Results 71 to 80 of about 881 (218)

Nowcasting Solar EUV Irradiance With Photospheric Magnetic Fields and the Mg II Index

Space Weather, Volume 22, Issue 4, April 2024.
Abstract A new method to nowcast spectral irradiance in extreme ultraviolet (EUV) and far ultraviolet (FUV) bands is presented here, utilizing only solar photospheric magnetograms and the Mg II index (i.e., the core‐to‐wing ratio). The EUV and FUV modeling outlined here is a direct extension of the SIFT (Solar Indices Forecasting Tool) model, based on ...
Kara L. Kniezewski, Samuel J. Schonfeld, Carl J. Henney   +2 more
wiley   +1 more source

Kink Instability of Flux Ropes in Partially Ionized Plasmas

The Astrophysical Journal
In the solar atmosphere, flux ropes are subject to current-driven instabilities that are crucial in driving plasma eruptions, ejections, and heating. A typical ideal magnetohydrodynamics instability developing in flux ropes is the helical kink, which ...
Giulia Murtas, Andrew Hillier, Ben Snow
doaj   +1 more source

Probabilistic Short‐Term Solar Driver Forecasting With Neural Network Ensembles

Space Weather, Volume 22, Issue 3, March 2024.
Abstract Space weather indices are used to drive forecasts of thermosphere density, which directly affects objects in low‐Earth orbit (LEO) through atmospheric drag force. A set of proxies and indices (drivers), F10.7, S10.7, M10.7, and Y10.7 are used as inputs by the JB2008, (https://doi.org/10.2514/6.2008‐6438) thermosphere density model.
Joshua D. Daniell, Piyush M. Mehta
wiley   +1 more source

Multiline Spectropolarimetric Observation of Flare Ribbon Fine Structures with ViSP/DKIST

The Astrophysical Journal
We present an analysis of flare ribbon fine structure observed during a GOES C2-class flare using high spatial and spectral resolution multiline spectropolarimetric observations from the ViSP instrument at the DKIST. The ViSP recorded full Stokes spectra
Rahul Yadav, Maria D. Kazachenko, Gianna Cauzzi, Cole A. Tamburri, Marcel Corchado, Ryan French   +5 more
doaj   +1 more source

Magnetoacoustic Portals and the Basal Heating of the Solar Chromosphere

The Astrophysical Journal, 2006
We show that inclined magnetic field lines at the boundaries of large-scale convective cells (supergranules) provide "portals" through which low-frequency ( 5 mHz) acoustic waves, which are believed to provide the dominant source of wave heating of the chromosphere. This result opens up the possibility that low-frequency magnetoacoustic waves provide a
James D. Armstrong, Stuart M. Jefferies, Bernhard Fleck, Alessandro Cacciani, T. J. Bogdan, T. J. Bogdan, Scott W. McIntosh   +6 more
openaire   +2 more sources

The IRIS2+ Inversion Tool: Recovering the Radiative Losses and the Thermodynamics in the Lower Solar Atmosphere

The Astrophysical Journal
We introduce an improved and fast inversion tool that is able to provide the thermodynamics of the solar atmosphere from the photosphere to the top of the chromosphere, as well as the integrated radiative losses (IRLs) in the chromosphere for data ...
Alberto Sainz Dalda, Jaime de la Cruz Rodríguez, Viggo Hansteen, Bart De Pontieu, Milan Gošić   +4 more
doaj   +1 more source

Numerical Simulations and Observations of Mg ii in the Solar Chromosphere

The Astrophysical Journal, 2023
The Mg ii h and k lines are among the best diagnostic tools of the upper solar chromosphere. This region of the atmosphere is of particular interest, as it is the lowest region of the Sun’s atmosphere where the magnetic field is dominant in the ...
Viggo H. Hansteen, Juan Martinez-Sykora, Mats Carlsson, Bart De Pontieu, Milan Gošić, Souvik Bose   +5 more
doaj   +1 more source

Calcium Bright Knots and the Formation of Chromospheric Anemone Jets on the Sun

The Astrophysical Journal Letters
Space-based observations show that the solar atmosphere from the solar chromosphere to the solar corona is filled with small-scale jets and is linked with small-scale explosions.
Kunwar Alkendra Pratap Singh, Keisuke Nishida, Kazunari Shibata   +2 more
doaj   +1 more source

Heating of the solar chromosphere by ionization pumping

The Astrophysical Journal, 1981
A new theory is proposed to explain the heating of the solar chromosphere, and possibly the corona, by the dissipation of hydrodynamic compression waves. The basis of the dissipative mechanism, here referred to as ionization pumping, is hysteresis caused by irreversible relaxation of the chromospheric medium to ionization equilibrium following pressure
openaire   +1 more source

High frequency oscillations in the solar chromosphere and their connection with heating [PDF]

Proceedings of the International Astronomical Union, 2007
AbstractHigh frequency acoustic waves have been suggested as a source of mechanical heating in the quiet solar chromosphere. To investigate this, we have observed intensity oscillations of several lines in the frequency interval 1.64-70mHz using data from the VTT Tenerife and the Dunn Solar Telescope at the National Solar Observatory.
Aleksandra Andic, M. Mathioudakis, F. P. Keenan, D. B. Jess, D. S. Bloomfield   +4 more
openaire   +1 more source