1,331 research outputs found
Multi-stage reconnection powering a solar coronal jet
Coronal jets are short-lived eruptive features commonly observed in polar
coronal holes and are thought to play a key role in the transfer of mass and
energy into the solar corona. We describe unique contemporaneous observations
of a coronal blowout jet seen by the Extreme Ultraviolet Imager onboard the
Solar Orbiter spacecraft (SO/EUI) and the Atmospheric Imaging Assembly onboard
the Solar Dynamics Observatory (SDO/AIA). The coronal jet erupted from the
south polar coronal hole, and was observed with high spatial and temporal
resolution by both instruments. This enabled identification of the different
stages of a breakout reconnection process producing the observed jet. We find
bulk plasma flow kinematics of ~100-200 km/s across the lifetime of its
observed propagation, with a distinct kink in the jet where it impacted and was
subsequently guided by a nearby polar plume. We also identify a faint faster
feature ahead of the bulk plasma motion propagating with a velocity of ~715
km/s which we attribute to untwisting of newly reconnected field lines during
the eruption. A Differential Emission Measure (DEM) analysis using the SDO/AIA
observations revealed a very weak jet signal, indicating that the erupting
material was likely much cooler than the coronal passbands used to derive the
DEM. This is consistent with the very bright appearance of the jet in the
Lyman- passband observed by SO/EUI. The DEM was used to estimate the
radiative thermal energy of the source region of the coronal jet, finding a
value of ergs, comparable to the energy of a nanoflare.Comment: 12 pages, 6 figures, accepted for publication in The Astrophysical
Journa
Investigating Remote-sensing Techniques to Reveal Stealth Coronal Mass Ejections
Eruptions of coronal mass ejections (CMEs) from the Sun are usually
associated with a number of signatures that can be identified in solar disc
imagery. However, there are cases in which a CME that is well observed in
coronagraph data is missing a clear low-coronal counterpart. These events have
received attention during recent years, mainly as a result of the increased
availability of multi-point observations, and are now known as 'stealth CMEs'.
In this work, we analyse examples of stealth CMEs featuring various levels of
ambiguity. All the selected case studies produced a large-scale CME detected by
coronagraphs and were observed from at least one secondary viewpoint, enabling
a priori knowledge of their approximate source region. To each event, we apply
several image processing and geometric techniques with the aim to evaluate
whether such methods can provide additional information compared to the study
of "normal" intensity images. We are able to identify at least weak eruptive
signatures for all events upon careful investigation of remote-sensing data,
noting that differently processed images may be needed to properly interpret
and analyse elusive observations. We also find that the effectiveness of
geometric techniques strongly depends on the CME propagation direction with
respect to the observers and the relative spacecraft separation. Being able to
observe and therefore forecast stealth CMEs is of great importance in the
context of space weather, since such events are occasionally the solar
counterparts of so-called 'problem geomagnetic storms'.Comment: 26 pages, 8 figures, 1 table, accepted for publication in Frontiers
in Astronomy and Space Science
The Eruption of a Magnetic Flux Rope Observed by Solar Orbiter and Parker Solar Probe
Magnetic flux ropes are a key component of coronal mass ejections, forming the core of these eruptive phenomena. However, determining whether a flux rope is present prior to eruption onset and, if so, the rope's handedness and the number of turns that any helical field lines make is difficult without magnetic field modeling or in situ detection of the flux rope. We present two distinct observations of plasma flows along a filament channel on 2022 September 4 and 5 made using the Solar Orbiter spacecraft. Each plasma flow exhibited helical motions in a right-handed sense as the plasma moved from the source active region across the solar disk to the quiet Sun, suggesting that the magnetic configuration of the filament channel contains a flux rope with positive chirality and at least one turn. The length and velocity of the plasma flow increased from the first to the second observation, suggesting evolution of the flux rope, with the flux rope subsequently erupting within ∼5 hr of the second plasma flow. The erupting flux rope then passed over the Parker Solar Probe spacecraft during its encounter (13), enabling in situ diagnostics of the structure. Although complex and consistent with the flux rope erupting from underneath the heliospheric current sheet, the in situ measurements support the inference of a right-handed flux rope from remote-sensing observations. These observations provide a unique insight into the eruption and evolution of a magnetic flux rope near the Sun
Slow solar wind sources
Context. The origin of the slow solar wind is still an open issue. One possibility that has been suggested is that upflows at the edge of an active region can contribute to the slow solar wind.
Aims. We aim to explain how the plasma upflows are generated, which mechanisms are responsible for them, and what the upflow region topology looks like.
Methods. We investigated an upflow region using imaging data with the unprecedented temporal (3 s) and spatial (2 pixels = 236 km) resolution that were obtained on 30 March 2022 with the 174 Å channel of the Extreme-Ultraviolet Imager (EUI)/High Resolution Imager (HRI) on board Solar Orbiter. During this time, the EUI and Earth-orbiting satellites (Solar Dynamics Observatory, Hinode, and the Interface Region Imaging Spectrograph, IRIS) were located in quadrature (∼92°), which provides a stereoscopic view with high resolution. We used the Hinode/EIS (Fe XII) spectroscopic data to find coronal upflow regions in the active region. The IRIS slit-jaw imager provides a high-resolution view of the transition region and chromosphere.
Results. For the first time, we have data that provide a quadrature view of a coronal upflow region with high spatial resolution. We found extended loops rooted in a coronal upflow region. Plasma upflows at the footpoints of extended loops determined spectroscopically through the Doppler shift are similar to the apparent upward motions seen through imaging in quadrature. The dynamics of small-scale structures in the upflow region can be used to identify two mechanisms of the plasma upflow: Mechanism I is reconnection of the hot coronal loops with open magnetic field lines in the solar corona, and mechanism II is reconnection of the small chromospheric loops with open magnetic field lines in the chromosphere or transition region. We identified the locations in which mechanisms I and II work
Evolution of dynamic fibrils from the cooler chromosphere to the hotter corona
Dynamic fibrils (DFs) are commonly observed chromospheric features in solar
active regions. Recent observations from the Extreme Ultraviolet Imager (EUI)
aboard the Solar Orbiter have revealed unambiguous signatures of DFs at the
coronal base, in extreme ultraviolet (EUV) emission. However, it remains
unclear if the DFs detected in the EUV are linked to their chromospheric
counterparts. Simultaneous detection of DFs from chromospheric to coronal
temperatures could provide important information on their thermal structuring
and evolution through the solar atmosphere. In this paper, we address this
question by using coordinated EUV observations from the Atmospheric Imaging
Assembly (AIA), Interface Region Imaging Spectrograph (IRIS), and EUI to
establish a one-to-one correspondence between chromospheric and transition
region DFs (observed by IRIS) with their coronal counterparts (observed by EUI
and AIA). Our analysis confirms a close correspondence between DFs observed at
different atmospheric layers, and reveals that DFs can reach temperatures of
about 1.5 million Kelvin, typical of the coronal base in active regions.
Furthermore, intensity evolution of these DFs, as measured by tracking them
over time, reveals a shock-driven scenario in which plasma piles up near the
tips of these DFs and, subsequently, these tips appear as bright blobs in
coronal images. These findings provide information on the thermal structuring
of DFs and their evolution and impact through the solar atmosphere.Comment: Accepted for publication in A&A Letters. Animation files are
available
https://drive.google.com/drive/folders/17-fqQz_P2T18llJ1jB6MJISMRvT5063F?usp=sharin
- …