Solar eclipse

About: Solar eclipse is a research topic. Over the lifetime, 2737 publications have been published within this topic receiving 22625 citations.

Global Non-Potential Magnetic Models of the Solar Corona During the March 2015 Eclipse

Abstract: Seven different models are applied to the same problem of simulating the Sun's coronal magnetic field during the solar eclipse on 2015 March 20. All of the models are non-potential, allowing for free magnetic energy, but the associated electric currents are developed in significantly different ways. This is not a direct comparison of the coronal modelling techniques, in that the different models also use different photospheric boundary conditions, reflecting the range of approaches currently used in the community. Despite the significant differences, the results show broad agreement in the overall magnetic topology. Among those models with significant volume currents in much of the corona, there is general agreement that the ratio of total to potential magnetic energy should be approximately 1.4. However, there are significant differences in the electric current distributions; while static extrapolations are best able to reproduce active regions, they are unable to recover sheared magnetic fields in filament channels using currently available vector magnetogram data. By contrast, time-evolving simulations can recover the filament channel fields at the expense of not matching the observed vector magnetic fields within active regions. We suggest that, at present, the best approach may be a hybrid model using static extrapolations but with additional energization informed by simplified evolution models. This is demonstrated by one of the models.

Atmospheric turbulence decay during the solar total eclipse of 11 August 1999

Abstract: The studies of turbulence decay were based in the past on measurements carried out in neutrally stratified wind tunnels and, more recently, on large-eddy simulation runs. Here the atmospheric turbulence decay process during the solar total eclipse of 11 August 1999 is examined. Thus a rapid transition from convective boundary-layer turbulence to that of a neutral or slightly stable one is considered. A u-v-w propeller anemometer and a fast response temperature sensor located in northern France on top of a 9-m mast recorded the turbulence observations. The measurements, in terms of turbulent kinetic energy decay with time, were found to be in good agreement with those prescribed by a theoretical model of turbulence decay recently proposed. In particular, it was found that the exponent of the power law describing the decay process has the value -2.

Suppression of the Polar Tongue of Ionization During the 21 August 2017 Solar Eclipse

Abstract: It has long been recognized that during solar eclipses, the ionosphere-thermosphere system changes greatly within the eclipse shadow, due to the rapid reduction of solar irradiation. However, the concept that a solar eclipse impacts polar ionosphere behavior and dynamics as well as magnetosphere-ionosphere coupling has not been appreciated. In this study, we investigate the potential impact of the 21 August 2017 solar eclipse on the polar tongue of ionization (TOI) using a high-resolution, coupled ionosphere-thermosphere-electrodynamics model. The reduction of electron densities by the eclipse in the middle latitude TOI source region leads to a suppressed TOI in the polar region. The TOI suppression occurred when the solar eclipse moved into the afternoon sector. The Global Positioning System total electron content observations show similar tendency of polar region total electron content suppression. This study reveals that a solar eclipse occurring at middle latitudes may have significant influences on the polar ionosphere and magnetosphere-ionosphere coupling. Plain Language Summary The ionosphere is the ionized part of Earth’s upper atmosphere extending from about 60 to 1,000 km. During solar storm events, the dayside ionospheric plasma can be transported from middle latitude into the polar region by the electric field, leading to a “tongue-like” structure, which is called the “tongue of ionization (TOI).” Meanwhile, the solar eclipse can dramatically decrease the ionospheric plasma density within the Moon’s shadow by the reduction of solar irradiation. Since the TOI structure is closely related to the middle latitude plasma density, it is interesting to explore the solar eclipse influences at middle latitudes on the polar ionospheric behavior associated with the polar TOI structure. On the basis of high-resolution simulations of the 21 August 2017 solar eclipse, it was reported that a significantly suppressed TOI occurred during the solar eclipse. The results provide new insights into the broad impacts of middleand highlatitude eclipses on the behavior and dynamics of the high-latitude ionosphere and the geospace system.

Detection of Short-Period Coronal Oscillations during the Total Solar Eclipse of 24 October, 1995

Abstract: An experiment to search for short-period oscillations in the solar corona was conducted during the total solar eclipse of 1995 October 24 at Kalpi, India The intensity in the continuum, centred around 5500 A and with a passband having a half-width of 240 A, was recorded at a counting rate of 20 Hz using a thermoelectric-liquid cooled photomultiplier The power-spectrum analysis of the data reveals that most of the power is contained in 6 frequencies below 02 Hz A least-square analysis gives the periods of the 6 frequency components to be 565, 195, 135, 80, 61, and 53 s These oscillations are found to be sinusoidal, and their amplitudes are found to lie in the rangelinebreak 02–13% of the coronal brightness Assuming these oscillations to be fast magnetosonic modes, the calculations indicate the availability of enough flux for the heating of the active regions in the solar corona

The Effect of the 1999 Total Solar Eclipse on the Ionosphere

Abstract: The localised “night” created as the moon's shadow travelled across the Earth during the total solar eclipse of 11th August 1999, produced changes in the ionosphere across Europe that were monitored with a variety of modern instrumentation. The passage of the 100km wide, super-sonic lunar shadow offered the opportunity to examine the changes in electron densities, radio absorption, neutral wind patterns and the possible generation of waves in the layers of the ionosphere. All these for an event for which the cause of the disturbance can be calculated with accuracy. Reported here are the results from the vertical ionosondes located under the path of totality and in the partial eclipse region and dual frequency GPS TEC measurements. The ionosondes showed that even in the partial shadow the peak electron densities of the F & E ionospheric layers decreased by as much as 20–35%. The TEC measurements showed that the vertical equivalent line integrated electron density dropped by 15% at the 97% partial eclipse north of the path of totality. The consequences of these observations are discussed in relation to making model predictions.