A New Pathway for Incorporating the Impact of Solar Flares and Other Space Activity into Climate Modelling

A recent development in climate research is the recognition that space activity such as solar flares, gamma ray bursts, supernovas etc. can have a significant impact on the Earth. The existing methods of modelling space activity do not model these phenomena explicitly. Instead, their effect on ionization rates is formulated and then built into existing climate models. In this paper, based on the authors’ earlier work, several analytical approaches for modelling a solar flare hitting the Earth are presented. These methods can also be used for modelling gamma-ray bursts or cosmic rays striking our planet. In addition, a method of calculating the total amount of radiation received during a solar flare is proposed. The future use of the proposed modelling approaches within comprehensive global climate models allows for explicit modelling of space activity and provides a new pathway for studying the possible effects of this activity on the Earth.

Latitudinal Distribution of Solar Flares and Their Association with Coronal Mass Ejections

Major solar flare events have been utilised to study the latitudinal frequency distribution of solar flares in northern and southern hemispheres for the period of 1986 to 2003. A statistical analysis has been performed to obtain the correlation between Coronal Mass Ejections (CMEs) and Forbush decrease (Fds) of cosmic ray intensity. Almost the same flares distribution in both hemispheres is found in association with CMEs. In a further analysis, it is noted that a larger number of CME-associated solar flares located in the northern hemisphere are found to be more effective in producing Forbush decreases.

Electron-Proton Pairing at High Temperatures, Solar Flares, and the FIP Effect

We analyze the line data from solar flares to present evidence for the emission spectrum of the recently discussed electron-proton pairs at high temperatures. We also point out that since the pairing phenomenon provides an additional source for these lines—the conventional source being the highly ionized high-Z atoms already existing in the solar atmosphere, we have a plausible explanation of the FIP effect.

Ensemble prediction model of solar proton events associated with solar flares and coronal mass ejections

An ensemble prediction model of solar proton events （SPEs）, combining the information of solar flares and coronal mass ejections （CMEs）, is built. In this model, solar flares are parameterized by the peak flux, the duration and the longitude. In addition, CMEs are parameterized by the width, the speed and the measurement position angle. The importance of each parameter for the occurrence of SPEs is estimated by the information gain ratio. We find that the CME width and speed are more informative than the flare’s peak flux and duration. As the physical mechanism of SPEs is not very clear, a hidden naive Bayes approach, which is a probability-based calculation method from the field of machine learning, is used to build the prediction model from the observational data. As is known, SPEs originate from solar flares and/or shock waves associated with CMEs. Hence, we first build two base prediction models using the properties of solar flares and CMEs, respectively. Then the outputs of these models are combined to generate the ensemble prediction model of SPEs. The ensemble prediction model incorporating the complementary information of solar flares and CMEs achieves better performance than each base prediction model taken separately.

A possible mechanism of stimulation of seismic activity by ionizing radiation of solar flares

A possible mechanism of earthquake triggering by ionizing radiation of solar flares is considered.A theoretical model and results of numerical calculations of disturbance of electric field,electric current,and heat release in lithosphere associated with variation of ionosphere conductivity caused by absorption of ionizing radiation of solar flares are presented.A generation of geomagnetic field disturbances in a range of seconds/tens of seconds is possible as a result of large-scale perturbation of a conductivity of the bottom part of ionosphere in horizontal direction in the presence of external electric field.Amplitude-time characteristics of the geomagnetic disturbance depend upon a perturbation of integral conductivity of ionosphere.Depending on relation between integral Hall and Pedersen conductivities of disturbed ionosphere the oscillating and aperiodic modes of magnetic disturbances may be observed.For strong perturbations of the ionosphere conductivities amplitude of pulsations may obtain^102 nT.In this case the amplitude of horizontal component of electric field on the Earth surface obtains 0.01 mV/m,electric current density in lithosphere-10-6 A/m2,and the power density of heat release produced by the generated current is 10-7 W/m3.It is shown that the absorption of ionizing radiation of solar flares can result in variations of a density of telluric currents in seismogenic faults comparable with a current density generated in the Earth crust by artificial pulsed power systems(geophysical MHD generator"Pamir・2"and electric pulsed facility"ERGU・600"),which provide regional earthquake triggering and spatiotemporal variation of seismic activity.Therefore,triggering of seismic events is possible not only by man-made pulsed power sources but also by the solar flares.The obtained results may be a physical basis for a novel approach to solve the problem of short・term earthquake prediction based on electromagnetic triggering phenomena.

Energy and spectral analysis of confined solar flares from radio and X-ray observations

The energy and spectral shape of radio bursts may help us understand the generation mechanism of solar eruptions,including solar flares,coronal mass ejections,eruptive filaments,and various scales of jets.The different kinds of flares may have different characteristics of energy and spectral distribution.In this work,we selected 10 mostly confined flare events during October 2014 to investigate their overall spectral behaviour and the energy emitted in microwaves by using radio observations from microwaves to interplanetary radio waves,and X-ray observations of GOES,RHESSI,and Fermi/GBM.We found that:all the confined flare events were associated with a microwave continuum burst extending to frequencies of9.4~15.4 GHz,and the peak frequencies of all confined flare events are higher than 4.995 GHz and lower than or equal to 17 GHz.The median value is around 9 GHz.The microwave burst energy(or nuence)and the peak frequency are found to provide useful criteria to estimate the power of solar flares.The observations imply that the magnetic field in confined flares tends to be stronger than that in 412 flares studied by Nita et al.(2004).All 10 events studied did not produce detectable hard X-rays with energies above~300 keV indicating the lack of efficient acceleration of electrons to high energies in the confined flares.

Statistical Study of the Geoeffectivity of Halo Coronal Mass Ejections Associated with X-Class Flares during Solar Cycles 23 and 24

By analysing a long series of data (1996-2019), we show that solar cycle 23 was more marked by violent solar flares and coronal mass ejections (CMEs) compared to solar cycle 24. In particular, the halo coronal mass ejections associated with X-class flares appear to be among the most energetic events in solar activity given the size of the flares, the speed of the CMEs and the intense geomagnetic storms they produce. Out of eighty-six (86) X-class halo CMEs, thirty-seven (37) or 43% are highly geoeffective;twenty-four (24) or approximately 28% are moderately geoeffective and twenty-five (25) or 29% are not geoeffective. Over the two solar cycles (1996 to 2019), 71% of storms were geoeffective and 29% were not. For solar cycle 23, about 78% of storms were geoeffective, while for solar cycle 24, about 56% were geoeffective. For the statistical study based on speed, 85 halo CMEs associated with X-class flares were selected because the CME of 6 December 2006 has no recorded speed value. For both solar cycles, 75.29% of the halo CMEs associated with X-class flares have a speed greater than 1000 km/s. The study showed that 42.18% of halo (X) CMEs with speeds above 1000 km/s could cause intense geomagnetic disturbances. These results show the contribution (in terms of speed) of each class of halo (X) CMEs to the perturbation of the Earth’s magnetic field. Coronal mass ejections then become one of the key indicators of solar activity, especially as they affect the Earth.

Quasi-periodic pulsations with double periods observed in Lyαemission during solar flares

Quasi-periodic pulsations(QPPs)are very common oscillation features during solar flares,which have been observed in almost the entire wavelengths.However,the flare-related QPPs with double periods in the Lyα emission,particularly within a period ratio of about 2,were rarely detected.In this paper,we report the QPPs with double periods in the full-disk Lyαemission during the impulsive phase of four solar flares,i.e.,SOL2016-Feb-12,SOL2014-Oct-24,SOL2014-Jun-10,and SOL2012-Nov-21.The fulldisk Lyαfluxes were recorded by the extreme-ultraviolet sensor on board the Geostationary Operational Environmental Satellite.Then,the quasi-periods are estimated by the Markov chain Monte Carlo(MCMC)sampling techniques.Finally,the double periods of around 3 and 1.5 min are detected in Lyαemissions,and their period ratio is roughly equal to 2.The 3-min QPP could also be detected in the local light curves measured by the Atmospheric Imaging Assembly at wavelengths of 304 and 1600A.Our observations suggest that the double periodic QPPs could be regarded as the fundamental and harmonic modes of acoustic waves,which should be helpful to understand magnetohydrodynamic waves in the solar chromosphere.However,we cannot rule out that the double periods are each caused by a different generation mechanism.

The Response of Debris-Flow Events to Solar Proton Flares(Ⅰ)

By analyzing the observation data from Dongchuan Debris Flow Observation and Research Station and historical data from year 1965 to 1990 gotten from National Astronomical Observatories/ Yunnan Observatory, the responding of debris flow in Jiangjia Ravine to Solar Proton Flare is studied. The following conclusion can be drawn. Solar Proton Flare, as one of most important astronomical factors, affects the activity of debris flow in Yunnan. Generally, from 1965 to 1990, the more active Solar Proton Flare is, the greater the probability of high frequency and large runoff of debris flow is. On the contrary, the less active Solar Proton Flare is, the greater the probability of low frequency, small runoff, and low sediment transport of debris flow is.

The Dependence between Solar Flare Emergence and the Average Background Solar X-Ray Flux Emission

Solar flares, sudden bursts of intense electromagnetic radiation from the Sun, can significantly disrupt technological infrastructure, including communication and navigation satellites. To mitigate these risks, accurate forecasting of solar activity is crucial. This study investigates the potential of the Sun’s background X-ray flux as a tool for predicting solar flares. We analyzed data collected by solar telescopes and satellites between the years 2013 and 2023, focusing on the duration, frequency, and intensity of solar flares. We compared these characteristics with the background X-ray flux at the time of each flare event. Our analysis employed statistical methods to identify potential correlations between these solar phenomena. The key finding of this study reveals a significant positive correlation between solar flare activity and the Sun’s background X-ray flux. This suggests that these phenomena are interconnected within the framework of overall solar activity. We observed a clear trend: periods with increased occurrences of solar flares coincided with elevated background flux levels. This finding has the potential to improve solar activity forecasting. By monitoring background flux variations, we may be able to develop a more effective early warning system for potentially disruptive solar flares. This research contributes to a deeper understanding of the complex relationship between solar flares and the Sun’s overall radiative output. These findings indicate that lower-resolution X-ray sensors can be a valuable tool for identifying periods of increased solar activity by allowing us to monitor background flux variations. A more affordable approach to solar activity monitoring is advised.

Rethinking the solar flare paradigm

It is widely accepted that solar flares involve release of magnetic energy stored in the solar corona above an active region, but existing models do not include the explicitly time-dependent electrodynamics needed to describe such energy release. A flare paradigm is discussed that includes the electromotive force （EMF） as the driver of the flare, and the flare-associated current that links different regions where magnetic reconnection, electron acceleration, the acceleration of mass motions and current closure occur. The EMF becomes localized across regions where energy conversion occurs, and is involved in energy propagation between these regions.

Shock Waves in the Solar Atmosphere

The discovery of shock waves at observations sun like stars quasi-zero method. Shock waves associated with solar flares in Ha, it is shown that the amplitude of shock waves decreases to the edge of the sun, it follows that these waves are global. The conclusion is that the appearance of these waves may be connected with explosions in the deeper layers of the sun.

Vector Magnetograph Observations by the Solar Flare Telescope at Boao

We report that vector magnetograph (VMG) observations of the solar photosphere are being carride out by the Solar Flare Telescope (SOFT) at BOAO. The VMG uses a narrow band Lyot filter (FWHM=0 125A) for Stokes parameter (I, Q, U, V) observations to obtain longitudinal and transverse fields. We have obtained a filter convolved line profile of Fe I 6302 5 for VMG by changing the central wavelength of the Lyot filter, which is consistent with the Sacremento Peak spectral atlas data. Using the line profile, we have determined calibration coefficients of longitudinal and transverse fields by the line slope method. Then we have compared vector fields of AR8422 observed at BOAO with those at Mitaka. The comparison shows that longitudinal fields are very similar to each other, but transverse fields are a little different. Finally, we present Hα and magnetic observations of AR8419 during its flaring activity (M3 1/1B).

Multi-wavelength study of energetic processes during solar flare occurrence

This paper is an attempt to understand the physical processes occurring in different layers of the solar atmosphere during a solar flare.For a complete understanding of the flare,we must analyze multiwavelength datasets,as emission at different wavelengths originates from different layers in the solar atmosphere.Also,flares are transient and localized events observed to occur at all longitudes.With these considerations,we have carried out multi-wavelength analysis of two representative flare events.One event occurred close to the center of the solar disk and the other occurred close to the limb.In the former case,we examine emission from the lower layers of the solar atmosphere.Therefore the chromosphere,transition region and also photospheric magnetogram can be analyzed.On the other hand,in the near-limb event,coronal features can be clearly examined.In this paper,the first event studied is the M1.1 class flare from the active region NOAA 10649 located at S10 E14 and the second event is the M1.4 class flare from the active region 10713 located at S12 W90.In both cases,we have acquired excellent multi-wavelength data sets.The observations from multi-instrumental data clearly demonstrate that flares occur in the vicinity of sunspots.These are regions of strong magnetic field with mixed polarity.

Study of ionospheric disturbances during solar flare events using the SuperDARN Hokkaido radar

It is well known that many types of ionospheric disturbances occur during solar flare events. The sudden increase in total electron content （SITEC） has been studied for several decades, but total electron content （TEC） data do not provide information on the altitudinal distribution of electron density changes. Previous studies used HF Doppler system data to investigate the contributions of the D-region and F-region ionospheric electron density changes by examining the HF radio wave frequency dependence on the Doppler shift values. In this study we examined the dependence of the elevation angle of the Doppler shift of ground scatter echoes using the SuperDARN Hokkaido radar. We analyzed solar flare events from Dec 2006 to Mar 2012. A sudden fade-out of echoes was observed in almost all the events we analyzed, which was the result of the radio absorption associated with a significant increase in electron density within the D-region ionosphere. In addition, we discovered positive Doppler shifts just before the sudden fade-out of echoes. The Doppler shift is negatively correlated with the elevation angle of received radar waves. It indicates that variation of electron density in the D-region ionosphere is dominant during solar flare events. This result is consistent with a previous study. We also compared the irradiation by X-ray and extreme ultra violet rays observed by the GOES-14 and GOES-15 satellites, which generated Doppler shifts. A positive Doppler shift is consistent with a change of X-ray

Geomagnetic solar flare effect on February 4 and 6，1986 at the china Antarctic Great wall Station

Taking the sampled every minute values of the horizontal, declination and vertical components H, D, Z and theintensity of total field F calculated from H and Z on the magnetograms at ten geomagnetic observatories in Chinain the same periods, and at the china Antarctic Great wan station (CAGWS), the authors conducted the maximum entropy analysis and band-pass filtration of these data and obtained the following results: (1) At the PeriodT=10-90 min geomagnetic solar flare effect (sfe) is evident on the sunlit hemisphere. It is more pronounced atperiods 15, 20, 25 and 30 min, and most prominent at 30-35 min. The solar X-ray spectra at the same timeshowed their peaks at 10 and 15 min ; (2) The period T=10-70 min of sfe at the CAGWS in the westernHemisphere was also recognizable after spectral analysis and filtration, but the corresponding period of the maximum amplitude was different from that in the sunlit hemisphere. The results further proved that the geomagnetic effect of solar flares could also be observed in the dark hemisphere I (3) The subsolar POints of two solar flareswere found around Lanzhou, and the associated current density in the ionosphere was about 24 A/km. Thetransitional zone from positive to negative sfe was found around the geographic latitude p￣ 22'-- 24'N, wherethe sfe in H-crochet was almost illegible.

Radio Fiber Fine Structure During the Solar Flare on July 14, 2000

On July 14, 2000, a type IV solar radio burst was observed at 10:43-11:00 UT with the 1-2 GHz digital spectrometer of National Astronomical Observatories of China (NAOC). Many fiber fine structures superposed on the type IV burst were detected in the same interval. A theoretical interpretation for the fibers is performed based upon a model of magnetic-mirror loop configuration in the solar corona. In this model, the source of the fiber emission is considered as the ducting of whistler solitons within the magnetic-mirror loop. A quantitative estimation using the observed data indicats that the magnetic field strength of the radio source is about 1.451×10 -2≤B 0≤2.734×10 -2 T, and that a fiber is composed of 4×10 15 solitons occupying a volume of about 1.2×108 km3. For the duct through which the whistler solitons passed within the magnetic-mirror loop, its diameter and the length are worked out, namely, d≈120 km and Δr≈104 km, respectively.

Waiting Time Distribution of Coronal Mass Ejections

Inspired by the finding that the large waiting time of solar flares presents a power-law distribution, we investigate the waiting time distribution (WTD) of coronal mass ejections (CMEs). SOHO/LASCO CME observations from 1996 to 2003 are used in this study. It is shown that the observed CMEs have a similar power-law behavior to the flares, with an almost identical power-law index. This strongly supports the viewpoint that solar flares and CMEs are different manifestations of the same physical process. We have also investigated separately the WTDs of fast-type and slow-type CMEs and found that their indices are identical, which imply that both types of CME may originate from the same physical mechanism.

Superpenumbral chromospheric flare

We observed a C-class flare at the outer boundary of the superpenumbra of a sunspot. The flare was triggered by an emerging magnetic bipolar region that was obliquely oriented with respect to the superpenumbral fibrils. The flare started due to the low height magnetic reconnection of emerging magnetic flux with a superpenumbral field resulting in hot multi-temperature plasma flows in the inverse Evershed flow channel and its overlying atmosphere. Inverse Evershed flows in the chromosphere start from the superpenumbra towards the sunspot that end at the outer boundary of the penumbra. The hot plasma flow towards the sunspot in the inverse Evershed channels show about 10 km s^-1 higher velocity in Ha wavelengths compared to the plasma emissions at various temperatures as seen in different AIA filters. Even though these velocities are about seven times higher than the typical inverse Evershed flow speeds, the flow is diminished at the outer boundary of the sunspot＇s penumbra. This suggests that the superpenumbral field lines that carry inverse Evershed flows are discontinued at the boundary where the penumbral field lines dive into the sun and these two sets of field lines are completely distinct. The discontinuity in the typical magnetic field and plasma properties at the adjoining of these two sets of field lines further leads to discontinuity in the characteristic magnetoacoustic and Alfvrn speeds, thereby stopping the plasma flows further on. The multi-temperature plasma in the inverse Evershed channels exhibits possible longitudinal oscillations initially during the onset of the flare, and later flows towards the sunspot. In the multi-temperature view, the different layers above the flare region have a mixture of supersonic as well as subsonic flows.

How Does the Diffusion Dynamics Reconnect the Magnetic Field？

We clarify how magnetic reconnection can be derived from magnetohydrodynamics （MHD） equations in a way that is easily understandable to university students. The essential mechanism governing the time evolution of the magnetic field is diffusion dynamics. The magnetic field is represented by two components. It is clarified that the diffusion of a component causes agene ration of another component that is initially zero and, accordingly, that the magnetic force lines are reconnected. For this reconnection to occur correctly, the initial magnetic field must be directed oppositely in the two regions, e.g., y 〉 0 and y 〈 O; must be concave （convex） for y 〉 0 （y 〈 0）; and must be saturated foryfar from the x axis, which would indicate the existence of the current sheet. It will be clear that our comprehension based on diffusion runs parallel to the common qualitative explanation about the magnetic reconnection.