the ground-station pairs are able to form particular spatial projection baselines with high resolution and sensitivity to study the detailed propagation of the nascent dynamic solar wind structure.

Energetic particle evolution during coronal mass ejection passage from 0.3 to 1 AU

We provide analysis of a coronal mass ejection (CME) that passed over Parker Solar Probe (PSP) on January 20, 2020 when the spacecraft was at just 0.32 AU. The Integrated Science Investigation of the Sun instrument suite measures energetic particle populations associated with the CME before, during, and after its passage over the spacecraft. We observe a complex evolution of energetic particles, including a brief ~2 h period where the energetic particle fluxes are enhanced and the nominal orientation of the energetic particle streaming outward from the Sun (from 30 to 100 keV nuc−1) abruptly reverses inward toward the Sun. This transient and punctuated evolution highlights the importance of magnetic field structures that connect the spacecraft to different acceleration sites, one of which is likely more distant from the Sun than PSP during the evolution of the CME. We discuss these characteristics and what they tell us about the source of the energetic particles. During this period, PSP was radially aligned with the Solar Terrestrial Relations Observatory A (STEREO-A), which measured the same CME when it passed 1 AU. The magnetic field measurements at both spacecraft are remarkably similar, indicating that the spacecraft are likely encountering the same portion of the magnetic structure that has not evolved significantly in transit. The energetic particle observations on the other hand, are quite different at STEREO-A, showing how transport effects have acted on the energetic particle populations and obscured the detailed properties present earlier in the development of the CME. This event provides a unique case study in how energetic particle populations evolve as CMEs propagate through the heliosphere.

Properties of Streamer Wave Events Observed during the STEREO Era

Abstract Transverse waves are sometimes observed in solar helmet streamers, typically after the passage of a coronal mass ejection (CME). The CME-driven shock wave moves the streamer sideways, and a decaying oscillation of the streamer is observed after the CME passage. Previous works generally reported observations of streamer oscillations taken from a single vantage point (typically the Solar and Heliospheric Observatory (SOHO) spacecraft). We conduct a data survey searching for streamer wave events observed by the COR2 coronagraphs on board the STEREO spacecraft. For the first time, we report observations of streamer wave events from multiple vantage points by using the COR2 instrument on both STEREO A and B, as well as the SOHO/LASCO C2+C3 coronagraphs. We investigate the properties of streamer waves by comparing the different events and performing a statistical analysis. Common observational features give us additional insight on the physical nature of streamer wave events. The most important conclusion is that there appears to be no relation between the speed of the CME and the phase speed of the resulting streamer wave, indicating that the streamer wave speed is determined by the physical properties of the streamer rather than the properties of the CME. This result makes streamer wave events excellent candidates for coronal seismology studies. From a comparison between the measured phase speeds and the phase speeds calculated from the measured periods and wavelengths, we could determine that the speed of the postshock solar wind flow in our streamers is around 300 km s−1.

The influence of coronal mass ejections on the gas dynamics of the atmosphere of a “hot Jupiter” exoplanet

The results of three-dimensional numerical simulations of the gas dynamics of the atmosphere of a "hot Jupiter" exoplanet during the passage of a coronal mass ejection (CME) from the central star are presented. These computations assumed the parameters for the stellar wind and the CME to be typical of the solar values. The characteristic variations of the flow pattern are considered for quasi-closed and closed (but appreciably distorted by the gravitational influence of the star) gaseous envelopes of the exoplanet. It is shown that a typical CME is sufficient to tear off the outer part of an asymmetric envelope that is located beyond the Roche lobe and carry it away from the exoplanet. This leads to a substantial increase in the mass-loss rate from the exoplanet envelope during the passage of CMEs. The mass-loss rate grows by about a factor of 11 for a closed envelope, and by about a factor of 14 for a quasi-closed envelope. Possible evolutionary consequences of the loss of part of the atmosphere during the passage of CMEs are discussed.

The relativistic solar particle event of 2005 January 20: origin of delayed particle acceleration

The highest energies of solar energetic nucleons detected in space or through gamma-ray emission in the solar atmosphere are in the GeV range. Where and how the particles are accelerated is still controversial. We search for observational information on the location and nature of the acceleration region(s) by comparing the timing of relativistic protons detected on Earth and radiative signatures in the solar atmosphere during the particularly well-observed 2005 Jan. 20 event. This investigation focuses on the post-impulsive flare phase, where a second peak was observed in the relativistic proton time profile by neutron monitors. This time profile is compared in detail with UV imaging and radio spectrography over a broad frequency band from the low corona to interplanetary space. It is shown that the late relativistic proton release to interplanetary space was accompanied by a distinct new episode of energy release and electron acceleration in the corona traced by the radio emission and by brightenings of UV kernels. These signatures are interpreted in terms of magnetic restructuring in the corona after the coronal mass ejection passage. We attribute the delayed relativistic proton acceleration to magnetic reconnection and possibly to turbulence in large-scale coronal loops. While Type II radio emission was observed in the high corona, no evidence of a temporal relationship with the relativistic proton acceleration was found.

Solar‐Storm/Lunar Atmosphere Model (SSLAM): An overview of the effort and description of the driving storm environment

On 29 April 1998, a coronal mass ejection (CME) was emitted from the Sun that had a significant impact at Earth. The terrestrial magnetosphere became more electrically active during the storm passage. Less explored is the effect of such a storm on an exposed rocky body like our Moon. The solar‐storm/lunar atmosphere modeling effort (SSLAM) brings together surface interactions, exosphere, plasma, and surface charging models all run with a common driver – the solar storm and CME passage occurring from 1 to 4 May 1998. We present herein an expanded discussion on the solar driver during the 1–4 May 1998 period that included the passage of an intense coronal mass ejection (CME) that had >10 times the solar wind density and had a compositional component of He++ that exceeded 20%. During this time, the plasma mass flux to the exposed lunar surface increased by over 20 times compared to the nominal solar wind, to a value near 10−13 kg/m2‐s. Over a two day CME passage by the Moon, this amount approaches 300 tons of added mass to the Moon in the form of individual proton and helium ions. Such an increase in ion flux should have a profound impact on sputtering loss rates from the surface, since this process scales as the mass, energy, and charge state of the incident ion. Associated loss processes were addressed by SSLAM and will be discussed herein.

The effect on the lunar exosphere of a coronal mass ejection passage

Solar wind bombardment onto exposed surfaces in the solar system produces an energetic component to the exospheres about those bodies. The solar wind energy and composition are highly dependent on the origin of the plasma. Therefore, using the measured composition of the slow wind, fast wind, solar energetic particle (SEP) population, and coronal mass ejection (CME), we have estimated the total sputter yield for each type of solar wind. We show that the heavy ions, especially the He++ and O+7, can greatly enhance the total sputter yield during times when the heavy ion population is enhanced. Folding in the flux with the yield of individual ions, we compute the source rate for several species during different types of solar wind. Finally, we use a Monte Carlo model developed to simulate the time‐dependent evolution of the lunar exosphere to study the sputtering component of the exosphere under the influence of a CME passage. We simulate the background exosphere of Na, K, Ca, and Mg. Simulations indicate that sputtering increases the mass of those constituents in the exosphere more than ten times the background values. The escalation of atmospheric density occurs within an hour of onset. The decrease in atmospheric density after the CME passage is also rapid, although takes longer than the increase. Sputtered neutral particles have a high probability of escaping the Moon, by both leaving the Hill Sphere and photoionization. Density and spatial distribution of the exosphere can be tested with the LADEE mission.

3-D reconstructions of the early-November 2004 CDAW geomagnetic storms: analysis of Ooty IPS speed and density data

Abstract. Interplanetary scintillation (IPS) remote-sensing observations provide a view of the solar wind covering a wide range of heliographic latitudes and heliocentric distances from the Sun between ~0.1 AU and 3.0 AU. Such observations are used to study the development of solar coronal transients and the solar wind while propagating out through interplanetary space. They can also be used to measure the inner-heliospheric response to the passage of coronal mass ejections (CMEs) and co-rotating heliospheric structures. IPS observations can, in general, provide a speed estimate of the heliospheric material crossing the observing line of site; some radio antennas/arrays can also provide a radio scintillation level. We use a three-dimensional (3-D) reconstruction technique which obtains perspective views from outward-flowing solar wind and co-rotating structure as observed from Earth by iteratively fitting a kinematic solar wind model to these data. Using this 3-D modelling technique, we are able to reconstruct the velocity and density of CMEs as they travel through interplanetary space. For the time-dependent model used here with IPS data taken from the Ootacamund (Ooty) Radio Telescope (ORT) in India, the digital resolution of the tomography is 10° by 10° in both latitude and longitude with a half-day time cadence. Typically however, the resolutions range from 10° to 20° in latitude and longitude, with a half- to one-day time cadence for IPS data dependant upon how much data are used as input to the tomography. We compare reconstructed structures during early-November 2004 with in-situ measurements from the Wind spacecraft orbiting the Sun-Earth L1-Point to validate the 3-D tomographic reconstruction results and comment on how these improve upon prior reconstructions.

Cosmic ray intensity during the passage of coronal mass ejections

Coronal Mass Ejections are vast structures of plasma and magnetic fields that are expelled from the sun into the heliosphere. This material is detected by remote sensing and in-situ spacecraft observations. The present study deals with the influence of four types of CMEs namely Asymmetric 'Full' Halo CMEs, Partial Halo CMEs, Asymmetric and Complex 'Full' Halo CMEs and 'Full' Halo CMEs on cosmic ray neutron monitor intensity. The data of ground based neutron monitor of Moscow and CME events observed with instruments onboard and Wind spacecraft have been used in the present analysis. The method of superposed epoch (Chree) analysis has been used to the arrival times of these CMEs. It is noteworthy that the frequency of occurrence of Asymmetric 'Full' Halo CMEs is significantly high, whereas frequency of occurrence of Asymmetric and Complex 'Full' Halo CMEs is low compared to other CMEs. Significant enhancement in cosmic ray intensity is observed after 4 days of the onset of asymmetric full halo and 6 days after the onset of full halo CMEs. The fluctuations in cosmic ray intensity are more prior to the onset of both types of the CMEs. However, during Partial Halo CMEs the cosmic ray intensity peaks, 8- 9 days prior to the onset of CMEs and depressed 3 days prior to the onset of CMEs, whereas in case of asymmetric and complex full CMEs, the intensity depressed 2 days prior to the onset of CMEs and enhanced 2 days after the onset of CMEs. The deviations in cosmic ray intensity are more pronounced in case for asymmetric and complex full halo CMEs compared to other CMEs.

Coronal radio-sounding detection of a CME during the 1997 Galileo solar conjunction

Frequency fluctuations of the Galileo S-band radio signal were recorded nearly continuously during the spacecraft’s solar conjunction from December 1996 to February 1997. A strong propagating disturbance, most probably associated with a coronal mass ejection (CME), was detected on 7 February when the radio ray path proximate point was on the west solar limb at about 54 solar radii from the Sun. The CME passage through the line of sight is characterized by a significant increase in the fluctuation intensity of the recorded frequency and by an increase in the plasma speed from about 234 km s −1 up to about 755 km s −1. These velocity estimates are obtained from a correlation analysis of frequency fluctuations recorded simultaneously at two widely-separated ground stations. The density turbulence power spectrum is found to steepen behind the CME front. The Galileo radio-sounding data are compared with SOHO/LASCO observations of the CME in the corona and with WIND spacecraft data near the Earth’s orbit.

Magnetosphere preconditioning under northward IMF: Evidence from the study of coronal mass ejection and corotating interaction region geoeffectiveness

Motivated by recent observations and simulations of the formation of a cold and dense plasma sheet in the tail of the magnetosphere under northward interplanetary magnetic field (IMF) and of the direct influence of the plasma sheet density on the ring current strength, this paper aims at (1) highlighting how the coupling of these effects may lead to a preconditioning of the magnetosphere under northward IMF and (2) performing first tests of the validity of this hypothesis. We have analyzed superposed epoch time series of various parameters to investigate the response of the magnetosphere (as indicated by the Dst index) to the passage of coronal mass ejections (CMEs) and corotating interaction regions (CIRs). We first focused on the difference between the measured Dst signature and that predicted by a semiempirical Dst model. For both CME‐ and CIR‐driven storms the superposed epoch results show that the model Dst predictions tend to underestimate the actual storm strength (by up to 10–30%) for events that are preceded by a substantial interval of northward IMF, as opposed to those with no such preceding northward IMF. We also analyzed Los Alamos geosynchronous spacecraft data for these events. The average density and temperature measured at storm onset are substantially higher and slightly lower, respectively, for the cases with preceding northward IMF intervals. These results suggest that solar wind structures may be more geoeffective if preceded by a northward IMF interval and they are consistent with the hypothesis of a preconditioning by a cold, dense plasma sheet. A colder and denser plasma sheet may lead to a stronger ring current when that plasma is convected inward during the main phase of an ensuing storm.

Solar wind electron characteristics inside and outside coronal mass ejections

We present a study of 9 months of data from the solar wind plasma electron instrument on the ACE spacecraft. Electron pitch angle distributions were used to identify intervals of counterstreaming halo electrons, which were observed ∼16% of the time that the spacecraft was not magnetically connected to the Earth's bow shock. Counterstreaming electrons presumably indicate a closed magnetic field topology and thus indicate the passage of coronal mass ejections (CMEs) in the solar wind. In this study, we separately examine electron moments at times with and without counterstreaming electrons, including both magnetic clouds and noncloud CMEs. The properties of both the core and halo electron populations were nearly identical at times with and without counterstreaming electrons. Both low and high electron densities and temperatures were observed in either type of event. In contrast, magnetic clouds, on average, showed increased densities and reduced temperatures. The core/halo density ratio and the total electron density were anticorrelated in all cases, indicating that the halo contributes more to the total electron density at low density times, regardless of magnetic topology. Total electron temperature and density were anticorrelated in all types of events. This consistent anticorrelation implies that such single‐spacecraft measurements of temperature and density cannot be used to determine a polytropic index for solar wind electrons. Instead, the anticorrelation may be due to pressure balance of the solar wind plasma or may be a remnant of coronal conditions.

The magnetospheric response to the CME passage of January 10–11, 1997, as seen at geosynchronous orbit

The response of the magnetosphere to the passage of the January 10–11, 1997 coronal mass ejection (CME) is described from the vantage point of geosynchronous orbit. Salient aspects of the observed response include 1) the global compression of the magnetosphere, including plasma sheet density enhancements and geosynchronous magnetopause crossings; 2) strongly stretched magnetotail field, with attendant substorm activity; 3) enhanced magnetospheric convection, leading to plasmaspheric erosion and dayside drainage; 4) no detectable superdense plasma sheet; and 5) propagating plasma‐sheet density fronts. The various aspects are related to the variations in the solar wind and interplanetary magnetic field impinging on the magnetosphere.