16 May – 5 June, 2005
This 3 week campaign is interruptible by Major Flare Watches
contact : karine.bocchialini/at/ias.u-psud.fr
LIST OF SEMINARS during MEDOC15 – 10:00 am, room 4-5:
Rim Turkmani on May 16 : cancelled
Eric Buchlin on May 18 : Statistical properties of turbulence and intermittency in the solar corona observed in EUV
Statistical properties of the fields observed on the Sun in EUV may help to understand turbulence in the solar corona and give clues to the processes involved in the heating of the corona to millions of degrees. In this study, we use a series of full-Sun images obtained in 1996 by the SUMER spectroheliograph on SoHO. Each observation consists of eight limb-to-limb raster scans in the lines Lyman epsilon, S VI 193.3nm, and S VI 194.4nm. Intensities, Doppler velocity shifts and line widths were computed on-board. A context spectrum was measured for each observation. Intensities and line-of-sight velocities data in a large central region of the Sun are then studied statistically: histograms of data values and of events, structure functions, and other statistics are computed. They can be compared to results obtained by imaging instruments like SoHO/EIT and to numerical simulations of MHD. Structure functions reveal that turbulence in the corona may be intermittent.
Alan Title on May 24 : Great Opportunities – Great Challenges
In 2006 Solar B will be launched in to a polar Sunrise-Sunset orbit carrying a diffraction limited 50 cm telescope with an advanced Stokes polarimeter, a 100 milliangstrom tunable filter, a broad-band imager. Also on Solar B is a EUV spectrometer and a full Sun x-Ray telescope. Solar B will transmit ~3.2 Gigabytes/day usually compressed to 3 bits/pixel or effectively about 10 to 12 Gigabytes/day of spectra and images. Two years later, 2008, the Solar Dynamics Observatory (SDO) will place the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) in ti a geo-synchronous orbit. Also on SDO is Extreme ultraviolet Variability Experiment (EVE). HMI maps the solar velocity and vector magnetic field with a cadence of 30 seconds and 5 minutes, respectively, with a spatial resolution of 1 arcsecond; while AIA maps the surface and corona in 10 spectral bands that sample the temperature range from 5000K to 20,000,000 K with a 10 second cadence and a spatial resolution of 1.2 arcseconds. Both HMI and AIA use 4096×4096 CCD cameras that readout in 2.3 seconds. The total data rate will be about 1.6 Terabytes/day. I will describe the great opportunity -A giant improvement on the SOHO era. The great challenges are for the solar community to understand and manage this immense data stream, to develop the analysis tools to extract physical properties from the data, and to construct models that can explain the observed phenomena.
Daniel Muller on May 25 : Coronal Rain – Theory and Observations
At high spatial and temporal resolution, coronal loops are observed to have a highly dynamic nature. Especially at transition region temperatures, blobs of cool plasma are frequently seen to "rain down" on the solar surface. Where is this coronal rain coming from? How much of this time-dependent behavior is due to changes in the total energy input into the loop and how much is due to intrinsic instabilities of the coronal plasma itself? I will present numerical simulations of coronal loops which indicate that any heating mechanism which dissipates energy predominantly at the footpoints of coronal loops is able to trigger a highly dynamic evolution due to a loss of thermal equilibrium at the loop apex.
The resulting process of plasma condensation or "catastrophic cooling"gives rise to high-speed downflows up to almost the free-fall speed and transient brightenings of transition region lines. Solving the non-equilibrium atomic rate equations self-consistently with the dynamic equations we are able to calculate time-dependent emission and line-shifts for a large number of transition region and coronal lines which are observed by SOHO and TRACE.
These results offer an explanation for recent observations of coronal rain. In contrast to earlier models, we suggest that the process of catastrophic cooling does not have to be initiated by a drastic decrease of the total loop heating but rather results from a loss of equilibrium at the loop apex. This is a natural consequence of heating concentrated at the footpoints of the loop, which can be constant in time.
Arek Berlicki on May 26 : Plasma flows during solar flares
An important aspect of flare evolution is the presence of plasma flows. These are characterised by asymmetrical profiles of spectral lines.
These asymmetries or line shifts (particularly in the blue wing)have been observed both in X-ray, EUV and in chromospheric lines. They are thought to be caused predominantly by vertical mass motions in flaring layers of the solar atmosphere.
It is now widely accepted that during solar flares the chromospheric plasma is evaporated into the corona providing material for the so-called post-flare loops. During the impulsive phase of solar flares the 'explosive' evaporation is observed. This kind of evaporation is caused predominantly by non-thermal electrons accelerated in the reconnection site in the corona and it
is characterised by large velocities of the plasma. Another situation occurs during the gradual phase of solar flares. Then, only a weak and slow chromospheric evaporation takes place.
This kind of upflow is referred to as 'gentle' evaporation and it could be driven by the conductive heat flux from a high-temperature flare plasma contained in magnetic tubes above the chromosphere.
The temperature of evaporating plasma is around 106-107 K during explosive evaporation and 104-105 K in the case of gentle evaporation.
Therefore, the plasma radiation is spreaded through a wide spectral range and different observational techniques and instruments must be applied to analyse these flows. The upflows in the optical and EUV spectral range were analysed using SOHO/CDS and ground base H-alpha data. The non-LTE techniques were
applied for H-alpha line emission.
We obtained the velocity of the hot and cool evaporating plasma and relate them spatially. The importance of spatially-resolved spectral observations in relation to our understanding of the flares is also presented.
Nicolas Decamp on May 27 : Particle acceleration and turbulence in flares
We will present a model of particle acceleration in a turbulent electric field in the RMHD approximation. Under this approximation, the structures generated by the turbulent cascade in the direction perpendicular to the magnetic field, propagate in the direction parallel to the magnetic field at the Alfvèn speed. The power law of the electric field induced should have a positive exponent and enhanced the phenomena associated to the small scales (dissipation, intermittency).
Our results (based on a p-model of turbulence coupled to a relativistic resolution of the motion equations) show that one part of the electrons accelerated is trapped (due to the structure of the potential field) and one part escapes. Studying the time evolution of the energy distribution of the escaping electrons, we found that the final distribution is reached in less than 0.1 s. This final energy distribution exhibits a power law, as well as a correlation between the heating and the accelerated particles. Finally, we show that the more important the intermittency (regulated by the p parameter) is, the higher the energies reached by the electrons are. Such a process should therefore be of key importance in the acceleration by a turbulent electric field.
Bernard Gelly on May 30 : THEMIS
Week 1 : May 16-22 (SUMER : detector A until ~May 19 ; detector B from ~May 20)
JOP124 : Oscillations in filaments and prominences – SUMER (PROM_OSC_LONG_15h.scl, PROM_OSC_LONG_15H4.scl), CDS, EIT
POC : Guillaume Pouget & Karine Bocchialini
JOP 177: Spicules- SUMER (SPIC_177_LBET_S7_6H.scl), EIT
POC : Zadig Mouradian
JOP180 : Magnetic Fields and Flows to Corona/Transition Region, EIT/TRACE/MDI/SUMER ((Detector A : vtt_sumer_qs_A.scl , vtt_sumer_ar_A.scl),/VTT,
POC: Andreas Lagg (lagg@mps.mpg.de) and Luca Teriaca for SUMER ; SUMER observing time : 8:00-12:00 UT
Observations of filaments – SUMER (Detector A, LYMAN_FIL.scl), CDS (arcont study)
POC : Brigitte Schmieder and Petr Heinzel
SUMER : Lyman lines
From ~May 20 (SUMER detector B):
JOP158: The fast solar wind from 1.05 to 4 solar radii – UVCS, SUMER (JOP158_O6SI8_6H_NA.scl, JOP158_O6SI8_9H_NA.scl), CDS
POC: Alan Gabriel
Polar coronal hole SUMER ( lwci_ch_june2004_A.scl ; lwci_ch_june2004_B.scl ; lwci_ch_june2004_C.scl ; lwci_ch_june2004_D.scl ; lwci_scat_1463_6h ; lwci_scat_june2004.scl )
POC : Laurent Dolla
Week 2 : May 23 – 29 (SUMER : detector B until ~May 24 with X = 0'' ; detector A from ~May 25)
First priority with SUMER until May 24:
JOP158: The fast solar wind from 1.05 to 4 solar radii – UVCS, SUMER (JOP158_O6SI8_6H_NA.scl, JOP158_O6SI8_9H_NA.scl), CDS
POC: Alan Gabriel
Polar coronal hole SUMER ( lwci_ch_june2004_A.scl ; lwci_ch_june2004_B.scl ; lwci_ch_june2004_C.scl ; lwci_ch_june2004_D.scl ; lwci_scat_1463_6h ; lwci_scat_june2004.scl )
POC : Laurent Dolla
From May 25 (for SUMER) :
JOP124 : Oscillations in filaments and prominences – SUMER (PROM_OSC_LONG_15h.scl, PROM_OSC_LONG_15H4.scl), CDS, EIT
POC : Guillaume Pouget & Karine Bocchialini
JOP 177: Spicules- SUMER (SPIC_177_LBET_S7_6H.scl), EIT
POC : Zadig Mouradian
Observations of filaments and/or prominences – SUMER (LYMAN_FIL.scl), CDS (arcont study)
POC : Brigitte Schmieder and Petr Heinzel
SUMER : Lyman lines
Active Region Campaign -CDS/VTT/THEMIS/TRACE
POC : Andrzej Fludra and Karin Muglach
CDS : from May 22 to 24, 2 to 3 hours between 7:00 and 14:00 UT ; from May 25 to 29, 5 to 7 hours during 7:00 – 14:00 UT
Week 3 : May 30 – June 5 (SUMER : detector A, until June 3)
JOP124 : Oscillations in filaments and prominences – SUMER (PROM_OSC_LONG_15h.scl, PROM_OSC_LONG_15H4.scl), CDS, EIT
POC : Guillaume Pouget & Karine Bocchialini
JOP 177: Spicules- SUMER (SPIC_177_LBET_S7_6H.scl), EIT
POC : Zadig Mouradian
JOP 174 – Plasma Condensation and Temporal Variations in Active Region Loops – CDS,SUMER,TRACE
POC : Terje Fredvik ; SUMER (FW_1400.scl) ; CDS : 17:00 – 24:00 UT ; TRACE : 18:00 – 24:00 UT
Active Region Campaign -CDS/VTT/THEMIS/TRACE
POC : Andrzej Fludra and Karin Muglach
CDS : 5 hours during VTT/THEMIS daytime : 5 to 7 hours during 7:00 – 14:00 UT
From May 30 to June 3 : Microflares, jets and macrospicule in and around PCH – EIT, TRACE, CORONAS, Pic du midi
POC: Serge Koutchmy and Leon Golub
From June 1 to June 3 : Ulysses quadrature, UVCS/Ulysses/SUMER (Ulyquad05_A.scl)
POC : Luca Teriaca
SUMER : 0:00 – 8:00 UT ; Pointing (-968",-411").
SUMER switched off on June 3.
Local Planners :
Week 1
SUMER : Thierry Appourchaux + Klaus Wilhelm from May 18 to May 22
CDS : Guillaume Pouget
EIT : Frederic Auchere
UVCS : Lucia Abbo (at MEDOC on May 19-20)
SOL : Jean-Claude Vial
Week 2
SUMER: Klaus Wilhelm from May 23 to May 24 + Arek Berlicki
CDS: Alan Gabriel
EIT: Frederic Auchere
SOL: Karine Bocchialini
Week 3
SUMER: Karine Bocchialini
CDS: Susanna Parenti
EIT: Frederic Auchere
SOL: Frédéric Auchère
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