Properties of stream interaction regions at Earth and Mars during the declining phase of SC 24 |
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Manuela Temmer Submitted: 2021-02-19 03:12
We inspect the evolution of stream interaction regions (SIRs) from Earth to Mars covering the distance range 1-1.5 AU, over the declining phase of solar cycle 24 (2014-2018). So far, studies only analyzed SIRs measured at Earth and Mars at different times. We compare existing catalogs for both heliospheric distances and arrive at a clean dataset for the identical time range. This allows a well-sampled statistical analysis and for the opposition phases of the planets an in-depth analysis of SIRs as they evolve with distance. We use in-situ solar wind data from OMNI and the MAVEN spacecraft as well as remote sensing data from SDO. A superposed epoch analysis is performed for bulk speed, proton density, temperature, magnetic field magnitude and total perpendicular pressure. Additionally, a study of events during the two opposition phases of Earth and Mars in the years 2016 and 2018 is conducted. SIR related coronal holes with their area as well as their latitudinal and longitudinal extent are extracted and correlated to the maximum bulk speed and duration of the corresponding high speed solar wind streams following the stream interaction regions. We find that while the entire solar wind HSS shows no expansion as it evolves from Earth to Mars, the crest of the HSS profile broadens by about 17%, and the magnetic field and total pressure by about 45% around the stream interface. The difference between the maximum and minimum values in the normalized superposed profiles increases slightly or stagnates from 1-1.5 AU for all parameters, except for the temperature. A sharp drop at zero epoch time is observed in the superposed profiles for the magnetic field strength at both heliospheric distances. Maximum solar wind speed has a stronger dependence on the latitudinal extent of the respective coronal hole than on its longitudinal extent. We arrive at an occurrence rate of fast forward shocks three times as high at Mars than at Earth.
Authors: Paul Geyer, Manuela Temmer, Jingnan Guo, Stephan G. Heinemann
Projects: None
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Publication Status: accepted for publication in A&A
Last Modified: 2021-02-20 22:48
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Deriving CME density from remote sensing data and comparison to in-situ measurements |
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Manuela Temmer Submitted: 2020-11-25 23:20
We determine the 3D geometry and deprojected mass of 29 well-observed coronal mass ejections (CMEs) and their interplanetary counterparts (ICMEs) using combined STEREO-SOHO white-light data. From the geometry parameters we calculate the volume of the CME for the magnetic ejecta (flux-rope type geometry) and sheath structure (shell-like geometry resembling the (I)CME frontal rim). Working under the assumption that the CME mass is roughly equally distributed within a specific volume, we expand the CME self-similarly and calculate the CME density for distances close to the Sun (15-30 Rs) and at 1AU. Specific trends are derived comparing calculated and in-situ measured proton densities at 1AU, though large uncertainties are revealed due to the unknown mass and geometry evolution: i) a moderate correlation for the magnetic structure having a mass that stays rather constant (~0.56-0.59), and ii) a weak correlation for the sheath density (~0.26) by assuming the sheath region is an extra mass - as expected for a mass pile-up process - that is in its amount comparable to the initial CME deprojected mass. High correlations are derived between in-situ measured sheath density and the solar wind density (~ -0.73) and solar wind speed (~0.56) as measured 24 hours ahead of the arrival of the disturbance. This gives additional confirmation that the sheath-plasma indeed stems from piled-up solar wind material. While the CME interplanetary propagation speed is not related to the sheath density, the size of the CME may play some role in how much material could be piled up.
Authors: M. Temmer, L. Holzknecht, M. Dumbovic, B. Vrsnak, N. Sachdeva, S.G. Heinemann, K. Dissauer, C. Scolini, E. Asvestari, A. M. Veronig, S. J. Hofmeister
Projects: None
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Publication Status: accepted for publication in JGR Space
Last Modified: 2020-11-30 16:54
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Coronal hole evolution from multi-viewpoint data as input for a STEREO solar wind speed persistence model |
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Manuela Temmer Submitted: 2018-02-01 01:52
We present a concept study of a solar wind forecasting method for Earth, based on persistence modeling from STEREO in-situ measurements combined with multi-viewpoint EUV observational data. By comparing the fractional areas of coronal holes (CHs) extracted from EUV data of STEREO and SoHO/SDO, we perform an uncertainty assessment derived from changes in the CHs and apply those changes to the predicted solar wind speed profile at 1AU. We evaluate the method for the time period 2008-2012, and compare the results to a persistence model based on ACE in-situ measurements and to the STEREO persistence model without implementing the information on CH evolution. Compared to an ACE based persistence model, the performance of the STEREO persistence model which takes into account the evolution of CHs, is able to increase the number of correctly predicted high-speed streams by about 12%, and to decrease the number of missed streams by about 23%, and the number of false alarms by about 19%. However, the added information on CH evolution is not able to deliver more accurate speed values for the forecast than using the STEREO persistence model without CH information which performs better than an ACE based persistence model. Investigating the CH evolution between STEREO and Earth view for varying separation angles over ~25-140? East of Earth, we derive some relation between expanding CHs and increasing solar wind speed, but a less clear relation for decaying CHs and decreasing solar wind speed. This fact most likely prevents the method from making more precise forecasts. The obtained results support a future L5 mission and show the importance and valuable contribution using multi-viewpoint data.
Authors: M. Temmer, J. Hinterreiter, M.A. Reiss
Projects: ACE,SDO-AIA,SoHO-EIT,STEREO
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Publication Status: The manuscript has been accepted for publication in the Journal of Space Weather and Space Climate (SWSC)
Last Modified: 2018-02-05 22:08
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On flare-CME characteristics from Sun to Earth combining remote-sensing image data with in-situ measurements supported by modeling |
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Manuela Temmer Submitted: 2017-03-05 23:42
We analyze the well observed flare-CME event from October 1, 2011 (SOL2011-10-01T09:18) covering the complete chain of action - from Sun to Earth - for a better understanding of the dynamic evolution of the CME and its embedded magnetic field. We study the solar surface and atmosphere associated with the flare-CME from SDO and ground-based instruments, and also track the CME signature off-limb from combined EUV and white-light data with STEREO. By applying 3D reconstruction techniques (GCS, total mass) to stereoscopic STEREO-SoHO coronagraph data, we track the temporal and spatial evolution of the CME in interplanetary space and derive its geometry and 3D-mass. We combine the GCS and Lundquist model results to derive the axial flux and helicity of the MC from in-situ measurements (Wind). This is compared to nonlinear force-free (NLFF) model results as well as to the reconnected magnetic flux derived from the flare ribbons (flare reconnection flux) and the magnetic flux encompassed by the associated dimming (dimming flux). We find that magnetic reconnection processes were already ongoing before the start of the impulsive flare phase, adding magnetic flux to the flux rope before its final eruption. The dimming flux increases by more than 25% after the end of the flare, indicating that magnetic flux is still added to the flux rope after eruption. Hence, the derived flare reconnection flux is most probably a lower limit for estimating the magnetic flux within the flux rope. We find that the magnetic helicity and axial magnetic flux are reduced in interplanetary space by ~50% and 75%, respectively, possibly indicating to an erosion process. A mass increase of 10% for the CME is observed over the distance range from ~4-20 Rs. The temporal evolution of the CME associated core dimming regions supports the scenario that fast outflows might supply additional mass to the rear part of the CME.
Authors: M. Temmer, J.K. Thalmann, K. Dissauer, A.M. Veronig, J. Tschernitz, J. Hinterreiter, L. Rodriguez
Projects: ACE,GOES X-rays,SDO-AIA,STEREO
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Publication Status: accepted for publication in Solar Physics
Last Modified: 2017-03-08 17:21
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Thermosphere and geomagnetic response to interplanetary coronal mass ejections observed by ACE and GRACE: Statistical results |
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Manuela Temmer Submitted: 2015-10-14 01:04
For the period July 2003 to August 2010, the interplanetary coronal mass
ejection (ICME) catalogue maintained by Richardson and Cane lists 106
Earth-directed events, which have been measured in-situ by plasma and field instruments onboard the ACE satellite. We present a statistical investigation of the Earth's thermospheric neutral density response by means of accelerometer measurements collected by the GRACE satellites, which are available for 104 ICMEs in the data set, and its relation to various geomagnetic indices and characteristic ICME parameters such as the impact speed, southward magnetic field strength (Bz). The majority of ICMEs causes a distinct density enhancement in the thermosphere, with up to a factor of eight compared to the pre-event level. We find high correlations between ICME Bz and thermospheric density enhancements (~0.9), while the correlation with the ICME impact speed is somewhat smaller (~0.7). The geomagnetic indices revealing the highest correlations are Dst and SYM-H (~0.9), the lowest correlations are obtained for kp and AE (~0.7), which show a nonlinear relation with the thermospheric density enhancements. Separating the response for the shock sheath region and the magnetic structure of the ICME, we find that the Dst and SYM-H reveal a tighter relation to the Bz minimum in the magnetic structure of the ICME, whereas the polar cap indices show higher correlations with the Bz minimum in the shock sheath region. Since the strength of the Bz component - either in the sheath or the magnetic structure of the ICME - is highly correlated (~0.9) with the neutral density enhancement, we discuss the possibility of satellite orbital decay estimates based on magnetic field measurements at L1, i.e. before
the ICME hits the Earth's magnetosphere. This will further stimulate progress in space weather understanding and applications regarding satellite operations.
Authors: S. Krauss, M. Temmer, A.M. Veronig, O. Baur, H. Lammer
Projects: ACE
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Publication Status: published in JGR; DOI: 10.1002/2015JA021702
Last Modified: 2015-10-15 07:27
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Interplanetary Propagation Behavior of the Fast Coronal Mass Ejection from 23 July 2012 |
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Manuela Temmer Submitted: 2014-11-25 00:14
The fast coronal mass ejection (CME) from 23 July 2012 raised attention due to its extremely short transit time from Sun to 1 AU of less than 21 h. In-situ data from STEREO-A revealed the arrival of a fast forward shock with a speed of more than 2200 km s-1 followed by a magnetic structure moving with almost 1900 km s-1. We investigate the propagation behavior of the CME shock and magnetic structure with the aim to reproduce the short transit time and high impact speed as derived from in-situ data. We carefully measure the 3D kinematics of the CME using the graduated cylindrical shell model, and obtain a maximum speed of 2580?280 km s-1 for the CME shock and of 2270?420 km s-1 for its magnetic structure. Based on the 3D kinematics, the drag-based model (DBM) reproduces the observational data reasonably well. To successfully simulate the CME shock, we find that the ambient flow speed should be of average value close to the slow solar wind speed (450 km s-1), and the initial shock speed at a distance of 30 Rs should not exceed ≈2300 km s-1, otherwise it would arrive much too early at STEREO-A. The model results indicate that an extremely low aerodynamic drag force is exerted on the shock, smaller by one order of magnitude compared to the average. As a consequence, the CME hardly decelerates in interplanetary space and maintains its high initial speed. The low aerodynamic drag can only be reproduced when reducing the density of the ambient solar wind flow, in which the massive CME propagates, to rho_sw=1-2 cm-3 at the distance of 1 AU. This result is consistent with the preconditioning of interplanetary space owing to a previous CME.
Authors: Manuela Temmer and Nariaki Nitta
Projects: SDO-AIA,SoHO-LASCO,STEREO
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Publication Status: in press for Solar Physics
Last Modified: 2014-11-25 08:18
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Characteristics of kinematics of a coronal mass ejection during the 2010 August 1 CME-CME interaction event |
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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 obtainthe direction of motion for both CMEs by applying several independentreconstruction methods and find that the CMEs head in similar directions. Thisprovides evidence that a full interaction takes place between the two CMEs thatcan be observed in the HI1 field-of-view. The full de-projected kinematics ofthe faster CME from Sun to Earth is derived by combining remote observationswith in situ measurements of the CME at 1 AU. The speed profile of the fasterCME (CME2; ~1200 km s-1) shows a strong deceleration over the distance range atwhich it reaches the slower, preceding CME (CME1; ~700 km s-1). By applying adrag-based model we are able to reproduce the kinematical profile of CME2suggesting that CME1 represents a magnetohydrodynamic obstacle for CME2 andthat, after the interaction, the merged entity propagates as a single structurein an ambient flow of speed and density typical for quiet solar windconditions. Observational facts show that magnetic forces may contribute to theenhanced deceleration of CME2. We speculate that the increase in magnetictension and pressure, when CME2 bends and compresses the magnetic field linesof 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.; Möstl, C.; Zic, T.; Veronig, A.M.; Bothmer, V.; Harrison, R.; Nitta, N.; Bisi, M.; Flor, O.; Eastwood, J.; Odstrcil, D.; Forsyth, R.
Projects: STEREO
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Publication Status: ApJ (in press)
Last Modified: 2012-02-09 11:25
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Influence of the ambient solar wind flow on the propagation behavior of interplanetary CMEs |
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Manuela Temmer Submitted: 2011-10-06 00:07
We study three CME/ICME events (2008 June 1-6, 2009 February 13-18, 2010April 3-5) tracked from Sun to 1 AU in remote-sensing observations of STEREOHeliospheric Imagers and in situ plasma and magnetic field measurements. Wefocus on the ICME propagation in IP space that is governed by two forces, thepropelling Lorentz force and the drag force. We address the question at whichheliospheric distance range the drag becomes dominant and the CME gets adjustedto the solar wind flow. To this aim we analyze speed differences between ICMEsand the ambient solar wind flow as function of distance. The evolution of theambient solar wind flow is derived from ENLIL 3D MHD model runs using differentsolar wind models, namely Wang-Sheeley-Arge (WSA) and MHD-Around-A-Sphere(MAS). Comparing the measured CME kinematics with the solar wind models we findthat the CME speed gets adjusted to the solar wind speed at very differentheliospheric distances in the three events under study: from below 30 Rs, tobeyond 1 AU, depending on the CME and ambient solar wind characteristics. ENLILcan be used to derive important information about the overall structure of thebackground solar wind, providing more reliable results during times of lowsolar activity than during times of high solar activity. The results from thisstudy enable us to get a better insight into the forces acting on CMEs over theIP space distance range, which is an important prerequisite in order to predicttheir 1 AU transit times.
Authors: Temmer, M., Rollett, T., Möstl, C., Veronig, A.M., Vrsnak, B.
Projects: STEREO
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Publication Status: ApJ (in press)
Last Modified: 2011-10-06 11:40
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Relation between the 3D-geometry of the coronal wave and associated CME during the 26 April 2008 event |
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Manuela Temmer Submitted: 2011-03-02 00:14
We study the kinematical characteristics and 3D geometry of alarge-scale coronal wave that occurred in association with the 26April 2008 flare-CME event. The wave was observed with the EUVIinstruments aboard both STEREO spacecraft (STEREO-A and STEREO-B) witha mean speed of ~240 km s -1. The wave is more pronounced in the easternpropagation direction, and is thus, better observable in STEREO-Bimages. From STEREO-B observations we derive two separate initiationcenters for the wave, and their locations fit with the coronal dimmingregions. Assuming a simple geometry of the wave we reconstruct its 3Dnature from combined STEREO-A and STEREO-B observations. We find thatthe wave structure is asymmetric with an inclination towards East. Theassociated CME has a deprojected speed of ~750±50 km s -1, and shows anon-radial outward motion towards the East with respect to theunderlying source region location. Applying the forward fitting modeldeveloped by Thernisien, Howard, and Vourlidas (2006), we derive theCME flux rope position on the solar surface to be close to the dimmingregions. We conclude that the expanding flanks of the CME most likelydrive and shape the coronal wave.
Authors: M. Temmer, A.M. Veronig, N. Gopalswamy, S. Yashiro
Projects: STEREO
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Publication Status: Solar Physics (in press)
Last Modified: 2011-03-02 08:59
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Analytic modeling of the Moreton wave kinematics |
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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
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Publication Status: ApJ, 2009, 702, p.1343
Last Modified: 2009-08-26 09:20
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Subject will be restored when possible |
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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., Gömöry, P., Stoiser, S., Maricic, D.
Projects: RHESSI,SoHO-EIT,SoHO-LASCO,TRACE
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Publication Status: ApJ Letters (accepted)
Last Modified: 2007-12-06 07:45
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Subject will be restored when possible |
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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., Gömöry, P., Stoiser, S., Maricic, D.
Projects: RHESSI,SoHO-EIT,SoHO-LASCO,TRACE
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Publication Status: ApJ Letters (accepted)
Last Modified: 2007-12-06 08:44
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Subject will be restored when possible |
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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., Gömöry, P., Stoiser, S., Maricic, D.
Projects: RHESSI,SoHO-EIT,SoHO-LASCO,TRACE
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Publication Status: ApJ Letters (accepted)
Last Modified: 2007-12-07 01:26
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