Flare Onset Research Articles

Radiative Magnetohydrodynamic Simulation of the Confined Eruption of a Magnetic Flux Rope: Magnetic Structure and Plasma Thermodynamics

It is widely believed that magnetic flux ropes are the key structure of solar eruptions; however, their observable counterparts are not clear yet. We study a flare associated with flux rope eruption in a comprehensive radiative magnetohydrodynamic simulation of flare-productive active regions, especially focusing on the thermodynamic properties of the plasma involved in the eruption and their relation to the magnetic flux rope. The preexisting flux rope, which carries cold and dense plasma, rises quasi-statically before the onset of eruptions. During this stage, the flux rope does not show obvious signatures in extreme ultraviolet (EUV) emission. After the flare onset, a thin “current shell” is generated around the erupting flux rope. Moreover, a current sheet is formed under the flux rope, where two groups of magnetic arcades reconnect and create a group of postflare loops. The plasma within the “current shell,” current sheet, and postflare loops are heated to more than 10 MK. The postflare loops give rise to abundant soft X-ray emission. Meanwhile, a majority of the plasma hosted in the flux rope is heated to around 1 MK, and the main body of the flux rope is manifested as a bright arch in cooler EUV passbands such as the AIA 171 Å channel.

Dynamic Property and Magnetic Nonpotentiality of Two Types of Confined Solar Flares

We analyze 152 large confined flares (GOES class ≥ M1.0 and ≤ 45° from disk center) during 2010−2019, and classify them into two types according to the criterion taken from the work of Li et al. “Type I” flares are characterized by slipping motions of flare loops and ribbons and a stable filament underlying the flare loops. “Type II” flares are associated with the failed eruptions of the filaments, which can be explained by the classical 2D flare model. A total of 59 flares are “Type I” flares (about 40%) and 93 events are “Type II” flares (about 60%). There are significant differences in distributions of the total unsigned magnetic flux (ΦAR) of active regions (ARs) producing the two types of confined flares, with “Type I” confined flares from ARs with a larger ΦAR than “Type II.” We calculate the mean shear angle ΨHFED within the core of an AR prior to the flare onset, and find that it is slightly smaller for “Type I” flares than that for “Type II” events. The relative nonpotentiality parameter ΨHFED/ΦAR has the best performance in distinguishing the two types of flares. About 73% of “Type I” confined flares have ΨHFED/ΦAR<1.0 × 10−21 degree Mx−1, and about 66% of “Type II” confined events have ΨHFED/ΦAR ≥ 1.0 × 10−21 degree Mx−1. We suggest that “Type I” confined flares cannot be explained by the standard flare model in 2D/3D, and the occurrence of multiple slipping magnetic reconnections within the complex magnetic systems probably leads to the observed flare.

Modeling the East‐West Asymmetry of Energetic Particle Fluence in Large Solar Energetic Particle Events Using the iPATH Model

AbstractIt has been noted that in large solar energetic particle (SEP) events, the peak intensities show an East‐West asymmetry with respect to the source flare locations. Using the 2D improved Particle Acceleration and Transport in the Heliosphere (iPATH) model, we investigate the origin of this longitudinal trend. We consider multiple cases with different solar wind speeds and eruption speeds of the coronal mass ejections (CMEs) and fit the longitudinal distributions of time‐averaged fluence by symmetric/asymmetric Gaussian functions with three time intervals of 8, 24 and 48 hr after the flare onset time respectively. The simulation results are compared with a statistical study of three‐spacecraft events. We suggest that the East‐West asymmetry of SEP fluence and peak intensity can be primarily caused the combined effect of an extended shock acceleration process and the evolution of magnetic field connection to the shock front. Our simulations show that the solar wind speed and the CME speed are important factors determining the East‐West fluence asymmetry.

Zhengqing fengtongning sustained-release tablets prevents gout flares in the process of ULT: A randomized, positive control, double-blind, double-simulation, multicenter trial.

Introduction:When initiating urate-lowering therapy, using anti-inflammatory prophylaxis therapy for at least 3 to 6 months is strongly recommended. Previous studies have found that zhengqing fengtongning sustained-release tablets (sinomenine) can improve inflammation in the acute phase of gout; however, the efficacy of urate-lowering therapy in reducing frequency of acute flares still needs to be investigated. The aim of the present study is to explore the efficacy and safety of sinomenine for prophylaxis of acute flares when initiating urate-lowering therapy.Methods and analysis:This randomized, placebo-controlled, double-blinded trial will include a total of 210 gout patients who meet the study criteria. The patients will be randomized (1:1) to the test group and the control group. The intervention is planned to be performed for 12 weeks with a follow-up of 12 weeks. All patients would be administered febuxostat (40 mg/d) and concomitant anti-inflammatory prophylaxis therapy. Sinomenine and colchicine placebo are administered in the sinomenine group, sinomenine placebo and colchicine are administered in the colchicine group. The primary outcome is the rate of acute gout flares in subjects within 12 weeks of the treatment period. The secondary outcomes include the times of acute gout flares and the duration of each acute flares within 12 weeks; the compliance rate in patients whose UA levels ≤6.0 mg/dL (360 μmol/L) at the weekend of 2nd, 4th, 8th, and 12th week in each group; the proportion of patients with ≥1 and ≥2 gout flares within 12 weeks; average visual analogue scale/score pain score during gout flares; and the oral dose of etoricoxib will be used to control the onset of acute flares within 12 weeks.Ethics and dissemination:The Institutional Medical Ethics Committee have approved the trial protocol. We plan to publish the results of this study in a peer-reviewed journal.Trial registration:ChiCTR, ChiCTR2100045114, Registered 8 April 2021 http://www.chictr.org.cn/showproj.aspx?proj=124688

The Flares of Low back pain with Activity Research Study (FLAReS): study protocol for a case-crossover study nested within a cohort study

BackgroundAlthough it is generally accepted that physical activity and flares of low back pain (LBP) are related, evidence for the directionality of this association is mixed. The Flares of Low back pain with Activity Research Study (FLAReS) takes a novel approach to distinguish the short-term effects of specific physical activities on LBP flares from the cumulative effects of such activities, by conducting a longitudinal case-crossover study nested within a cohort study. The first aim is to estimate the short-term effects (≤ 24 h) of specific physical activities on LBP flares among Veterans in primary care in the Veterans Affairs healthcare system. The second aim is to estimate the cumulative effects of specific activities on LBP-related functional limitations at 1-year follow-up.MethodsUp to 550 adults of working age (18—65 years) seen for LBP in primary care complete up to 36 “Scheduled” surveys over 1-year follow-up, and also complete unscheduled “Flare Window” surveys after the onset of new flares. Each survey asks about current flares and other factors associated with LBP. Surveys also inquire about activity exposures over the 24 h, and 2 h, prior to the time of survey completion (during non-flare periods) or prior to the time of flare onset (during flares). Other questions evaluate the number, intensity, duration, and/or other characteristics of activity exposures. Other exposures include factors related to mood, lifestyle, exercise, concurrent treatments, and injuries. Some participants wear actigraphy devices for weeks 1–4 of the study. The first aim will examine associations between 10 specific activity categories and participant-reported flares over 1-year follow-up. The second aim will examine associations between the frequency of exposure to 10 activity categories over weeks 1–4 of follow-up and long-term functional limitations at 12 months. All analyses will use a biopsychosocial framework accounting for potential confounders and effect modifiers.DiscussionFLAReS will provide empirically derived estimates of both the short-term and cumulative effects of specific physical activities for Veterans with LBP, helping to better understand the role of physical activities in those with LBP.Trial RegistrationClinicalTrials.gov NCT04828330, registered April 2, 2021.

Multiwavelength Signatures of Episodic Nullpoint Reconnection in a Quadrupolar Magnetic Configuration and the Cause of Failed Flux Rope Eruption

Abstract In this paper, we present multiwavelength observations of the triggering of a failed-eruptive M-class flare from active region NOAA 11302 and investigate the possible reasons for the associated failed eruption. Photospheric observations and nonlinear force-free field extrapolated coronal magnetic field revealed that the flaring region had a complex quadrupolar configuration with a preexisting coronal nullpoint situated above the core field. Prior to the onset of the M-class flare, we observed multiple periods of small-scale flux enhancements in GOES and RHESSI soft X-ray observations from the location of the nullpoint. The preflare configuration and evolution reported here are similar to the configurations presented in the breakout model, but at much lower coronal heights. The core of the flaring region was characterized by the presence of two flux ropes in a double-decker configuration. During the impulsive phase of the flare, one of the two flux ropes initially started erupting, but resulted in a failed eruption. Calculation of the magnetic decay index revealed a saddle-like profile where the decay index initially increased to the torus-unstable limits within the heights of the flux ropes, but then decreased rapidly and reached negative values, which was most likely responsible for the failed eruption of the initially torus-unstable flux rope.

Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. V. Space and Ground Millimeter-VLBI Imaging of OJ 287

Abstract We present the first polarimetric space very long baseline interferometry (VLBI) observations of OJ 287, observed with RadioAstron at 22 GHz during a perigee session on 2014 April 4 and five near-in-time snapshots, together with contemporaneous ground VLBI observations at 15, 43, and 86 GHz. Ground-space fringes were obtained up to a projected baseline of 3.9 Earth diameters during the perigee session, and at a record 15.1 Earth diameters during the snapshot sessions, allowing us to image the innermost jet at an angular resolution of ∼50μ as, the highest ever achieved at 22 GHz for OJ 287. Comparison with ground-based VLBI observations reveals a progressive jet bending with increasing angular resolution that agrees with predictions from a supermassive binary black hole model, although other models cannot be ruled out. Spectral analyses suggest that the VLBI core is dominated by the internal energy of the emitting particles during the onset of a multiwavelength flare, while the parsec-scale jet is consistent with being in equipartition between the particles and magnetic field. Estimated minimum brightness temperatures from the visibility amplitudes show a continued rising trend with projected baseline length up to 1013 K, reconciled with the inverse-Compton limit through Doppler boosting for a jet closely oriented to the line of sight. The observed electric vector position angle suggests that the innermost jet has a predominantly toroidal magnetic field, which, together with marginal evidence of a gradient in rotation measure across the jet width, indicates that the VLBI core is threaded by a helical magnetic field, in agreement with jet formation models.

A DEFT Way to Forecast Solar Flares

Abstract Solar flares have been linked to some of the most significant space weather hazards at Earth. These hazards, including radio blackouts and energetic particle events, can start just minutes after the flare onset. Therefore, it is of great importance to identify and predict flare events. In this paper we introduce the Detection and EUV Flare Tracking (DEFT) tool, which allows us to identify flare signatures and their precursors using high spatial and temporal resolution extreme-ultraviolet (EUV) solar observations. The unique advantage of DEFT is its ability to identify small but significant EUV intensity changes that may lead to solar eruptions. Furthermore, the tool can identify the location of the disturbances and distinguish events occurring at the same time in multiple locations. The algorithm analyzes high temporal cadence observations obtained from the Solar Ultraviolet Imager instrument aboard the GOES-R satellite. In a study of 61 flares of various magnitudes observed in 2017, the “main” EUV flare signatures (those closest in time to the X-ray start time) were identified on average 6 minutes early. The “precursor” EUV signatures (second-closest EUV signatures to the X-ray start time) appeared on average 14 minutes early. Our next goal is to develop an operational version of DEFT and to simulate and test its real-time use. A fully operational DEFT has the potential to significantly improve space weather forecast times.

Purinergic Signaling in the Regulation of Gout Flare and Resolution.

Gout flares require monosodium urate (MSU) to activate the NLRP3 inflammasome and secrete sufficient IL-1β. However, MSU alone is not sufficient to cause a flare. This is supported by the evidence that most patients with hyperuricemia do not develop gout throughout their lives. Recent studies have shown that, besides MSU, various purine metabolites, including adenosine triphosphate, adenosine diphosphate, and adenosine bind to different purine receptors for regulating IL-1β secretion implicated in the pathogenesis of gout flares. Purine metabolites such as adenosine triphosphate mainly activate the NLRP3 inflammasome through P2X ion channel receptors, which stimulates IL-1β secretion and induces gout flares, while some purine metabolites such as adenosine diphosphate and adenosine mainly act on the G protein-coupled receptors exerting pro-inflammatory or anti-inflammatory effects to regulate the onset and resolution of a gout flare. Given that the purine signaling pathway exerts different regulatory effects on inflammation and that, during the inflammatory process of a gout flare, an altered expression of purine metabolites and their receptors was observed in response to the changes in the internal environment. Thus, the purine signaling pathway is involved in regulating gout flare and resolution. This study was conducted to review and elucidate the role of various purine metabolites and purinergic receptors during the process.

Probing Current Sheet Instabilities from Flare Ribbon Dynamics

Abstract The presence of current sheet instabilities, such as the tearing mode instability, are needed to account for the observed rate of energy release in solar flares. Insights into these current sheet dynamics can be revealed by the behavior of flare ribbon substructure, as magnetic reconnection accelerates particles down newly reconnected field lines into the chromosphere to mark the flare footpoints. Behavior in the ribbons can therefore be used to probe processes occurring in the current sheet. In this study, we use high-cadence (1.7 s) IRIS Slit Jaw Imager observations to probe for the growth and evolution of key spatial scales along the flare ribbons—resulting from dynamics across the current sheet of a small solar flare on 2016 December 6. Combining analyses of spatial scale growth with Si iv nonthermal velocities, we piece together a timeline of flare onset for this confined event, and provide evidence of the tearing mode instability triggering a cascade and inverse cascade toward a power spectrum consistent with plasma turbulence.

Solar Flare X‐Ray Impacts on Long Subionospheric VLF Paths

AbstractSolar flares increase the electron number concentration in the daytime ionosphere, potentially affecting radiowave propagation over several frequency ranges. In this study, we use ionospheric observations to determine both peak magnitudes and time variations of solar flare X‐rays without using the direct measurement from the flare. Ground‐based observations of VLF transmitter phase perturbations are compared against measured X‐ray flux levels during solar flares. Flare fluxes derived here from VLF phases on a west‐east subionospheric path are compared with those from a previously analyzed north‐south path. Using a wider selection of solar flares, including M‐class flares for the first time, the best‐fit equations and root mean square (RMS) errors are computed with improved standard deviation (SD) uncertainty estimates for the peak fluxes. Good agreement is found between peak long X‐ray wavelength fluxes (XL, 0.1–0.8 nm) derived for M‐class and X‐class flares and those measured by the GOES satellites. Linear regression analysis on the two paths shows the uncertainties increase in inverse proportion to the path length. Investigations were made with a limited set of “operational” parameters that could be used to derive XL fluxes. No increases in RMS or SD uncertainty levels were introduced by the removal of satellite‐based regression parameters such as the XL flux level measured before the flare onset. As such, these techniques support the idea of nowcasting M‐class and X‐class flares from entirely ground‐based measurements.

Glomerular Disease in Temporal Association with SARS-CoV-2 Vaccination: A Series of 29 Cases.

Immune responses to vaccination are a known trigger for a new onset of glomerular disease or disease flare in susceptible individuals. Mass immunization against SARS-CoV-2 in the COVID-19 pandemic provides a unique opportunity to study vaccination-associated autoimmune kidney diseases. In the recent literature, there are several patient reports demonstrating a temporal association of SARS-CoV-2 immunization and kidney diseases. Here, we present a series of 29 cases of biopsy-proven glomerular disease in patients recently vaccinated against SARS-CoV-2 and identified patients who developed a new onset of IgA nephropathy, minimal change disease, membranous nephropathy, ANCA-associated GN, collapsing glomerulopathy, or diffuse lupus nephritis diagnosed on kidney biopsies postimmunization, as well as recurrent ANCA-associated GN. This included 28 cases of de novo GN within native kidney biopsies and one disease flare in an allograft. The patients with collapsing glomerulopathy were of Black descent and had two APOL1 genomic risk alleles. A brief literature review of patient reports and small series is also provided to include all reported cases to date (n=52). The incidence of induction of glomerular disease in response to SARS-CoV-2 immunization is unknown; however, there was no overall increase in incidence of glomerular disease when compared with the 2 years prior to the COVID-19 pandemic diagnosed on kidney biopsies in our practice. Glomerular disease to vaccination is rare, although it should be monitored as a potential adverse event.

S2452 Two Cases of Ulcerative Colitis Flare Following SARS-CoV-2 mRNA Vaccination

Introduction: The advent of mRNA vaccines has been a major component of the vaccination effort against COVID-19. Immunization with mRNA vaccines has been associated with a systemic inflammatory response.1 We present two cases of patients with ulcerative colitis (UC) in long-term remission who experienced flare following vaccination. Case description/methods: Patient 1: A 50-year-old female with history of UC in remission of 4 years on mesalamine who received both doses of the mRNA-1273 mRNA vaccine, 28 days apart, presented with diarrhea and bloody stools that developed 1 week after dose 1. Patient had worsening diarrhea 1 week following vaccination that progressed to hematochezia. Abdominopelvic CT demonstrated contiguous colitis. She was treated with mesalamine and methylprednisolone. Her symptoms improved in 2 days, and she was discharged on a steroid taper. Patient 2: A 52-year-old female with history of UC in remission of 5 years on mesalamine who received both doses of the BNT162b2 mRNA vaccine, 21 days apart, presented with abdominal pain, diarrhea, and bloody stool that developed 1 day after dose 2. Abdominopelvic CT demonstrated diffuse colitis, and she underwent colonoscopy, which was aborted due to extensive colitis. Sigmoid colon biopsy confirmed crypt abscess formation architectural distortion and ulceration. She was treated with mesalamine and methylprednisolone. Her acute disease was complicated by bowel perforation, and she underwent total colectomy. Discussion: The presence of an environmental trigger is frequently linked to onset of disease flare in patients with UC.2 These two patients were in symptomatic remission on 5-ASA maintenance agents for several years prior to vaccination. The lack of clear alternate environmental changes in these patients suggests provocation of flare by the inflammatory response following vaccination. Existing literature evaluating SARS-CoV-2 mRNA vaccine adverse-events in patients with UC suggests that gastrointestinal side-effects are uncommon.3 In addition, biologic agent use may decrease rate of vaccine-related adverse events.3 Recommendations from an international expert consensus favors vaccination of patients with UC.4 In addition, recent literature demonstrates strong immunologic response following vaccination of patients with UC despite concurrent use of biologic agents.5 Consideration should be given to pre-treatment of patients with UC in remission to decrease risk of flare.Figure 1.: References.

Bempedoic Acid: A New Non-statin Drug for the Treatment of Dyslipidemia.

Statins are currently the first-line drugs for managing dyslipidemia due to their substantial clinical efficacy in reducing low-density lipoprotein cholesterol (LDL-C) and the risk of atherosclerotic cardiovascular disease (ASCVD). However, many patients do not reach their LDL-C target despite taking high-dose statins and some patients are intolerant of these drugs. Therefore, an additional or alternative pharmacological intervention may be required. Bempedoic acid is a novel lipid-lowering drug recently approved for the treatment of dyslipidemia. This review describes the pharmacology of bempedoic acid and its clinical role in patients with dyslipidemia. Bempedoic acid, via its active coenzyme A (CoA) form, inhibits adenosine triphosphate (ATP)-citrate lyase, and reduces hepatic cholesterol synthesis through the mevalonate pathway. The reduction in plasma LDL-C by bempedoic acid is approximately 20%. In addition, this drug is able to lower the level of high-sensitivity C-reactive protein (hs-CRP) by 20%, which suggests anti-inflammatory activity. Bempedoic acid is well tolerated by the majority of patients. Possible common adverse drug reactions include upper respiratory tract infection, urinary tract infection and arthralgia. Serum creatinine and uric acid should be monitored since increased creatinine and hyperuricemia-associated new onset of gout and gout flares have been reported in patients taking bempedoic acid. Decreased hemoglobin levels and rare tendon ruptures have also been observed. Due to its efficacy and good safety profile, bempedoic acid might serve as a potential therapeutic alternative for the management of dyslipidemia.

Tolerance of COVID-19 vaccination in patients with systemic lupus erythematosus: the international VACOLUP study.

Tolerance of COVID-19 vaccination in patients with systemic lupus erythematosus: the international VACOLUP study.

Serum uric acid control for prevention of gout flare in patients with asymptomatic hyperuricaemia: a retrospective cohort study of health insurance claims and medical check-up data in Japan

ObjectivesIn patients with gout, treating to target serum uric acid levels (sUA) of ≤6.0 mg/dL is universally recommended to prevent gout flare. However, there is no consensus on asymptomatic hyperuricaemia....

P677 Fungal abundance is related to inflammatory status in Ulcerative Colitis

Abstract Background Fungi account for approximately 0.1% of the total microorganisms in the gut. Despite the vast body of literature on the bacterial component of the gut microbiota, little has been published on the fungal microbiota. Fungal-bacterial interactions may be significant in inflammatory bowel disease (IBD), with several lines of evidence linking fungi and IBD. Our study aimed to explore and compare the fungal and bacterial loads in fecal samples from different ulcerative colitis (UC) patients’ groups. Methods Using two qPCR systems to amplify the ITS2 sequence from fungi and the 16srRNA gene from bacteria, we characterized and compared fungal and bacterial loads in 3 groups: 1) UClr: UC patients in long-term remission (≥5 years of flare-free disease, clinical, endoscopic and histological remission at inclusion); 2) UCsr: UC patients in short-term remission (3 months in clinical remission at inclusion and previously more than one relapse/year); 3) UCfl: UC patients with active disease (CAI &amp;gt;4 at inclusion). We obtained two frozen fecal samples from all subjects, except for the UCfl group from which we obtained 1 sample at flare onset. Results were expressed in copies/g of feces. Results We included 87 UC patients, 29 in UClr, 20 in UCsr, and 38 in UCfl groups. Median age was 39 years, women comprised 52%. Fecal samples contained a significantly lower number of ITS2 gene copies (median 9.27E+05) than 16srRNA gene copies (median 4.28E+11). 16s rRNA gene copies were similar among the different groups with a median 3.88E+11 for UClr, median 5.29E+11 for UCsr, and median 4.315E+11 for UCfl patients (FDR p=0.65). In contrast, copies of ITS2 gene were increased in UCfl (median 1.95E+06) when compared to UClr (3.68E+04, FDR p=0.0036) but not significantly different to UCsr (5.24E+05 copies, FDR p=0.20). We analyzed the variation between samples over time; we compared the number of copies of ITS2 and 16s rRNA genes in fecal samples collected at two different time points: basal versus 8-weeks. We calculated overall fold changes that reflect stability over time. We found a trend for a more significant variation in the quantity of the ITS2 gene than the 16srRNA gene, but this was not significant. Analysis of the ITS2/16S rRNA ratio assessing the frequency of fungi compared to bacteria showed that this ratio was higher in UCfl (median 6.94E-06) when compared to UClr (median 2.63E-07, FDR p=0.0005) and UCsr patients (median 5.60E-07, FDR p=0.0072), there were no differences between UClr and UCsr patients. Conclusion Fungal abundance was increased in UC flare patients compared to UC patients in long remission, while there were no differences in bacterial abundance. This high number of fungi could be involved in the inflammatory response of UC patients.

Factors related to the onset and recurrence of flares in hidradenitis suppurativa patients treated with adalimumab.

Hidradenitis suppurativa (HS) is characterized by periodic worsening of symptoms. However, clinical parameters associated with flare are still to be established. The aim of this study was to investigate factors associated with flare outbreak in HS patients in treatment with adalimumab. Moderate-severe HS patients were included in this retrospective analysis. In total, 115 HS patients treated with adalimumab from 5 Italian centers were reviewed. Gender, ages at onset/baseline, therapeutic delay, family history, Body Mass Index, smoking, comorbidities, phenotypes, body areas involved, Hurley stage, International Hidradenitis Suppurativa Severity Score System (IHS4), Dermatology Life Quality Index (DLQI) and Visual Analogue Scale for pain (pain-VAS) were collected at baseline. Flares were modelled with baseline features using univariate and multivariate Cox regression. The factors significantly correlated with flares in the univariate model were analyzed using a recurrent event survival analysis (Andersen-Gill model) to assess the relation between them and flares recurrence. During the observation period 80.9% of patients developed flares, detecting 252 flares, overall. A univariate model identified five risk factors associated with the outbreak of flares: age, therapeutic delay, groin involvement, Hurley III, higher IHS4, whereas, from multivariate model, only IHS4 resulted to be significantly correlated. Additionally, flares were positively associated with higher DLQI and pain-VAS. Finally, the Andersen-Gill model showed four factors correlated with flares recurrence: age, therapeutic delay, Hurley III and higher IHS4. An early treatment of HS may prevent both the disease progression and reduce the recurrence of flares.

Hinode/EIS Coronal Magnetic Field Measurements at the Onset of a C2 Flare

Abstract We study Hinode/EIS observations of an active region taken before, during, and after a small C2.0 flare in order to monitor the evolution of the magnetic field and its relation to the flare event. We find that while the flare left the active region itself unaltered, the event included a large magnetic field enhancement (MFE), which consisted of a large magnetic field strength increase to values just short of 500 G in a rather small region where no magnetic field was measured before. This MFE is observed during the impulsive phase of the flare at the footpoints of flare loops, its magnetic energy is sufficient to power the radiative losses of the entire flare, and has completely dissipated after the flare. We argue that the MFE might occur at the location of the reconnection event triggering the flare, and note that it formed within 22 minutes of the flare start (as given by the EIS raster return time). These results open the door to a new line of studies aimed at determining whether MFEs can be flare precursor events or used for Space Weather forecasts, what advance warning time they could provide and if this time is long enough to allow for mitigation procedures to be implemented; as well as to explore which physical processes lead to MFE formation and dissipation, whether such processes are the same in both long-duration and impulsive flares, and whether they can be predicted by theoretical models.

Triggers for acute flare in adults with, or at risk of, knee osteoarthritis: a web-based case-crossover study in community-dwelling adults

SummaryObjectiveTo identify proximate causes (‘triggers’) of flares in adults with, or at risk of, knee osteoarthritis (OA), estimate their course and consequences, and determine higher risk individuals.MethodsIn this 13-week web-based case-crossover study adults aged ≥40 years, with or without a recorded diagnosis of knee OA, and no inflammatory arthropathy who self-reported a knee flare completed a questionnaire capturing information on exposure to 21 putative activity-related, psychosocial and environmental triggers (hazard period, ≤72 h prior). Comparisons were made with identical exposure measurements at four 4-weekly scheduled time points (non-flare control period) using conditional logistic regression. Flare was defined as a sudden onset of worsening signs and symptoms, sustained for ≥24 h. Flare characteristics, course and consequence were analysed descriptively. Associations between flare frequency and baseline characteristics were estimated using Poisson regression.ResultsOf 744 recruited participants (mean age [SD] 62.1 [10.2] years; 61% female), 376 reported 568 flares (hazards) and provided 867 valid control period measurements. Thirteen exposures (eight activity-related, five psychosocial/environmental) were positively associated with flare onset within 24 h (strongest odds ratio estimate, knee buckling: 9.06: 95% confidence interval [CI] 5.86, 13.99; weakest, cold/damp weather: 1.45: 95%CI 1.12, 1.87). Median flare duration was 5 days (IQR 3, 8), less common if older (incident rate ratio [IRR] 0.98: 95%CI 0.97, 0.99), more common if female (IRR 1.85: 95%CI 1.43, 2.39).ConclusionsMultiple activity-related, psychosocial and environmental exposures are implicated in triggering flares. This evidence can help inform prevention and acute symptom management for patients and clinicians.