the radio sun norh 17 ghz / 1.8 cm vla 1.4 ghz / 21 cm nrh 0.327 ghz / 91 cm karl-ludwig klein...
TRANSCRIPT
![Page 1: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/1.jpg)
The Radio Sun
NoRH 17 GHz / 1.8 cm
VLA 1.4 GHz / 21 cm
NRH 0.327 GHz / 91 cm
Karl-Ludwig Klein
Observatoire de Paris - [email protected]
![Page 2: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/2.jpg)
The solar corona
© C. Viladrich, SAF
QuickTime™ et undécompresseur codec YUV420
sont requis pour visionner cette image.
EUV images - SoHO/EIT QuickTime™ et undécompresseur codec YUV420
sont requis pour visionner cette image.
Magnetograms - SoHO/MDI
A >1 MK plasma whose structure and dynamics are governed by magnetic fields
emerging fom the interior.
![Page 3: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/3.jpg)
• Emission processes 1 : thermal plasma– free-free– gyroresonance (enhanced opt depth at = sce; s=2, 3, 4)
Radio observations of the solar atmosphere
• Radio waves from the solar atmosphere : – propagation at >pe ne decreases with increasing altitude
– sounding of different heights at different frequencies (0 RS-1 AU)
NoRH 17 GHz / 1.8 cm
VLA 1.4 GHz / 21 cm
NRH 0.327 GHz / 91 cm
![Page 4: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/4.jpg)
Emission processes 2 : radio bursts– (gyro)synchrotron (cm-
m-) – collective emission at
pe or 2pe (pene;
bursts, dm-m-) identification of moving
exciters : electron beams, shock waves
Radio observations of the solar atmosphere
• Radio waves from the solar atmosphere : – propagation at >pe ne decreases with increasing altitude
– sounding of different heights at different frequencies (0 RS-1 AU)
ETH ZurichAIP Potsdam - OSRA Tremsdorf
![Page 5: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/5.jpg)
Solar radio astronomy in Europe
![Page 6: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/6.jpg)
• Accessible from ground: 1 mm–30 m (300 GHz-10 MHz)
Solar radio instrumentation
• 2 types of observations :Spectroscopy of the whole Sun (bursts)Aperture synthesis imaging
![Page 7: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/7.jpg)
• Plasma diagnostics of the corona (ne, T, B) and the origin of the solar wind
• Large-scale coronal disturbances: mass ejections (CME), shocks
• The Sun as a particle accelerator :– Mildly relativistic electrons in flares (gyrosynchrotron) – « Quiet-time » non thermal e--populations– e- accelerated during CME and at coronal shocks– Energetic particle acceleration and propagation in the corona and
interplanetary space
Observations of the solar corona at radio
![Page 8: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/8.jpg)
• Plasma diagnostics of the corona (ne, T, B) and the origin of the solar wind
• Large-scale coronal disturbances: mass ejections (CME), shocks
• The Sun as a particle accelerator :– Mildly relativistic electrons in flares (gyrosynchrotron) – « Quiet-time » non thermal e--populations– e- accelerated during CME and at coronal shocks– Energetic particle acceleration and propagation in the corona and
interplanetary space
• Outlook: solar radio telescopes for the future
Observations of the solar corona at radio
![Page 9: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/9.jpg)
Radio emission of the quiet solar atmosphere
Plasma diagnostics (ne, T, B) of an
extended region from the
chromosphere to the corona
![Page 10: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/10.jpg)
+-
h
A multi frequency view of the radio Sun
2004 Jun 25 2004 Jun 27 2004 Jun 28 2004 Jun 29
Nan
çay
Rad
iohe
liogr
aph
410
MH
z
Sib
eria
n S
olar
R
adio
Tel
esco
pe5.
7GH
z
Nob
eyam
a R
adio
helio
grap
h 17
GH
z
Different structures at : active regions (GHz), coronal holes
![Page 11: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/11.jpg)
Brig
htne
ss te
mpe
ratu
re [K
]
106
105
Wavelength [m]
1 20.6
T b (c
oron
al ho
le)Low :
Tb = Te = 6.7105 K
High :
Tb << Te
ne = 2.3108 cm-3
T b (average corona)
Mercier & Chambe 2009 ApJ 700, L137
Coronal plasma parameters
Bremsstrahlung: brightness spectrum depends on ne & Te
Nançay Radioheliograph
![Page 12: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/12.jpg)
Gyromagnetic radiation
• Electron cyclotron frequency
• Low speed electron (T=106 K) : cyclotron line (unobservable in corona , since pe>ce ) and low harmonics (=s0 , 0=ce , s=1,2,3)
• Synchrotron rad., relativistic e: 0=ce/ ; beaming high s, max. intensity at
23
2c ce =
Inte
nsit
y
Time Frequency
B
4
12.8 [MHz]
2 10 Tcee
eB B
m
π −= ≈
![Page 13: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/13.jpg)
€
τ ,gr =ξs2s
2s+1s!
neLB
ν1,77 ×10−10Te( )
s−1×
1± cosϑ( )2
sinϑ( )2s−2
δ ν − sν ce( )
=sce (s=2 … 4 for Te2106 K)
-> 5 GHz (6 cm) if s=3, B=600 G
Resonant surf., depth ~100 km
=5
GHz, s=
3
=8,4
GHz,
s=3
chromosphère
600 G
1000 G
>3 ce
,max
€
Tb = Te τ( )exp −τ( )dτ0
τ 0
∫ , τ = τ ff + τ gr
Gyroresonance emission: a tool for coronal magnetic field measurements
• Gyroresonance emission
![Page 14: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/14.jpg)
• τgr>1 : Tb on iso-B surface (=sce ; in general not plane)• Above sunspots (intense B)• Confirmed technique: cf. Alissandrakis, Kundu, Lantos 1980, A&A 82, 30
• Future: broadband spectrographic imaging
Lee et al. 1999, ApJ 510, 413Lee et al. 1998, ApJ 501, 853
Gyroresonance emission: a tool for coronal magnetic field measurements
Optical + VLA
![Page 15: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/15.jpg)
• The corona emits bremsstrahlung at cm-to-m- (quiet corona), optically thin or thick.– Determination of coronal plasma parameters from bremsstrahlung
spectrum (ne, Te); comparison with othe diagnostics (EUV line spectroscopy); origin of solar wind; nature of coronal electron population (maxwellian ?)
– Determination of coronal magnetic fields: circular polarisation of optically thin bremsstrahlung, depolarisation (not shown here), gyroresonance emisssion.
• Perspective : Multi-frequency mapping of the Sun by the Frequency Agile Solar Radiotelescope (FASR).
• Not addressed here: recombination lines from the chromosphere. ALMA ?
• Further reading : Aschwanden, Physics of the Solar Corona; papers in Solar and Space Weather Radiophysics, see FASR web site http://www.ovsa.njit.edu/fasr
Thermal radio emission from the solar corona: summary
![Page 16: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/16.jpg)
Bursts of gyrosynchrotron radiation from solar flares
Evidence of electron
acceleration to relativistic energies
in the corona
![Page 17: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/17.jpg)
Observed microwave spectra
Whole Sun spectra of solar radio bursts: Nita et al 2004 ApJ 605, 528
Ow
ens Valley S
olar Array
![Page 18: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/18.jpg)
• Observation of a microwave burst spectrum with dense frequency coverage (Owens Valley Solar Array)
• Continuous spectrum (practically)
>>0, >1 : gyrosynchrotron radiation
• (1, >>1 : synchrotron radiation)
• Corona: hundreds of keV, occasionally higher energies
Observations : Owens Valley,Nita, Gary, Lee 2004, ApJ 605, 528
Opt
. thi
ck Opt. thin
Gyrosynchrotron interpretation
![Page 19: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/19.jpg)
• Solar radio burst : usually observed up to some tens of GHz.
• New: =212 GHz (SST1): synchrotron emission from relativistic e-:
=10
• Slope of the microwave spectrum
Trottet et al. 2002 A&A
Relativistic electrons at the Sun
(1) Univ. Mackenzie Sao Paulo
232 ce ≈
€
Sν ∝ν− δ −1( )
2 for N E( )dE ∝ E−δ dE
![Page 20: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/20.jpg)
• Time profile (microwaves, HXR, gamma-rays): electron acceleration from 100 eV (quiet corona) to hundreds (sometimes tousands) of keV in a few seconds to a few tens of seconds
• Consistent with e-spectrum
inferred from gamma-ray bremsstrahlung (h> 300 keV; Trottet et al. 1998 AA 334, 1099 )
Relativistic electrons at the Sun
![Page 21: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/21.jpg)
A gyrosynchrotron model source
Bastian, Benz, Gary 1998, ARAAOptically thick:
loop top
Optically thin: foot points
More detailed models: Preka-Papadema & Alissandrakis AA 139, 507; 1988 AA 191, 365: 1992 AA 257, 307 Klein & Trottet 1984, AA 141, 67
![Page 22: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/22.jpg)
Microwave source morphologies
Loop (LF) + footpoints (HF): Nindos et al. 2000, ApJ 533, 1053
Compact loop : Kundu et al. 2001, ApJ 547, 1090
17 GHz
SXR+HXR
Multiple sources :• footpoints (cospatial 17 GHz,
HXR)• compact or extended loops Nishio et al. 1997, ApJ 489, 976Hanaoka 1996, 1997, Solar Phys.
![Page 23: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/23.jpg)
• Microwaves from solar flares are gyrosynchrotron rad.
• Co-evolution with HXR, gamma-ray continuum; electron acceleration to MeV energies (from 100 eV in the corona) within a few seconds.
• Electron spectrum consistent with that inferred from the gamma-ray continuum (NOT HXR continuum: mildly relativistic electrons !)
• Further reading : Bastian, Benz, Gary 1998 ARAA 36, 131; Pick, Klein, Trottet 1990 ApJS 73, 165; Benka & Holman 1994 ApJ 435, 469)
Gyrosynchrotron radiation from solar flares : summary
![Page 24: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/24.jpg)
Particle acceleration and magnetic reconnection
Hard X-ray
and
radio bursts, and a cartoon scenario
![Page 25: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/25.jpg)
Particle acceleration in a simple flare
• A set of complementary observations of EM emissions from flare-accelerated electrons :
– Hard X-rays (h > 20 keV): energy spectra and imaging
– Radio emission : spectra and imaging from ground (400 GHz > > 20 MHz)
– Radio emission : spectra from space ( < 14 MHz)
Vilm
er et al. 2002 Solar P
hys 210, 261
5 min
![Page 26: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/26.jpg)
Hard X-ray emission from electron beams
e beam
HXR
Image EUV TRACE / NASA
• Beam of suprathermal electrons travelling downward through the corona.
• Collisions with ambient protons : bremsstrahlung,
h < energy(e)• Particularly efficient when
ambient density high (chromosphere) : frequently observed ‘footpoint’ sources at h>20 keV.
![Page 27: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/27.jpg)
RHESSI HXR + TRACE : Krucker et al. 2008 ApJ 678, L63
Hard X-ray emission from electron beams
• Beam of suprathermal electrons travelling downward through the corona.
• Collisions with ambient protons : bremsstrahlung,
h < energy(e)• Particularly efficient when
ambient density high (chromosphere) : frequently observed ‘footpoint’ sources at h>20 keV.
• Low energy e deposit their E in the corona.
![Page 28: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/28.jpg)
Particle acceleration in a simple flare
• A set of complementary observations of EM emissions from flare-accelerated electrons :
– Hard X-rays (h > 20 keV): energy spectra and imaging
– Radio emission : spectra and imaging from ground (400 GHz > > 20 MHz)
– Radio emission : spectra from space ( < 14 MHz)
Vilm
er et al. 2002 Solar P
hys 210, 261
5 min
![Page 29: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/29.jpg)
1) Electromagnetic waves
2) Langmuir waves = electron plasma oscillations (ES waves, cannot exist in vacuum):
… but can couple to EM waves and than escape from the source (cf. solar radio bursts)
2 2 2 23
2pe thkω ω υ= +
ω
ω/k=c
k
ωpe
EM w
ave
Langmuir wave
High-frequency waves in a plasma : isotropic case (B=0)
![Page 30: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/30.jpg)
• Beam of suprathermal electrons travelling through the corona
• “Bump in tail” instability
f/υ// > 0 : growth of Langmuir waves,
pene
• Plateau (quasi-linear relaxation)
Maxwellian
Beam
υ//
f(υ//)
The Langmuir waves cannot escape from the corona, but …
Radio emission from electron beams
![Page 31: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/31.jpg)
• Electron beam rising into the corona Langmuir waves at decreasing
• Coupling with ion sound waves (S<<L) or Langmuir waves EM waves at T = L + S L pe “fundamental”
T = L + L= 2L 2pe “harmonic”
• Short radio burst that drifts from high to low (“type III” burst)
e beam
Height (time)
Fre
quen
cy
high ne
high
low ne
low
Radio emission from electron beams
![Page 32: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/32.jpg)
• Hard X-rays from the low atmosphere (chromosphere) - e precipitated downward to ne > 1012 cm-3, bremsstrahlung with ambient p, h<energy(e).
• Radio emission (type III) from outward propagating e beams, =2pene, start < 400 MHz : ne < 109 cm-3, energy ~10 keV.
Acceleration region in the corona, injects particles downward (chromosphere) & upward (high corona, IP space)
Particle acceleration in a simple flareV
ilmer et al. 2002 S
olar Phys 210, 261
5 min
![Page 33: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/33.jpg)
Particle acceleration associated with magnetic reconnection ? A simple scenario.
Particle acceleration region in a reconnecting coronal current sheet.
Electric fields : - plasma inflow (-VB)
- turbulence- termination shock (outflow/ambient plasma)
Vilmer et al. 2002 Solar Phys
![Page 34: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/34.jpg)
Mechanisms of charged particle acceleration
• Extended CS cannot exist in the solar corona : instabilities (e.g., tearing), fragmentation. Also : pb with high particle fluxes.
• Numerous regions with small-scale E fields, X points, O points and (contracting) magnetic islands.
• Multiple acceleration sites embedded in coronal plasma sheets.
Aschwanden 2002 SSR 101, 1
![Page 35: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/35.jpg)
Non thermal electrons in the corona outside flares
• Hot plasma (17 & 5.7 GHz), non thermal electrons (164 MHz)• electron beams in IP space (1000-20) kHz (1 day overview) Quasi-continuous electron acceleration in an active region, origin of
non-maxwellian particle populations in IP space ?
17 GHz Nobeyama 5.7 GHz Irkutsk 0.164 GHz Nançay
(20-1000 kHz) WAVES/WIND
24 h
Wind/WAVES
![Page 36: The Radio Sun NoRH 17 GHz / 1.8 cm VLA 1.4 GHz / 21 cm NRH 0.327 GHz / 91 cm Karl-Ludwig Klein Observatoire de Paris - Meudon Ludwig.klein@obspm.fr](https://reader033.vdocuments.site/reader033/viewer/2022051401/56649cb15503460f949763ca/html5/thumbnails/36.jpg)
Outlook: solar radio telescopes for the future
• The ideal solar imaging radio telescope : broadband cm-m-, 0.01-1 R above the photosphere, high cadence– The Frequency-Agile Solar Radio Telescope (FASR) 30 MHz-30 GHz– dm-: Chinese RH (underway) 400-1600 MHz– Nobeyama Radioheliograph 17 & 34 GHz (chromosphere/low corona -
flares and quiescent)– Siberian Solar Radio Telescope Irkutsk 5 GHz (low corona)– Nançay Radioheliograph 450-150 MHz (corona 0.5 R)
• General purpose synthesis arrays at m-– LOFAR, Europe : (200-30) MHz (NL; under construction/deployment)– MWA, Australia : (300-30) MHz (MIT-australian cooperation)– Solar use to be explored, under discussion
• Sub-mm-IR imaging at high cadence: SST; extend to FIR (space)
• Maintain whole Sun patrol instrumentation: flares mm-Dm-