HAO Science Objectives for HMI

1
Solar Dermatology - A brief tour through the
esoteric terminology


Anemone Arcade Bright Point Coronal Hole
Coronal Mass Ejection Coronal Rain
Cusp Disparation Brusque Erupting Filament
Eruptive Prominence Evershed Flow Faculae
Filamant Filigree Moreton Wave Moss
Nanoflare Network Neutral Line Plage Polar
Plume Pore Postflare Loops Prominence Streamer
Belt Spicule Sunspot Penumbra Sunspot
Umbra Supergranulation Two-Ribbon Flare Tadpole
2
The blemished sun! Ourselves, the
dermatologists.


In 1611, Galileo wrote "Spots are on the surface
of the solar body where they are produced and
also dissolved, some in shorter and others in
longer periods. They are carried around the Sun
an important occurrence in itself." Galileo's
drawings from 2 June 8 July 1613 are shown as a
movie above. Galileos ideas got him into
trouble with church leaders, because all heavenly
bodies were supposed to be perfect, that is
without blemish.
3


Coronal Hole A region of the Suns corona that
appears dark in pictures taken with a
coronagraph, and that shows up as a void in X-ray
and extreme ultraviolet images. Coronal holes are
of very low density (typically 100 times lower
than the rest of the corona) and have an open
magnetic field structure. This open structure
allows charged particles to escape from the Sun
and results in coronal holes being the primary
source of the solar wind.
4
Anemone (Windflower) An active region that,
when viewed in the corona, does not have
connections to any other magnetic concentrations.
This often happens when an active region emerges
in a coronal hole.


Arcade A system of loops observed in the solar
atmosphere, thought to be structured by magnetic
fields and brightened after a flare. Trace 171
Angstrom image,1 x 106 K 8 Nov 2000. (Loops are
on the order of 100 Mm above the loop footpoints.)
5
Q What are some of the most outstanding
questions in Solar Physics? A Spiro
Antiochos Why do the loops in the corona look
so smooth if they are supposed to be tangled and
mangled by the photospheric motions? There is
thought to be a tangling that produces complex
geometries that, in turn, lead to nanoflares
releasing energy through magnetic reconnection.
However, in the TRACE images, the loops look
smooth and parallel, i.e., combed.


6
Coronal Rain Material that condenses in the
Suns corona and falls along curved paths onto
the chromosphere. Observed in H-alpha light at
the solar limb above strong sunspots, coronal
rain consists of gas ejected by a loop prominence
that returns, several hours later, along the
outline of the now invisible loop.


Coronal Mass Ejection A huge eruption of
material from the Suns corona into
interplanetary space. CMEs are the most energetic
of solar explosions and eject up to100 billion
kilograms of multi-million-degree plasma at
speeds ranging from 10 to 2,000 km/s. They often
look like bubbles. CMEs originate in regions
where the magnetic field is closed. These storms
can disrupt power grids, damage satellite
systems, and threaten the safety of astronauts.
(X17 and X10 flares and the two associated CMEs,
LASCO C2)
7
Filament A strand of relatively cool gas
suspended by magnetic fields over the solar
photosphere so that it appears as a dark line
over the Suns disk. A filament on the limb of
the Sun seen in emission against the dark sky is
called a prominence. Filaments often mark areas
of magnetic shearing and can be seen only in the
centers of strong spectral line, such as H-alpha
or the H and K lines of calcium.


8
Filament This brief movie shows 3 frames. The
first shows the Sun in white light taken by the
MDI instrument. This instrument observes the
Sun's surface and does not "see" the filaments at
all. However, this image is then replaced by an
EIT 195 instrument image in which the subtly
darker filaments can be discerned. Finally, an
EIT 304 image is revealed underneath in which the
filaments are even easier to see.


9
Erupting Filament The disappearance of a
filament, often associated with a flare. The
filament erupts into the corona. There is an
activation phase with increased mass motions,
expansion, etc. When these eruptions are
observed on the limb - they are known as erupting
prominences.


Disparation Brusque The sudden disappearance of
a filament.
A filament in Jan 2007 shown in O V line and a
day later caught as it is erupting.
10
Sunspot Umbra the dark core of a sunspot, cooler
than the surrounding photosphere because is
suppresses convection. Average size is 10000
km, but can be as large as 60000 km.


Sunspot Penumbra the lighter areas, marked by a
radial filamentary structure. Typical size is
5000 km. Waves are observed to move across the
penumbral structures. Structure is thought to
be uncombed. Image credit Friedrich
Woeger, KIS, and Chris Berst and Mark Komsa -
taken here at the Dunn Tower.
11
Evershed Flow The horizontal flow of gas in the
penumbrae of a sunspots the effect is named
after its discoverer, the English astronomer John
Evershed (1864-1956). The maximum outflow
velocity is about 2 km/s. Image from Tom Berger,
Dutch Open Telescope.


12
Q What are some of the most outstanding
questions in Solar Physics? A Gene Parker
The Sunspot is without explanation. Why is the
Sun obliged to create them? We understand a lot
about them, excepting why the Sun is compelled by
the basic laws of physics to create cool,
magnetic spots. .

• ? Other main sequence stars show evidence of
  starspots and cyclical magnetic activity.
• ? Other stars show evidence of an atmospheric
  temperature inversion which means that coronal
  heating and corona formation is a universal
  process for cool stars.

13
Granulation caused by convection, the grainy
appearance of the solar photosphere is produced
by the tops of these convective cells.The rising
part of the granules is located in the center
where the plasma is hotter. The outer edge of the
granules is darker due to the cooler descending
plasma. The diameter of a typical granule is on
the order of 1000km and lasts 8 to 20 minutes
before dissipating. The vertical flow is 1
km/s. Hinode movie in G-band (430 nm) and Ca II
H (397 nm) showing granules and flux. Bright
Point bright regions observed in intergranular
lanes. They are thought to be magnetic flux
tubes and are bright due to hot-wall radiation.
Often observed in G-band - 430.5 nm.


14
Filigree A string of bright points on the Sun's
photosphere that are sometimes visible in
intergranular lanes in continuum images the
smallest points are only about 150 km and last
for hours. Filigrees are thought to be places
where flux tubes penetrate the photosphere.
Filigree were originally observed in H-alpha, but
are also seen in G-band.


15
Plage observed as bright features in
chromospheric emission and are found surrounding
sunspots (active regions). Plage are linked to
the increased irradiance during solar maximum.


16
Faculae A bright area observed near the limb,
commonly seen near an active region, such as a
sunspot, or where such a region is about to form.
Faculae, which last on average about 15 days.
Faculae are the chromospheric signature of
filigree. In high-res, the facular grains appear
as brightenings projected on the limbward
neighboring granule - the hot wall effect.
www.uni-sw.gwdg.de/.../ solphys/egranulen.html


17
Moreton Wave A shock wave in the Suns
chromosphere that is produced by a large solar
flare and expands outward at about 1,000 km/s. It
usually appears as a slowly moving diffuse arc of
brightening in H-alpha or coronal line, and may
travel for several hundred thousand km. Moreton
waves are always accompanied by meter-wave radio
bursts they are named after the American solar
astronomer Gail Moreton.


Nanoflare A proposed coronal heating mechanism
in which small-scale currents are dissipated
through impulsive magnetic reconnection (Parker,
1988). Each event releases 1024 ergs and has an
associated plasma flow that broadens coronal
lines.
18
Moss TRACE May 30, 1998. In this image, there
is a blue, black and white spongy structure
between the bases of the coronal loops. Solar
moss consists of hot gas which emits extreme
ultraviolet light. It occurs in large patches,
about 15,000 km in extent, and appears between
18,000 km above the Sun's visible surface. It
looks "spongy" because the patches are composed
of small bright elements interlaced with dark
voids caused by jets of cooler gas from the
chromosphere. The solar moss appears only below
high pressure coronal loops in active regions,
typically persisting for a day.


19
Supergranulation interpreted as the largest
scale of convection, roughly 30,000 km cell size.
It is a predominantly horizontal flow with
velocities of 300-500 m/s observed in the
photosphere. In comparison, the vertical upflow
at the cell center is on the order of 50 m/s and
downflow at the cell boundaries is 100 m/s.
Orange peel image doppler velocity with
rotation subtracted and p-modes removed.
(Hathaway, MDI)


Network Chromospheric emission spatially
correlated with the supergranulation cell
boundaries. It is believed that the horizontal
flow of supergranulation sweeps magnetic fields
into the cell boundaries. Lifetime of the
network is 1 day. Best seen in Ca II H K.
20
Polar Plumes Polar plumes appear prominently in
white light coronagraph observations of coronal
holes as distinct, strongly collimated flow
tubes. They might carry the bulk of the mass and
energy of the solar wind emanating from polar
regions. Electron density is greater in plumes
(8x). Temperature is lower (20). Density
contrast between plume and inter-plume area
disappears by 7 Rsun. The image (Dec 23 1996)
shows the Streamer Belt along the Sun's equator,
where the low latitude solar wind originates.
Over the polar regions, one sees the polar plumes
all the way out to the edge of the field of view.
The frame was selected to show Comet SOHO-6, one
of seven sungrazers discovered by LASCO, before
it plunged into the Sun.


21


Pore the smallest magnetic phenomena on the Sun
which can be distinguished in white light. They
have no penumbra and are much smaller than
sunspots - the size of one or a few granules.
Lifetimes are on the order of a day. Magnetic
field is 1500 Gauss.
22
Q What are some of the most outstanding
questions in Solar Physics? A Han
Uitenbroek How does the magnetic flux stay
coherent as it rises through the convection zone
to the solar surface? The forces it experiences
en route should shred it -- only a strong twist
could keep it together. Do we observe this
twist? .


Yuhong Fans 1999 simulation of a flux tube
rising and experiencing a kink instability.
23
Q What are some of the most outstanding
questions in Solar Physics? A Aimee Norton
How strongly coupled are the North and South
hemispheres of the Sun? The sunspot cycle and
the polar field strengths have been seen to
progress at least 6-10 months out of phase in the
last cycle. How out of phase can the hemispheres
get? .


24
Two ribbon flare Two ribbons lie at the feet of
the flare loops, often occurs in a decaying
active region. Neutral line runs parallel to and
in between the ribbons - 195 Angstroms Trace. The
backbone is the Cusp , it would be the apex of
the loops if viewed edge-on. NEXT MOVIE
Post-flare loops Transverse structures located
between the two ribbons after a flare, seen in
H-alpha, transition zone and coronal lines.
Arcade Tadpoles also seen in the next movie.
Trace 171 Angstroms.


25
Q What are some of the most outstanding
questions in Solar Physics? A Joe
Giacalone The Sun is an efficient particle
accelerator. How? Youve heard one theory -
perpendicular shocks - but it remains an
open-ended question. Image from ACE. .


26


27
Prominence an elongated structure full of
material 100x cooler and denser than the corona
(like cool clouds). Held up by magnetic
structures, they can live for weeks/months, and
are seen as bright against the black background
of space. They can reach heights of several
100,000 km above the limb. They eventually
become unstable and erupt. A prominence would be
a filament if observed on the disk. Hedgerow
A series of filament/prominence loops that appear
like croquet loops and have adjacent legs.


28
Prominence, spicule forest, Hinode SOT wing of
H-alpha Q A Rob Rutten Why do you see all
the mottles, fibrils, spicules, etc, in H-alpha
and not Ca II K? Ca II K is supposed to be more
opaque than H-alpha.


29


Spicules jets of hot material seen in the
chromosphere, flowing 20 km/sec from the
photosphere, lasting about 5 minutes, structured
by the magnetic field. Thought to be caused by
acoustic waves leaking through the atmosphere.
Swedish Solar Telescope. Spicules are also
referred to as fibrils and mottles.
30
More Outstanding Questions in Solar Physics
Spiro Antiochos What is the structure of the
magnetic field in a filament/prominence? Is it
loops? Is it twisted spaghetti? Structure.
Where does the ejection first start - high or
low? Rob Rutten Why do I see the same active
region pattern in H-alpha and TRACE 195?
H-alpha is 10000 K (low chromosphere) and Trace
195 1.5 x 106 K (corona). Shouldnt they look
different? Aimee Norton How can the toroidal
field at the base of the convection zone be
super-equipartition? 30-100 kiloGauss? Gene
Parker When you write down the dynamo
equations - one is the strength of cyclonic
convection and the other is nonuniform rotation,
need to put in effective turbulent diffusion
coefficient (1011 cm2/s). Only turbulent
diffusion can fit this bill. So we look at the
surface and we see turbulence and convection -
300 km scale, velocity 1 km/s. Turbulent should
be 1/3 scale vel 1011. What is the
problem? Turb. Diffusion is based on scalar
quantity but we need a vector field which has its
own internal stresses. Lower conv. Zone - 2-3000
G stored through. And this force is equal to the
turb diffusion. How does turb difficusion
proceed? (same problem exists with the galaxy -
need 1025 cm2/s . How does turb diffusion work
with the current dynamo. Internal rotation
profile of the sun is not reproduced by
hydrodynamics. So we infer magnetic field
stresses are involved.


31
More Outstanding Questions in Solar Physics
Spiro Antiochos What is the structure of the
magnetic field in a filament/prominence? Is it
loops? Is it twisted spaghetti? Structure.
Where does the ejection first start - high or
low? Rob Rutten Why do I see the same active
region pattern in H-alpha and TRACE 195?
H-alpha is 10000 K (low chromosphere) and Trace
195 1.5 x 106 K (corona). Shouldnt they look
different? Aimee Norton How can the toroidal
field at the base of the convection zone be
super-equipartition? 105Gauss! Emerging flux
tube models have inferred a strong
super-equipartition field strength of order
10-100 times the kinetic energy density of the
differential rotation. How is this? (Parker,
1994) Gene Parker When you write down the
dynamo equations - one important ingredient is
the strength of cyclonic convection and the other
is nonuniform rotation. However, you need to
include an effective turbulent diffusion
coefficient (1011 cm2/s). Only turbulent
diffusion can fit this bill. How can we include
an effective turbulent diffusion term that works
withour current picture of the solar dynamo?
This same problem exists with the galactic
dynamo!


32
GEEK PICTIONARY! The Rules Come up and draw a
solar and heliospheric phrase. You will
compete against another team that is drawing the
same term. No symbols, numbers, or words can
be drawn on your page.


33
More Outstanding Questions in Solar Physics
Spiro Antiochos What is the structure of the
magnetic field in a filament/prominence? Is it
loops? Is it twisted spaghetti? Structure.
Where does the ejection first start - high or
low? Rob Rutten Why do I see the same active
region pattern in H-alpha and TRACE 195?
H-alpha is 10000 K (low chromosphere) and Trace
195 1.5 x 106 K (corona). Shouldnt they look
different? Aimee Norton How can the toroidal
field at the base of the convection zone be
super-equipartition? 105Gauss! Thin flux tube
models of emerging flux loops through the solar
convective envelope (Section?5.1) have inferred a
strong super-equipartition field strength of
order for the toroidal magnetic field at the
base of the solar convection zone. Generation of
such a strong field is dynamically difficult
since the magnetic energy density of a field is
about 10-100 times the kinetic energy density of
the differential rotation, Parker, 1994, Rempel
and Schussler, 2001. Gene Parker When you
write down the dynamo equations - one important
ingredient is the strength of cyclonic convection
and the other is nonuniform rotation. However,
you need to include an effective turbulent
diffusion coefficient (1011 cm2/s). Only
turbulent diffusion can fit this bill. So we look
at the surface and we see turbulence and
convection - 300 km scale, velocity 1 km/s.
Turbulent should be 1/3 scale vel 1011.
What is the problem? Turb. Diffusion is based on
scalar quantity but we need a vector field which
has its own internal stresses. Lower conv. Zone
- 2-3000 G stored through. And this force is
equal to the turb diffusion. How does turb
difficusion proceed? (same problem exists with
the galaxy - need 1025 cm2/s . How can we
include an effective turbulent diffusion term
that works withour current picture of the solar
dynamo? Internal rotation profile of the sun is
not reproduced by hydrodynamics. So we infer
magnetic field stresses are involved.