Solar Surge Research Articles

Solar surge and cost shifts: Heterogenous effects of redistribution in the electricity bills in Japan

This study investigates the impact of daily intermittency in solar energy on retail electricity bills, focusing on the “Duck Curve” and “Peak Shifting” phenomena and their varying effects on different consumer groups. Notably, commercial and industrial users exhibit higher demand around midday, while residential users peak during morning and evening hours. This prompts a crucial question: do peak shifting and redistribution effects differ among consumer groups due to their distinct electricity consumption patterns? Our analysis centers on Japan's power system, which has witnessed significant solar energy penetration, with solar capacity growing from 42 GW in 2016 to 83 GW in 2022. Utilizing monthly electricity consumption data and employing robustness checks through instrumental variable methods, we empirically demonstrate that increased solar penetration leads to higher electricity prices for residential consumers but reduced costs for commercial-industrial users. Additionally, we uncover the mediating role of pumped hydro storage (PHS) stations in stabilizing prices during peak and off-peak periods by managing energy demand variability, thereby mitigating economic impacts across consumer groups. This study highlights the issue of cross-class subsidization, where certain groups bear disproportionately higher electricity costs due to increased renewable energy penetration. It underscores the necessity for carefully crafted policy interventions to uphold market fairness and sustainability alongside large-scale renewable penetration, ensuring a balanced and equitable energy transition.

Self-absorption in solar surge as observed by IRIS

Self-absorption in solar surge as observed by IRIS

First detection of metric emission from a solar surge

We report the first detection of metric radio emission from a surge, observed with the Nançay Radioheliograph (NRH), STEREO, and other instruments. The emission was observed during the late phase of the M9 complex event SOL2010-02-012T11:25:00, described in a previous publication. It was associated with a secondary energy release, also observed in STEREO 304 Å images, and there was no detectable soft X-ray emission. The triangulation of the STEREO images allowed for the identification of the surge with NRH sources near the central meridian. The radio emission of the surge occurred in two phases and consisted of two sources, one located near the base of the surge, apparently at or near the site of energy release, and another in the upper part of the surge; these were best visible in the frequency range of 445.0 to about 300 MHz, whereas a spectral component of a different nature was observed at lower frequencies. Sub-second time variations were detected in both sources during both phases, with a 0.2–0.3 s delay of the upper source with respect to the lower, suggesting superluminal velocities. This effect can be explained if the emission of the upper source was due to scattering of radiation from the source at the base of the surge. In addition, the radio emission showed signs of pulsations and spikes. We discuss possible emission mechanisms for the slow time variability component of the lower radio source. Gyrosynchrotron emission reproduced the characteristics of the observed total intensity spectrum at the start of the second phase of the event fairly well, but failed to reproduce the high degree of the observed circular polarization or the spectra at other instances. On the other hand, type IV-like plasma emission from the fundamental could explain the high polarization and the fine structure in the dynamic spectrum; moreover, it gives projected radio source positions on the plane of the sky, as seen from STEREO-A, near the base of the surge. Taking all the properties into consideration, we suggest that type IV-like plasma emission with a low-intensity gyrosynchrotron component is the most plausible mechanism.

Kelvin–Helmholtz instability in solar cool surges

We study the conditions for onset of Kelvin–Helmholtz (KH) instability in a cool solar surge observed in NOAA AR 8227 on 1998 May 30. The jet with speeds in the range of 45–50kms−1, width of 7Mm, and electron number density of 3.83×1010cm−3 is assumed to be confined in a twisted magnetic flux tube embedded in a magnetic field of 7G. The temperature of the plasma flow is of the order of 105K while that of its environment is taken to be 2×106K. The electron number density of surrounding magnetized plasma has a typical value for the TR/lower corona region of 2×109cm−3. Under these conditions, the Alfvén speed inside the jet is equal to 78.3kms−1. We model the surge as a moving magnetic flux tube for two magnetic field configurations: (i) a twisted tube surrounded by plasma with homogeneous background magnetic field, and (ii) a twisted tube which environment is plasma with also twisted magnetic field. The magnetic field twist in given region is characterized by the ratio of azimuthal to the axial magnetic field components evaluated at the flux tube radius. The numerical studies of appropriate dispersion relations of MHD modes supported by the plasma flow in both magnetic field configurations show that the Kelvin–Helmholtz instability can only occur for MHD waves propagating in axial direction, but with high negative azimuthal mode numbers, and the instability occurs at sub-Alfvénic critical flow velocities in the range of 24–60kms−1.

Kelvin–Helmholtz instability of magnetohydrodynamic waves propagating on solar surges

In the present paper, we study the evolutionary conditions for Kelvin--Helmholtz (KH) instability in a high-temperature solar surge observed in NOAA AR11271 using the Solar Dynamics Observatory data on 2011 August 25. We study the propagation of normal MHD modes in a flux tube considering the two cases, notably of untwisted magnetic flux tube and the twisted one. The numerical solution to the dispersion relation shows that the kink ($m = 1$) wave traveling in an untwisted flux tube becomes unstable if the jet speed exceeds $1060$ km\,s$^{-1}$ -- a speed which is inaccessible for solar surges. A weak twist (the ratio of azimuthal to longitudinal magnetic field component) of the internal magnetic field in the range of $0.025$--$0.2$ does not change substantially the critical flow velocity. Thus, one implies that, in general, the kink mode is stable against the KH instability. It turns out, however, that the $m = -2$ and $m = -3$ MHD modes can become unstable when the twist parameter has values between $0.2$ and $0.4$. Therefore, the corresponding critical jet speed for instability onset lies in the range of $93.5$--$99.3$ km\,s$^{-1}$. The instability wave growth rate, depending on the value of the wavelength, is of the order of several dozen inverse milliseconds. It remains to be seen whether these predictions will be observationally validated in future in the coronal jet-like structures in abundant measure.

THE KINEMATICS AND PLASMA PROPERTIES OF A SOLAR SURGE TRIGGERED BY CHROMOSPHERIC ACTIVITY IN AR11271

We observe a solar surge in NOAA AR11271 using SDO AIA 304 image data on 25 August, 2011. The surge rises vertically from its origin upto a height of 65 Mm with a terminal velocity of 100 km/s, and thereafter falls and fades gradually. The total life time of the surge was 20 min. We also measure the temperature and density distribution of the observed surge during its maximum rise, and found an average temperature and density of 2.0 MK and 4.1 x 109 cm-3, respectively. The temperature map shows the expansion and mixing of cool plasma lagging behind the hot coronal plasma along the surge. As SDO/HMI temporal image data does not show any detectable evidence of the significant photospheric magnetic field cancellation for the formation of the observed surge, we infer that it is probably driven by magnetic reconnection generated thermal energy in the lower chromosphere. The radiance (thus mass density) oscillations near the base of the surge are also evident, which may be the most likely signature of its formation by a reconnection generated pulse. In support of the present observational base-line of the triggering of the surge due to chromospheric heating, we devise a numerical model with conceivable implementation of VAL-C atmosphere and a thermal pulse as an initial trigger. We find that the pulse steepens into a slow shock at higher altitudes that triggers plasma perturbations exhibiting the observed features of the surge, e.g., terminal velocity, height, width, life-time, and heated fine structures near its base.

DOT tomography of the solar atmosphere

We present an analysis of high temporal and spatial resolution CaII H chromospheric limb observations obtained with the Dutch Open Telescope (DOT). We focus on a solar surge observed both by the DOT in CaII H and the Transition Region and Coronal Explorer (TRACE) satellite in the 195 A and 1600 A passbands. The surge is observed in active region AR10486 located near the solar limb, a region which two hours later produced the largest X-flare ever recorded. It consists of relatively cold gas of about 10 4 −10 5 K. In TRACE images the surge is followed for almost 2.5 h, shrinking and expanding at the same location several times. From DOT images we find outward propagating intensity disturbances, with velocities higher than 50 km s −1 , indicative of upward material motion. The latter is also suggested by the good correlation between the DOT and TRACE surge apparent height curves, their apparent time delay and a phase difference analysis. A spectral wavelet analysis of the brightness variations within and along the surge shows a predominant period of ∼6 min, the first ever reported for this kind of structures. Magnetic reconnection at the bottom of the surge as its driving mechanism is suggested by the observed inverted “Y” shape configuration and is further supported by a phase difference analysis.

The solar surge of 1982-12-30

We describe the morphology of the flare-accompanying solar surge of 1982-12-30 at S10W20 on the solar disk and give the time evolution of its velocity field. Observations of the spectrum show that there was rotating motion of 20–30 km/s during the ascent, which decreased in the course of time.

Circular oscillations around the foot of surges

Using the solar magnetic field telescope of Beijing Observatory, we obtained radial velocity data of a solar surge. We discuss the structure of the surge and the motion around the footpoint. We point out that the circular oscillation around the footpoint is probably caused by the drifting motion of charged particles under the action of a macroscopic oscillating electric field generated by two-way diffusion of electrons and ions in the course of the surge.

On the solar surge association with microwave and hard X-ray emission bursts

It is found that 20% solar surges are associated with microwave bursts (2800–15000 MHz) and also that solar surges are not associated with hard X-ray bursts (17–40 keV).

Longitudinal distribution of the cool solar surges

This investigation shows that solar surges are poorly associated with sudden ionospheric disturbances (X-ray) implying that solar surge material is cool and does not heat the corona. The investigation also shows that solar surges are most prolific at longitudes 80°, 110°, 260°, and 290°.

Dynamics of solar surge during its descending stage

Using the basic picture and formulae presented in Paper [1], and taking into consideration that, 1) during the descending phase a weaker magnetic field must be used and 2) the effect of atmosphereic resistance must be allowed for near the end, the dynamical features of a solar surge during its fall are satisfactorily explained.

Dynamics of solar surge during its ascending stage

We propose that the ascending front of a solar surge results from the ejection of plasmoid caused by the Maxwellian stresses of the reconnected field lines in the neutral current sheet above a satellite spot plus the explosive expansion of the matter inside. This model can effectively explain the main dynamical features in both the accelerating and decelerating phases during the rise of the surge.

A possible acceleration mechanism for a solar surge

We examine a non-linear mechanism for a solar surge in which plasma regions of high electrical conductivity and macroscopic dimension can be rapidly accelerated without diffusion of magnetic field. The mechanism is suggested by Rust's observations, which show that surges occur near sunspots in regions of reversed magnetic polarity. For the purposes of numerical calculation, we replace the magnetic field near a polarity reversal in a sunspot by magnetic fields of current loops. The relaxation of the magnetic field generated by two antiparallel coaxial current loops in an incompressible plasma is traced by computer. The results suggest that plasma in the form of a vortex ring can be expelled at the Alfven velocity from active solar regions.