Falconer, David A.

Moore, Ronald L.

Snyder, Ian R.

Sterling, Alphonse C.

NASA Technical Reports Server

Exploring He II 304 Å Spicules and 
Macrospicules at the Solar Limb
Alphonse C. Sterling1, Ian R. Snyder2,3,4 ,
David A. Falconer5,1, & Ronald L. Moore5,1
1. NASA/MSFC
2. Vassar College
3. NASA/MSFC Research Experience for Undergraduates (REU) Student
4. Companion poster: SH51C-4179
5. U of Alabama Huntsville
https://ntrs.nasa.gov/search.jsp?R=20150001482 2019-08-31T14:19:37+00:00Z
A. Sterling, Dec 2014 AGU, San Francisco
Macrospicules (in 304 Å He II): Bohlin et al. (1975), Withbroe et al. (1976).
EUV Spicules:  e.g., Xia et al. (2005).
A. Sterling, Dec 2014 AGU, San Francisco
There is a “sea” of EUV spicules at ~30˝
above white-light limb (≡“EUV spicules”).
Occasionally there are very tall ejections
(≡“macrospicules”).   Our macrospicules have
hotter “coronal jet” counterparts. 
Main Question: Are the macrospicules larger
versions of the EUV spicules?
Explore this by studying properties of both
features.
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A. Sterling, Dec 2014 AGU, San
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AIA 304 Å He II.  Movies of polar regions.
12 sec cadence (EUV spicules), 36 sec cadence (macrospicules).
For EUV spicules (33 in total).  Each movie covered periods of ~90 min,
concurrent with Hinode HOP runs.
Three periods during 2014; no coronal holes. (Movies 1-3.)
One period during 2011, when there was a small coronal hole.  (Movie 4.)
Selection not totally random, but included some “minor” events.
Macrospicules; five in total: 
One occurred during Movie 3.  
Four others from 3 additional movies, all from 2010.
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Data Sets
A. Sterling, Dec 2014 AGU, San
Francisco
Determined length-with-time trajectory of each
feature. 
Three measurements, 1σ error bars.
Determined lifetime, from “committed” start, until fall
or fade.
Determined velocities from the length measurements
(some smoothing applied).
Fit with second-order polynomial, to determine best-
fit acceleration:                              .     
Compare obtained acceleration with that of solar
gravity. 
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Analysis
h(t) = h(0)− at2
A. Sterling, Dec 2014 AGU, San
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A. Sterling, Dec 2014 AGU, San
Francisco
A. Sterling, Dec 2014 AGU, San
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A. Sterling, Dec 2014 AGU, San
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A. Sterling, Dec 2014 AGU, San
Francisco
Length vs. Maximum
Velocity
Velocities:
EUV Spicules: 20 ~ 70, 150 km/s
Macrospicules: ~100---200 km/
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Lengths:
EUV Spicules: 10K ~ 20K, ~30K km
Macrospicules: ~40K---100K km
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A. Sterling, Dec 2014 AGU, San
Francisco
Slope: 0.16±0.03
A. Sterling, Dec 2014 AGU, San
Francisco
Lifetime vs. Maximum
Velocity
Lifetimes:
EUV Spicules: 100 ~ 1000 sec
Macrospicules: ~1000 --- 2000 sec
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A. Sterling, Dec 2014 AGU, San
Francisco
Slope: 3.4±1.3
A. Sterling, Dec 2014 AGU, San
Francisco
Fextra could be due to, e.g., thermal energy
(pressure)
ratio [=g/a] < 1 =>    F = -mg + Fextra
Acceleration Ratio vs. Maximum Velocity
Plots
A. Sterling, Dec 2014 AGU, San
Francisco
The above suggests that there are quantitative
differences between EUV spicules and
macrospicules.  There is also an important
morphological difference between the two
features:  Brightenings (or lack thereof) at their
respective bases at onset time...
A. Sterling, Dec 2014 AGU, San
Francisco
A. Sterling, Dec 2014 AGU, San
Francisco
A. Sterling, Dec 2014 AGU, San
Francisco
Indications are that macrospicules (as defined here) and EUV spicules have
some differences in behavior (especially length vs. max velocity), and appearance
(base brightenings in macrospicules). 
From De Pontieu et al. (2011) and Pereira et al. (2014), “EUV spicules” are
almost certainly “spicules” in many cases.  Our macrospicules are “coronal jets.”
 So our results suggest that spicules and coronal jets have different driving
mechanisms. (Still preliminary.)
Among EUV spicules themselves, those in polar coronal holes tend to be longer
and faster than those in quiet-Sun polar regions.
Both EUV spicules and macrospicules follow largely parabolic profiles.
 Macrospicules tend to fade in EUV 304 Å more often than do the EUV spicules.
Both EUV spicules and macrospicules tend to have g/a>1, suggesting an
auxiliary force besides gravity is acting on the material.  (Agrees with Moschou et
al. 2013.)
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Summary of Results
A. Sterling, Dec 2014 AGU, San
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A. Sterling, Dec 2014 AGU, San
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A. Sterling, Dec 2014 AGU, San
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A. Sterling, Dec 2014 AGU, San
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Length vs. Lifetime


Exploring He II 304 A Spicules and Macrospicules at the Solar Limb

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