Novos aspectos da atividade solar em ondas submilimétricas

Novos aspectos da atividade solar
em ondas submilimétricas
e banda THz
4th El Leoncito Solar Physics School – CASLEO & Universidad de La
Punta – San Juan & San Luis, Argentina
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Radiação eletromagnética
Energia de um fóton E = hν = hc/λ erg
h: cste. Planck
c: velocidade da onda e.m. (luz, rádio, etc.)
λ: comprimento de onda; ν: freqüência
Estado da radiação e.m. descrito pelo vetor de Poynting instantâneo:
P = E x H (W m-2 = V m-1 x A m-1)
Função da direção e grau de polarização
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Sensoriamento passivo
Objeto no espaço compreendendo ângulo
sólido Ω (sr), a temperatura aparente de ruido
equivalente T (K)
Outros parâmetros da radiação recebida derivados da
aproximação de Rayleigh-Jeans para a lei de Planck
descrevendo radiação de corpo negro:
hBrilhância radioelétrica
B(θ,ϕ) = 2 k T(θ,ϕ)/ λ2 W. m-2 Hz-1 sr-1
iDensidade de fluxo
S = (2 k/λ2) ∫∫ T(θ,ϕ) dΩ W. m-2 .Hz-1
Rayleigh-Jeans
k : cste. Boltzmann
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DEFINIÇÕES
Radiometria: detecção de radiação eletromagnética na forma
de ruído randômico cuja potência é definida em termos de
temperatura equivalente, numa frequência f, banda
passante B.
Outros parâmetros: direção no espaço; polarização; espectro
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“Janelas” da atmosfera terrestre para ondas eletromagnéticas
A rádio-astronomia explora o espaço exterior
a partir do solo nas faixas de freqüência para
as quais a é baixa a opacidade da ionosfera
(ondas decamétricas-microondas) e da troposfera (micro-ondas-submilimétrico)
Mid-IR
SST
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Planetas
Nebulosas.
estrelas em
formação
Supernovas
Galáxias
Cometas
Ruídos radioelétricos do
Universo próximo e distante
Meio extragalático
Sol
RADIÔMETRO
Sensor
radiométrico
Filtro
Potência de ruido
Diagnóstico remoto de fenômenos astrofísicos através das ondas
de rádio que emitem
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SOLAR BURSTS SPECTRA AT HIGHER FREQUENCIES AS KNOWN IN PAST MILLENIUM
Unusual
DIFFERENT FLARE
EMISSION MECHANISMS
MAY FIT INTO THIS UNKNOWN
SPECTRAL RANGE
First tries:
(Single beam slow scans)
Typical
250 GHz brightnings on AR,
Clark & Park 1968,
250 GHz and 15 THz
raster scans and
tracking ARs, Hudson 1975
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To observe solar burst emission at f> 100 GHz:
SOLAR SUBMILLIMETER-WAVE TELESCOPE
El Leoncito Astronomical Complex, San Juan, Argentina
Altitude 2550 m
1.5 m Cassegrain reflector, 3 m
radome, 4 radiometers at 212
GHz, 2 radiometers at 405 GHz
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SST six beams projected on the solar disk
(for April 6, 2001)
SOHO Magnetogram
Upgraded pointing model (2006)
1-4: 212 GHz
5,6: 405 GHz
Absolute pointing accuracy: 10” r.m.s
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Active Centers Emission
Simultaneous solar images for May 20,
2002, beams 1 (212 GHz) and 5 (405 GHz)
Active centers spectra
distinct submm-w component
Silva et al., 2005
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New Terahertz Solar Burst Source – Evidence
4 November 2003
OVSA
SST
SOHO EIT previous to the flare
Kaufmann et al 2004
Source size < 10”
Brigthness at peak P1 Tb > 3-5 107 K
(405 and 212 GHz)
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PULSE REPETITION RATES ARE LINEARLY PROPORTIONAL TO FLUXES
November 4, 2003
- FLUXES = ∆E/∆t = R (s-1) 〈ε〉 watts
- FLARE ACCELERATOR PRODUCE DISCRETE
REPETITIVE ENERGETIC INJECTIONS
ε≈ 2-8 1013 J at 212 and 405 GHz
ε≈ 4-9 1014 J at 1.3-4.0 to 0.15-0.5 MeV
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“U-spectra” (Castelli 1972)
T-rays
Complete solar burst spectrum “W-shaped” in the MHz – THz range
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Submillimeter bursts emission with superimposed rapid pulsations
5 sec sample on March 22, 2000
April 6, 2001 solar burst
212 GHz
5 ms
Owens Valley
212 GHz time profile
Pulse occurrence rates
Sub-second
pulses are
common to all
solar bursts
observed
with or without
observable
impulsive
bulk emission
405 GHz
5 ms
Kaufmann et al. (2002)
Suggested spectral trend for the sub-second spikes
(α ≈ 2)
1000
log flux (SFU)
YOHKOH
Gamma rays
2
100
May 21, 1984
10
March 22, 2000
August 25, 2001
1
10
100
1000
log f (GHz)
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Ejeção de massa coronal (CME) é o mais energético transiente solar.
Provoca grandes perturbações no meio interplanetário e impacto
no meio ambiente espacial e campo geomagnético da Terra
Energia ≈ 1032 ergs,
igual a produzida pelas
maiores explosões
solares, às quais nem
sempre os CMEs estão
associados
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Pulsating Bursts association to CME launch times
PULSATING BURST OF APRIL 6, 2001
LASCO C2
BULK EMISSION
WAVELET
DECOMPOSITION
LASCO C3
CME POSITION ABOVE SURFACE VS. TIME
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August 25, 2001 flare, CME
and submm-w pulses
Scalograms
405 GHz
GOES-10
212 GHz
405 GHz
LASCO C2 Coronagraph
212 GHz
405 GHz
CME positions
With time
(Raulin et al. 2002)
Zoom
The repetition rate of submm-w pulses is proportional to flux
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Solar observations in the THz range are essential to understand the initial flare emission processes!
30 THz
30SST
THz
added
added
- TO IMPROVE UNDERSTANDING OF
FLARE ACCELERATOR
- TO BETTER EXPLAIN FLUXES
TIME-HISTORIES AT MICROWAVES,
THz RANGE, HARD X-RAYS
- RELATIVE IMPORTANCES OF ISR
AND BREMSSSTRAHLUNG TO
PRODUCE HARD X- AND GAMMA RAY
data
not
enough
to
fully ?
describe
physical
processes
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Present plans for El Leoncito
SST
30 THz Camera (7-15 µ)
τ ≈ 0.15
CCS photometers
τ ≈ 0.6
H-α
τ ≈ 1.4
(Transmission for Mauna Kea, 4100 m altitude, 1.2 mm pwv, Jefferies 1993)
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Coelostat and optical setup next to SST and 10-µ camera
El Leoncito SST facility
Jensch-Zeiss 30 cm coelostat
10 µm camera at
newtonian focus
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10 µm D.O.T. - like setup at Bernand Lyot Solar Observatory, Campinas, Brazil
11 September 2007
Mid-IR plages
NSO magnetogram
Meudon Ca plages
10.5 cm objective
Marcon et al 2008
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Mid-IR (10 Micro m) pulses and GOES soft X-ray
30 THz burst associated to GOES B 2.0 X-ray event, December 10, 2007
2,50E-07
Movie
Mid-IR flare fireworks!
2,00E-07
1,50E-07
Fux W m-2
Ta = 0.5-4 K; S = 10-70 SFU
1,00E-07
5,00E-08
5 frames/s
system ∆T ≈ 0.2 K rms
0,00E+00
10:30:43
10:33:36
10:36:29
10:39:22
10:42:14
10:45:07
10:48:00
10:50:53
10:53:46
10:56:38
10:59:31
-5,00E-08
Universal Time Dec 10, 2007
5 frames/second; accelerated
Short 1.5 - 4.0 A
Long 1.0 - 1.8 A
Dif ∆T K
Movie
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December 13, 2007 (during GOES B class burst)
80 seconds, 5 fps, December 13, 2007
Excess flash brightning
in the solar disk~ 200 K
Temperature enhancement
at input of mid-IR
telescope ~0.5-1 K
Flux density ~ 20 SFU
FOV ~25”
Duration ~ few seconds
Results consistent with a
1-2” sources, intrinsic brightning
of ~ 60,000 K
Mid-IR microflashes
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BURST SOURCE PARAMETERS DIFFICULT TO RECONCILE TO ANY
THERMAL INTERPRETATION
T-BURST COMPONENT ATTRIBUTED TO NON-THERMAL ELECTRONS
Electron energies > 10 MeV, Magnetic fields ~ 103 gauss
New interpretation possibilities
-SYNCHROTRON BY POSITRONS
-LANGMUIR WAVES
-BUNCHING OF ELECTRON BEAMS (same physics as in laboratory accelerators)
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A SIMPLER POSSIBILITY
Same physics as in laboratory
BUNCHING OF ACCELERATED UR ELECTRON BEAMS
SUN
FLUX ∝ Po [N(incoherent) + f N2(coherent)]
CSR
ISR
Lab
THE MECHANISM IS SO EFFICIENT THAT JUST
A SMALL FRACTION OF ELECTRONS BUNCHED
WITHIN SOLAR ACCELERATED BEAM (i.e. form
factor f <<1) ARE ENOUGH TO ACCOUNT FOR
THE BROADBAND COHERENT SYNCHROTRON
EMISSION
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Synchrotron emission power components
One bunch
N electrons (> MeV)
P = Po [N(incoherent) + f N2(coherent)]
Microbunch
length scale lb ≤ λ (e.m. wavelength)
Bunch
Power by single electron Po ∝ e2
(Ingelman and Siegbahn, 1998)
n multiple fractured bunches
P(total) = n Po [N(incoherent) + f N2(coherent)]
f ⇒ form factor, probability finding the electron in the same energy level or angular loss cone
ϕ +∆ϕ. f ≈ 0 for lb >> λ (incoherent); f ≈ 1 for lb << λ (coherent)
Ripples observed in solar burst time profiles are suggested signatures of multiple bunches being accelerated
accounting for observed [occurrence rates ∝ flux] and [total energy ∝ ∑ ∆ε] burst description
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Simulation
Klopf, 2008
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SIRA
SST DESIR
Mid-IR
FULL SPECTRAL COVERAGE NEEDED
SUBMM & IR
UNEXPLORED
SIRA
SST DESIR
Mid-IR
LOG FREQUENCY (Hz)
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DESIR
Optical layout
SMESE
France-China
Platform
launch 2012
Photometer/imagers for the 25-35 µm (10 THz)
and 100-200 µm (2 THz) bands
Le 5 Mars 2002
Spectroscopie par TF
CNES(France) + CNSA(China)
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Solar submillimeter to Infra-red Activity – SIRA (phase I)
(submitted to Brazilian funding agencies)
45 & 90 GHz
Patrol polarimeters
SST 212 &
405 GHz
DESIR
2 & 10 THz
Mid-IR
GBO
Planned SIRA (phase II) – GBO at 650 & 850 GHz, space at 3 THz
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