|
Characteristics of kinematics of a coronal mass ejection during the 2010 August 1 CME-CME interaction event
|
|
Manuela Temmer Submitted: 2012-02-09 00:31
We study the interaction of two successive coronal mass ejections (CMEs)
during the 2010 August 1 events using STEREO/SECCHI COR and HI data. We obtain
the direction of motion for both CMEs by applying several independent
reconstruction methods and find that the CMEs head in similar directions. This
provides evidence that a full interaction takes place between the two CMEs that
can be observed in the HI1 field-of-view. The full de-projected kinematics of
the faster CME from Sun to Earth is derived by combining remote observations
with in situ measurements of the CME at 1 AU. The speed profile of the faster
CME (CME2; ~1200 km/s) shows a strong deceleration over the distance range at
which it reaches the slower, preceding CME (CME1; ~700 km/s). By applying a
drag-based model we are able to reproduce the kinematical profile of CME2
suggesting that CME1 represents a magnetohydrodynamic obstacle for CME2 and
that, after the interaction, the merged entity propagates as a single structure
in an ambient flow of speed and density typical for quiet solar wind
conditions. Observational facts show that magnetic forces may contribute to the
enhanced deceleration of CME2. We speculate that the increase in magnetic
tension and pressure, when CME2 bends and compresses the magnetic field lines
of CME1, increases the efficiency of drag.
Authors: Temmer, M.; Vrsnak, B.; Rollett, T.; Bein, B.; de Koning, C.A.; Liu, Y.; Bosman, E.; Davies, J.A.; M?stl, C.; Zic, T.; Veronig, A.M.; Bothmer, V.; Harrison, R.; Nitta, N.; Bisi, M.; Flor, O.; Eastwood, J.; Odstrcil, D.; Forsyth, R.
Projects: STEREO
|
Publication Status: ApJ (in press)
Last Modified: 2012-02-09 11:25
|
 
 
|
|
|
Influence of the ambient solar wind flow on the propagation behavior of interplanetary CMEs
|
|
Manuela Temmer Submitted: 2011-10-06 00:07
We study three CME/ICME events (2008 June 1-6, 2009 February 13-18, 2010
April 3-5) tracked from Sun to 1 AU in remote-sensing observations of STEREO
Heliospheric Imagers and in situ plasma and magnetic field measurements. We
focus on the ICME propagation in IP space that is governed by two forces, the
propelling Lorentz force and the drag force. We address the question at which
heliospheric distance range the drag becomes dominant and the CME gets adjusted
to the solar wind flow. To this aim we analyze speed differences between ICMEs
and the ambient solar wind flow as function of distance. The evolution of the
ambient solar wind flow is derived from ENLIL 3D MHD model runs using different
solar wind models, namely Wang-Sheeley-Arge (WSA) and MHD-Around-A-Sphere
(MAS). Comparing the measured CME kinematics with the solar wind models we find
that the CME speed gets adjusted to the solar wind speed at very different
heliospheric distances in the three events under study: from below 30 Rs, to
beyond 1 AU, depending on the CME and ambient solar wind characteristics. ENLIL
can be used to derive important information about the overall structure of the
background solar wind, providing more reliable results during times of low
solar activity than during times of high solar activity. The results from this
study enable us to get a better insight into the forces acting on CMEs over the
IP space distance range, which is an important prerequisite in order to predict
their 1 AU transit times.
Authors: Temmer, M., Rollett, T., M?stl, C., Veronig, A.M., Vrsnak, B.
Projects: STEREO
|
Publication Status: ApJ (in press)
Last Modified: 2011-10-06 11:40
|
 
 
|
|
|
Relation between the 3D-geometry of the coronal wave and associated CME during the 26 April 2008 event
|
|
Manuela Temmer Submitted: 2011-03-02 00:14
We study the kinematical characteristics and 3D geometry of a
large-scale coronal wave that occurred in association with the 26
April 2008 flare-CME event. The wave was observed with the EUVI
instruments aboard both STEREO spacecraft (STEREO-A and STEREO-B) with
a mean speed of ~240 km/s. The wave is more pronounced in the eastern
propagation direction, and is thus, better observable in STEREO-B
images. From STEREO-B observations we derive two separate initiation
centers for the wave, and their locations fit with the coronal dimming
regions. Assuming a simple geometry of the wave we reconstruct its 3D
nature from combined STEREO-A and STEREO-B observations. We find that
the wave structure is asymmetric with an inclination towards East. The
associated CME has a deprojected speed of ~750±50 km/s, and shows a
non-radial outward motion towards the East with respect to the
underlying source region location. Applying the forward fitting model
developed by
Thernisien, Howard, and Vourlidas (2006), we derive the
CME flux rope position on the solar surface to be close to the dimming
regions. We conclude that the expanding flanks of the CME most likely
drive and shape the coronal wave.
Authors: M. Temmer, A.M. Veronig, N. Gopalswamy, S. Yashiro
Projects: STEREO
|
Publication Status: Solar Physics (in press)
Last Modified: 2011-03-02 08:59
|
 
 
|
|
|
Analytic modeling of the Moreton wave kinematics
|
|
Manuela Temmer Submitted: 2009-08-26 01:49
The issue whether Moreton waves are flare-ignited or CME-driven, or a combination of both, is still a matter of debate. We develop an analytical model describing
the evolution of a large-amplitude coronal wave emitted by the expansion of a circular source surface in order to mimic the evolution of a Moreton wave. The model results
are confronted with observations of a strong Moreton wave observed in association with the X3.8/3B flare/CME event from January 17, 2005. Using different input parameters
for the expansion of the source region, either derived from the real CME observations (assuming that the upward moving CME drives the wave), or synthetically generated scenarios (expanding flare region, lateral expansion of the CME flanks), we calculate the kinematics of the associated Moreton wave signature. Those model input parameters are determined which fit the observed Moreton wave kinematics best. Using the measured kinematics of the upward moving CME as the model input, we are not able to reproduce the observed Moreton wave kinematics. The observations of the
Moreton wave can be reproduced only by applying a strong and impulsive acceleration for the source region expansion acting in a piston mechanism scenario. Based on these
results we propose that the expansion of the flaring region or the lateral expansion of the CME flanks is more likely the driver of the Moreton wave than the upward moving
CME front.
Authors: Temmer, M., Vrsnak, B., Zic, T., Veronig, A.M.
Projects: RHESSI,SoHO-MDI,SoHO-LASCO
|
Publication Status: ApJ, 2009, 702, p.1343
Last Modified: 2009-08-26 09:20
|
 
 
|
|
|
Subject will be restored when possible
|
|
Manuela Temmer Submitted: 2007-12-06 04:29
We study two well observed, fast halo CMEs, covering the full CME kinematics including the initiation and impulsive acceleration phase, and their associated flares. We find a close synchronization between the CME acceleration profile and the flare energy release as indicated by the RHESSI hard X-ray flux -- onsets as well as peaks occur simultaneously within 5~min. These findings indicate a close physical connection between both phenomena, and are interpreted in terms of a feed-back relationship between the CME dynamics and the reconnection process in the current sheet beneath the CME.
Authors: Temmer, M., Veronig, A.M., Vrsnak, B., Ryb?k, J., G?m?ry, P., Stoiser, S., Maricic, D.
Projects: RHESSI,SoHO-EIT,SoHO-LASCO,TRACE
|
Publication Status: ApJ Letters (accepted)
Last Modified: 2007-12-06 07:45
|
 
 
|
|
|
Subject will be restored when possible
|
|
Manuela Temmer Submitted: 2007-12-06 04:29
We study two well observed, fast halo CMEs, covering the full CME kinematics including the initiation and impulsive acceleration phase, and their associated flares. We find a close synchronization between the CME acceleration profile and the flare energy release as indicated by the RHESSI hard X-ray flux -- onsets as well as peaks occur simultaneously within 5~min. These findings indicate a close physical connection between both phenomena, and are interpreted in terms of a feed-back relationship between the CME dynamics and the reconnection process in the current sheet beneath the CME.
Authors: Temmer, M., Veronig, A.M., Vrsnak, B., Rybak, J., Gomory, P., Stoiser, S., Maricic, D.
Projects: RHESSI,SoHO-EIT,SoHO-LASCO,TRACE
|
Publication Status: ApJ Letters (accepted)
Last Modified: 2007-12-06 08:44
|
 
 
|
|
|
Subject will be restored when possible
|
|
Manuela Temmer Submitted: 2007-12-06 04:29
We study two well observed, fast halo CMEs, covering the full CME kinematics including the initiation and impulsive acceleration phase, and their associated flares. We find a close synchronization between the CME acceleration profile and the flare energy release as indicated by the RHESSI hard X-ray flux -- onsets as well as peaks occur simultaneously within 5~min. These findings indicate a close physical connection between both phenomena, and are interpreted in terms of a feed-back relationship between the CME dynamics and the reconnection process in the current sheet beneath the CME.
Authors: Temmer, M., Veronig, A.M., Vrsnak, B., Rybak, J., Gomory, P., Stoiser, S., Maricic, D.
Projects: RHESSI,SoHO-EIT,SoHO-LASCO,TRACE
|
Publication Status: ApJ Letters (accepted)
Last Modified: 2007-12-07 01:26
|
 
 
|
|
|
Energy release rates of H-alpha flare ribbons and locations of HXR sources
|
|
Manuela Temmer Submitted: 2006-09-19 23:19
Local reconnection and energy release rates for an X3.8 flare that occurred
on 17 January, 2005 are derived. In particular, we distinguished between Hα flare ribbon segments that were accompanied by RHESSI hard X-ray (HXR) footpoints and those without HXRs. We find that the reconnection and energy release rates are not uniform along the flare ribbons but much larger at the locations where the HXR footpoints are observed. The difference is about two orders of magnitude in case of the energy release rates and one order of magnitude for the reconnection rates (with peak values up to 8 kV/m). These differences are enough to explain the different flare morphologies typically observed in HXRs (compact footpoints) and Hα /UV (extended ribbons) by the limited dynamic range of present HXR instruments. Our results are consistent with a scenario where the electrons are accelerated primarily along a certain subsystem of magnetic loops as outlined by the hard X-ray footpoints, and only a minor fraction (for the 17 January, 2005 flare estimated to about 1/15) goes into the large flare arcade outlined by the Hα ribbons and EUV postflare loops.
Authors: Temmer, M., Veronig, A., Vrsnak, B., Miklenic, C.
Projects: RHESSI
|
Publication Status: ApJ (accepted)
Last Modified: 2006-09-21 10:46
|
 
 
|
|
|
SHRINKING AND COOLING OF FLARE LOOPS IN A TWO-RIBBON FLARE
|
|
Manuela Temmer Submitted: 2005-12-19 02:38
We analyze the evolution of the flare/postflare loop system in the two-ribbon
flare of 3 November 2003, utilizing multi-wavelength observations that cover
the temperature range from several tens MK down to 10^4 K. A non-uniform growth of the loop system enables us to identify analogous patterns in the height-time, h(t), curves measured at different temperatures. The “knees”, “plateaus”, and “bends” in a higher-temperature curve appear after a certain time delay at lower heights in a lower-temperature curve. We interpret such a shifted replication as a track of a given set of loops (reconnected field lines) while shrinking and cooling after being released from the reconnection site. Measurements of the height/time shifts between h(t) curves of different temperatures provide a simultaneous estimate of the shrinkage speed and cooling rate in a given temperature domain, for a period of almost ten hours after the flare impulsive phase. From the analysis we find: a) Loop shrinkage is faster at higher temperatures – in the first hour of the loop system growth the shrinkage velocity at 5 MK is 20–30 km/s, whereas at 1 MK it amounts to 5 km/s; b) Shrinking becomes slower as the flare decays – ten hours after the impulsive phase the shrinkage velocity at 5 MK becomes 5 km/s; c) The cooling rate decreases as the flare decays – in the 5 MK range it is 1 MK/min
in the first hour of the loop system growth, whereas ten hours later it decreases to 0.2 MK/min; d) During the initial phase of the loop system growth the cooling rate is larger at higher temperatures, whereas in the late phases the cooling rate apparently does not depend on the temperature; e) A more detailed analysis of shrinking/cooling around 1 hour after the impulsive phase reveals a deceleration of the loop shrinkage, amounting to a~10m/s^2 in theT < 5 MK range; f) In the same interval the conductive cooling dominates down to T~3 MK, whereas radiation becomes dominant below T~2 MK; g) A few hours after the impulsive phase the radiation becomes dominant across the whole T < 5 MK range. These findings are compared with results of previous studies and discussed in the framework of relevant
models.
Authors: Vrsnak, B., Veronig, A., Temmer, M., Karlicky, M., Lin, J.
Projects: RHESSI,Soho-EIT
|
Publication Status: Solar Physics (accepted)
Last Modified: 2005-12-19 02:40
|
 
 
|
|
|
Does solar flare activity lag behind sunspot activity?
|
|
Manuela Temmer Submitted: 2003-05-26 03:11
Recently, Wheatland & Litvinenko (2001) have suggested that over the solar cycle both the flaring rate and the magnetic free energy in the corona lag behind the energy supply to the system. To test this model result, we analyzed the evolution of solar flare occurrence with regard to Sunspot Numbers (as well as sunspot areas), using Hα flare data available for the period 1955-2002, and soft X-ray flare data (GOES 1-8 Angstroem) for the period 1976-2002. For solar cycles 19, 21 and 23, we find a characteristic time lag between flare activity and sunspot activity in the range ~10 < tau < ~15 months, consistent with the model predictions by Wheatland & Litvinenko (2001). The phenomenon turns out to be more prominent for high-energetic flares. The investigation of solar activity separately for the northern and southern hemisphere, allows us to exclude any bias due to overlapping effects from the activity of both hemispheres and confirms the dynamic relevance of the delay phenomenon. Yet, no characteristic time lag tau > 0 is found for solar cycles 20 and 22. The finding that in odd-numbered cycles flare activity is statistically delayed with respect to sunspot activity, while in even-numbered cycles it is not, suggests a connection to the 22-year magnetic cycle of the Sun. Further insight into the connection to the 22-year magnetic cycle could possibly be gained when a 22-year variation in the energy supply rate is taken into account in the Wheatland & Litvinenko (2001) model. The existence of a 22-year modulation in the energy supply rate is suggested by the empirical Gnevyshev-Ohl rule, and might be caused by a relic solar field.
Authors: Temmer, M., Veronig, A. and Hanslmeier, A.
Projects: None
|
Publication Status: Solar Physics (in press)
Last Modified: 2003-05-26 03:11
|
 
 
|
|
|
Statistical analysis of solar H-alpha flares
|
|
Manuela Temmer Submitted: 2002-10-02 09:35
A statistical analysis of a large data set of Hα flares comprising almost 100 000 single events that occurred during the period January 1975 to December 1999 is presented. We analyzed the flares evolution steps, i.e. duration, rise times, decay times and event asymmetries. Moreover, these parameters characterizing the temporal behavior of flares, as well as the spatial distribution on the solar disk, i.e. N-S and E-W asymmetries, are analyzed in terms of their dependency on the solar cycle. The main results are: 1) The duration, rise and decay times increase with increasing importance class. The increase is more pronounced for the decay times than for the rise times. The same relation is valid with regard to the brightness classes but in a weaker manner. 2) The event asymmetry indices, which characterize the proportion of the decay to the rise time of an event, are predominantly positive (ca. 90%). For about 50% of the events the decay time is even more than 4 times as long as the rise time. 3) The event asymmetries increase with the importance class. 4) The flare duration and decay times vary in phase with the solar cycle; the rise times do not. 5) The event asymmetries do not reveal a distinct correlation with the solar cycle. However, they drop during times of solar minima, which can be explained by the shorter decay times found during minimum activity. 6) There exists a significant N-S asymmetry over longer periods, and the dominance of
one hemisphere over the other can persist for more than one cycle. 7) For certain cycles there may be evidence that the N-S asymmetry evolves with the solar cycle, but in general this is not the case. 8) There exists a slight but significant E-W asymmetry with a prolonged eastern excess.
Authors: M. Temmer, A. Veronig, A. Hanslmeier, W. Otruba, and M. Messerotti
Projects:
|
Publication Status: A&A 375, 2001, 1049–1061
Last Modified: 2002-10-02 09:35
|
 
 
|
|
|
|
Key
|
 | Go to main E-Print page. |
 | Download Preprint. |
 | Submitters Homepage. |
 | Edit Entry. |
 | Delete abstract. |
|
|
|