The Aditya-L1 mission of ISRO Tripathi, Durgesh; Chakrabarty, D.; Nandi, A. ...
Proceedings of the International Astronomical Union,
08/2022, Letnik:
18, Številka:
S372
Journal Article
Recenzirano
The Aditya-L1 is the first space-based solar observatory of the Indian Space Research Organization (ISRO). The spacecraft will carry seven payloads providing uninterrupted observations of the Sun ...from the first Lagrangian point. Aditya-L1 comprises four remote sensing instruments, viz. a coronagraph observing in visible and infrared, a full disk imager in Near Ultra-Violet (NUV), and two full-sun integrated spectrometers in soft X-ray and hard X-ray. In addition, there are three instruments for in-situ measurements, including a magnetometer, to study the magnetic field variations during energetic events. Aditya-L1 is truly a mission for multi-messenger solar astronomy from space that will provide comprehensive observations of the Sun across the electromagnetic spectrum and in-situ measurements in a broad range of energy, including magnetic field measurements at L1.
We study the triggering mechanism of a limb-prominence eruption and the associated coronal mass ejection (CME) near AR 12342 using Solar Dynamics Observatory and Large Angle and Spectrometric ...Coronagraph/Solar Heliospheric Observatory observations. The prominence is seen with an embedded flux thread (FT) at one end and bifurcates from the middle to a different footpoint location. The morphological evolution of the FT is similar to that of an unstable flux rope (FR), which we regard as a prominence-embedded FR. The FR twist exceeds the critical value. In addition, the morphology of the prominence plasma in 304 images marks the helical nature of the magnetic skeleton, with a total of 2.96 turns along arc length. The potential field extrapolation model indicates that the critical height of the background magnetic field gradient falls within the inner corona (105 Mm), which is consistent with the extent of coronal plasma loops. These results suggest that the helical kink instability in the embedded FR caused the slow rise of the prominence to the height of the torus instability domain. Moreover, the differential emission measure analysis unveils heating of the prominence plasma to coronal temperatures during an eruption, suggesting reconnection-related heating underneath the upward rising embedded FR. The prominence starts with a slow rise motion of 10 km s−1, which is followed by fast and slow acceleration phases that have an average acceleration of 28.9 m s−2 and 2.4 m s−2 in C2 and C3 field of view, respectively. As predicted by previous numerical simulations, the observed synchronous kinematic profiles of the CME leading edge and the core support the involved FR instability in the prominence initiation.
Solar active regions (ARs) that produce strong flares and coronal mass ejections (CMEs) are known to have a relatively high non-potentiality and are characterized by δ-sunspots and sheared magnetic ...structures. In this study, we conduct a series of flux emergence simulations from the convection zone to the corona and model four types of active regions that have been observationally suggested to cause strong flares, namely the spot-spot, spot-satellite, quadrupole, and inter-AR cases. As a result, we confirm that δ-spot formation is due to the complex geometry and interaction of emerging magnetic fields, and we find that the strong-field, high-gradient, highly sheared polarity inversion line (PIL) is created by the combined effect of the advection, stretching, and compression of magnetic fields. We show that free magnetic energy builds up in the form of a current sheet above the PIL. It is also revealed that photospheric magnetic parameters that predict flare eruptions reflect the stored free energy with high accuracy, while CME-predicting parameters indicate the magnetic relationship between flaring zones and entire ARs.
ABSTRACT The unusually large active region (AR) NOAA 2192, observed in 2014 October, was outstanding in its productivity of major two-ribbon flares without coronal mass ejections. On a large scale, a ...predominantly north-south oriented magnetic system of arcade fields served as a strong top and lateral confinement for a series of large two-ribbon flares originating from the core of the AR. The large initial separation of the flare ribbons, together with an almost absent growth in ribbon separation, suggests a confined reconnection site high up in the corona. Based on a detailed analysis of the confined X1.6 flare on October 22, we show how exceptional the flaring of this AR was. We provide evidence for repeated energy release, indicating that the same magnetic field structures were repeatedly involved in magnetic reconnection. We find that a large number of electrons was accelerated to non-thermal energies, revealing a steep power-law spectrum, but that only a small fraction was accelerated to high energies. The total non-thermal energy in electrons derived (on the order of 1025 J) is considerably higher than that in eruptive flares of class X1, and corresponds to about 10% of the excess magnetic energy present in the active-region corona.
ABSTRACT We present a series of 3D nonlinear simulations of solar-like convection, carried out using the Anelastic Spherical Harmonic code, that are designed to isolate those processes that drive and ...shape meridional circulations (MCs) within stellar convection zones. These simulations have been constructed so as to span the transition between solar-like differential rotation (DR; fast equator/slow poles) and "anti-solar" DR (slow equator/fast poles). Solar-like states of DR, which arise when convection is rotationally constrained, are characterized by a very different convective Reynolds stress (RS) than anti-solar regimes, wherein convection only weakly senses the Coriolis force. We find that the angular momentum transport by convective RS plays a central role in establishing the meridional flow profiles in these simulations. We find that the transition from single-celled to multi-celled MC profiles in strong and weak regimes of rotational constraint is linked to a change in the convective RS, which is a clear demonstration of gyroscopic pumping. Latitudinal thermal variations differ between these different regimes, with those in the solar-like regime conspiring to suppress a single cell of MC, whereas the cool poles and warm equator established in the anti-solar states tend to promote single-celled circulations. Although the convective angular momentum transport becomes radially inward at mid-latitudes in anti-solar regimes, it is the MC that is primarily responsible for establishing a rapidly rotating pole. We conclude with a discussion of how these results relate to the Sun, and suggest that the Sun may lie near the transition between rapidly rotating and slowly rotating regimes.
The emergence of active regions (ARs) closely relates to the solar dynamo and dynamical atmospheric phenomena. With high-resolution and long-lasting observations from the New Vacuum Solar Telescope, ...we report a new dynamic activity phenomenon named "fan-shaped activity (FSA)" in the emerging phase of NOAA AR 12700. The FSAs are clearly observed at H wavelengths and are closely related to the dynamics of the adjacent arch filament system (AFS), including thread deformation and material downward motions. On 2018 February 26, the two most representative FSAs appeared around 05:21 UT and 06:03 UT, respectively, and they first ascended and then decayed within around 10 minutes. At the ascending phase, accompanied by the uplifting of an adjacent AFS, each FSA launches up at one end of the AFS and extends for up to ∼11 Mm. At the decaying phase, the FSA gradually vanishes, and material downflows toward the other end of the AFS are detected. After checking the evolution of the magnetic fields of AR 12700, we find that each FSA is located between the end of an AFS and an adjacent magnetic patch with the same polarity and launches at the onset of the collision and compression between these two magnetic patches. We propose that the collision lifts up the AFS, and then the initially compact AFS laterally expands, resulting in the formation of FSA. A cartoon model is proposed to depict the activities.
ABSTRACT In this paper we present a topological magnetic field investigation of seven two-ribbon flares in sigmoidal active regions observed with Hinode, STEREO, and Solar Dynamics Observatory. We ...first derive the 3D coronal magnetic field structure of all regions using marginally unstable 3D coronal magnetic field models created with the flux rope insertion method. The unstable models have been shown to be a good model of the flaring magnetic field configurations. Regions are selected based on their pre-flare configurations along with the appearance and observational coverage of flare ribbons, and the model is constrained using pre-flare features observed in extreme ultraviolet and X-ray passbands. We perform a topology analysis of the models by computing the squashing factor, Q, in order to determine the locations of prominent quasi-separatrix layers (QSLs). QSLs from these maps are compared to flare ribbons at their full extents. We show that in all cases the straight segments of the two J-shaped ribbons are matched very well by the flux-rope-related QSLs, and the matches to the hooked segments are less consistent but still good for most cases. In addition, we show that these QSLs overlay ridges in the electric current density maps. This study is the largest sample of regions with QSLs derived from 3D coronal magnetic field models, and it shows that the magnetofrictional modeling technique that we employ gives a very good representation of flaring regions, with the power to predict flare ribbon locations in the event of a flare following the time of the model.
The oscillations of a slowly rotating star have long been classified into spheroidal and toroidal modes. The spheroidal modes include the well-known 5-min acoustic modes used in helioseismology. Here ...we report observations of the Sun’s toroidal modes, for which the restoring force is the Coriolis force and whose periods are on the order of the solar rotation period. By comparing the observations with the normal modes of a differentially rotating spherical shell, we are able to identify many of the observed modes. These are the high-latitude inertial modes, the critical-latitude inertial modes, and the equatorial Rossby modes. In the model, the high-latitude and critical-latitude modes have maximum kinetic energy density at the base of the convection zone, and the high-latitude modes are baroclinically unstable due to the latitudinal entropy gradient. As a first application of inertial-mode helioseismology, we constrain the superadiabaticity and the turbulent viscosity in the deep convection zone.
Dark halos around solar active regions Lezzi, S. M.; Andretta, V.; Murabito, M. ...
Astronomy and astrophysics (Berlin),
12/2023, Letnik:
680
Journal Article
Recenzirano
Context.
Dark areas around active regions (ARs) were first observed in chromospheric lines more than a century ago and are now associated with the H
α
fibril vortex around ARs. Nowadays, large areas ...surrounding ARs with reduced emission relative to the quiet Sun (QS) are also observed in spectral lines emitted in the transition region (TR) and the low corona. For example, they are clearly seen in the SDO/AIA 171 Å images. We name these chromospheric and TR-coronal dark regions “dark halos” (DHs). Coronal DHs are poorly studied and, because their origin is still unknown, to date it is not clear if they are related to the chromospheric fibrillar ones. Furthermore, they are often mistaken for coronal holes (CHs).
Aims.
Our goal is to characterize the emission properties of a DH by combining, for the first time, chromospheric, TR, and coronal observations in order to provide observational constraints for future studies on the origin of DHs. This study also aims to investigate the different properties of DHs and CHs and provide a quick-look recipe to distinguish between them.
Methods.
We studied the DH around AR NOAA 12706 and the southern CH that were on the disk on April 22, 2018 by analyzing IRIS full-disk mosaics and SDO/AIA filtergrams to evaluate their average intensities, normalized to the QS. In addition, we used the AIA images to derive the DH and CH emission measure (EM) and the IRIS Si
IV
1393.7 Å line to estimate the nonthermal velocities of plasma in the TR. We also employed SDO/HMI magnetograms to study the average magnetic field strength inside the DH and the CH.
Results.
Fibrils are observed all around the AR core in the chromospheric Mg
II
h&k IRIS mosaics, most clearly in the h
3
and k
3
features. The TR emission in the DH is much lower than in the QS area, unlike in the CH. Moreover, the DH is much more extended in the low corona than in the chromospheric Mg
II
h
3
and k
3
images. Finally, the intensities, EM, spectral profile, nonthermal velocity, and average magnetic field strength measurements clearly show that DHs and CHs exhibit different characteristics, and therefore should be considered as distinct types of structures on the Sun.
The Solar Orbiter mission Müller, D.; St. Cyr, O. C.; Zouganelis, I. ...
Astronomy and astrophysics (Berlin),
10/2020, Letnik:
642
Journal Article
Recenzirano
Odprti dostop
Aims.
Solar Orbiter, the first mission of ESA’s 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.
Methods.
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.
Results.
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 mission’s science objectives. Its science return will be augmented further by coordinated observations with other space missions and ground-based observatories.
PDF
