We revisit the observations of filament eruption, extreme-ultraviolet (EUV) wave, and CME which originated from the active region (AR) NOAA 12887 on 28 October 2021. We analyze a jet which initiated close to the flare loop footpoints, and its impact on neighboring loops. The event was observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) satellite at various wavebands and by the Solar TErrestrialRElations Observatory-Ahead (STEREO-A) with its Extreme-Ultraviolet Imager( EUVI) and COR1 instruments with a different view angle from SDO.We show that the EUV-wave event consists of several waves as well as non-wave phenomena. The wave componentsinclude: the fast-mode part of the EUV wave event, creation of oscillations in nearby loops, and the appearance of wave trains. The non wave component consists of stationary fronts. We analyze selected oscillating loops and find that the periods of these oscillations range from 230 – 549 s. On the other hand the jet material lights loops which form a 3D null point. We evidence the existence of a pseudo-streamer and its relationship with the CME (flux rope).Our numerical MHD simulations with high resolution evidence the existence of a pseudo-streamer, and its relationship with the CME (flux rope). We catch the dynamic reconnection process between the flux rope and the pseudo-streamer and discuss the validity of our method compared to static methods.

The solar corona is highly structured by bunches of magnetic field lines forming either loops, or twisted flux ropes representing prominences/filaments, or very dynamic structures such as jets. The aim of this paper is to understand the interaction between filament channels and jets. We use high-resolution H α spectra obtained by the ground-based telescope Télescope Héliographique pour l'Etude du Magnétisme et des Instabilités Solaires on the Canary Islands and data from Helioseismic Magnetic Imager and Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. In this paper we present a multiwavelength study of the interaction of filaments and jets. They both consist of cool plasma embedded in magnetic structures. A jet is particularly well studied in all the AIA channels with a flow reaching 100–180 km s −1 . Its origin is linked to cancelling flux at the edge of the active region. Large Doppler shifts in H α are derived in a typical area for a short time (order of minute). They correspond to flows around 140 km s −1 . In conclusion we conjecture that these flows correspond to some interchange of magnetic field lines between the filament channel and the jets leading to cool plasmoid ejections or reconnection jets perpendicularly to the jet trajectory.

We performed an analysis of the extreme-ultraviolet (EUV) wave event on 2022 March 31. The event originated from active region (AR) 12975 located at N13W52 in the field of view of the Atmospheric imaging Assembly (AIA) and exactly at the west limb viewed by the EUV Imager (EUVI) of the Solar Terrestrial Relations Observatory-Ahead (STEREO-A) satellite. The EUV wave was associated with an M9.6 class flare. The event was also well observed by Mauna Loa Solar Observatory and COR1 coronagraphs. We revealed here evident coexistence of two components of EUV waves in AIA as well as in EUVI images, i.e., a fast-mode wave and a nonwave, which was predicted by the EUV wave hybrid model. The speeds of the fast-mode and nonwave EUV wave components in AIA vary from ∼430 to 658 km s ^−1 and ∼157 to 205 km s ^−1 , respectively. The computed speeds in STEREO-A for the fast-mode wave and nonwave components are ∼520 and ∼152 km s ^−1 , respectively. Another wave emanated from the source AR and interacted with ambient coronal loops, showing evident reflection in the EUV images above the solar limb. The speed of the reflected wave in the plane of the sky is ∼175 km s ^−1 . With the precise alignments, we found that the fast-mode EUV wave is just ahead of the coronal mass ejection (CME), and the nonwave component is cospatial with the frontal loop of the accompanied CME. The event also showed stationary fronts.

During their propagation, coronal mass ejections (CMEs) and prominences sometimes display a nonradial motion. During the years after the solar minimum, the CME central position angle tended to be offset closer to the equator compared to that of the associated prominence eruptions (PE). No such effect was observed during solar maximum. The purpose of this paper is to investigate the latitudinal offsets of CMEs with respect to their source regions. We study 256 events from SC 24 and SC 25, listed in the Coordinate Data Analysis Workshop Data Center. We analyzed the CMES radial offset from the associated PEs by comparing their latitudes in the plane of the sky. This work is an extension of the previous work by Gopalswamy et al., but with an independent data set. We have confirmed the systematic equatorward offset of CME from the solar source region for the rising phase of Solar Cycle 25. Our analysis of the relation between CME linear speed and PE-CME latitudinal offset indicated that the velocities of the deflected CMEs are mainly in the range of 200 and 800 km s ^−1 . In this study, we compared the nonradial offsets for the rising and decay phases of SC 24 and our analysis has shown that during the decay phase more events deflected toward the pole can be observed. The observed variation is attributed to the presence of a substantial number of low-latitude coronal holes during the decay phase and to the influence from nearby active regions.

Extreme-ultraviolet (EUV) waves are one of the large-scale phenomena on the Sun. They are defined as large propagating fronts in the low corona with speeds ranging from a few tens km/s to a multiple of 1000 km/s. They are often associated with solar filament eruptions, flares, or coronal mass ejections (CMEs). EUV waves show different features, such as, wave and nonwave components, stationary fronts, reflection, refraction, and mode conversion. Apart from these, they can hit the nearby coronal loops and filaments/prominences during their propagation and trigger them to oscillate. These oscillating loops and filaments/prominences enable us to diagnose coronal parameters such as the coronal magnetic field strength. In this article, we present the different observed features of the EUV waves along with existing models.

In this paper, we present for the first time a comprehensive statistical study between type II radio bursts from the metric (m) to the dekameric-hectometric (DH) domain and their associated solar and space weather (SW) phenomena, namely, solar flares (SFs), sunspot (SN) configurations, filament eruptions, coronal mass ejections (CMEs), their interplanetary (IP) counterparts (ICMEs) and shocks, in situ detected particles and geomagnetic storms (GSs). The m-only and m+DH radio signatures are identified from dynamic spectra provided by the ground-based RSTN stations distributed over the globe together with Wind/WAVES satellite data. The DH-only type IIs are adopted from a ready catalog based on Wind/WAVES spacecraft data. We perform the temporal and spatial association between the radio emission and the listed above activity events during solar cycle (SC) 24, separately for the three sub-categories, m-only, m+DH and DH-only type IIs. A quantitative assessment on the occurrence rates is presented as a function of the strength of the specific SW phenomena: highest rates are obtained with CMEs, SFs, filament eruptions, and SN configurations, whereas a much weaker relationship is found with ICMEs, IP shocks, energetic particles, and GSs. The potential of the obtained rates to be used in empirical or physics-based models for SW forecasting is discussed.

In this study, we compile a catalog of metric type II radio bursts using the Radio Solar Telescope Network (RSTN) to study the occurrence, associations, and properties of the emission and their parent solar activity phenomena. According to the intensity and clarity of the radio emission features, we have divided the m-type II radio bursts into two qualitative categories, namely certain and uncertain. We analyzed RSTN data in Solar Cycle 24 (2009 – 2019), which is freely available from four worldwide stations: Learmonth, Sanvito, Sagamore Hills, and Palehua. Through careful visual inspection, we have collected all metric type II bursts detected in the range of 25 – 180 MHz. The relationships between these bursts and solar eruptive events, such as solar flares and coronal mass ejections (CMEs), are studied, and the results are presented and discussed. The outcomes could be used to reveal the occurrence of solar and space-weather activities based on the ground-based radio perspective. The newly assembled catalog of metric type II and associated solar events will be made freely available to the solar scientific community.

The event of October 28 2021 was very geoeffective with particles accelerated to high energies resulting in ground level enhancements (GLEs). It is important to understand the scenario leading to such energetic particle acceleration which can be done by studying the origin of this event from the Sun to the Earth through the heliosphere. The acceleration of particles was justified by two acceleration processes, one due to the flare during the impulsive phase, and the second by the coronal mass ejection (CME), which prolonged the low level proton emission (Zhang, Gan et al 2022, Klein et al 2022).The first step of our study was to understand the relationship between the flare, the EUV wave and the CME using the SDO, STEREO- A/COR1 and SOHO/LASCO observations (Devi et al 2022). The second step was to model the CME (Guo et al 2023).We found that a fast-mode EUV wave front propagates ahead the CME front. The eruption was modeled by a flux rope using the Regularized Biot-Savart Laws in a data-driven background obtained with HMI magnetograms. The CME was well recovered with its three components and the shock fitted with the observations. We plan to study the evolution of this flux rope in the solar wind by using EUHFORIA.

Prominence oscillations are one of interesting phenomena in the solar atmosphere, which can be utilized to infer the embedded magnetic field magnitude. We present here the transverse oscillations of two different prominences located at the East solar limb on 2011 February 11 using the multi-wavebands data of the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO) satellite. A prominence eruption was observed towards the east direction with an average speed of ~275 km/s. The eruption is fitted with the combination of a linear and an exponential functions of time. An extreme ultraviolet (EUV) wave event was associated with the prominence eruption. This EUV wave triggered the oscillations of both prominences on the East limb. We computed the period of each prominence using the wavelet analysis method. The oscillation period varies from 14 to 22 min. The magnetic field of the prominences was derived, which ranges from 14 to 20 G.

We present the observations of an extreme-ultraviolet (EUV) wave, which originated from the active region (AR) NOAA 12887 on 28 October 2021 and its impact on neighbouring loops. The event was observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) satellite at various wavebands and by the Solar TErrestrial RElations Observatory-Ahead (STEREO-A) with its Extreme-Ultraviolet Imager (EUVI) and COR1 instruments with a different view angle than SDO. We show that the EUV wave event consists of several waves as well as non-wave phenomena. The wave components include: the fast-mode part of the EUV wave event, creation of oscillations in nearby loops, and the appearance of wave trains. The non-wave component consists of stationary fronts. We analyze selected oscillating loops and find that the periods of these oscillations range from 230 - 549 s. Further, we compute the density ratio inside and outside the loops and the magnetic field strength. The computed density ratio and magnetic field are found in the range of 1.08 - 2.92 and 5.75 - 8.79 G, respectively. Finally, by combining SDO and STEREO-A observations, we find that the observed EUV wave component propagates ahead of the CME leading edge.

We present here the kinematics of the EUV wave associated with a GOES M1.0-class solar flare, which originates in NOAA AR 12740. The event is thoroughly observed with Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO) with high spatio-temporal resolutions. This event displays many features of EUV waves, which are very decisive for the understanding of the nature of EUV waves. These features include: a fast-mode wave, a pseudo wave, a slow-mode wave and stationary fronts, probably due to mode conversion. One fast-mode wave also propagates towards the coronal hole situated close to the north pole and the wave speed does not change when it encounters the coronal hole. We intend to provide self-consistent interpretations for all these different features.

We present the observations of three sympathetic filament eruptions occurring on 19 July 2015 namely F1, F2, and F3. The events were observed in UV/EUV wavelengths by Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory and by Global Oscillation Network Group telescope in Hα line. As filament F1 starts to erupt, a part of it falls close to the location of the F2 and F3 filaments. This causes the eruption of F2 and F3 during which the two filaments merge together and trigger a medium-class CME and a longduration GOES C2.1 class flare. We discuss the dynamics and kinematics of these three filament eruptions and related phenomena.

In this study, we investigate an extreme ultraviolet (EUV) wave event on 2010 February 11, which occurred as a limb event from the Earth viewpoint and a disk event from the Solar Terrestrial Relations Observatory-Behind viewpoint. We use the data obtained by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory in various EUV channels. The EUV wave event was launched by a partial prominence eruption. Compared with some EUV wave events in previous works, this EUV wave event contains a faster wave with a speed of ∼445 ± 6 km s −1 , which we call a coronal Moreton wave, and a slower wave with a speed of ∼298 ± 5 km s −1 , which we call the Extreme Ultraviolet Imaging Telescope (EIT) wave. The coronal Moreton wave is identified as a fast-mode wave and the EIT wave is identified as an apparent propagation due to successive field-line stretching. We also observe a stationary front associated with the fast-mode EUV wave. This stationary front is explained as mode conversion from the coronal Moreton wave to a slow-mode wave near a streamer.

Context. Prominence eruptions provide key observations to understand the launch of coronal mass ejections as their cold plasma traces a part of the unstable magnetic configuration. Aims. We select a well observed case to derive observational constraints for eruption models. Methods. We analyze the prominence eruption and loop expansion and contraction observed on 02 March 2015 associated with a GOES M3.7 class flare (SOL2015-03-02T15:27) using the data from Atmospheric Imaging Assembly (AIA) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We study the prominence eruption and the evolution of loops using the time-distance techniques. Results. The source region is a decaying bipolar active region where magnetic flux cancellation is present for several days before the eruption. AIA observations locate the erupting prominence within a flux rope viewed along its local axis direction. We identify and quantify the motion of loops in contraction and expansion located on the side of the erupting flux rope. Finally, RHESSI hard X-ray observations identify the loop top and two foot-point sources. Conclusions. Both AIA and RHESSI observations support the standard model of eruptive flares. The contraction occurs 19 min after the start of the prominence eruption indicating that this contraction is not associated with the eruption driver. Rather, this prominence eruption is compatible with an unstable flux rope where the contraction and expansion of the lateral loop is the consequence of a side vortex developing after the flux rope is launched.

We analyze the observations of EUV loop evolution associated with the filament eruption located at the border of an active region (AR). The event SOL2013-03-16T14:00 was observed with a large difference in view point by the Solar Dynamics Observatory and Solar Terrestrial Relations Observatory. The filament height is fitted with the sum of a linear and exponential function. These two phases point to different physical mechanisms such as tether-cutting reconnection and a magnetic instability. While no X-ray emission is reported, this event presents classical eruption features like separation of double ribbons and the growth of flare loops. We report the migration of the southern foot of the erupting filament flux rope due to the interchange reconnection with encountered magnetic loops of a neighboring AR. Parallel to the erupting filament, a stable filament remains in the core of the AR. The specificity of this eruption is that coronal loops, located above the nearly joining ends of the two filaments, first contract in phase, then expand and reach a new stable configuration close to the one present at the eruption onset. Both contraction and expansion phases last around 20 minutes. The main difference with previous cases is that the PIL bent about 180° around the end of the erupting filament because the magnetic configuration is at least tripolar. These observations are challenging for models that interpreted previous cases of loop contraction within a bipolar configuration. New simulations are required to broaden the complexity of the configurations studied.

We have analysed the Ca-K images obtained at Kodaikanal Observatory as a function of latitude and time for the period of 1913 - 2004 covering the Solar Cycle 15 to 23. We have classified the chromospheric activity into plage, Enhanced Network (EN), Active Network (AN), and Quiet Network (QN) areas to differentiate between large strong active and small weak active regions. The strong active regions represent toroidal and weak active regions poloidal component of the magnetic field. We find that plages areas mostly up to 50 deg latitude belt vary with about 11-year Solar Cycle. We also find that weak activity represented by EN, AN and QN varies with about 11-year with significant amplitude up to about 50 deg latitude in both the hemispheres. The amplitude of variation is minimum around 50 deg latitude and again increases by small amount in the polar region. In addition, the plots of plages, EN, AN and QN as a function of time indicate the maximum of activity at different latitude occur at different epoch. To determine the phase difference for the different latitude belts, we have computed the cross-correlation coefficients of other latitude belts with 35 deg latitude belt. We find that activity shifts from mid-latitude belts towards equatorial belts at fast speed at the beginning of Solar Cycle and at slower speed as the cycle progresses. The speed of shift varies between approximately 19 and 3 m/s considering all the data for the observed period. This speed can be linked with speed of meridional flows those believed to occur between convection zone and the surface of the Sun.

We study a complex GOES M1.1 circular ribbon flare and related pre-flare activity on 26 January 2015 [SOL2015-01-26T16:53] in the solar active region NOAA 12268. This flare activity was observed by the Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The examination of photospheric magnetograms during the extended period, prior to the event, suggests the successive development of a so-called “anemone” type magnetic configuration. The Nonlinear Force Free Field (NLFFF) extrapolation reveals a fan-spine magnetic configuration with the presence of a coronal null-point. We found that the pre-flare activity in the active region starts ≈15 min prior to the main flare in the form of localized bright patches at two locations. A comparison of locations and spatial structures of the pre-flare activity with magnetic configuration of the corresponding region suggests onset of magnetic reconnection at the null-point along with the low-atmosphere magnetic reconnection caused by the emergence and the cancellation of the magnetic flux. The main flare of M1.1 class is characterized by the formation of a well-developed circular ribbon along with a region of remote brightening. Remarkably, a set of relatively compact parallel ribbons formed inside the periphery of the circular ribbon which developed lateral to the brightest part of the circular ribbon. During the peak phase of the flare, a coronal jet is observed at the north-east edge of the circular ribbon, which suggests interchange reconnection between large-scale field lines and low-lying closed field lines. Our investigation suggests a combination of two distinct processes in which ongoing pre-flare null-point reconnection gets further intensified as the confined eruption along with jet activity proceeded from within the circular ribbon region which results to the formation of inner parallel ribbons and corresponding post-reconnection arcade.

Solar jets observed at the limb are important to determine the location of reconnection sites in the corona. In this study, we investigate six recurrent hot and cool jets occurring in the active region NOAA 12644 as it is crossing the west limb on April 04, 2017. These jets are observed in all the UV/EUV filters of SDO/AIA and in cooler temperature formation lines in IRIS slit jaw images. The jets are initiated at the top of a double chamber vault with cool loops on one side and hot loops on the other side. The existence of such double chamber vaults suggests the presence of emerging flux with cool loops, the hot loops being the reconnected loops similarly as in the models of Moreno-Insertiset al. 2008, 2013 and Nóbrega-Siverio et al. 2016. In the preliminary phase of the main jets, quasi periodic intensity oscillations accompanied by smaller jets are detected in the bright current sheet between the vault and the preexisting magnetic field. Individual kernels and plasmoids are ejected in open field lines along the jets. Plasmoids may launch torsional Alfven waves and the kernels would be the result of the untwist of the plasmoids in open magnetic field as proposed in the model of Wyper et al. 2016.

Context. Hot coronal jets are a basic observed feature of the solar atmosphere whose physical origin is still actively debated. Aims. We study six recurrent jets that occurred in active region NOAA 12644 on April 4, 2017. They are observed in all the hot filters of AIA as well as cool surges in IRIS slit–jaw high spatial and temporal resolution images. Methods. The AIA filters allow us to study the temperature and the emission measure of the jets using the filter ratio method. We studied the pre-jet phases by analysing the intensity oscillations at the base of the jets with the wavelet technique. Results. A fine co-alignment of the AIA and IRIS data shows that the jets are initiated at the top of a canopy-like double-chambered structure with cool emission on one and hot emission on the other side. The hot jets are collimated in the hot temperature filters, have high velocities (around 250 km s−1) and are accompanied by cool surges and ejected kernels that both move at about 45 km s−1. In the pre-phase of the jets, we find quasi-periodic intensity oscillations at their base that are in phase with small ejections; they have a period of between 2 and 6 min, and are reminiscent of acoustic or magnetohydrodynamic waves. Conclusions. This series of jets and surges provides a good case study for testing the 2D and 3D magnetohydrodynamic emerging flux models. The double-chambered structure that is found in the observations corresponds to the regions with cold and hot loops that are in the models below the current sheet that contains the reconnection site. The cool surge with kernels is comparable with the cool ejection and plasmoids that naturally appears in the models.