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Register a new userSolar origins of a strong stealth CME detected by Solar Orbiter
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Aims.We aim to locate the origin of a stealth coronal mass ejection (CME) detected in situ by the MAG instrument on board Solar Orbiter, and make connections between the CME observed at the Sun, and the interplanetary CME (ICME) measured in situ. Methods. Remote sensing data are analysed using advanced image processing techniques to identify the source region of the stealth CME, and the global magnetic field at the time of the eruption is examined using Potential Field Source Surface (PFSS) models. The observations of the stealth CME at the Sun are compared with the magnetic field measured by the Solar Orbiter spacecraft, and plasma properties measured by the Wind spacecraft. Results. The source of the CME is found to be a quiet Sun cavity in the northern hemisphere. We find that the stealth CME has a strong magnetic field in situ, despite originating from a quiet Sun region with an extremely weak magnetic field. Conclusions. The interaction of the ICME with its surrounding environment is the likely cause of a higher magnetic field strength measured in situ. Stealth CMEs require multi-wavelength and multi-viewpoint observations in order to confidently locate the source region, however their elusive signatures still pose many problems for space weather forecasting. The findings have implications for Solar Orbiter observing sequences with instruments such as EUI that are designed to capture stealth CMEs
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Stealth coronal mass ejection (CMEs) are eruptions from the Sun that are not associated with appreciable low-coronal signatures. Because they often cannot be linked to a well-defined source region on the Sun, analysis of their initial magnetic configuration and eruption dynamics is particularly problematic. In this manuscript, we address this issue by undertaking the first attempt at predicting the magnetic fields of a stealth CME that erupted in 2020 June from the Earth-facing Sun. We estimate its source region with the aid of off-limb observations from a secondary viewpoint and photospheric magnetic field extrapolations. We then employ the Open Solar Physics Rapid Ensemble Information (OSPREI) modelling suite to evaluate its early evolution and forward-model its magnetic fields up to Parker Solar Probe, which detected the CME in situ at a heliocentric distance of 0.5 AU. We compare our hindcast prediction with in-situ measurements and a set of flux rope reconstructions, obtaining encouraging agreement on arrival time, spacecraft crossing location, and magnetic field profiles. This work represents a first step towards reliable understanding and forecasting of the magnetic configuration of stealth CMEs and slow, streamer-blowout events.
On 2020 April 19 a coronal mass ejection (CME) was detected in situ by Solar Orbiter at a heliocentric distance of about 0.8 AU. The CME was later observed in situ on April 20th by the Wind and BepiColombo spacecraft whilst BepiColombo was located very close to Earth. This CME presents a good opportunity for a triple radial alignment study, as the spacecraft were separated by less than 5$^circ$ in longitude. The source of the CME, which was launched on April 15th, was an almost entirely isolated streamer blowout. STEREO-A observed the event remotely from -75.1$^circ$ longitude, which is an exceptionally well suited viewpoint for heliospheric imaging of an Earth directed CME. The configuration of the four spacecraft has provided an exceptionally clean link between remote imaging and in situ observations of the CME. We have used the in situ observations of the CME at Solar Orbiter, Wind, and BepiColombo, and the remote observations of the CME at STEREO-A in combination with flux rope models to determine the global shape of the CME and its evolution as it propagated through the inner heliosphere. A clear flattening of the CME cross-section has been observed by STEREO-A, and further confirmed by comparing profiles of the flux rope models to the in situ data, where the distorted flux rope cross-section qualitatively agrees most with in situ observations of the magnetic field at Solar Orbiter. Comparing in situ observations of the magnetic field between spacecraft, we find that the dependence of the maximum (mean) magnetic field strength decreases with heliocentric distance as $r^{-1.24 pm 0.50}$ ($r^{-1.12 pm 0.14}$), in disagreement with previous studies. Further assessment of the axial and poloidal magnetic field strength dependencies suggests that the expansion of the CME is likely neither self-similar nor cylindrically symmetric.
We present SDO/AIA observation of three types of fast-mode propagating magnetosonic waves in a GOES C3.0 flare on 2013 April 23, which was accompanied by a prominence eruption and a broad coronal mass ejection (CME). During the fast rising phase of the prominence, a large-scale dome-shaped extreme ultraviolet (EUV) wave firstly formed ahead of the CME bubble and propagated at a speed of about 430 km/s in the CMEs lateral direction. One can identify the separation process of the EUV wave from the CME bubble. The reflection effect of the on-disk counterpart of this EUV wave was also observed when it interacted with a remote active region. Six minutes after the first appearance of the EUV wave, a large-scale quasi-periodic EUV train with a period of about 120 seconds appeared inside the CME bubble, which emanated from the flare epicenter and propagated outward at an average speed up to 1100 km/s. In addition, another narrow quasi-periodic EUV wave train was observed along a closed-loop system connecting two adjacent active regions, which also emanated from the flare epicenter, propagated at a speed of about475 km/s and with a period of about 110 seconds. We propose that all the observed waves are fast-mode magnetosonic waves, in which the large-scale dome-shaped EUV wave ahead of the CME bubble was driven by the expansion of the CME bubble, while the large-scale quasi-periodic EUV train within the CME bubble and the narrow quasi-periodic EUV wave train along the closed-loop system were excited by the intermittent energy-releasing process in the flare. Coronal seismology application and energy carried by the waves are also estimated based on the measured wave parameters.
Solar Orbiter, the first mission of ESAs Cosmic Vision 2015-2025 programme and a mission of international collaboration between ESA and NASA, will explore the Sun and heliosphere from close up and out of the ecliptic plane. It was launched on 10 February 2020 04:03 UTC from Cape Canaveral and aims to address key questions of solar and heliospheric physics pertaining to how the Sun creates and controls the Heliosphere, and why solar activity changes with time. To answer these, the mission carries six remote-sensing instruments to observe the Sun and the solar corona, and four in-situ instruments to measure the solar wind, energetic particles, and electromagnetic fields. In this paper, we describe the science objectives of the mission, and how these will be addressed by the joint observations of the instruments onboard. The paper first summarises the mission-level science objectives, followed by an overview of the spacecraft and payload. We report the observables and performance figures of each instrument, as well as the trajectory design. This is followed by a summary of the science operations concept. The paper concludes with a more detailed description of the science objectives. Solar Orbiter will combine in-situ measurements in the heliosphere with high-resolution remote-sensing observations of the Sun to address fundamental questions of solar and heliospheric physics. The performance of the Solar Orbiter payload meets the requirements derived from the missions science objectives. Its science return will be augmented further by coordinated observations with other space missions and ground-based observatories.
The goal of this paper is to study the smallest brightening events observed in the EUV quiet Sun. We use commissioning data taken by the EUI instrument onboard the recently launched Solar Orbiter mission. On 2020 May 30, EUI was situated at 0.556AU from the Sun. Its HRIEUV telescope 17.4nm passband reached an exceptionally high two-pixel spatial resolution of 400km. The size and duration of small-scale structures is determined in the HRIEUV data, while their height is estimated from triangulation with the simultaneous SDO/AIA data. This is the first stereoscopy of small scale brightenings at high resolution. We observed small localised brightenings (campfires) in a quiet Sun region with lengthscales between 400km and 4000km and durations between 10 and 200s. The smallest and weakest of these HRIEUV brightenings have not been observed before. Simultaneous HRILYA observations do not show localised brightening events, but the locations of the HRIEUV events correspond clearly to the chromospheric network. Comparison with simultaneous AIA images shows that most events can also be identified in the 17.1nm, 19.3nm, 21.1nm, and 30.4nm passbands of AIA, although they appear weaker and blurred. DEM analysis indicates coronal temperatures peaking at log(T)~6.1-6.15. We determined the height of a few campfires, which is between 1000 and 5000km above the photosphere. We conclude that campfires are mostly coronal in nature and are rooted in the magnetic flux concentrations of the chromospheric network. We interpret these events as a new extension to the flare/microflare/nanoflare family. Given their low height, the EUI campfires could be a new element of the fine structure of the transition region/low corona: apexes of small-scale loops that are internally heated to coronal temperatures.
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