The Height Structure of the Solar Atmosphere from the Extreme-Ultraviolet Perspective

1998 ◽  
Vol 504 (2) ◽  
pp. L127-L130 ◽  
Author(s):  
J. Zhang ◽  
S. M. White ◽  
M. R. Kundu
Keyword(s):  
Solar Atmosphere ◽  
Extreme Ultraviolet

The Sun

2015 ◽  
Author(s):  
Joanna D. Haigh ◽  
Peter Cargill
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Atmosphere ◽  
Space Weather ◽  
Extreme Ultraviolet ◽  
The Sun ◽  
Base Level ◽  
Earth’S Climate ◽  
The Magnetic Field ◽  
Terrestrial Magnetic Field

This chapter discusses how there are four general factors that contribute to the Sun's potential role in variations in the Earth's climate. First, the fusion processes in the solar core determine the solar luminosity and hence the base level of radiation impinging on the Earth. Second, the presence of the solar magnetic field leads to radiation at ultraviolet (UV), extreme ultraviolet (EUV), and X-ray wavelengths which can affect certain layers of the atmosphere. Third, the variability of the magnetic field over a 22-year cycle leads to significant changes in the radiative output at some wavelengths. Finally, the interplanetary manifestation of the outer solar atmosphere (the solar wind) interacts with the terrestrial magnetic field, leading to effects commonly called space weather.

scholarly journals Solar EUV Photoelectric Observations from Skylab

1974 ◽  
Vol 57 ◽  
pp. 497-500
Author(s):  
E. M. Reeves ◽  
P. V. Foukal ◽  
M. C. E. Huber ◽  
R. W. Noyes ◽  
E. J. Schmahl ◽  
...  
Keyword(s):  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Three Dimensional ◽  
Active Regions ◽  
Normal Incidence ◽  
Ionic Species ◽  
Ultraviolet Region ◽  
Spatial Image ◽  
Lyman Continuum ◽  
Solar Blind

Most of the atomic species originating in the solar atmosphere between the upper chromosphere and the corona have their strong characteristic wavelengths in the extreme ultraviolet region of the spectrum. A simple normal-incidence spectrometer system with solar blind detectors such as the Harvard instrument operating between approximately 250 Å and 1350 Å is ideally suited for observing in this most interesting range of the solar atmosphere where the temperature rises outward from 104 to 3 × 106 K. The temperature range represented by the various atomic and ionic species in the extreme ultraviolet is associated with many types of solar structure, prominences and filaments, the supergranulation cells and network, active regions and their associated loop structures and other features. Simultaneous observations in lines of different characteristic temperatures provide a three-dimensional probe of the solar atmosphere. In the instrument, the principal polychromatic position observes the Lyman continuum, Lα, C II, C III, O IV, O VI, and Mg x with seven detectors simultaneously from the same spatial image element, 5″ in size. Approximately 60 additional polychromatic positions are used routinely to carry out specific observing programs, for example, covering several lines of a given stage of ionization, observing lines or continuum from specific species of interest such as helium in prominences, comparing combinations of lines from a given ionic species such as O v where the relative intensities give a rather direct measurement of the density at a given temperature, or measuring differing positions in the Lyman continuum providing intensity measurements which can be interpreted in terms of the departure from ionization equilibrium.

A Discussion on the physics of the solar atmosphere - The quiet Sun in the extreme ultraviolet

1976 ◽  
Vol 281 (1304) ◽  
pp. 319-329 ◽  
Keyword(s):  
Transition Region ◽  
Solar Atmosphere ◽  
Spherical Symmetry ◽  
Extreme Ultraviolet ◽  
Coronal Holes ◽  
Intensity Data ◽  
Periodic Oscillations ◽  
Quiet Sun ◽  
Temperature Range ◽  
Ultraviolet Spectrometer

Observations of the quiet Sun with the Harvard extreme ultraviolet spectrometer on the Skylab mission are reported for the chromosphere, transition region, and corona. The changing structure of the network is examined over the temperature range from 10 4 to 1.5 x 10 6 K, and the distribution of intensities in the cell interiors and the network examined from the standpoint of creating characteristic models. Observations of traces of periodic oscillations at 300 s in the cells for T ⩽ 2 x 10 4 is reported together with the absence of any periodic contributions at higher temperatures or periodic effects at any height in the network elements. Frequent non-periodic brightenings are observed, however, and their characteristics discussed. Observations of the increased thickness of the transition region in coronal holes, as well as other properties are discussed in limited detail. Observations of the centre-to-limb behaviour of transition region and coronal lines are used to construct coronal models, and the assumptions of spherical symmetry evaluated from the intensity data. The effects of spicules on the limb and disk data are discussed in relation to the observations.

A Discussion on the physics of the solar atmosphere - The solar extreme ultraviolet continuum

1976 ◽  
Vol 281 (1304) ◽  
pp. 305-317
Keyword(s):  
Solar Atmosphere ◽  
Theoretical Consideration ◽  
Extreme Ultraviolet ◽  
The Sun ◽  
Temperature Minimum ◽  
Continuous Emission ◽  
Ultraviolet Continuum ◽  
Unknown Source

The most recent results on the e.u.v. continuous emission of the Sun are reviewed, and intercompared. They are discussed in terms of the distribution of temperature in the solar atmosphere particularly in view of determining more precisely the value of the temperature minimum. An attempt will be made to interpret the discrepancies which exist between the observations and the results deduced from theoretical consideration in terms of an unknown source of continuous opacity.

scholarly journals Magnetically coupled atmosphere, fast sausage MHD waves, and forced magnetic field reconnection during the SOL2014-09-10T17:45 flare

2020 ◽  
Vol 643 ◽  
pp. A140
Author(s):  
H. Mészárosová ◽  
P. Gömöry
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Free Field ◽  
Mhd Waves ◽  
Field Energy ◽  
Plasma Flows ◽  
The Individual ◽  
The Waves

Aims. We study the physical properties and behaviour of the solar atmosphere during the GOES X1.6 solar flare on 2014 September 10. Methods. The steady plasma flows and the fast sausage MHD waves were analysed with the wavelet separation method. The magnetically coupled atmosphere and the forced magnetic field reconnection were studied with the help of the Vertical-Current Approximation Non-linear Force-Free Field code. Results. We studied a mechanism of MHD wave transfer from the photosphere without dissipation or reflection before reaching the corona and a mechanism of the wave energy distribution over the solar corona. We report a common behaviour of (extreme)ultraviolet steady plasma flows (speed of 15.3 → 10.9 km s−1) and fast sausage MHD waves (Alfvén speed of 13.7 → 10.3 km s−1 and characteristic periods of 1587 → 1607 s), propagating in cylindrical plasma waveguides of the individual atmospheric layers (photosphere → corona) observed by SDO/AIA/HMI and IRIS space instruments. A magnetically coupled solar atmosphere by a magnetic field flux tube above a sunspot umbra and a magnetic field reconnection forced by the waves were analysed. The solar seismology with trapped, leakage, and tunnelled modes of the waves, dissipating especially in the solar corona, is discussed with respect to its possible contribution to the outer atmosphere heating. Conclusions. We demonstrate that a dispersive nature of fast sausage MHD waves, which can easily generate the leaky and other modes propagating outside of their waveguide, and magnetic field flux tubes connecting the individual atmospheric layers can distribute the magnetic field energy across the active region. This mechanism can contribute to the coronal energy balance and to our knowledge on how the coronal heating is maintained.

scholarly journals An Analysis of Spikes in Atmospheric Imaging Assembly (AIA) Data

Solar Physics ◽  
2021 ◽  
Vol 296 (12) ◽  
Author(s):  
Peter R. Young ◽  
Nicholeen M. Viall ◽  
Michael S. Kirk ◽  
Emily I. Mason ◽  
Lakshmi Pradeep Chitta
Keyword(s):  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Solar Surface ◽  
Coronal Holes ◽  
Active Regions ◽  
Detection Algorithm ◽  
Solar Dynamics Observatory ◽  
Processing Pipeline ◽  
High Resolution Images ◽  
Solar Dynamics

AbstractThe Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) returns high-resolution images of the solar atmosphere in seven extreme ultraviolet (EUV) wavelength channels. The images are processed on the ground to remove intensity spikes arising from energetic particles hitting the instrument, and the despiked images are provided to the community. In this article, a three-hour series of images from the 171 Å channel obtained on 28 February 2017 was studied to investigate how often the despiking algorithm gave false positives caused by compact brightenings in the solar atmosphere. The latter were identified through spikes appearing in the same detector pixel for three consecutive frames. 1096 examples were found from the 900 image frames. These “three-spikes” were assigned to 126 dynamic solar features, and it is estimated that the three-spike method identifies 19% of the total number of features affected by despiking. For any ten-minute sequence of AIA 171 Å images there are around 37 solar features that have their intensity modified by despiking. The features are found in active regions, quiet Sun, and coronal holes and, in relation to solar surface area, there is a greater proportion within coronal holes. In 96% of the cases, the despiked structure is a compact brightening with a size of two arcsec or less, and the remaining 4% have narrow, elongated structures. By applying an EUV burst detection algorithm, we found that 96% of the events could be classified as EUV bursts. None of the spike events are rendered invisible by the AIA processing pipeline, but the total intensity over an event’s lifetime can be reduced by up to 67%. Users are recommended to always restore the original intensities in AIA data when studying short-lived or rapidly evolving features that exhibit fine-scale structure.

scholarly journals Explosive events in the solar atmosphere seen in extreme-ultraviolet emission lines

2005 ◽  
Vol 431 (1) ◽  
pp. 339-344 ◽  
Author(s):  
J. E. Mendoza-Torres ◽  
J. P. Torres-Papaqui ◽  
K. Wilhelm
Keyword(s):  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Emission Lines ◽  
Ultraviolet Emission ◽  
Explosive Events

A burst model for line emission in the solar atmosphere. II - Coronal extreme ultraviolet lines

1992 ◽  
Vol 398 ◽  
pp. 692 ◽  
Author(s):  
U. Feldman ◽  
J. M. Laming ◽  
P. Mandelbaum ◽  
W. H. Goldstein ◽  
A. Osterheld
Keyword(s):  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Line Emission
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