Author name code: maurya ADS astronomy entries on 2022-09-14 author:"Maurya, Ram Ajor" ------------------------------------------------------------------------ Title: Magnetic and Velocity Field Topology in Active Regions of Descending Phase of Solar Cycle 23 Authors: Maurya, R. A.; Ambastha, A. Bibcode: 2020SoPh..295..106M Altcode: 2020arXiv200613602M We analyze the topology of photospheric magnetic fields and sub-photospheric flows of several active regions (ARs) that are observed during the peak to descending phase of Solar Cycle 23. Our analysis shows clear evidence of hemispheric preferences in all the topological parameters such as the magnetic, current and kinetic helicities, and the `curl-divergence'. We found that 68%(67%) ARs in the northern (southern) hemisphere with negative (positive) magnetic helicity. Same hemispheric preference sign is found for the current helicity in 68%(68%) ARs. The hemispheric preferences are found to exist statistically for all the time except in a few ARs observed during the peak and the end phases of the solar cycle. This means that magnetic fields are dominantly left(right)-helical in scales smaller than individual ARs of northern(southern) hemisphere. We found that magnetic and current helicity parameters show equatorward propagation similar to the sunspot cycle. The kinetic helicity showed similar hemispheric trend to that of magnetic and current helicity parameters. There are 65%(56%) ARs with negative (positive) kinetic helicity as well as divergence-curl, at the depth of 2.4 Mm, in the northern (southern) hemisphere. The hemispheric preference of the kinetic helicity becomes more evident at larger depths, e.g., 69%(67%) at the depth of 12.6 Mm. A similar hemispheric trend of kinetic helicity to that of the current helicity supports the mean-field dynamo model. We also found that the hemispheric preference of all the parameters increases with the field strength of ARs. The topology of photospheric magnetic fields and near-surface sub-photospheric flow fields did not show good association but the correlation between them enhances with depths, which could be indicating more aligned flows at deeper layers of ARs. Title: Multi-wavelength view of an M2.2 solar flare on 26 november 2000 Authors: Chandra, R.; Verma, V. K.; Rani, S.; Maurya, R. A. Bibcode: 2017NewA...51..105C Altcode: 2016arXiv160805796C In this paper, we present a study of an M2.2 class solar flare of 26 November 2000 from NOAA AR 9236. The flare was well observed by various ground based observatories (ARIES, Learmonths Solar Observatory) and space borne instruments (SOHO, HXRS, GOES) in time interval between 02:30 UT to 04:00 UT. The flare started with long arc-shape outer flare ribbon. Afterwards the main flare starts with two main ribbons. Initially the outer ribbons start to expand with an average speed (∼20 km s-1) and later it shows contraction. The flare was associated with partial halo coronal mass ejection (CMEs) which has average speed of 495 km s-1. The SOHO/MDI observations show that the active region was in quadrupolar magnetic configuration. The flux cancellation was observed before the flare onset close to flare site. Our analysis indicate the flare was initiated by the magnetic breakout mechanism. Title: Strong Blue Asymmetry in Hα Line as a Preflare Activity Authors: Cho, Kyuhyoun; Lee, Jeongwoo; Chae, Jongchul; Wang, Haimin; Ahn, Kwangsu; Yang, Heesu; Lim, Eun-kyung; Maurya, Ram Ajor Bibcode: 2016SoPh..291.2391C Altcode: 2016SoPh..tmp..131C; 2020arXiv200506404C Chromospheric activities before solar flares provide important clues to the mechanisms that initiate solar flares, but are as yet poorly understood. We report a significant and rapid Hα line broadening before the solar flare SOL2011-09-29T18:08 that was detected using the unprecedented high-resolution Hα imaging spectroscopy with the Fast Imaging Solar Spectrograph (FISS) installed on the 1.6 m New Solar Telescope (NST) at Big Bear Solar Observatory. The strong Hα broadening extends as a blue excursion up to −4.5 Å and as a red excursion up to 2.0 Å, which implies a mixture of velocities in the range of −130 kms−1 to 38 km s−1 derived by applying the cloud model, comparable to the highest chromospheric motions reported before. The Hα blueshifted broadening lasts for about six minutes and is temporally and spatially correlated with the start of a rising filament, which is later associated with the main phase of the flare as detected by the Atmosphere Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The potential importance of this Hα blueshifted broadening as a preflare chromospheric activity is briefly discussed within the context of the two-step eruption model. Title: Fundamental-mode Oscillations of Two Coronal Loops within a Solar Magnetic Arcade Authors: Jain, Rekha; Maurya, Ram A.; Hindman, Bradley W. Bibcode: 2015ApJ...804L..19J Altcode: 2015arXiv150407822J We analyze intensity variations, as measured by the Atmospheric Imaging Assembly in the 171 Å passband, in two coronal loops embedded within a single coronal magnetic arcade. We detect oscillations in the fundamental mode with periods of roughly 2 minutes and decay times of 5 minutes. The oscillations were initiated by interaction of the arcade with a large wavefront issuing from a flare site. Further, the power spectra of the oscillations evince signatures consistent with oblique propagation to the field lines and for the existence of a two-dimensional waveguide instead of a one-dimensional one. Title: On the Association of Topologies of the Photospheric Magnetic Fields and Sub-photospheric Flows of Active Regions Authors: Maurya, Ram Ajor Bibcode: 2014cosp...40E2042M Altcode: Solar magnetic fields are believed to be generated near the solar tachocline jointly by differential rotation and turbulent motion, which are further transported toward the photosphere by convective flows. Therefore, we expect linear correlation between the topologies of the photospheric magnetic fields and the sub-photospheric flows. If observed magnetic fields conserve their helicity when they rise through the convection zone, the variation of kinetic helicity in the convection zone may be used as an observational tool for study the solar interior. Another important aspect of studying these parameters is due to their role in the energetic transients, e.g., flares and CMES. In order to examine the correlation between the two kinds of topologies, we analysed the photospheric and sub-photospheric properties of several active regions of the solar cycle 23 and 24. We computed the near sub-photospheric flows and topology parameters (e.g., vorticity, kinetic helicity) using local heliosiesmic techniques employed to the Doppler velocity observations. The photospheric magnetic field topology parameters, e.g., magnetic and current helicities, were determined from the magnetic field observations. We found opposite hemispheric trend in the topologies of the sub-photospheric flows and the photospheric magnetic fields. Details of the analysis will be presented in the paper. Title: Activity-related variations of high-degree p-mode amplitude, width, and energy in solar active regions Authors: Maurya, R. A.; Ambastha, A.; Chae, J. Bibcode: 2014A&A...561A.123M Altcode: 2013arXiv1310.6458M Context. Solar energetic transients such as flares and coronal mass ejections occur mostly within active regions (ARs) and release large amounts of energy, which is expected to excite acoustic waves by transferring the mechanical impulse of the thermal expansion of the flare on the photosphere. On the other hand, strong magnetic fields of AR sunspots absorb the power of the photospheric oscillation modes.
Aims: We study the properties of high-degree p-mode oscillations in flaring and dormant ARs and compare them with those in corresponding quiet regions (QRs) to find the association of the mode parameters with magnetic- and flare-related activities.
Methods: We computed the mode parameters using the ring-diagram technique. The magnetic-activity indices (MAIs) of ARs and QRs were determined from the line-of-sight magnetograms. The flare indices (FIs) of ARs were obtained from the GOES X-ray fluxes. Mode parameters were corrected for foreshortening, duty cycle, and MAI using multiple non-linear regression.
Results: Our analysis of several flaring and dormant ARs observed during the Carrington rotations 1980-2109 showed a strong association of the mode amplitude, width, and energy with magnetic and flare activities, although their changes are combined effects of foreshortening, duty cycle, magnetic-activity, flare-activity, and measurement uncertainties. We find that the largest reduction in mode amplitude and background power of an AR are caused by the angular distance of the AR from the solar disc centre. After correcting the mode parameters for foreshortening and duty cycle, we find that the mode amplitudes of flaring and dormant ARs are lower than in corresponding QRs reducing with increasing MAI, suggesting a stronger mode power suppression in ARs with larger magnetic fields. The mode widths in ARs are larger than in corresponding QRs and increase with MAI, indicating shorter lifetimes of modes in ARs than in QRs. The variations in mode amplitude and width with MAI are not same in different frequency bands. The largest amplification (reduction) in mode amplitude (mode width) of dormant ARs is found in the five-minute frequency band. The average mode energy of both the flaring and dormant ARs is smaller than in their corresponding QRs, reducing with increasing MAI. But the average mode energy reduction rate in flaring ARs is smaller than in dormant ARs. Moreover, the increase in mode width rate in dormant (flaring) ARs is followed by a decrease (increase) in the amplitude variation rate. Furthermore, including the mode corrections for MAI shows that mode amplitude and mode energy of flaring ARs escalate with FI, while the mode width shows an opposite trend, suggesting excitations of modes and growth in their lifetimes by flares. The increase (decrease) in mode amplitude (width) is larger in the five-minute and higher-frequency bands. The enhancement in width variation rate is followed by a rapid decline in the amplitude variation rate. Title: Chromospheric Doppler Velocity Oscillations in a Sunspot Authors: Maurya, R. A. Bibcode: 2013ASPC..478..339M Altcode: 2013arXiv1310.6462M We analyse the chromospheric Doppler velocity oscillations in a sunspot using the high resolution spectral observations obtained from the Fast Imaging Solar Spectrograph (FISS) of the New Solar Telescope at the Big Bear Solar Observatory. The Doppler velocity maps are constructed from the bisectors of the spectral observations. We find that the peak power frequency decreases gradually from the umbra to outward. Title: Seismology of Flaring and Dormant Active Regions Authors: Maurya, R. A. Bibcode: 2013ASPC..478..231M Altcode: 2013arXiv1310.6464M We study photospheric and sub-photospheric properties of active and quiet regions observed during 11 - 17 February 2011 including the first X-class flare X2.2 of the solar cycle 24 which occurred in the active region NOAA 11158 on 15 February 2011. The p-mode parameters and sub-photospheric flows are computed from the ring-diagrams and inversions. We found larger frequency shifts in active regions than quiet regions. The active region NOAA 11158 shows stronger twisted sub-photospheric flows than dormant active regions. The kinetic helicity density of sub-photospheric flows of the active region NOAA 11158 shows different structure on the flare day than the pre- and post-flare days. Title: Temperature of Solar Prominences Obtained with the Fast Imaging Solar Spectrograph on the 1.6 m New Solar Telescope at the Big Bear Solar Observatory Authors: Park, Hyungmin; Chae, Jongchul; Song, Donguk; Maurya, Ram Ajor; Yang, Heesu; Park, Young-Deuk; Jang, Bi-Ho; Nah, Jakyoung; Cho, Kyung-Suk; Kim, Yeon-Han; Ahn, Kwangsu; Cao, Wenda; Goode, Philip R. Bibcode: 2013SoPh..288..105P Altcode: We observed solar prominences with the Fast Imaging Solar Spectrograph (FISS) at the Big Bear Solar Observatory on 30 June 2010 and 15 August 2011. To determine the temperature of the prominence material, we applied a nonlinear least-squares fitting of the radiative transfer model. From the Doppler broadening of the Hα and Ca II lines, we determined the temperature and nonthermal velocity separately. The ranges of temperature and nonthermal velocity were 4000 - 20 000 K and 4 - 11 km s−1. We also found that the temperature varied much from point to point within one prominence. Title: Velocities and Temperatures of an Ellerman Bomb and Its Associated Features Authors: Yang, Heesu; Chae, Jongchul; Lim, Eun-Kyung; Park, Hyungmin; Cho, Kyuhyoun; Maurya, Ram Ajor; Song, Donguk; Kim, Yeon-Han; Goode, Philip R. Bibcode: 2013SoPh..288...39Y Altcode: We investigated the velocity and temperature characteristics of an Ellerman bomb (EB) and its associated features based on observations made with the Fast Imaging Solar Spectrograph (FISS) and a broadband TiO filter of the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. In the TiO images of the photospheric level, we found a granular cell expanding in two opposite directions near the site of the EB. When one end of this granule reached the EB site, the transverse speed of the tip of the expanding granule rapidly decreased and the EB brightened. The wings of the Hα profile of the EB indicated that the EB was blueshifted up to 7 km s−1. About 260 s after the EB brightening, a surge was seen in absorption and varied from a blueshift of 20 km s−1 to a redshift of 40 km s−1 seen in the Hα and Ca II 8542 Å lines. From the Doppler absorption width of the two lines determined by applying the cloud model, we estimated the mean temperature of the surge material to be about 29000 K and the mean speed of nonthermal motion to be about 11 km s−1. We discuss the physical implications of our results in terms of magnetic reconnection and processes related to it. Title: Chromospheric Sunspot Oscillations in Hα and Ca II 8542 Å Authors: Maurya, Ram Ajor; Chae, Jongchul; Park, Hyungmin; Yang, Heesu; Song, Donguk; Cho, Kyuhyoun Bibcode: 2013SoPh..288...73M Altcode: We study chromospheric oscillations including umbral flashes and running penumbral waves in a sunspot of active region NOAA 11242 using scanning spectroscopy in Hα and Ca II 8542 Å with the Fast Imaging Solar Spectrograph (FISS) at the 1.6 meter New Solar Telescope at the Big Bear Solar Observatory. A bisector method is applied to spectral observations to construct chromospheric Doppler-velocity maps. Temporal-sequence analysis of these shows enhanced high-frequency oscillations inside the sunspot umbra in both lines. Their peak frequency gradually decreases outward from the umbra. The oscillation power is found to be associated with magnetic-field strength and inclination, with different relationships in different frequency bands. Title: Helicity injection by flux motions and its role in flare and CMEs Authors: Panditi, Vemareddy; Ambastha, A.; Maurya, R.; Chae, J.; Ambstha, A.; Maurya, R. A.; Chae, J. Bibcode: 2013SPD....4430003P Altcode: An investigation of helicity injection by photospheric shear motions is carried out for two active regions (ARs), NOAA 11158 and 11166, using line-of-sight magnetic field observations obtained from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. We derived the horizontal velocities in the ARs from the differential affine velocity estimator (DAVE) technique. Persistent strong shear motions at maximum velocities in the range of 0.6-0.9 km s-1 along the magnetic polarity inversion line and outward flows from the peripheral regions of the sunspots were observed in the two ARs. The helicities injected in NOAA 11158 and 11166 during their six-day evolution period were estimated as 14.16x10$^42$ Mx$^2$ and 9.5x10$^42$ Mx$^2$, respectively. The estimated injection rates decreased up to 13% by increasing the time interval between the magnetograms from 12 minutes to 36 minutes, and increased up to 9% by decreasing the DAVE window size from 21x18 to 9x6 pixel$^2$, resulting in 10% variation in the accumulated helicity. In both ARs, the flare-prone regions (R2) had inhomogeneous helicity flux distribution with mixed helicities of both signs and coronal mass ejection (CME) prone regions had almost homogeneous distribution of helicity flux dominated by a single sign. The temporal profiles of helicity injection showed impulsive variations during some flares/CMEs due to negative helicity injection into the dominant region of positive helicity flux. A quantitative analysis reveals a marginally significant association of helicity flux with CMEs but not flares in AR 11158, while for the AR 11166, we find a marginally significant association of helicity flux with flares but not CMEs, providing evidence of the role of helicity injection at localized sites of the events. These short-term variations of helicity flux are further discussed in view of possible flare-related effects. This study suggests that flux motions and spatial distribution of helicity injection are important to understanding the complex nature of the magnetic flux system of the AR, and how it can lead to conditions favorable for eruptive events. Title: On the Role of Rotating Sunspots in the Activity of Solar Active Region NOAA 11158 Authors: Panditi, Vemareddy; Ambastha, A.; Maurya, R. Bibcode: 2013SPD....44..120P Altcode: We study the role of rotating sunspots in relation to the evolution of various physical parameters characterizing the non-potentiality of the active region (AR) NOAA 11158 and its eruptive events using the magnetic field data from the Helioseismic and Magnetic Imager (HMI) and multi-wavelength observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. From the evolutionary study of HMI intensity and AIA channels, it is observed that the AR consists of two major rotating sunspots, one connected to a flare-prone region and another with coronal mass ejection (CME). The constructed space-time intensity maps reveal that the sunspots exhibited peak rotation rates coinciding with the occurrence of major eruptive events. Further, temporal profiles of twist parameters, namely, average shear angle, αav, αbest, derived from HMI vector magnetograms, and the rate of helicity injection, obtained from the horizontal flux motions of HMI line-of-sight magnetograms, correspond well with the rotational profile of the sunspot in the CME-prone region, giving predominant evidence of rotational motion causig magnetic non-potentiality. Moreover, the mean value of free energy from the virial theorem calculated at the photospheric level shows a clear step-down decrease at the onset time of the flares revealing unambiguous evidence of energy release intermittently that is stored by flux emergence and/or motions in pre-flare phases. Additionally, distribution of helicity injection is homogeneous in the CME-prone region while in the flare-prone region it is not and often changes sign. This study provides a clear picture that both proper and rotational motions of the observed fluxes played significant roles in enhancing the magnetic non-potentiality of the AR by injecting helicity, twisting the magnetic fields and thereby increasing the free energy, leading to favorable conditions for the observed transient activity.Abstract (2,250 Maximum Characters): We study the role of rotating sunspots in relation to the evolution of various physical parameters characterizing the non-potentiality of the active region (AR) NOAA 11158 and its eruptive events using the magnetic field data from the Helioseismic and Magnetic Imager (HMI) and multi-wavelength observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. From the evolutionary study of HMI intensity and AIA channels, it is observed that the AR consists of two major rotating sunspots, one connected to a flare-prone region and another with coronal mass ejection (CME). The constructed space-time intensity maps reveal that the sunspots exhibited peak rotation rates coinciding with the occurrence of major eruptive events. Further, temporal profiles of twist parameters, namely, average shear angle, αav, αbest, derived from HMI vector magnetograms, and the rate of helicity injection, obtained from the horizontal flux motions of HMI line-of-sight magnetograms, correspond well with the rotational profile of the sunspot in the CME-prone region, giving predominant evidence of rotational motion causig magnetic non-potentiality. Moreover, the mean value of free energy from the virial theorem calculated at the photospheric level shows a clear step-down decrease at the onset time of the flares revealing unambiguous evidence of energy release intermittently that is stored by flux emergence and/or motions in pre-flare phases. Additionally, distribution of helicity injection is homogeneous in the CME-prone region while in the flare-prone region it is not and often changes sign. This study provides a clear picture that both proper and rotational motions of the observed fluxes played significant roles in enhancing the magnetic non-potentiality of the AR by injecting helicity, twisting the magnetic fields and thereby increasing the free energy, leading to favorable conditions for the observed transient activity. Title: Rotating sunspots and their role in the activity of solar active region NOAA 11158 Authors: Vemareddy, P.; Ambastha, A.; Maurya, R. A. Bibcode: 2013enss.confE...6V Altcode: We study the role of rotating sunspots in relation to the evolution of various physical parameters characterizing the non-potentiality of the active region (AR) NOAA 11158 and its eruptive events using the magnetic field data from the Helioseismic and Magnetic Imager (HMI) and multi-wavelength observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. From the evolutionary study of HMI intensity and AIA channels, it is observed that the AR consists of two major rotating sunspots, one connected to a flare-prone region and another with coronal mass ejection (CME). The constructed space-time intensity maps reveal that the sunspots exhibited peak rotation rates coinciding with the occurrence of major eruptive events. Further, temporal profiles of twist parameters, namely, average shear angle, α_{av}, α_{best}, derived from HMI vector magnetograms, and the rate of helicity injection, obtained from the horizontal flux motions of HMI line-of-sight magnetograms, correspond well with the rotational profile of the sunspot in the CME-prone region, giving predominant evidence of rotational motion causing magnetic non-potentiality. Moreover, the mean value of free energy from the virial theorem calculated at the photospheric level shows a clear step-down decrease at the onset time of the flares revealing unambiguous evidence of energy release intermittently that is stored by flux emergence and/or motions in pre-flare phases. Additionally, distribution of helicity injection is homogeneous in the CME-prone region while in the flare-prone region it is not and often changes sign. This study provides a clear picture that both proper and rotational motions of the observed fluxes played significant roles in enhancing the magnetic non-potentiality of the AR by injecting helicity, twisting the magnetic fields and thereby increasing the free energy, leading to favorable conditions for the observed transient activity. Title: Helicity Injection by the Shearing Motion of Fluxes in Relation to Flares and Coronal Mass Ejections Authors: Vemareddy, P.; Ambastha, A.; Maurya, R. A.; Chae, J. Bibcode: 2013enss.confE...8V Altcode: An investigation of helicity injection by photospheric shear motions is carried out for two active regions (ARs), NOAA 11158 and 11166, using line-of-sight magnetic field observations obtained from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. We derived the horizontal velocities in the ARs from the differential affine velocity estimator (DAVE) technique. Persistent strong shear motions at maximum velocities in the range of 0.6-0.9 km s^{-1} along the magnetic polarity inversion line and outward flows from the peripheral regions of the sunspots were observed in the two ARs. The helicities injected in NOAA 11158 and 11166 during their six-day evolution period were estimated as 14.16x10^{42} Mx^2 and 9.5×10^{42} Mx^2, respectively. The estimated injection rates decreased up to 13% by increasing the time interval between the magnetograms from 12 minutes to 36 minutes, and increased up to 9% by decreasing the DAVE window size from 21×18 to 9×6 pixel2, resulting in 10% variation in the accumulated helicity. In both ARs, the flare-prone regions (R2) had inhomogeneous helicity flux distribution with mixed helicities of both signs and coronal mass ejection (CME) prone regions had almost homogeneous distribution of helicity flux dominated by a single sign. The temporal profiles of helicity injection showed impulsive variations during some flares/CMEs due to negative helicity injection into the dominant region of positive helicity flux. A quantitative analysis reveals a marginally significant association of helicity flux with CMEs but not flares in AR 11158, while for the AR 11166, we find a marginally significant association of helicity flux with flares but not CMEs, providing evidence of the role of helicity injection at localized sites of the events. These short-term variations of helicity flux are further discussed in view of possible flare-related effects. This study suggests that flux motions and spatial distribution of helicity injection are important to understanding the complex nature of the magnetic flux system of the AR, and how it can lead to conditions favorable for eruptive events. Title: Chromospheric Waves and Oscillations in Sunspots Authors: Maurya, R. A.; Chae, J. Bibcode: 2013enss.confE..45M Altcode: We studied the chromospheric oscillations in and around a sunspot of the active region NOAA 11242 using high spectral and spatial resolution observations in the spectral lines Hα and Ca II 8542Å obtained from the Fast Imaging Solar Spectrograph (FISS) of 1.6 meter New Solar Telescope (NST) at Big Bear Solar Observatory. A suitable bisector method is applied to the spectral observations, to construct the chromospheric Doppler Velocity maps. Time series analysis of Doppler maps, in both the spectral bands, revealed enhanced high frequency oscillations inside the umbra of the sunspot. The frequency of oscillations gradually decreases from the umbra to outward. We have found clear evidence of two boundaries for the peak power frequency transformation, one of which occurs close to the umbral and penumbral boundary, and the other near the penumbral and super-penumbral boundary of the sunspot. The oscillation power is found to be associated with magnetic field strength and inclination, although they showed different relationships in different frequency bands. Title: On the Role of Rotating Sunspots in the Activity of Solar Active Region NOAA 11158 Authors: Vemareddy, P.; Ambastha, A.; Maurya, R. A. Bibcode: 2012ApJ...761...60V Altcode: 2012arXiv1210.3912V We study the role of rotating sunspots in relation to the evolution of various physical parameters characterizing the non-potentiality of the active region (AR) NOAA 11158 and its eruptive events using the magnetic field data from the Helioseismic and Magnetic Imager (HMI) and multi-wavelength observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. From the evolutionary study of HMI intensity and AIA channels, it is observed that the AR consists of two major rotating sunspots, one connected to a flare-prone region and another with coronal mass ejection (CME). The constructed space-time intensity maps reveal that the sunspots exhibited peak rotation rates coinciding with the occurrence of major eruptive events. Further, temporal profiles of twist parameters, namely, average shear angle, αav, αbest, derived from HMI vector magnetograms, and the rate of helicity injection, obtained from the horizontal flux motions of HMI line-of-sight magnetograms, correspond well with the rotational profile of the sunspot in the CME-prone region, giving predominant evidence of rotational motion causing magnetic non-potentiality. Moreover, the mean value of free energy from the virial theorem calculated at the photospheric level shows a clear step-down decrease at the onset time of the flares revealing unambiguous evidence of energy release intermittently that is stored by flux emergence and/or motions in pre-flare phases. Additionally, distribution of helicity injection is homogeneous in the CME-prone region while in the flare-prone region it is not and often changes sign. This study provides a clear picture that both proper and rotational motions of the observed fluxes played significant roles in enhancing the magnetic non-potentiality of the AR by injecting helicity, twisting the magnetic fields and thereby increasing the free energy, leading to favorable conditions for the observed transient activity. Title: On the Injection of Helicity by the Shearing Motion of Fluxes in Relation to Flares and Coronal Mass Ejections Authors: Vemareddy, P.; Ambastha, A.; Maurya, R. A.; Chae, J. Bibcode: 2012ApJ...761...86V Altcode: 2012arXiv1202.5195V An investigation of helicity injection by photospheric shear motions is carried out for two active regions (ARs), NOAA 11158 and 11166, using line-of-sight magnetic field observations obtained from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. We derived the horizontal velocities in the ARs from the differential affine velocity estimator (DAVE) technique. Persistent strong shear motions at maximum velocities in the range of 0.6-0.9 km s-1 along the magnetic polarity inversion line and outward flows from the peripheral regions of the sunspots were observed in the two ARs. The helicities injected in NOAA 11158 and 11166 during their six-day evolution period were estimated as 14.16 × 1042 Mx2 and 9.5 × 1042 Mx2, respectively. The estimated injection rates decreased up to 13% by increasing the time interval between the magnetograms from 12 minutes to 36 minutes, and increased up to 9% by decreasing the DAVE window size from 21 × 18 to 9 × 6 pixel2, resulting in 10% variation in the accumulated helicity. In both ARs, the flare-prone regions (R2) had inhomogeneous helicity flux distribution with mixed helicities of both signs and coronal mass ejection (CME) prone regions had almost homogeneous distribution of helicity flux dominated by a single sign. The temporal profiles of helicity injection showed impulsive variations during some flares/CMEs due to negative helicity injection into the dominant region of positive helicity flux. A quantitative analysis reveals a marginally significant association of helicity flux with CMEs but not flares in AR 11158, while for the AR 11166, we find a marginally significant association of helicity flux with flares but not CMEs, providing evidence of the role of helicity injection at localized sites of the events. These short-term variations of helicity flux are further discussed in view of possible flare-related effects. This study suggests that flux motions and spatial distribution of helicity injection are important to understanding the complex nature of the magnetic flux system of the AR, and how it can lead to conditions favorable for eruptive events. Title: On the Injection of Helicity by Shearing Motion of Fluxes in Relation to Flares and CMEs Authors: Panditi, Vemareddy; Ambastha, Ashok; Maurya, Ram Ajor Bibcode: 2012cosp...39.1440P Altcode: 2012cosp.meet.1440P An investigation of helicity injection by photospheric shear motions is presented for two active regions (ARs) NOAA 11158 and 11166, using line-of-sight magnetic field observations obtained from the Helioseismic and magnetic Imager (HMI) on-board Solar Dynamics Observatory (SDO). We derived the horizontal flux velocities in the ARs from Differential Affine Velocity Estimator (DAVE) technique. During the six day evolution period of the ARs, we found persistent strong shear motions at a maximum velocity in the range of 0.5-0.7 km-s-1 along the magnetic polarity inversion line (PIL) and outward flows from the peripheral regions of the sunspots. The helicities injected in AR 11158 and AR 11166 during the six days' period were estimated as 13.30×10^42 Mx2 and 9.5×10^42 Mx2, respectively. Temporal profiles of helicity injection showed impulsive variations at the onset times of flares/CMEs due to the negative helicity injection in the dominant region of positive helicity density. The spatial examination of helicity density maps showed that these variations resulted mainly due to the negative helicity injection in the regions of opposite helicity that were co-spatial with flaring sites. These co-spatial and co-temporal variations of helicity injection with flares are interpreted to be due to the relaxation from the state of high shear by the observed motions to a lower or shear-free state releasing energy in the form of eruptive events. This agrees with the simulations by Kusano et al. (2004) for the triggering mechanism of flares. However, for the flares of smaller magnitude no clear evidence of such changes was available. We expect that this difficulty could be addressed by careful calculations for the emergence term of helicity injection using the vector magnetic field data. Our study suggests that the existence of opposite helicity fluxes can trigger eruptive events, viz., flares and CMEs, and promises to be useful in forecasting the transient activity of ARs. Title: Photospheric Transients and Spectral Line Changes Associated with a Large X2.2 Flare Authors: Ambastha, Ashok; Maurya, Ram Ajor; Panditi, Vemareddy Bibcode: 2012cosp...39...42A Altcode: 2012cosp.meet...42A Solar energetic transients occurring in solar atmosphere are associated with catastrophic release of energy in the solar corona. These transients inject a part of their energy by various physical processes to the deeper, denser photospheric layer at which velocity and magnetic fields are measured using suitable spectral lines. Some signatures of these processes have been observed during the first X-class flare of the current solar cycle 24 in Active Region NOAA 11158 of 2011 February 15 using the data obtained from the Helioseismic and Magnetic Imager (HMI) on board Solar Dynamics Observatory (SDO). In particular, we detected short-lived magnetic and Doppler velocity transients together with abnormal polarity reversals during the impulsive phase of this large energetic flare. The observed photospheric changes associated with energetic transients have been an issue of serious debates as the magnetic (and Doppler) measurements are expected to be affected by flare-induced line profile changes. We explain the observed transient phenomena during the flare's impulsive phase using the SDO-HMI spectral data obtained before, during and after the flare. The corresponding physical processes are discussed in the light of recent flare models. Title: Filament Eruption in NOAA 11093 Leading to a Two-Ribbon M1.0 Class Flare and CME Authors: Vemareddy, P.; Maurya, R. A.; Ambastha, A. Bibcode: 2012SoPh..277..337V Altcode: 2011SoPh..tmp..413V; 2011arXiv1103.3168V; 2011SoPh..tmp..416V; 2011arXiv1103.3168R We present a multi-wavelength analysis of an eruption event that occurred in active region NOAA 11093 on 7 August 2010, using data obtained from SDO, STEREO, RHESSI, and the GONG Hα network telescope. From these observations, we inferred that an upward slow rising motion of an inverse S-shaped filament lying along the polarity inversion line resulted in a CME subsequent to a two-ribbon flare. Interaction of overlying field lines across the filament with the side-lobe field lines, associated EUV brightening, and flux emergence/cancelation around the filament were the observational signatures of the processes leading to its destabilization and the onset of eruption. Moreover, the time profile of the rising motion of the filament/flux rope corresponded well with flare characteristics, viz., the reconnection rate and hard X-ray emission profiles. The flux rope was accelerated to the maximum velocity as a CME at the peak phase of the flare, followed by deceleration to an average velocity of 590 km s−1. We suggest that the observed emergence/cancelation of magnetic fluxes near the filament caused it to rise, resulting in the tethers to cut and reconnection to take place beneath the filament; in agreement with the tether-cutting model. The corresponding increase/decrease in positive/negative photospheric fluxes found in the post-peak phase of the eruption provides unambiguous evidence of reconnection as a consequence of tether cutting. Title: Velocity and Magnetic Transients Driven by the X2.2 White-light Flare of 2011 February 15 in NOAA 11158 Authors: Maurya, R. A.; Vemareddy, P.; Ambastha, A. Bibcode: 2012ApJ...747..134M Altcode: 2011arXiv1106.4166M The first X-class flare of the current solar cycle 24 occurred in Active Region NOAA 11158 during its central meridian passage on 2011 February 15. This two-ribbon white-light flare was observed by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. During the peak phase of the flare, we detected magnetic and Doppler velocity (DV) transients appearing near the umbral boundary of the main sunspot. These transients persisted for a few minutes and showed spatial and temporal correspondence with the flare kernels. The observed magnetic polarity at the transients' locations underwent a sign reversal, together with a large enhancement in DVs. We explain this observational phenomenon using the HMI spectral data obtained before, during, and after the flare. These changes were reflected in the maps of the active region in all the Stokes parameters. Association of the transient features with various signatures of the flare and the cause and effects of their appearance are also presented on the basis of present theoretical models. Title: Spectral line profile changes associated with energetic solar transients Authors: Ambastha, Ashok; Maurya, Ram A. Bibcode: 2012ASInC...6..197A Altcode: 2012arXiv1203.3326A Solar energetic transients occurring in solar atmosphere are associated with catastrophic release of energy in the solar corona. These transients inject a part of their energy by various physical processes to the deeper, denser photospheric layer at which velocity and magnetic fields are measured using suitable spectral lines. Serious questions have been raised about the nature of the observed magnetic (and velocity) field changes associated with energetic transients as their measurements are expected to be affected by flare-induced line profile changes. In this paper, we shall discuss some recent progress on our understanding of the physical processes associated with such events. Title: Long term evolution of super active regions Authors: Maurya, Ram Ajor Bibcode: 2011ASInC...3..102M Altcode: In the solar cycle 23, there were some active regions (ARs) which produced energetic events, e.g. flares, CMEs, of unprecedented magnitudes during their disc passes, termed as super active regions (SARs). For example, NOAA 10486 stood unrivaled as it produced flares of unprecedented magnitude, such as X17/4B, X10/2B and X28 in quick succession. Occurrence of flares of such magnitude at this rate evidently requires extremely rapid energy buildup mechanism. Therefore, from their energetic considerations, these SARs are expected to possess distinctly different sup-photospheric flows as compared to less productive ARs. Study of such SARs is expected to provide important insights in our understanding of flare productivity, characterization of ARs, and in space-weather predictions. We derived sup-photospheric flows beneath these SARs using ring diagram technique, one of the local helioseismic techniques. We found strong and largely twisted sub-photospheric flows in the interior of SARs as compared to ARs. We present maps of sub-photospheric flows beneath some SARs and their evolution from one to next Carrington rotation. Title: Kinetic and magnetic helicities in solar active regions Authors: Maurya, Ram Ajor; Ambastha, Ashok; Reddy, Vema Bibcode: 2011JPhCS.271a2003M Altcode: We have studied the kinetic and magnetic helicities in sub-photospheric flows and photospheric magnetic fields, respectively, of a sample of 91 ARs of solar cycle 23. Hemispheric trend is investigated in the kinetic helicity of sub-photospheric flows averaged in the depth range of 2.5-12 Mms. Magnetic helicity parameters for the ARs are derived using photospheric vector magnetograms to examine their correlation with the corresponding kinetic helicities. We found no significant association between the two helicity parameters. Title: Variations in p-mode parameters and sub-surface flows of active regions with flare activity Authors: Maurya, R. A.; Ambastha, A. Bibcode: 2011ASInC...2..189M Altcode: 2011arXiv1106.4180M We examine the characteristic properties of photospheric p-modes and sub-photospheric flows of active regions (ARs) observed during the period of 26-31 October 2003. Using ring diagram analysis of Doppler velocity data obtained from the Global Oscillations Network Group (GONG), we have found that p-mode parameters evolve with ARs and show a strong association with flare activity. Sub-photospheric flows, derived using inversions of p-modes, show strong twist at the locations of ARs, and large variation with flare activity. Title: A Study of Oscillations in Solar Active Regions Authors: Maurya, Ram Ajor Bibcode: 2010PhDT.........2M Altcode: Solar active regions (ARs) are three-dimensional magnetic structures extending from deep sub-photosphere to coronal heights. These ARs are responsible for producing most of the energetic transients, such as flares and Coronal Mass Ejections (CMEs). The energetic charged particles released during these transients may also affect the measurements of magnetic and Doppler velocity fields. In addition, the energetic transients are expected to excite p-mode oscillations in ARs by imparting a mechanical impulse associated with their thermal expansion on the photosphere.

While studying the magnetic and velocity fields in AR NOAA 10486, we detected some puzzling moving transient features during the X17/4B and the X10/2B flares of 28 and 29 October 2003, respectively. We have examined the origin of these features and their relationship with various other aspects of the flares, viz., hard X-ray emission sources and flare kernels observed at different layers of solar atmosphere.

We have determined the characteristic properties of local oscillation modes by applying the ring diagram technique to 3-D power spectra of NOAA 10486. Strong evidence of substantial increase in mode amplitude and systematic variations in sub-surface flows are found from comparison of the pre- to the post-are phases of energetic flares. Furthermore, we have found statistically significant association between the mode energy and flare energy from the study of several ARs of Solar Cycle 23.

Our study has revealed strongly twisted, sheared flows in the interior of flaring ARs having complex magnetic fields. Using the Doppler data obtained for a sample of 74 ARs, we discovered steep gradients in meridional velocity at depths ranging from 1.5 to 5 Mm in flare productive ARs. The gradients showed an interesting hemispheric trend of negative (positive) sign in the northern (southern) hemispheres. An important inference derived from our analysis is that the location of the deepest zero vertical vorticity is correlated with the remaining lifetime of ARs. These new findings may be employed as important tool for predicting the life expectancy of an AR and space weather predictions. Finally, we have found using the data for 91 ARs of solar cycle 23 that kinetic helicity in sub-photospheric flows and magnetic helicity in photospheric magnetic fields show very weak correlation. Title: Sub-surface Meridional Flow, Vorticity, and the Lifetime of Solar Active Regions Authors: Maurya, R. A.; Ambastha, A. Bibcode: 2010ApJ...714L.196M Altcode: 2010arXiv1003.5273M Solar sub-surface fluid topology provides an indirect approach to examine the internal characteristics of active regions (ARs). Earlier studies have revealed the prevalence of strong flows in the interior of ARs having complex magnetic fields. Using the Doppler data obtained by the Global Oscillation Network Group project for a sample of 74 ARs, we have discovered the presence of steep gradients in meridional velocity at depths ranging from 1.5 to 5 Mm in flare productive ARs. The sample of these ARs is taken from the Carrington rotations 1980-2052 covering the period 2001 August-2007 January. The gradients showed an interesting hemispheric trend of negative (positive) signs in the northern (southern) hemisphere, i.e., directed toward the equator. We have discovered three sheared layers in the depth range of 0-10 Mm, providing evidence of complex flow structures in several ARs. An important inference derived from our analysis is that the location of the deepest zero vertical vorticity is correlated with the remaining lifetime of ARs. This new finding may be employed as a tool for predicting the life expectancy of an AR. Title: A Technique for Automated Determination of Flare Ribbon Separation and Energy Release Authors: Maurya, R. A.; Ambastha, A. Bibcode: 2010SoPh..262..337M Altcode: 2009arXiv0910.4245M; 2010SoPh..tmp...21M We present a technique for automatic determination of flare ribbon separation and the energy released during the course of two-ribbon flares. We have used chromospheric Hα filtergrams and photospheric line-of-sight magnetograms to analyse flare ribbon separation and magnetic field structures, respectively. Flare ribbons were first enhanced and then extracted by the technique of "region growing", i.e., a morphological operator to help resolve the flare ribbons. Separation of flare ribbons was then estimated from the magnetic-polarity reversal line using an automatic technique implemented into an Interactive Data Language (IDLTM) platform. Finally, the rate of flare-energy release was calculated using photospheric magnetic field data and the corresponding separation of the chromospheric Hα flare ribbons. This method could be applied to measure the motion of any feature of interest (e.g., intensity, magnetic, Doppler) from a given point of reference. Title: Magnetic and Velocity Field Changes Related to the Solar Flares of 28 and 29 October 2003 Authors: Maurya, R. A.; Ambastha, A. Bibcode: 2010ASSP...19..517M Altcode: 2010mcia.conf..517M; 2009arXiv0906.3965M Magnetic and velocity field measurements of solar active regions suffer from ambiguities caused by the change in spectral line profiles that occur during the impulsive phase of a major flare. This leads to difficulties in correct interpretation of any flare-related changes. Using magnetic and Doppler movies taken with GONG and MDI, we have detected transient, "moving" features around the peak phases of the X17.2/4B flare observed on 28 October 2003 and the X10/2B flare observed on 29 October 2003 in super-active region NOAA 10486. These features were located near the compact acoustic sources reported earlier by Donea and Lindsey (2005) and the seismic sources reported by Zharkova and Zharkov (2007).We find a moving feature, spatially and temporally associated with the flare ribbons, that separates away at speeds ranging from 30 to 50 km s-1 as observed in photospheric white light and in temperature-minimum (1600 Å), chromospheric (Hα), and transition-region (284Å ) intensities.We suggest that such moving features arise from the line-profile changes attributed to downward electron jets associated with the flare, and do not reflect real changes in the photospheric magnetic and velocity fields. However, abrupt and persistent changes in the pre- and post-flare phases were also found, which do not seem to be affected by line-profile changes. The detailed results have been appeared in Maurya and Ambastha (2009). Title: Flows in Flaring and Dormant Active Regions Authors: Maurya, R. A.; Ambastha, A. Bibcode: 2010ASSP...19..516M Altcode: 2010mcia.conf..516M During cycle 23, some active regions (ARs) produced extremely energetic flares and coronal mass ejections. These ARs are expected to be distinct from dormant ARs and quiet regions (QRs). It is of interest to identify whether the internal structure and dynamics of ARs is related to their outburst activity. For this investigation, we have obtained subsurface velocity flows in several ARs and QRs using ring diagram analysis, and derived the corresponding vorticities and kinetic helicity densities. Title: The Association of Energetic Events with p-Mode Energy Authors: Maurya, Ram Ajor; Ambastha, Ashok Bibcode: 2010cosp...38.3025M Altcode: 2010cosp...38.3025A; 2010cosp.meet.3025M The energetic events, e.g., flares, CMEs, etc. release large amount of energy, which may be able to excite acoustic waves (p-mode) by exerting mechanical impulse of the thermal expansion of the flare on the photosphere. This implied that during an energetic flare, energy of p-modes must be weighted by the energy of excited modes. To get the inferences of flare related enhances of p-mode energy, we have derived the magnetic energy released during a flare from magnetic field observations and associated p-mode energy from ring-diagram analysis. For the statistical studied of their association, we took samples of several high energy flares from Carrington rota-tions 1980-2052 covering the period August 2001-January 2007. We find significant relationship between them. A detailed description of our findings will be presented in the paper. Title: Variations in p-Mode Parameters with Changing Onset Time of a Large Flare Authors: Maurya, R. A.; Ambastha, A.; Tripathy, S. C. Bibcode: 2009ApJ...706L.235M Altcode: 2009arXiv0910.4247M It is expected that energetic solar flares releasing a large amount of energy at the photosphere may be able to excite the acoustic (p-) modes of oscillations. We have determined the characteristic properties of mode parameters by applying the ring diagram technique to three-dimensional power spectra obtained for solar active region NOAA 10486 during the long-duration energetic X17.2/4B flare of 2003 October 28. Strong evidence of substantial increase in mode amplitude and systematic variations in sub-surface flows, i.e., meridional and zonal components of velocity, kinetic helicity, and vorticity, is found from comparison of the pre- to the post-flare phases. Title: Transient Magnetic and Doppler Features Related to the White-Light Flares in NOAA 10486 Authors: Maurya, R. A.; Ambastha, A. Bibcode: 2009SoPh..258...31M Altcode: 2009arXiv0903.2138M Rapidly moving transient features have been detected in magnetic and Doppler images of super-active region NOAA 10486 during the X17/4B flare of 28 October 2003 and the X10/2B flare of 29 October 2003. Both these flares were extremely energetic white-light events. The transient features appeared during impulsive phases of the flares and moved with speeds ranging from 30 to 50 km s−1. These features were located near the previously reported compact acoustic (Donea and Lindsey, Astrophys. J.630, 1168, 2005) and seismic sources (Zharkova and Zharkov, Astrophys. J.664, 573, 2007). We examine the origin of these features and their relationship with various aspects of the flares, viz., hard X-ray emission sources and flare kernels observed at different layers: i) photosphere (white-light continuum), ii) chromosphere (Hα 6563 Å), iii) temperature minimum region (UV 1600 Å), and iv) transition region (UV 284 Å). Title: Magnetic and velocity field variations in the active regions NOAA 10486 and NOAA 10488 Authors: Maurya, Ram Ajor; Ambastha, Ashok Bibcode: 2008JApA...29..103M Altcode: We study the magnetic and velocity field evolution in the two magnetically complex active regions NOAA 10486 and NOAA 10488 observed during October-November 2003. We have used the available data to examine net flux and Doppler velocity time profiles to identify changes associated with evolutionary and transient phenomena. In particular, we report detection of rapid moving features observed in NOAA 10486 during the maximum phase of the X17.2/4B superflare of October 28, 2003. The velocity of this moving feature is estimated around 40 km/s, i.e., much greater than the usual Hα flare-ribbons' separation speed of 3-10 km/s, but similar to the velocity of seismic waves, i.e., ∼45 km/s reported earlier by Kosovichev & Zharkova (1998). Title: Hα intensity oscillations in large flares Authors: Maurya, Ram Ajor; Ambastha, Ashok Bibcode: 2008JApA...29..249M Altcode: We reinvestigate the problem of Hα intensity oscillations in large flares, particularly those classified as X-class flares. We have used high spatial and temporal resolution digital observations obtained from Udaipur Solar Observatory during the period 1998-2006 and selected several events. Normalized Lomb-Scargle periodogram method for spectral analysis was used to study the oscillatory power in quiet and active chromospheric locations, including the flare ribbons.