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Date:Geoeffectiveness Prediction of CMEs
Abstract
Coronal mass ejections (CMEs), the most important pieces of the puzzle that drive space weather, are continuously studied for their geomagnetic impact. We present here an update of a logistic regression method model, that attempts to forecast if a CME will arrive at the Earth and it will be associated with a geomagnetic storm defined by a minimum Dst value smaller than −30 nT. The model is run for a selection of CMEs listed in the LASCO catalogue during the solar cycle 24. It is trained on three fourths of these events and validated for the remaining one fourth. Based on five CME properties (the speed at 20 solar radii, the angular width, the acceleration, the measured position angle and the source position – binary variable) the model successfully predicted 98% of the events from the training set, and 98% of the events from the validation one.
On the Prediction of Geoeffectiveness of CMEs During the Ascending Phase of SC24 Using a Logistic Regression Method
Abstract
Coronal mass ejections (CMEs) are pieces of the puzzle that drive space weather. Numerous methods (theoretical, numerical and empirical) are being used to predict whether the CME will be geoeffective or not. We present here an attempt to predict the geoeffectiveness of a given CME using a modified version of logistic regression model proposed by Srivastava (2005), using only initial CME parameters. Our model attempts to forecast if the CME will be associated with geomagnetic storm defined by a minimum Dst value <-30 nT.We applied this modified logistic regression model for CMEs detected by LASCO during the ascending phase of solar cycle 24 (April 1, 2010 to June 30, 2011). Although the hit rate and proportion correctness were not promising for the training CME set, we obtained good hit rates and proportion correctness for the validation set.We expect to improve the model upon applying it to a dataset comprising an entire solar cycle.
A Study of Solar and Interplanetary Parameters of CMEs Causing Major Geomagnetic Storms during SC 23
Abstract
In this paper we analyse 25 Earth-directed and strongly geoeffective interplanetary coronal mass ejections (ICMEs) which occurred during solar cycle 23, using data provided by instruments on SOHO (Solar and Heliospheric Observatory), ACE (Advanced Composition Explorer) and geomagnetic stations. We also examine the in situ parameters, the energy transfer into magnetosphere, and the geomagnetic indexes. We compare observed travel times with those calculated by observed speeds projected into the plane of the sky and de-projected by a simple model. The best fit was found with the projected speeds. No correlation was found between the importance of a flare and the geomagnetic Dst (disturbance storm time) index. By comparing the in situ parameters with the Dst index we find a strong connection between some of these parameters (such as Bz, Bs · V and the energy transfer into the magnetosphere) with the strength of the geomagnetic storm. No correlation was found with proton density and plasma temperature. A superposed epoch analysis revealed a strong dependence of the Dst index on the southward component of interplanetary magnetic field, Bz, and to the Akasofu coupling function, which evaluates the energy transfer between the ICME and the magnetosphere. The analysis also showed that the geomagnetic field at higher latitudes is disturbed before the field around the Earth's equator.
Studies of Coronal Mass Ejections that Have Produced Major Geomagnetic Storms
Abstract
Twenty five major geomagnetic storms (Dst≤150 nT) associated with clear coronal mass ejections (CMEs) at the Sun were produced in the period 1996 - 2008. There were 57 possible coronal mass ejections (CMEs) which could have produced these storms. We are studying these CMEs in order to see their propagation and possible interaction into the interplanetary space. We will also investigate possible connection between CMEs and solar seismic signatures. Their in-situ signatures and their correlation with geomagnetic indexes are also analyzed.
Solar-Terrestrial Connections: Geomagnetic Storms Induced by Coronal Mass Ejections
Abstract
Not available.
A Comparison of the Acoustic Hardness of Acoustically Active and Non-Active Solar Flares
Abstract
Recent corrections to some of the GONG+intensity images of flares allow us to image the acoustic power of white light flare signatures. The images clearly show compact regions of white light power at 6 mHz, which are well correlated spatially with the seismic signatures of the flares, when the flare proved to be acoustically active. It has been a puzzle why some of the white light flares, mainly very strong flares, did not induced any seismic waves into the photosphere. We believe that a comparison of the white light spectral hardness of two flares (one seismically active and another one seismically quiet) is the clue to understand the physics of the sun quakes.
Recent Developments in Solar Quakes Studies
Abstract
Observations in hard and soft X-rays, chromospheric lines, and the visible continuum, together with helioseismic observations, make it possible to model the 3-dimensional profile of a sunquake from the corona into the subphotosphere of the active region that hosts the flare. Chromospheric line observations show us the part of the solar atmosphere where high-energy electrons are thought to cause thick-target heating that causes intense white-light emission and drives seismic waves into the active region subphotosphere. We have made a preliminary analysis of observations for some of the strongest acoustically noisy flares, including spectral observations in line NaD1 (586.9 nm) and line-center observations in Hα. Hα line-center observations will be shown for other sunquakes in Solar Cycle 23. Hinode will give us especially high-resolution chromospheric-line observations of acoustically active flares in Solar Cycle 24.
From Gigahertz to Millihertz: A Multiwavelength Study of the Acoustically Active 14 August 2004 M7.4 Solar Flare
Abstract
We carried out an electromagnetic acoustic analysis of the solar flare of 14 August 2004 in active region AR10656 from the radio to the hard X-ray spectrum. The flare was a GOES soft X-ray class M7.4 and produced a detectable sun quake, confirming earlier inferences that relatively low energy flares may be able to generate sun quakes. We introduce the hypothesis that the seismicity of the active region is closely related to the heights of coronal magnetic loops that conduct high-energy particles from the flare. In the case of relatively short magnetic loops, chromospheric evaporation populates the loop interior with ionised gas relatively rapidly, expediting the scattering of remaining trapped high-energy electrons into the magnetic loss cone and their rapid precipitation into the chromosphere. This increases both the intensity and suddenness of the chromospheric heating, satisfying the basic conditions for an acoustic emission that penetrates into the solar interior.
Chromospheric Line Emission Analysis of the July 16, 2004 Sun Quake
Abstract
Observations in chromospheric lines and the visible continuum together with photospheric helioseismic measurements make possible to image a 3-dimensional profile of a sun quake in a flaring region. Chromospheric line observations show us the part of the solar atmosphere where high-energy electrons are thought to cause thick target heating that then could also cause intense white-light emission and could drive seismic waves into the active region subphotosphere, we present here the preliminary results of the sun quake of July 16, 2004.
Outstanding Results of Romanian Solar Physics Research in the Frame of International Cooperation and PhD Grants Abroad
Abstract
The valuable results of the Romanian solar physics group in different fields of solar and solar-terrestrial researches are revised. A new index, Qx, was defined by us in order to give an evaluation of the Soft X-Ray (SXR) flare energy, similarly to the Q index for Hα flares. Seismic emission from solar flares is distinguished by its origin in plain view above the photosphere, as opposed to convective emission, which is hidden beneath the photosphere. To understand the physics of the acoustic radiation responsible for solar quakes a systematic survey covering a large number of X-class and some M-class solar flares observed by SOHO/MDI during 1996 and 2006 has been undertaken. A number of papers present the dynamics of the solar corona in the minimum phase (1996) and during the ascending phase (1998) of the solar cycle, using spectral data of LASCO-C1/SoHO experiment. In particular, the emergence of the slow solar wind at the above mentioned solar cycle phases was studied. A series of contributions subscribe to ongoing efforts to resolve plasma's fine-scale structure and dynamics at the base of coronal holes, aiming to better identify the fast solar wind origin in low solar atmosphere. Data from the highest resolution solar spectrograph, SUMER/SoHO, in EUV emission lines from transition region and corona were analyzed. We have also analyzed the cyclic distribution of high-speed streams in solar wind during the 1964-1996 interval (Solar Cycles nos. 20-22) as compared to the classical aspect of the 11-year cycle by sunspot relative numbers (Wolf numbers). The presence in heliosphere of the cool neutral Helium, among the other interstellar neutrals, was analyzed. The neutrals are ionized by charge exchange, photo ionization, and electron impact. Helium is focused by the Sun's gravitational field on the downwind side.
Helioseismic Analysis of the Solar Flare-Induced Sunquake of 2005 January 15
Abstract
We report the discovery of one of the most powerful sunquakes detected to date, produced by an X1.2-class solar flare in active region AR10720 on 2005 January 15. We used helioseismic holography to image the source of seismic waves emitted into the solar interior from the site of the flare. Acoustic egression power maps at 3 and 6 mHz with a 2-mHz bandpass reveal a compact acoustic source strongly correlated with impulsive hard X-ray and visible-continuum emission along the penumbral neutral line separating the two major opposing umbrae in the δ-configuration sunspot that predominates AR10720. At 6 mHz the seismic source has two components, an intense, compact kernel located on the penumbral neutral line of the δ-configuration sunspot that predominates AR10720, and a significantly more diffuse signature distributed along the neutral line up to ∼15 Mm east and ∼30 Mm west of the kernel. The acoustic emission signatures were directly aligned with both hard X-ray and visible continuum emission that emanated during the flare. The visible continuum emission is estimated at 2.0 × 1023 J, approximately 500 times the seismic emission of ∼4 × 1020 J. The flare of 2005 January 15 exhibits the same close spatial alignment between the sources of the seismic emission and impulsive visible continuum emission as previous flares, reinforcing the hypothesis that the acoustic emission may be driven by heating of the low photosphere. However, it is a major exception in that there was no signature to indicate the inclusion of protons in the particle beams thought to supply the energy radiated by the flare. The continued strong coincidence between the sources of seismic emission and impulsive visible continuum emission in the case of a proton-deficient white-lightflare lends substantial support to the ‘back-warming’ hypothesis, that the low photosphere is significantly heated by intense Balmer and Paschen continuum-edge radiation from the overlying chromosphere in white-light flares.
Study of the Seismically Active Flare of July 16, 2004
Abstract
Sunquakes have proven to be the most powerful events occurring at the solar surface. They are triggered by the impulsive flares produced in the corona, just above the acoustically active regions. Not every impulsive flare produces seismic waves emanating from the highly depressed photosphere, just beneath the flare. So far, we have identified a few mechanisms which can deliver acoustic energy into the photosphere: 1) the back-warming radiation suddenly heating the photosphere; 2) a strong shock-like compression wave propagating downwards into the chromosphere; 3) relativistic particles delivering directly the energy and momentum into the photosphere; and, 4) probably the magnetic tension at the feet of the loops. In order to discriminate which of these is the most efficient or dominated during a particular acoustically active flare, we have analysed the coronal and chromospheric emission of the regions just above the seismic source. We have performed a multiwavelength analysis of the active region 10649 that hosted the acoustically active solar flare of July 16, 2004. The spatial coincidence between the emissions at different layers of the sun, from the photosphere to the corona, suggests that high-energy particles travel through the coronal layers from the reconnection site, hit the solar chromosphere warming it up, which then, responds by sending further into the photosphere enough energy (carried either by the shock wave or by the Balmer and Pachen radiation) to produce a seismic event.
Chromospheric Line Emission in Seismically Active Flares
Abstract
Some flares are known to drive seismic transients into the solar interior. The effects of these seismic transients are seen in helioseismic observations of the Sun's surface thousands of km from their sources in the hour succeeding the impulsive phase of the flare. Energetic particles impinging from the corona into the chromosphere are known to drive strong, downward-propagating shocks in active region chromospheres during the impulsive phases of flares. Hα observations have served as an important diagnostic of these shocks, showing intense emission with characteristic transient redshifts. In most flares no detectable transients penetrate beneath the active region photosphere. In those that do, there is a strong correlation between compact white-light emission and the signature of seismic emission. This study introduces the first known Hα observations of acoustically active flares, centered in the core of the line. The morphology of line-core emission Hα in the impulsive phase of the flare is similar to that of co-spatial line-core emission in NaD 1, encompassing the site of seismic emission but more extended. The latter shows a compact red shift in the region of seismic emission, but a similar feature is known to appear in a conjugate magnetic footpoint from which no seismic emission emanates. Radiative MHD modelling based on the profiles of chromospheric line emission during the impulsive phases of flares can contribute significantly to our understanding of the mechanics of flare acoustic emission penetrating into the solar interior and the conditions under which it occurs.
Seismic Emission from a M9.5-class Solar Flare
Abstract
Following the discovery of a few significant seismic sources at 6.0 mHz from the large solar flares of October 28 and 29, 2003, we have extended SOHO/MDI helioseismic observations to moderate M-class flares. We report the detection of seismic waves emitted from the β γ δ active region NOAA 9608 on September 9, 2001. A quite impulsive solar flare of type M9.5 occurred from 20:40 to 20:48 UT. We used helioseismic holography to image seismic emission from this flare into the solar interior and computed time series of egression power maps in 2.0 mHz bands centered at 3.0 and 6.0 mHz. The 6.0 mHz images show an acoustic source associated with the flare some 30 Mm across in the East West direction and 15 Mm in the North South direction nestled in the southern penumbra of the main sunspot of AR 9608. This coincides closely with three white-light flare kernels that appear in the sunspot penumbra. The close spatial correspondence between white-light and acoustic emission adds considerable weight to the hypothesis that the acoustic emission is driven by heating of the lower photosphere. This is further supported by a rough hydromechanical model of an acoustic transient driven by sudden heating of the low photosphere. Where direct heating of the low photosphere by protons or high-energy electrons is unrealistic, the strong association between the acoustic source and co-spatial continuum emission can be regarded as evidence supporting the back-warming hypothesis, in which the low photosphere is heated by radiation from the overlying chromosphere. This is to say that a seismic source coincident with strong, sudden radiative emission in the visible continuum spectrum indicates a photosphere sufficiently heated so as to contribute significantly to the continuum emission observed.
New Detection of Acoustic Signatures from Solar Flares
Abstract
With the advancement of local helioseismic techniques such as helioseismic holography we have now detected numerous seismic sources of varying size and intensity produced by solar flares. We have performed a systematic survey of the SOHO-MDI database in search for seismic waves from X-class flares produced during 1996-2005. The detection of acoustically active flares has opened a new and promising connection between helioseismology and flare physics. The main question we ask is: why are some large flares acoustically active while most are acoustically inactive? We also address questions such as: Is photospheric heating by high-energy protons a major factor in seismic emission from flares? What is the effect of magnetic fields in the acoustics of a flare?
Magnetohelioseismic Analysis of AR10720 Using Helioseismic Holography
Abstract
We report on the recent discovery of one of the most powerful sunquakes detected to date produced by the January 15, 2005 X1.2 solar flare in active region 10720. We used helioseismic holography to image the acoustic source of the seismic waves produced by the flare. Egression power maps at 6 mHz with a 2 mHz bandwidth reveal a strong, compact acoustic source correlated with the footpoints of a coronal loop that hosted the flare. Using data from various solar observatories, we present a comprehensive analysis of the acoustic properties of the sunquake and investigate the role played by the configuration of the photospehric magnetic field in the production of flare generated sunquakes.
Seismic Emission from M-class Solar Flares
Abstract
Not available.
The Acoustically Active Solar Flare of 2005 January 15
Abstract
Not available.
Significant Acoustic Activity in AR10720 on January 15, 2005
Abstract
We report the recent discovery of one of the most acoustically powerful flare detected to date produced by the January 2005 2005, X1.2 solar flare in AR10720. We used helioseismic holography to image the acoustic source of the seismic waves produced by the flare. Egression Power maps at 6 mHz show a strong, extended acoustic signature which is the focus of the solar quake. At approximately 20 minutes after the appearance of the flare signature, we could also see the seismic response of the photosphere to the energy deposited by the flare in the form of "ripples" on the solar surface.
Seismic Radiation from M-class Solar Flares
Abstract
Helioseismic holography is a technique used to image the sources of seismic disturbances observed at the solar surface. It has been used to detect acoustic emission, known as sun quakes, radiated from X-class solar flares. Since the seismic power emitted by the X-class flares has proved to be independent of the strength of the flare, we have undertaking a systematic search for seismic signatures from M-class solar flares, observed by SOHO-MDI.We have detected significant acoustic emission from a few M-class solar flares.
A Survey of X-class Solar Flares during 2001 and 2002 in Search for Seismic Radiation
Abstract
Not available.