The Energetics of
Sunspots and Faculae:
Fluid Dynamics vs.
Magnetic Inhibition
Kenneth Schatten
ai-solutions
&
Hans Mayr
NASA –GSFC
Code 910.4
Sunspots and Faculae: Fluid
Dynamics vs. Magnetic
Inhibition
• SOME “HOME PHOTOS”
• METEOROLOGICAL CONCEPTS: WHAT
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MAKES CLOUDS & HURRICANES
FLUID DYNAMICS VS. MAGNETIC
INHIBITION – WHAT IS THIS ALL ABOUT?
• MAGNETIC FIELD PLAYS AN IMPORTANT ROLE IN
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THE STRUCTURE ABOVE PHOTOSPHERE
FLUID DYNAMICS MAY PLAY AN IMPORTANT ROLE
IN ENERGETICS OF ACTIVE REGION FEATURES
FACULA OBSERVATIONS
TOUGH OBSERVATIONAL QUESTION: ARE FACULAE
UPLIFTED STRUCTURES?
RELATION TO CLIMATE & USRA OPPORTUNITY
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METEOROLOGICAL
CONCEPTS
• MAIN POINT: FOR STORMS, THERE ARE 2
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KINDS OF INSTABILITIES: 1) CONDITIONAL
INSTABILITY (FOR CLOUDS); 2) HURRICANES
ARE A 2ND KIND OF INSTABILITY
STABILITY OF THE ATMOSPHERE
CONDITIONAL INSTABILITY (CI)
HURRICANE DEVELOPMENT AND ENERGETICS
CISK (CONDITIONAL INSTABILITY OF THE
SECOND KIND) – CHARNEY AND ELIASSEN
IMPORTANCE OF OCEANS: KERRY EMANUEL
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Atmospheric Stability
Compare an air parcel’s
temperature (Tp) with the
environmental temperature (Te)
at a given altitude
if Tp > Te, parcel rises
if Tp = Te parcel does not
move up or down
if Tp < Te parcel sinks
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CONDITIONAL INSTABILITY
Determining Air Parcel Temperature: Rising air parcels and adiabatic cooling
consider a rising parcel of air -->>
As the parcel rises, it will adiabatically expand and cool (recall our discussion in
chapter 5 about rising parcels of air)
adiabatic - a process where the parcel temperature changes due to an expansion or
compression, no heat is added or taken away from the parcel
the parcel expands since the lower pressure outside allows the air molecules to push
out on the parcel walls
since it takes energy for the parcel molecules to "push out" on the parcel walls, they
use up some of their internal energy in the process.
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therefore,
the parcel also cools since temperature is proportional to molecular internal
energy
Dry versus Moist-Adiabatic Process
the moist adiabatic lapse rate is less than the dry adiabatic
lapse rate because as vapor condenses into water (or water
freezes into ice) for a saturated parcel, latent heat is released
into the parcel, mitigating the adiabatic cooling
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Atmospheric Stability
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Absolute Stability
Absolute Stability
Absolute Instability
Conditional Instability
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CONDITIONAL INSTABLILITY: 1ST
KIND:CLOUDS COMPETE FOR ENERGY
Photograph by: Holle
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The downward motion inhibits further convection and the
growth of additional thermals from below, which is why fair
weather cumulus typically have expanses of clear sky between
them. Without a continued supply of rising air, the cloud
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begins to erode and eventually disappears.
OVERVIEW OF HURRICANES: CISK
• Convergence at the surface leads to
convergence of moisture.
• The convection or thunderstorms that
form release latent heat which
intensifies the surface low.
• The warm core column of air will create
an upper level high pressure center.
• The weak shear allows the storm to
remain vertical and allows for the latent
heat release to enhance the surface
low.
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Hurricane Structure:CISK
This feedback mechanism continues as long as the favorable conditions for
hurricane growth continue to exist. The energy for the growth of the storm comes
from the ocean (evaporation).
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Hurricane Development: CISK
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Latent energy (the
conversion of
Water vapor to liquid water)
releases energy which
drives the circulation and
causes the “strong heating”
Shown.
Strong
Heating
L
Strong
Convergence
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RELEVANCE TO
GLOBAL CHANGE:
CISK, AND
THERMODYNAMICS
WHAT MAKES HURRICANES SO
FEROCIOUS?
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KERRY EMANUEL: OCEANS RESUPPLY OF MOIST AIR IS KEY TO ENERGETICS OF
HURRICANES (AND THEY LIVE OFF (DRIVEN LIKE A HEAT ENGINE) OF ∆Τ
ΒΕΤWEEN LOWER TROPOSPHERE AND STRATOSPHERE) –GLOBAL WARMING
INTENSIFIES THE ENERGY AVAILABLE (KERRY PREDICTED STRONGER AND
MORE FREQUENT HURRICANES DUE TO GLOBAL WARMING)
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HOW DOES ALL THIS RELATE TO
THE SUN? - FLUID DYNAMICS VS.
MAGNETIC INHIBITION
•GRANULATION –
CLOUDS
ACTIVE REGION
FEATURES:
SPOTS AND
FACULAE –
HURRICANES?
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FLUID DYNAMICS VS.
MAGNETIC INHIBITION
TWO DISTINCT REGIONS:
1. Above the photosphere (τ<1), the
magnetic field is in a low beta
environment (plasma press. to field
press.).
2. Below the photosphere (τ>1), a high
beta environment largely exists.
So, Hans and I ask ?: what is the role of
FLUID DYNAMICS VS. FIELD
INHIBITION, below the photosphere?
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SOLAR VS. TERR. METEOROLOGY
• SOLAR (FOR TAU >1); THE SAHA EQN. GOVERNS AMOUNT OF
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IONIZATION STATE; CHEMICAL ABUNDANCE ESSENTIALLY
CONSTANT; THUS ‘RELATIVE HUMIDITY’ IS GOVERNED BY
THERMO. STATE VARIABLES
NEVERTHELESS, DENSITYAND IONIZATION STATE CAN BE A
LOCAL FUNCTION OF TEMP. (HOT AND COLD LOCATIONS), WITH
TIME HISTORY.
IONIZATION PLAYS THE SAME ROLE AS LATENT ENERGY
GRANULES MAY BE THE 1ST KIND OF INSTABILITY
IN OUR VIEW, SUNSPOTS MAY BE A 2ND KIND OF INSTABILITY,
WITH MAGNETIC FIELD PLAYING THE ROLE OF GUIDING THE
CIRCULATION INTO A LARGE SCALE MOTION, WHICH MAKES THE
PROCESS OF CONVECTION MORE EFFICIENT –
THIS LAST POINT AFFECTS HOW ACTIVE REGIONS AFFECT
CLIMATE!!! – THE SECULAR EFFECT OF ACTIVE REGIONS
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Fountains of fire on the sun, who can reach a height of half a million km. These
arcs of fire follow the lines of the electromagnetic field and not of the gravitation
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field of the sun. Photo in the ultraviolet light via NASA satellite TRACE.
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Gas Movement in the Convection Layer
Courtesy: McREL
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FIELD INHIBITION VS FLUID DYNAMICS
• FIELD INHIBITION
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• FLUID DYNAMICS
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SPRUIT FIELD INHIBITION “WELL”
SUNSPOT & FACULA MODELS
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SCHATTEN & MAYR “IONHURRICANE” MODEL
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Number of authors also thought
about Flows around and below
spots
• Meyer et al. (1974) predicted the existence of
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the converging flow ( 1 km s-1, at a depth of
several Mm) as a collar around the sunspot, to
provide it with confinement and stability.
Parker (1979) cluster model for sunspots, and a
downdraft beneath the sunspot, in the
convection zone, is needed for cooling.
Zhao, Kosovichev and Duvall, Jr. (2001) used
time-distance helioseis. to examine flows.
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FIELD INHIBITION VS FLUID DYNAMICS
(SUNSPOTS ARE WELLS IN BOTH MODELS)
• FIELD INHIBITION (FI)
• FIELD PRESSURE
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CREATES WELLS FOR
SPOTS AND FACULAE
FACULAE BRIGHT DUE
TO “HOT WALLS”
EXTRA BRIGHTNESS
NEAR LIMB REQUIRES
‘HOT GAS’
OVERALL EFFECT OF FI
MODEL IS TO REDUCE
ENERGY TRANSPORT
• FLUID DYNAMICS (FD)
• VERTICAL MOMENTUM
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EQN. DRIVES “HEIGHT”
OF FEATURES. FACULAE HILLOCKS BECAUSE OF
LARGER “SCALE HEIGHT”
FACULAE - BRIGHT :
UPLIFTED STRUCTURES
WHICH FACE OBSERVER
MORE “NORMALLY”
OVERALL EFFECT OF FD
MODEL IS THAT FIELD
ENHANCES ENERGY
TRANSPORT
FACULAE: KEY TO OBSERVATIONALLY
DECIDING AN ANSWER BETWEEN 2 VIEWS
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A TOUGH OBSERVATIONAL
QUESTION:
• ONE OBSERVES A “HOT WALL.” HOW DO WE
DECIDE WHETHER IT IS UPLIFTED (A HILLOCK OR
MESA) VS. DEPRESSED (A WELL), WHEN THERE IS
NO “SEA LEVEL” ON THE SUN?
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In Hillock Model, it was recognized
that field does play a role in
evacuating the flux tube.
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FACULAR OBSERVATIONS
• GENERAL APPEARANCE OF FACULAE
(CENTER TO LIMB VARIATIONS & COLOR)
• FACULAE BLANKET SUNSPOTS
• STELLMACHER & WIEHR
• RECENT BERGER ET AL. OBSERVATIONS?
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GENERAL APPEARANCE OF FACULAE (CENTER:LIMB
CONTRAST & COLOR). SOLID LINES ARE SIMPLE THEORETICAL
MODEL OF HILLOCKS, AND DASHED LINES ARE OBSERVATIONS AT THREE
DIFFERENT COLORS.
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FACULAE BLANKET SUNSPOTS
•UPLIFTED FACULAE CAN REDUCE THE APPARENT AREA OF SUNSPOTS DUE TO
“SHIELDING”, WHICH THE NEXT FIGURE SHOWS (A GRAPH OF AREA OF SUNSPOTS
VS. DISK POSITION AND PLAGE /FACULAR SIZE)
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SOLAR ACTIVITY FEATURES
THE APPARENT AREA OF SUNSPOTS IS FAIRLY FLAT (LEFT SIDE OF LOWER
GRAPH) WHEN PLAGE ARE SMALL, BUT IS REDUCED NEAR LIMB DUE TO
“SHIELDING”, WHEN PLAGE ARE LARGE (RIGHT SIDE OF LOWER GRAPH).
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Time-Distance Helioseismology
• Zhao & Kosovichev
(2001, 2003)
– Blue – cool; Red –
hot
• Inward flows near
surface help to
confine and
stabilise spot
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SUN-CLIMATE: WHAT IS THE
EFFECT OF ACTIVE REGIONS?
Composite TSI from Fröhlich (2000)
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Willson (1997) and Willson and
Mordvinov (2003) used the Nimbus
7/ERB results to relate the nonoverlapping ACRIM I and ACRIM
II data sets.
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Fröhlich and Lean (1998) and
Fröhlich (2000) used ERBS to
relate ACRIM I and ACRIM II.
• HOW DO WE
UNDERSTAND
∆Ε ∼ Rz ?
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HOW DO WE UNDERSTAND ∆Ε∼Rz?
• IN EARLY MODELS OF ACTIVE REGIONS, ∆Ε ∼ 0.
• PRESENT VIEW, ACTIVE REGIONS SERVE AS AN AID IN
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TRANSPORTING ENERGY OUTWARD BY AIDING LARGE
SCALE FLOW. THIS HAPPENS AS THE TURBULENT
VISCOSITY IS REDUCED WHEN THE FIELD AIDS LARGE
SCALE FLOW PATTERNS
AS A CONSEQUENCE, B FIELD OF ACTIVE REGION
INCREASES THE EFFICIENCY OF CONVECTIVE ENERGY
TRANSPORT.
Thus ∆Ε >0 PROPORTIONAL TO ACTIVITY
HOW DOES ∆Ε∼Rz OCCUR? (NEXT FIGURE)
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ENERGETICS:HOW DOES ∆Ε∼Rz OCCUR?
• We offer following simplified global picture:
• The photosphere ~ a surface of constant
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temperature (like the surface of pot of boiling
water), so it has an area, “A”
Energy radiating from surface ~ σA T**4.
• To reduce radiation, since T~ constant: reduce A
• So a sunspot, effectively removes area, ∆A,
from the radiating photosphere.
• Faculae, by crinkling surface, increases ∆A
• OVERALL, SINCE ACTIVITY AIDS OVERALL
FLOW, ∆Α increases , thus ∆Ε∼ ∆Α ∼Rz.
• NEVERTHELESS, DEEP SECULAR CHANGES:????
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CLIMATE EFFECTS/USRA
INTERESTS
A Workshop
To Formulate a New Research Approach on
SOLAR VARIABILITY ON DECADAL TO
MILLENIAL TIMESCALES:
Influence on Earth Climate Change and
Prediction
April 26-27, 2004
Patuxent Wildlife Center
10901 Scarlet Tanager Loop, Laurel, MD
20708
Sponsored by
The Universities Space Research Association
http://www.usra.edu/hq/meetings/scw/
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CONCLUSIONS
• FACULAE MAY HOLD THE CLUE TO:
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FLUID DYNAMICS VS. FIELD INHIBITION
TOUGH OBSERVATIONAL QUESTION:
ARE FACULAE UPLIFTED STRUCTURES?
EFFECT ON CLIMATE: THE OVERALL
EFFECT OF FLUID DYNAMICAL MODEL IS
THE MAGNETIC FIELD ENHANCES
ENERGY TRANSPORT, ALLOWING A
POSITIVE EFFECT OF ACTIVITY UPON
ENERGY FLOW: ∆Ε∼Rz.
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