Most fast coronal mass ejections (CMEs) originate from solar active regions (ARs). Non-potentiality of ARs plausibly determines the speed of CMEs in the outer corona. Several other unexplored parameters might be important as well. To find out the relation between the intial speed of CMEs and the non-potentiality of source ARs, we identified over a hundred of CMEs with source ARs via their co-produced flares. The speed of the CMEs are collected from the SOHO LASCO CME catalog. We have used vector magnetograms obtained with HMI/SDO, to evaluate various magnetic non-potentiality parameters, e.g. magnetic free-energy proxies, twist, shear angle, signed shear angle, net current etc. We have also included several other parameters e.g. total unsigned flux, magnetic area of ARs, area of sunspots, to investigate their correlation, if any, with the initial speeds of CMEs. Our preliminary results show that the ARs with larger non-potentiality and area produce faster CMEs but they can also produce slow ones. The ARs with lesser non-potentiality and area generally produce only slower CMEs.

sunspots↗

NASA NTRS2014

Exploring He II 304 A Spicules and Macrospicules at the Solar Limb

No abstract available

macrospicules↗

NASA NTRS2014

Speed of CMEs and the Magnetic Non-Potentiality of Their Source ARs

Most fast coronal mass ejections (CMEs) originate from solar active regions (ARs). Non-potentiality of ARs is expected to determine the speed and size of CMEs in the outer corona. Several other unexplored parameters might be important as well. To find out the correlation between the initial speed of CMEs and the non-potentiality of source ARs, we associated over a hundred of CMEs with source ARs via their co-produced flares. The speed of the CMEs are collected from the SOHO LASCO CME catalog. We have used vector magnetograms obtained mainly with HMI/SDO, also with Hinode (SOT/SP) when available within an hour of a CME occurrence, to evaluate various magnetic non-potentiality parameters, e.g. magnetic free-energy proxies, computed magnetic free energy, twist, shear angle, signed shear angle etc. We have also included several other parameters e.g. total unsigned flux, net current, magnetic area of ARs, area of sunspots, to investigate their correlation, if any, with the initial speeds of CMEs. Our preliminary results show that the ARs with larger non-potentiality and area mostly produce fast CMEs but they can also produce slower ones. The ARs with lesser non-potentiality and area generally produce only slower CMEs, however, there are a few exceptions. The total unsigned flux correlate with the non-potentiality parameters and area of ARs but some ARs with large unsigned flux are also found to be least non-potential. A more detailed analysis is underway.

Tiwari, Sanjiv K.↗

NASA NTRS2014

New Aspects of a Lid-Removal Mechanism in the Onset of an Eruption Sequence that Produced a Large Solar Energetic Particle (SEP) Event

No abstract available

solar energetic particle↗

NASA NTRS2014

SDO and STEREO Observations of Prominence Dynamics During a Series of Eight Homologous Flares

Homologous flares are eruptive events that occur repetitively in the same active region, with similar structure and morphology. A series of at least eight homologous flares occurred in active region NOAA 11237 over 16 - 17 June 2011. A filament is rooted in the active region with an overlying coronal cavity. The active region appears on the southeast solar limb as seen from SDO/AIA, and on the disk as viewed from STEREO-B/EUVI; the dual perspective allows us to study in detail behavior of prominence/filament material entrained in the magnetic field of the repeatedly-erupting system. Each of the eruptions was mainly confined, with active-region prominence material being ejected from the core of the erupting region onto outer-lobe loops of the active region. The eruption series repeatedly disrupted material of a quiet-Sun extension of the prominence, and that material became suspended at progressively higher heights above the surface. Two final eruptions from the core region destabilized the field holding that material, instigating a coronal mass ejection (CME).

homologous flares↗

NASA NTRS2014

Transition-Region/Coronal Signatures of Penumbral Microjets: Hi-C, SDO/AIA and Hinode (SOT/FG) Observations

Penumbral microjets are bright, transient features seen in the chromosphere of sunspot penumbrae. Katsuaka et al. (2007) noted their ubiquity and characterized them using the Ca II H-line filter on Hinode's Solar Optical Telescope (SOT). The jets are 1000{4000 km in length, 300{400 km in width, and last less than one minute. It was proposed that these penumbral microjets could contribute to the transition-region and coronal heating above sunspots. We examine whether these microjets appear in the transition-region (TR) and/or corona or are related{ temporally and spatially{ to similar brightenings in the TR and/or corona. First, we identify penumbral microjets with the SOT's Ca II H-line filter. The chosen sunspot is observed on July 11, 2012 from 18:50:00 UT to 20:00:00 UT at approx. 14 inches, -30 inches. We then examine the sunspot in the same field of view and at the same time in other wavelengths. We use the High Resolution Coronal Imager Telescope (Hi-C) at 193A and the 1600A, 304A, 171A, 193A, and 94A passbands of the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamic Observatory. We include examples of these jets and where they should appear in the other passbands, but find no signifcant association, except for a few jets with longer lifetimes and bigger sizes seen at locations in the penumbra with repeated stronger brightenings. We conclude that the normal microjets are not heated to transition-region/coronal temperatures, but the larger jets are.

Tiwari, Sanjiv K.↗

NASA NTRS2014

Miniature Filament Eruptions and their Reconnections in X-Ray Jets: Evidence for a New Paradigm

We investigate the onset of approximately10 random X-ray jets observed by Hinode/XRT. Each jet was near the limb in a polar coronal hole, and showed a ``bright point'' in an edge of the base of the jet, as is typical for previously-observed X-ray jets. We examined SDO/AIA EUV images of each of the jets over multiple AIA channels, including 304 Ang, which detects chromospheric emissions, and 171, 193, and 211 Ang, which detect cooler-coronal emissions. We find the jets to result from eruptions of miniature (size less than approximately 10 arcsec) filaments from the bases of the jets. Much of the erupting-filament material forms a chromospheric-temperature jet. In the cool-coronal channels, often the filament appears in absorption and the jet in emission. The jet bright point forms at the location from which the miniature filament is ejected, analogous to the formation of a standard solar flare in the wake of the eruption of a typical larger-scale chromospheric filament. Thus these X-ray jets and their bright points are made by miniature filament eruptions. They are evidently produced the same way as an on-disk coronal jet we observed in Adams et al. (2014); that on-disk jet had no obvious emerging magnetic field in its base. We conclude that, for many jets, the standard idea of X-ray jets forming from reconnection between emerging flux and preexisting coronal field is incorrect. ACS and RLM were supported by funding from NASA/LWS, Hinode, and ISSI.

Sterling, Alphonse C.↗

NASA NTRS2014

Magnetic Untwisting in Solar Jets that Go into the Outer Corona in Polar Coronal Holes

We present results from 14 exceptionally high‐reaching large solar jets observed in the polar coronal holes. EUV movies from SDO/AIA show that each jet is similar to many other similar‐size and smaller jets that erupt in coronal holes, but each is exceptional in that it goes higher than most other jets, so high that it is observed in the outer corona beyond 2.2 R(sub Sun) in images from the SOHO/LASCO/C2 coronagraph. For these high‐reaching jets, we find: (1) the front of the jet transits the corona below 2.2 R(sub Sun) at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most jets display oscillatory swaying having an amplitude of a few degrees and a period of order 1 hour. We conclude that these jets are magnetically driven, propose that the driver is a magnetic‐untwisting wave that is grossly a large‐amplitude (i.e., nonlinear) torsional Alfven wave that is put into the reconnected open magnetic field in the jet by interchange reconnection as the jet erupts, and estimate from the measured spinning and swaying that the magnetic‐untwisting wave loses most of its energy in the inner corona below 2.2 R(sub Sun). From these results for these big jets, we reason that the torsional magnetic waves observed in Type‐II spicules should dissipate in the corona in the same way and could thereby power much of the coronal heating in coronal holes.

Moore, Ronald L.↗

NASA NTRS2014

MAG4 Versus Alternative Techniques for Forecasting Active-Region Flare Productivity

MAG4 (Magnetogram Forecast), developed originally for NASA/SRAG (Space Radiation Analysis Group), is an automated program that analyzes magnetograms from the HMI (Helioseismic and Magnetic Imager) instrument on NASA SDO (Solar Dynamics Observatory), and automatically converts the rate (or probability) of major flares (M- and X-class), Coronal Mass Ejections (CMEs), and Solar Energetic Particle Events. MAG4 does not forecast that a flare will occur at a particular time in the next 24 or 48 hours; rather the probability of one occurring.

Falconer, David A.↗

NASA NTRS2014

MAG4 Versus Alternative Techniques for Forecasting Active-Region Flare Productivity

MAG4 is a technique of forecasting an active region's rate of production of major flares in the coming few days from a free-magnetic-energy proxy. We present a statistical method of measuring the difference in performance between MAG4 and comparable alternative techniques that forecast an active region's major-flare productivity from alternative observed aspects of the active region. We demonstrate the method by measuring the difference in performance between the "Present MAG4" technique and each of three alternative techniques, called "McIntosh Active-Region Class," "Total Magnetic Flux," and "Next MAG4." We do this by using (1) the MAG4 database of magnetograms and major-flare histories of sunspot active regions, (2) the NOAA table of the major-flare productivity of each of 60 McIntosh active-region classes of sunspot active regions, and (3) five technique-performance metrics (Heidke Skill Score, True Skill Score, Percent Correct, Probability of Detection, and False Alarm Rate) evaluated from 2000 random two-by-two contingency tables obtained from the databases. We find that (1) Present MAG4 far outperforms both McIntosh Active-Region Class and Total Magnetic Flux, (2) Next MAG4 significantly outperforms Present MAG4, (3) the performance of Next MAG4 is insensitive to the forward and backward temporal windows used, in the range of one to a few days, and (4) forecasting from the free-energy proxy in combination with either any broad category of McIntosh active-region classes or any Mount Wilson active-region class gives no significant performance improvement over forecasting from the free-energy proxy alone (Present MAG4).

Falconer, David A.↗

NASA NTRS2014

New Aspects of a Lid-Removal Mechanism in the Onset of a SEP-Producing Eruption Sequence

We examine a sequence of two ejective eruptions from a single active region on 2012 January 23, using magnetograms and EUV images from SDO/HMI and SDO/AIA, and EUV images from STEREO. Cheng et al. (2013) showed that the first eruption's ("Eruption 1'') flux rope was apparent only in "hotter'' AIA channels, and that it removed overlying field that allowed the second eruption (``Eruption 2'') to begin via ideal MHD instability; here we say Eruption 2 began via a ``lid removal'' mechanism. We show that during Eruption-1's onset, its flux rope underwent ``tether weakening'' (TW) reconnection with the field of an adjacent active region. Standard flare loops from Eruption 1 developed over Eruption-2's flux rope and enclosed filament, but these overarching new loops were unable to confine that flux rope/filament. Eruption-1's flare loops, from both TW reconnection and standard-flare-model internal reconnection, were much cooler than Eruption-2's flare loops (GOES thermal temperatures of approx. 9 MK compared to approx. 14 MK). This eruption sequence produced a strong solar energetic particle (SEP) event (10 MeV protons, >10(exp 3) pfu for 43 hrs), apparently starting when Eruption-2's CME blasted through Eruption-1's CME at 5-10 R_s. This occurred because the two CMEs originated in close proximity and in close time sequence: Eruption-1's fast rise started soon after the TW reconnection; the lid removal by Eruption-1's ejection triggered the slow onset of Eruption 2; and Eruption-2's CME, which started approx. 1 hr later, was three times faster than Eruption-1's CME.

Sterling, Alphonse C.↗

NASA NTRS2014

MAG4 Versus Alternative Techniques for Forecasting Active-Region Flare Productivity

Falconer, David A.↗

NASA NTRS2014

Hi-C Observations of an Active Region Corona, and Investigation of the Underlying Magnetic Structure

Hi-C: first observational evidence of field line braiding in the AR corona; NLFFF extrapolations support. Flux emergence and/or cancellation in the coronal braided region generate large stresses and tension in the coronal field loops which is released as heat in the corona. The field in these sub-regions are highly sheared and have apparent high speed plasma flows, therefore, the contribution from shearing flows to power the coronal and transition region heating can not be ruled out! The spatial resolution of Hi-C is five times better than AIA. The cadence of Hi-C is 2.5 - 6 times better than AIA. The 193 Å was selected because of the strong emission line of Fe XII (peak formation temperature of 1.5 MK). Hi-C collected data for 345 s @ 5.4 s cadence. The Hi-C target region was NOAA AR 11520; 11 July 2012, 18:51-18:57 UT. NLFFF extrapolation confirms the braided structure, and free magnetic energy estimates in the given volume.

Tiwari, Sanjiv K.↗

NASA NTRS2013

An SDO/AIA-Observed Filament Eruption Triggered by a Lid-Removal Onset Mechanism

An eruption of a solar filament often presages the onset of a more general solar eruption, often leading to a solar flare and coronal mass ejection (CME). Among the mechanisms suggested for triggering eruptions are flux cancellation, flux emergence, tether‐cutting reconnection, and breakout reconnection. Here we present an example of a filament eruption due to a different trigger mechanism, which we call ``lid removal,'' whereby a magnetic structure overlying the filament is removed by a preceding adjacent eruption, rendering MHD unstable the magnetic system containing the filament and resulting in the subsequent eruption of the filament. This filament eruption occurred on 23 Jan 2013, and was well‐seen in SDO/AIA 193 Ang images. Prior to its eruption the filament was at an approximately constant height above the solar surface for approx. 4 hours, before smoothly lifting off. Evidence for the overlying "lid'' field was difficult to discern in 193 Ang images, but was apparent in hotter coronal images, such as SDO/AIA 335. Removal of the lid field was due to an eruption of that field visible in the hotter‐corona images. In this way, the lid‐removal filament‐eruption mechanism is similar to recent observations of connected or cascading eruptions originating from magnetically‐linked locations.

Sterling, Alphonse C.↗