Solar eclipse

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

Solar eclipse effects observed in the planetary boundary layer over a desert

Abstract: Boundary-layer meteorologicalmeasurements were made before, during, and after theMay 10, 1994 partial (94%) solar eclipse over thedesert at the Atmospheric Profiler Research Facilityat White Sands Missile Range, New Mexico, U.S.A. A largenumber of sensors were located in the middle of theTularosa Basin to measure mean and turbulentquantities and the refractive index structureparameter (Cn2). This event permitted a rareopportunity to measure, examine, and document theeffects upon the atmospheric boundary layer of asudden cut-off and subsequent turn-on of the sun'sradiant energy. At the peak of the eclipse, whichoccurred for more than three hours, all of the heatexchange parameters were affected, the turbulentprocesses were diminished, and the refractive indexstructure parameter decreased dramatically. A time-heightdisplay from the FM-CW radar shows a Kelvin–Helmholtzwave that developed during theeclipse. The results of several analyses arepresented to document and characterize the eclipse-modifiedboundary layer.

The solar eclipse of 2006 and the origin of raylike features in the white-light corona

Abstract: Solar eclipse observations have long suggested that the white-light corona is permeated by long fine rays. By comparing photographs of the 2006 March 29 total eclipse with current-free extrapolations of photospheric field measurements and with images from the Solar and Heliospheric Observatory (SOHO), we deduce that the bulk of these linear features fall into three categories: (1) polar and low-latitude plumes that overlie small magnetic bipoles inside coronal holes, (2) helmet streamer rays that overlie large loop arcades and separate coronal holes of opposite polarity, and (3) pseudostreamer rays that overlie twin loop arcades and separate coronal holes of the same polarity. The helmet streamer rays extend outward to form the plasma sheet component of the slow solar wind, while the plumes and pseudostreamers contribute to the fast solar wind. In all three cases, the rays are formed by magnetic reconnection between closed coronal loops and adjacent open field lines. Although seemingly ubiquitous when seen projected against the sky plane, the rays are in fact rooted inside or along the boundaries of coronal holes.

SAMI3 prediction of the impact of the 21 August 2017 total solar eclipse on the ionosphere/plasmasphere system

Abstract: We present quantitative predictions of the impact of the upcoming total solar eclipse on the ionosphere and plasmasphere using the Naval Research Laboratory (NRL) model Sami3 is Also a Model of the Ionosphere (SAMI3). The eclipse will occur over the continental United States on 21 August 2017. Our simulation results indicate that in the vicinity of the eclipse (1) the total electron content (TEC) decreases by up to ∼ 5 TEC units (TECU; 1 TECU = ×1016 m−2) which is a ∼ 35% decrease in TEC, (2) the electron density decreases by a factor of ∼ 50% in the F region, (3) the electron temperature decreases by up to ∼800 K in the plasmasphere, and (4) the O+ velocity changes from ∼40 m s−1 upward to ∼20 m s−1 downward in the F region. Interestingly, the continental size modification of the ionospheric conductance modifies the global electric field, which should lead to measurable changes in the TEC in the southern conjugate hemisphere ( ≲1 TECU).

Mapping the Distribution of Electron Temperature and Fe Charge States in the Corona with Total Solar Eclipse Observations

Abstract: The inference of electron temperature from the ratio of the intensities of emission lines in the solar corona is valid only when the plasma is collisional. Once collisionless, thermodynamic ionization equilibrium no longer holds, and the inference of an electron temperature and its gradient from such measurements is no longer valid. At the heliocentric distance where the transition from a collision-dominated to a collisionless plasma occurs, the charge states of different elements are established, or frozen-in. These are the charge states which are subsequently measured in interplanetary space. We show in this study how the 2006 March 29 and 2008 August 1 eclipse observations of a number of Fe emission lines yield an empirical value for a distance, which we call Rt , where the emission changes from being collisionally to radiatively dominated. Rt ranges from 1.1 to 2.0 R ☉, depending on the charge state and the underlying coronal density structures. Beyond that distance, the intensity of the emission reflects the distribution of the corresponding Fe ion charge states. These observations thus yield the two-dimensional distribution of electron temperature and charge state measurements in the corona for the first time. The presence of the Fe X 637.4 nm and Fe XI 789.2 nm emission in open magnetic field regions below Rt , such as in coronal holes and the boundaries of streamers, and the absence of Fe XIII 1074.7 nm and Fe XIV 530.3 nm emission there indicate that the sources of the solar wind lie in regions where the electron temperature is less than 1.2 × 106 K. Beyond Rt , the extent of the Fe X [Fe9+] and Fe XI emission [Fe10+], in comparison with Fe XIII [Fe12+] and Fe XIV [Fe13+], matches the dominance of the Fe10+ charge states measured by the Solar Wind Ion Composition Spectrometer, SWICS, on Ulysses, at –43° latitude at 4 AU, in March-April 2006, and Fe9+ and Fe10+ charge states measured by SWICS on the Advanced Composition Explorer, ACE, in the ecliptic plane at 1 AU, at the time of both eclipses. The remarkable correspondence between these two measurements establishes the first direct link between the distribution of charge states in the corona and in interplanetary space.