Flux-freezing breakdown in high-conductivity magnetohydrodynamic turbulence

Coronal mass ejections (CMEs) are solar eruptions that involve large-scale changes to the magnetic topology of an active region. There exists a range of models for CME onset which are based on twisted or sheared magnetic field above a polarity inversion line (PIL). We present observational evidence that topological changes at PILs, in the photosphere, form a key part of CME onset, as implied by many models. In particular, we study the onset of 30 CMEs and investigate topological changes in the photosphere by calculating the magnetic winding flux, using the artop code. By matching the times and locations of winding signatures with CME observations produced by the almanac code, we confirm that these signatures are indeed associated with CMEs. Therefore, as well as presenting evidence that changes in magnetic topology at the photosphere are a common signature of CME onset, our approach also allows for the finding of the source location of a CME within an active region.

Based on our previous works regarding solar eruptions, we focus on the relationships among different eruptive phenomena, such as solar flares, eruptive prominences and coronal mass ejections (CMEs). The three processes show clear correlations under certain circumstances. The correlation between a CME and solar flare depends the energy that stored in the relevant magnetic structure, which is available to drive the eruption: the more energy that is stored, the better the correlation is; otherwise, the correlation is poor. The correlation between a CME and eruptive prominence, on the other hand, depends on the plasma mass concentration in the configuration prior to the eruption: if the mass concentration is significant, a CME starts with an eruptive prominence, otherwise, a CME develops an without an apparent associated eruptive prominence. These results confirm that solar flares, eruptive prominences and CMEs are different significances of a single physical process that is related to the energy release in a disrupted coronal magnetic field. The impact of gravity on CME propagation and the above correlations is also investigated. Our calculations indicate that the effect of gravity is not significant unless the strength of the background field in the disrupted magnetic configuration becomes weak, say weaker than 30 G.

The period between late October and early November of 2003 included a series of large solar events that resulted in some of the most extreme space weather of the current solar cycle. Space weather has been defined as the conditions on the sun and in the solar wind, magnetosphere, ionosphere, and thermosphere that can influence the performance and reliability of space-borne and ground-based technological systems. Adverse conditions in the space environment can cause disruption of satellite operations, communications, navigation, and electric power distribution grids, leading to a variety of socioeconomic losses (National Science Foundation 2000). The space weather events of October–November 2003 were initiated by three very large sunspot clusters that became visible on the Sun over a period of approximately 7 days beginning on 18 October, 2003. One of these clusters, region 486, became the largest sunspot group of the current solar cycle and the largest seen since 1991. This sudden increase in sunspots induced a series of solar flares and coronal mass ejections (CMEs), (Department of Commerce 2004). Solar flares are explosions on the surface of the Sun that produce a quick directed high-speed blast of charged particles and electromagnetic energy. One of the largest solar flares ever seen on the Sun occurred on 28 October. It was the third largest detected since regular monitoring began approximately 30 years ago and the largest since April 2001 (US Department of Commerce 2004). This activity was accompanied by a CME. CME’s are huge bubbles of plasma ejected from the Sun that speed into space. They disrupt the flow of the solar wind and produce disturbances that can strike the Earth with sometimes-catastrophic results (http://science.nasa.gov/ssl/pad/solar/ cmes.htm). This particular CME was one of the fastest on record in that it left the sun with a speed of 2,500 km/s, five times the average speed (Murtagh 2004). Figure 1 illustrates the observed active regions on 27 October together with the images of the solar flare and CME recorded on 28 October as observed by the SOHO spacecraft (http://sohowww.nascom.nasa.gov/). These events resulted in a severe geomagnetic storm in the Earth’s environment at 06:00 UT on 29 October. The disturbance levels on the Sun remained high for several days with a second powerful CME occurring at approximately 21:00 UT on 29 October. Figure 2 illustrates the planetary 3-h Kp indices for the period of 29 October 2003 to 1 November 2003. The Kp index is derived from 13 global magnetic observatories. It is a measure of the disturbance level of the geomagnetic field by auroral ionospheric currents. Kp values greater than 4 represent disturbed conditions. As the Kp values increase, the severity of the storm increases. Kp values of 9 represent the most extreme disturbed conditions and occur only a few times during the course of each 11-year solar cycle (http://www.sec.noaa.gov/NOAAscales). Note that Kp values of 9 were reached multiple times during 29–30 October in response to the CME activity.

Hostile space weather is one of the principal threats to modern human technology because of the dependency of our lives on satellites. Solar coronal mass ejections, solar flares, and high‐speed solar wind streams often cause some sequences of damaging disturbances within the Earth's magnetosphere, in the atmosphere, and even on the Earth's surface. The time‐varying Sun, as the main source of space weather causes geomagnetic storms and substorms in many ways with coronal mass ejections (CME) being possibly the most harmful among them. CMEs cause transient magnetized plasma flows as interplanetary consequences, which drive the geomagnetic storms and substorms in the Earth's magnetosphere. It is shown that the cyclic solar activity has chaotic characteristics. It seems that the chaotic modeling of solar and geomagnetic activity indices is an important approach for analysis and prediction of the solar extreme events. This is particularly useful for engineers and designers interested in space weather prediction and its applications. One of the most important tools for eliciting the chaotic trends is the “Lyapunov exponents,” which is a useful measure of the stability of a dynamic system. This paper analyzes the variation of Lyapunov exponents (LE) for three solar and geomagnetic activity indices during CMEs: the sunspot number, disturbance storm time, and proton temperature. The analysis has been carried out using the technique of adaptive LE estimation adopted from previous works; the suitable window for which has been determined via trial and error. It is shown that the LE of these solar and geomagnetic activity indices varies rapidly during CMEs. The variation in LEs creates a pattern as a precursor for the forthcoming CME. This precursor, which is an oscillation in the values of Les, begins several steps sooner than the CME's occurrence. Then, during the CME, the LEs decrease to a small positive or a negative value, which demonstrates that during an anomaly such as a CME the chaotic characteristics of solar and geomagnetic activity indices decrease and solar and geomagnetic activity indices follow more regular dynamics.

Developments in our knowledge of coronal mass ejections (CMEs) have shown that many of these transients occur in association with solar flares. On the occasions when there is a common occurrence of the eruption and the flare, it is most likely that the flare is of high intensity and/or long-duration (Burkepile, Hundhausen, and Webb, 1994; Munro et al., 1979; Webb and Hundhausen, 1987). A model for the relationship between the long-duration event and eruption has been developed (Carmichael, 1964; Sturrock, 1966; Hirayama, 1974; Kopp and Pneuman, 1976), but not so for the high-intensity flares and eruptions. This work investigates the magnetic topology changes that occur for a X1.2 GOES classification flare which has no associated CME. It is found that the flare is likely to result from the interaction between two pre-existing loops low in the corona, producing a confined flare. Slightly higher in the corona, a loop is observed which exhibits an outward motion as a result of the reconfiguration during reconnection. The objective of this work is to gain insight on the magnetic topology of the event which is critical in order to determine whether a high-intensity flare is likely to be related to a CME or not.

Many aspects of the Sun‐Mars interaction have been investigated during solar transient events with measurements from multiple spacecrafts and also simulation efforts. Limited discussion has been paid to magnetic topology response to disturbed upstream conditions. The implications of topology changes include, but are not limited to, the pattern of energetic particle precipitation into the Martian atmosphere and the impact on cold ion escape during solar transient events as low‐energy ion escape is dependent on magnetic topology. In this study, we investigate the magnetic topology response to the 2017 September interplanetary coronal mass ejection (ICME) event with measurements collected by the Mars Atmospheric and Volatile EvolutioN spacecraft. It is found that the interface between draped interplanetary magnetic field and closed field lines was moved from 800–1400 km in altitude during quiet conditions to 200–400 km after ICME arrived at Mars and then relaxed back to high altitudes again after the event. To gain insight into magnetic topology response on a global scale, we first validate magnetic topology from a time‐dependent simulation with a single‐fluid multispecies magnetohydrodynamic (MHD) model by comparing magnetic topology determined from Mars Atmospheric and Volatile EvolutioN data, which shows a good agreement. Then we present MHD predictions of global magnetic topology changes during this ICME event. In addition to a deeper interplanetary magnetic field penetration, MHD results suggest more open field lines in response to the ICME event.

The inner heliosphere, spanning from the solar corona to Earth's orbit, is a dynamic region where energetic particles are accelerated and transported. Understanding these processes is crucial for comprehending space weather phenomena and their impact on Earth. This paper discusses the key mechanisms involved in particle acceleration near the Sun, primarily driven by solar flares and coronal mass ejections (CMEs), and the subsequent transport of these particles in the solar wind. Furthermore, we address the influence of Solar Energetic Particles (SEPs) and Galactic Cosmic Rays (GCRs) on the global electric circuit (GEC). SEPs, produced by solar flares and CMEs, and GCRs, originating from outside the solar system, both contribute to the ionization of the Earth's atmosphere. This ionization significantly impacts the conductivity of the atmosphere, particularly in the polar regions. Change of ionization due to SEPs and GCRs can alter the potential difference between the ionosphere and the ground, influencing the flow of current within the global electric circuit. These changes can lead to observable effects, such as variations in atmospheric conductivity and potential gradients, and may even influence weather patterns.

Abstract. This article summarises the results of an analysis of solar radio bursts (SRBs) detected by the Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometer hosted by the University of Rwanda. The data analysed were detected during the first year (2014–2015) of the instrument operation. Using quick plots provided by the e-CALLISTO website, a total of 201 intense and well-separated solar radio bursts detected by the CALLISTO station located in Rwanda, are found consisting of 4 type II, 175 type III and 22 type IV radio bursts. It is found that all analysed type II and ∼ 37 % of type III bursts are associated with impulsive solar flares, while the minority (∼ 13 %) of type IV radio bursts are associated with solar flares. Furthermore, all type II radio bursts are associated with coronal mass ejections (CMEs), ∼ 44 % of type III bursts are associated with CMEs, and the majority (∼ 82 %) of type IV bursts were accompanied by CMEs. With aid of the atmospheric imaging assembly (AIA) images on board the Solar Dynamics Observatory (SDO), the location of open magnetic field lines of non-flare-associated type III radio bursts are shown. The same images are used to show the magnetic loops in the solar corona for type IV radio bursts observed in the absence of solar flares and/or CMEs. Findings from this study indicate that analysis of SRBs that are observed from the ground can provide a significant contribution to the early diagnosis of solar transients phenomena, such as solar flares and CMEs, which are major drivers of potential space weather hazards.

Previous attempts to produce three-dimensional (3-D) reconstructions of coronal mass ejections (CMEs) have required either modeling efforts or comparisons with secondary associated eruptions near the solar surface. This is because coronagraphs are only able to produce sky-plane-projected images of CMEs and it has hence been impossible to overcome projection effects by using coronagraphs alone. The SECCHI suite aboard the twin STEREO spacecraft allows us to provide the means for 3-D reconstruction of CMEs directly from coronagraph measurements alone for the first time. We present these measurements from two CMEs observed in November 2007. By identifying common features observed simultaneously with the LASCO coronagraphs aboard SOHO and the COR coronagraphs aboard STEREO we have triangulated the source region of both CMEs. We present the geometrical analysis required for this triangulation and identify the location of the CME in solar-meridional, ecliptic, and Carrington coordinates. None of the two events were associated with an easily detectable solar surface eruption, so this triangulation technique is the only means by which the source location of these CMEs could be identified. We present evidence that both CMEs originated from the same magnetic structure on the Sun, but from a different magnetic field configuration. Our results reveal some insight into the evolution of the high corona magnetic field, including its behavior over time scales of a few days and its reconfiguration after a major eruption.

Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are results of eruptions of magnetic flux ropes (MFRs). However, a heated debate is on whether MFRs pre-exist before the eruptions or they are formed during the eruptions. Several coronal signatures, \textit{e.g.}, filaments, coronal cavities, sigmoid structures and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre-existing MFR scenario. There is almost no reported observation about MFR formation during the eruption. In this letter, we present an intriguing observation of a solar eruptive event occurred on 2013 November 21 with the Atmospheric Imaging Assembly on board the \textit{Solar Dynamic Observatory}, which shows a detailed formation process of the MFR during the eruption. The process started with the expansion of a low-lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly-formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved-in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob ($\sim$ 10 MK), presumably a MFR, producing a CME. We suggest that two spatially-separated magnetic reconnections occurred in this event, responsible for producing the flare and the hot blob (CME), respectively.

On August 14, 2010 a wide-angled coronal mass ejection (CME) was observed. This solar eruption originated from a destabilized filament that connected two active regions and the unwinding of this filament gave the eruption an untwisting motion that drew the attention of many observers. In addition to the erupting filament and the associated CME, several other low-coronal signatures that typically indicate the occurrence of a solar eruption were associated with this event. However, contrary to what was expected, the fast CME (v > 900 km s−1 ) was accompanied by only a weak C4.4 flare. We investigate the various eruption signatures that were observed for this event and focus on the kinematic evolution of the filament in order to determine its eruption mechanism. Had this solar eruption occurred just a few days earlier, it could have been a significant event for space weather. The risk of underestimating the strength of this eruption based solely on the C4.4 flare illustrates the need to include all eruption signatures in event analyses in order to obtain a complete picture of a solar eruption and assess its possible space weather impact.

Context. Solar hard X-ray (HXR) observations provide diagnostics of the hottest plasmas and of nonthermal electron populations present during solar flares and coronal mass ejections. HXR images of specific energy ranges often contain overlapping contributions of these components, complicating their interpretation. This is even more challenging as HXR imagers generally use an indirect imaging system. Aims. Our work aims to separately image individual spectral components, such as thermal loops, superhot sources, and nonthermal footpoint sources, rather than obtaining images of specific energy ranges that show a combination of all components. Methods. We introduced a new method called “spectral component imaging” and applied it to observations provided by the Spectrometer/Telescope for Imaging X-rays (STIX) aboard Solar Orbiter. First, the flare integrated HXR spectrum was fit with individual spectral components to get the relative contributions (“weights”) of each component in each native STIX energy channel. In a second step, a set of linear equations was created based on these weights and the observed, energy-dependent STIX visibilities. The visibilities of the individual spectral components were derived by means of a linear least-squares approach and were subsequently utilized for image reconstructions. Results. We demonstrate the effectiveness of spectral component imaging on four different flares observed by STIX. This method provides powerful diagnostics, particularly for flares with hot and superhot components, allowing us to spatially separate these two thermal components. We applied our methodology to the nonthermal peak of the X7.1 flare SOL2024-10-01, and we find that the superhot component is located 4.8 Mm away from the hot thermal loops. The thermal energy of the superhot component is approximately 20% of the energy content of the hot component, highlighting the significance of superhot components in the total flare energy budget. Conclusions. Spectral component imaging provides a powerful tool to image individual spectral components (i.e., thermal and nonthermal X-ray sources), rather than creating images over fixed energy ranges. Because there is no need to select an energy range, spectral component imaging has the potential to automate the image reconstruction process and to establish a robust STIX image database once the spectral components have been defined.

Sunspot is known as the area with the highest solar magnetic activity and has the coolest region compared to its surrounding. It is also influenced by sunspot complexity and magnetic field strength. The huge explosion of solar energetic particles in the interplanetary space due to Coronal Mass Ejections (CMEs) and solar flares is believed due to instability of magnetic field and complexity magnetic field in the sunspot. Due to these events, the intense solar radio emission also known as solar radio bursts were released to the Earth. Delta (δ) sunspot is one of the largest magnetic classification of sunspot and seen mostly released solar flares and CMEs, however, Beta Gamma (βγ) sunspot has the highest formation from 2012 to 2016 compared to other type of bursts and has tendency to produce solar flares and CMEs. The data were collected using Space Weather Website (SWPC) and NOAA, e-CALLISTO network and LPDA. The data were collected within 5 years (2012-2016) and reveals βγ sunspot has (349 counts) (62.77%), followed by βγσ sunspot (160 counts) (28.78%), δ sunspot (39 counts) (7.01%) and βγ sunspot (8 counts) (1.44%), thus, highlights the highest type of magnetic classification occurred on Active Region (AR) was βγ sunspot. Highest formation of βγ sunspot illustrated the complexity of the βγ sunspot due instability of magnetic field inside AR and has tendency to produce flares and CMEs compared to other types of magnetic classifications. Furthermore, βγ sunspot demonstrated a tendency to generate Type II burst, Type III burst, Type IV burst and combination of bursts which we classified as selected events. This finding proved that Type IV burst has the highest formation of burst followed by Type III burst, Type II burst and selected events. Type IV burst has counted for 161 counts (56.29%), Type III burst (100 counts) (34.96%), Type II burst (14 counts) (4.9%) and selected events (11 days) (3.85%). The type of bursts was determined by the range frequency of burst and the duration of burst. The different types of bursts have different ranges of frequency and duration of bursts. Type IV burst displayed the highest formation due its associated phenomena mostly was sunspot where the location of events occurred, followed by Type III burst (solar flares), Type II burst (CMEs) and selected events. These findings were important in solar activity study as prediction and forecast for Solar Cycle 25. These significant findings manage the process of shutting down the system from breakdown due to high energetic particles being released from solar flares and CMES. This prediction can shut down the system in satellites and prevent the power grid and telecommunication system from breakdown.

Solar energetic particle (SEP) events have been observed by the Parker Solar Probe (PSP) spacecraft since its launch in 2018. These events include sources from solar flares and coronal mass ejections (CMEs). The IS⊙IS instrument suite on board PSP is measuring ions over energies from ∼ 20 keV nucleon−1 to 200 MeV nucleon−1 and electrons from ∼ 20 keV to 6 MeV. Previous studies sought to group CME characteristics based on their plasma conditions and arrived at general descriptions with large statistical errors, leaving open questions on how to properly group CMEs based solely on their plasma conditions. To help resolve these open questions, the plasma properties of CMEs have been examined in relation to SEPs. Here, we reexamine one plasma property, the solar wind proton temperature, and compare it to the proton SEP intensity in a region immediately downstream of a CME-driven shock for seven CMEs observed at radial distances within 1 au. We find a statistically strong correlation between proton SEP intensity and bulk proton temperature, indicating a clear relationship between SEPs and the conditions in the solar wind. Furthermore, we propose that an indirect coupling of SEP intensity to the level of turbulence and the amount of energy dissipation that results is mainly responsible for the observed correlation between SEP intensity and proton temperature. These results are key to understanding the interaction of SEPs with the bulk solar wind in CME-driven shocks and will improve our ability to model the interplay of shock evolution and particle acceleration.

Solar activities are natural phenomena that occur at the solar surface by ejecting energy into interplanetary space and consequently hitting Earth’s atmosphere where the commencement of geomagnetic storms. Generally, solar radio bursts originated at the same level as the solar flares, Coronal Mass Ejections (CMEs) and shock at solar atmosphere which the Sun project the radio energy into the interstellar medium. This is a novel study to investigate the correlation between solar burst type IV and type III based on their properties. The analysis is based on the statistical data of type IV and type III solar bursts from 2006 – 2011. The statistics of solar burst type IV associated with type III were obtained through e-Callisto (Compact Astronomical Low-frequency Low-cost Instrument for Spectroscopy Transportable Observatory) Spectrometer in the years 2006 until 2011. The aim of this study is to find out whether type III bursts preserved energy to solar bursts type IV thus led to the formation of geomagnetic storm. Statistical data from this study showed that most of the burst type IV were preceded and followed by type III burst. The total number of type IV events studied was 37, with 20 preceded by type III and the remainder with other types. Predominantly, solar bursts events are accompanied with great solar flares (class X and M) producing major storms. Although the study did not show much correlation between bursts type IV and type III in producing these storms, there are several possible explanations for this result. It may be the case that solar events such as solar flare, CMEs and active region ejected from the solar disc is not heading towards Earth and the energy has eventually dispersed into the interplanetary medium.