Editing Chromosphere (section)

== Phenomena ==

{{further|Solar phenomena}}

[[file:the Solar Chromosphere at the highest possible resolution.png|thumb|right|High-resolution observations of the solar chromosphere show hair-like spicules, here shown in a false colored image made in borderline ultraviolet radiation of calcium K-line.]]

Many different phenomena can be observed in chromospheres.

=== Plage ===

{{main|Solar plage}}

A plage is a particularly bright region within stellar chromospheres, which are often associated with magnetic activity.<ref name="degrijs21" />

=== Spicules ===

{{main|Solar spicule}}

The most commonly identified feature in the solar chromosphere are spicules. Spicules rise to the top of the chromosphere and then sink back down again over the course of about 10 minutes.<ref>{{Cite book |last=Wilkinson |first=John |url=https://www.worldcat.org/oclc/773089685 |title=New eyes on the sun : a guide to satellite images and amateur observation |date=2012 |publisher=Springer |isbn=978-3-642-22839-1 |location=Berlin |oclc=773089685}}</ref>

=== Oscillations ===

Since the first observations with the instrument SUMER on board [[Solar and Heliospheric Observatory|SOHO]], periodic oscillations in the solar chromosphere have been found with a frequency from {{Val|3|u=mHz}} to {{Val|10|u=mHz}}, corresponding to a characteristic periodic time of three minutes.<ref>{{cite journal |author1=Carlsson, M. |author2=Judge, P. |author3=Wilhelm, K. |title= SUMER Observations Confirm the Dynamic Nature of the Quiet Solar Outer Atmosphere: The Internetwork Chromosphere | journal= The Astrophysical Journal| year= 1997 | volume= 486|issue=1 |page= L63 | bibcode = 1997ApJ...486L..63C | doi = 10.1086/310836 |arxiv = astro-ph/9706226 |s2cid=119101577 }}</ref> Oscillations of the radial component of the plasma velocity are typical of the high chromosphere. The photospheric granulation pattern usually has no oscillations above {{Val|20|u=mHz}}; however, higher frequency waves ({{Val|100|u=mHz}}, or a {{Val|10|u=s}} period) were detected in the solar atmosphere (at temperatures typical of the transition region and corona) by [[TRACE]].<ref>{{cite journal | author= De Forest, C.E. | title= High-Frequency Waves Detected in the Solar Atmosphere | journal= The Astrophysical Journal | year= 2004 | volume= 617| issue= 1 | page= L89 | bibcode=2004ApJ...617L..89D | doi=10.1086/427181 | doi-access= free }}</ref>

=== Loops ===

{{see also|Coronal loop}}

Plasma loops can be seen at the border of the solar disk in the chromosphere. They are different from [[Solar prominence|solar prominences]] because they are concentric arches with maximum temperature of the order {{Val|0.1|u=MK}} (too low to be considered coronal features). These cool-temperature loops show an intense variability: they appear and disappear in some UV lines in a time less than an hour, or they rapidly expand in 10–20 minutes. Foukal<ref>{{cite journal |author= Foukal, P.V. |title= The pressure and energy balance of the cool corona over sunspots |journal= The Astrophysical Journal |year= 1976 |volume= 210 |page= 575 |bibcode=1976ApJ...210..575F |doi=10.1086/154862 }}</ref> studied these cool loops in detail from the observations taken with the EUV spectrometer on [[Skylab]] in 1976. When the plasma temperature of these loops becomes coronal (above {{Val|1|u=MK}}), these features appear more stable and evolve over longer times.