Radio Diagnostics of Energetic Electrons from Solar Flares, CMEs and Shocks: Nicole Vilmer LESIA Observatoire de Paris UMR 8109 CNRS, UPMC, Université.
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Radio Diagnostics of Energetic Electrons from Solar Flares, CMEs and
Shocks:
Nicole VilmerLESIA Observatoire de Paris
UMR 8109 CNRS, UPMC, Université Paris-Diderot
ESPM 14 8-12 SEPTEMBER 2014TRINITY COLLEGE DUBLIN
DUBLIN
Electromagnetic radiation from energetic electrons
Dauphin et al., 2005
X-rays
MicrowavesGyrosynchrotron Emissions
Meter wavesPlasma emissions
Energetic electrons from the active Sun produce electromagnetic radiation in a very extended domain :
X-ray and Gamma-ray emissions
Radio emissions in the 10 kHz to >500 GHz domain
IIm
fb(Hz)= 2.8 1B (G)
fp(kHz)=9ne
cm- 3
INPUT of RADIO OBSERVATIONS in the GHz-MHz range
to SOLAR and HELIOSPHERIC PHYSICS
- What are the physical mechanisms leading to particle acceleration?
- What are the physical mechanisms leading to instabilities and eruptive activity in the coronal plasma?
1 GHz
100 MHz
10 MHz
1 MHz
INPUT of RADIO OBSERVATIONS in the 1 GHz-1 MHz range to SOLAR and HELIOSPHERIC PHYSICS
Plasma radio emissions from « non-thermal » electrons predominant below 1 GHz
Particle acceleration in flares and CMEs
Propagation of particles from the acceleration site to the interplanetary medium
Triggering and evolution of coronal mass ejections and shocks in the low corona
Radio emissions are TRACERS of dynamical processes (e.g. shocks) and of electron propagation in the corona and interplanetary medium.
Type III ( e beams)
Type II (shock)
Wind/WAVES(satellite)
Nançay DAM
Nançay ORFEES
Spectral identification of imaged radio sources
Nançay NRH
150 MHzPositions (2X1D) of radio
sources
http://radio-monitoring.obspm.fr/index.php
fp = 9 √ Ne
(kHz) cm-3
Radio emissions in the corona
2 Rs
NRH
LOFAR
VLA, OVSA
CSRH
327 MHz237 MHz164 MHz
Radio diagnostics of electron beams acceleration sites? propagation in the corona, in the interplanetary medium? Injection from the flare site to the IP medium? Radio diagnostics of shocks and
CMEs acceleration sites? origin of the shock wave?
~10000 types III « bursts » observed by the NRHin the frequency range 450-150 MHz from 1998 to 2008 (Saint-Hilaire, et al. , 2013)
Statistical studies on « coronal » type III bursts: flux distributions
Number of type III events in 3 months (with NRH observations)Blue: f 10.7 index (SFU)Red: Sunspot number
Statistical studies on « coronal » type III bursts:
Very close to results for radio bursts at higher frequencies (above 1GHz) slope of (-1.8)(Nita et al., 2002)Variation of radio flux with
frequency
(See also results on a type III burst between 3-50 MHz (Dulk et al., 2001)Constraints to type III emission models?
dN/dS= 0.34 ν−2:9S−1.7sfu-1 day-1
(( sfu−1 day−1
Coronal and Interplanetary type III bursts?
What about interplanetary type III bursts??
156 interplanetary Type III bursts with Stereo
Peak at 1 MHz for 156 type III bursts observed with STEREO (see Krupar et al., 2014)
Electron acceleration sites?
ARE THE TYPE III GENERATING ELECTRONS A PART OF THE SAME POPULATION AS HXR GENERATING ELECTRONS?
A question debated for many years:(e.g. Kane, 1971; 1981; Raoult et al., 1985, Hamilton, et al., 1995; Aschwanden et al., 1995; Benz et al., 2005; 2007)
Some Recent Results!
Radio and X-ray diagnostics of flare energetic electrons
Vilmer et al. 2002
RADIO
X-RAYS
One of the cartoon (how common?)
Electrons travelling downwards into the chromosphere radiate X-rays in dense (ne=1012 cm-3) plasma via Bremsstrahlung. Detected X-rays are usually in the 6-100 keV energy rangeElectrons travelling upwards can induce Langmuir waves which in turn produce coherent radio emission (type III) in the rarefied (ne<109 cm-3) coronal and interplanetary plasma. Detected radio frequencies are from around 400 MHz down to 2 MHZ
Standard picture ?Electron acceleration in the coronaPropagation both upwards and downwards. NRH and RHESSI
observations
ARE THE TYPE III GENERATING ELECTRONS A PART OF THE SAME POPULATION AS HXR GENERATING ELECTRONS?
For some events : YES See correlations between type III starting frequencies and HXR spectral index
Starting frequency of the radio type III burst (red) and HXR spectral index (green)
Reid, et al. 2011See also Raoult et al., 1985
ARE THE TYPE III GENERATINGELECTRONS A PART OF THE SAME POPULATION AS HXR GENERATING ELECTRONS?For some events : YES Is it the common rule?
Systematic search using RHESSI flare list and PHOENIX 2 catalogue of type III bursts30 events between 2002 and 2009
17/30 events (50% ) with correlations Use of a density model (exponential model derived from Saint Hilaire et al., 2013) to change frequency to height and thick target model to go from HXR spectral index to electron spectral index. Conclusion: For half of the events type III generating electrons are part of the same population as HXR generating electrons-
CC=-0.86
Reid et al., 2014
CC=0.85
Deducing the characteristics of acceleration region: height and size d using combined radio and X-ray observations and numerical simulations (Reid et al., 2011, 2014)
10 events: h (acceleration height) in the 25Mm to 180 Mm ranged (acceleration size) in the 2.1 to 16 MmConclusion: Extended acceleration region «high » in the coronaBUT flares with open field lines (metric type III burts)
What are the characteristics of the acceleration region?
onacceleratitypeIII hdh
From X-rays time of flight measurements H~ 20 Mm (see Aschwanden et al. , 1998))
Need of future imaging spectroscopy < 500 MHz(e.g. Chinese Solar RadioHeliograph,FASR,…)
Tracing electron beams in the corona with radio dynamics imaging
spectroscopyFirst observations of type IIIdm bursts1-2 GHzWith the new technique ofradio dynamic imaging spectroscopy recently upgraded Karl G. Jansky Very LargeArray (VLA). (Chen et al., 2013)Energy release height < 15 MmNote the spread of Positions at a given finjection of electron beamsin a fibrous coronaD<100 km
More to be learnt with the CSRH…
Tracing the path of electron beams in the corona to the IP medium
NRH
fluxRH
ESSI fluxRadio spectrum
Do all coronal type III bursts have X-ray counterparts?30% to 50% of type III events (only type III emissions) havea ssociated hard X-ray flares. Do all coronal type III bursts have an interplanetary counterpart?50% of events have emission < 14 MHz Bias for the more intense events having interplanetary emissionStudy based on >1000 type III bursts over 10 years of data
See poster by Reid,Vilmer
Flare Morphology
The “ standard” flare model is
very simplified. The reality is
more complicated
Particles can be injected into
different magnetic
structures during the course of a
flare.
This can influence whether the
electron beam makes it into
interplanetary space.
Tracing radio emitting electron beams in the corona to
the IP mediumLOFAR observations of type III radio burts at 50-55 MHz, 40-45 MHz and 30-35 MHz(tied-array mode) see Morosan et al., 2014 and talk
Type III sources at theflank of the CME
Another site of electron acceleration …Also seen at lower frequencies…
Radio diagnostics of electron beams acceleration sites? propagation in the corona, in the interplanetary medium? Injection from the flare site to the IP medium? Radio diagnostics of energetic
electrons from CMEs and shocks acceleration sites? origin of the shock wave?
Where are the electron acceleration sites
in the corona?Role of the Coronal Mass Ejection CME development and propagationCME interaction with other magnetic structures (open B lines, streamers) for the production of energetic electrons
Related to the shock wave?? (1)In the reconnection sheet formed below the CME?? (2)In the interaction regions during the evolution of the magnetic features ?? (3)
INPUT OF RADIO IMAGES…
Adapted from Démoulin et al., 2012
11
2
3
Electron acceleration in current Sheets in flares and CMEs
Evidence from Spectrography
Multifrequency imaging
Reconnection
Pick, Démoulin et al., 2005
Kliem, et al. 2000,Karlicky et al., 2002, 2004
S
M
Quasi periodic episodes from magnetic
reconnection in CS
Evidence for electron acceleration due to CME interaction
Electron acceleration (type III bursts) due to reconnection at the lateral flanks of CMEs
Démoulin et al., 2012
Type III position at 164 MHz and movement
Radio CME
Electron acceleration (herringbones) due to shock acceleration at the lateral flank of the CME Carley et al.,
2013
Positions of the bursty source at 150 MHz
- Shock in flares and CMEsCoronal type II bursts: signature of MHD shock waves (Wild & Smerd, 1972; Mann, 1995; Cairns 2011,…)Origin of the coronal shock wave?Flare blast wavePiston driven shock (eruptive magnetoplasma) structure A lot of discussions(Aurass 1997; Cliver et al., 1999; Vrsnak & Cliver 2008,…)Need to study the relative positions of radio type II sources and eruptive plasmaBut very few observations of type II bursts starting at high enough frequencies to compare positions of radio type II sources (e.g. with the NRH) with the positions of eruptive plasmas (seen in X-ray, EUV) A few studied cases of type II bursts starting at HF (~ 500 MHz)Gopalswamy et al., 1997; Klein et al., 1999; Dauphin et al., 2006, Magdalenic et al., 2010, Magdalenic et al., 2012; Bain et al., 2012; Zimovets et al;, 2012; Zucca et al., 2014 & posters
Klein et al., 1999
3
Positions of radio sources at the beginning of the type II emission at each frequencySource at 432 MHz above the LE of hot plasmaIncrease of the distance between the LE and the type II positions at lower frequencies
Origin of the shock in the low corona
Zimovets et al., 2012
Hot
Hot plasmacentroid /leading edge500 km/s
Type II1500- 2000km/s
Warm plasma 1100 km/s
Origin of the shock in the low coronaFlare blast wave or
piston driven? Two strong evidences in favour of the piston-driven shock wave scenario for this case: -location of the type-II burst source above the apex of the eruptive plasma leading edge -similar propagation direction of the type II and LE of the eruptive plasma But: how to explain the difference between the velocity of Leading edge of the eruptive plasma and the velocity of the shock (type II sources)?See e.g. numerical simulations of the propagation of a shock wave in a gravitationally stratified corona the shock wave (once created) can propagate faster through the corona than its driver .(piston driven and then freely propagating blast wave) See also very recent Type II/CME/ejecta observations by Carley, Pick (posters)
Pomoell et al., 2008
FR
shock
Origin of the shock in the interplanetary mediumGeneral agreement on the origin of Interplanetary
Shocks (IP shocks): CME driven (Cane et al. 1987; Gopalswamy et al., 2000)
Where are the radio type II sources in the IP Medium??
- Positions derived through triangulation of emissions observed by 2 spacecrafts ( STEREO B and WIND ) from 625 to 425 kHz
- 3D reconstruction of the CME (SOHO, STEREO)
Magdalenic et al., 2014
The source of the type II burst is at the southern flank of the CME!Close to the location of the interaction of the CME/shock and nearby coronal streamer!!
Observations of type II sources with LOFAR??
Magdalenic et al., 2014
See also talk by Susino
Radio Diagnostics of Energetic Electrons from Solar Flares, CMEs and Shocks
Radio emissions (1GHz-100 kHz) are TRACERS of dynamical processes (e.g. shocks) and of electron propagation in the corona and interplanetary medium
Electron acceleration sites?
Acceleration regions deduced from x-rays, radio imaging at 1 GHz<15 Mm,Combined X-ray/ radio observations (25 -200 Mm)BUT NO Images yet of the acceleration sites Input of radio images and spectra below 500 MHz! CSRH, FASR, other decimetric radioheliographs?)
Role of the CME development and interaction with ambient magnetic structureDifferent sites for electron acceleration (in extended CS below the CME flux rope, in interaction regions with surrounding B fields?
Formation of the shock ?Input of radio images below 100 MHz (LOFAR observations) Combination with space missions
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