Characteristics of events with metric-to-decahectometric type II radio bursts associated with CMEs and flares in relation to SEP events

A gradual solar energetic particle (SEP) event is thought to happen when particles are accelerated at a shock due to a fast coronal mass ejection (CME). To quantify what kind of solar eruptions can result in such SEP events, we have conducted detailed investigations on the characteristics of CMEs, solar flares and m-to-DH wavelength type II radio bursts (herein after m-to-DH type II bursts) for SEP-associated and non-SEP-associated events, observed during the period of 1997-2012. Interestingly, 65% of m-to-DH type II bursts associated with CMEs and flares produced SEP events. The SEP-associated CMEs have higher sky-plane mean speed, projection corrected speed, and sky-plane peak speed than those of non-SEP-associated CMEs respectively by 30%, 39%, and 25%, even though the two sets of CMEs achieved their sky-plane peak speeds at nearly similar heights within LASCO field of view. We found Pearson's correlation coefficients between the speeds of CMEs speeds and logarithmic peak intensity of SEP events are cc = 0.62 and cc = 0.58, respectively. We also found that the SEP-associated CMEs are on average of three times more decelerated (-21.52 m/s2) than the non-SEP-associated CMEs (-5.63 m/s2). The SEP-associated m type II bursts have higher frequency drift rate and associated shock speed than those of the non-SEP-associated events by 70% and 25% respectively. The average formation heights of m and DH type II radio bursts for SEP-associated events are lower than for non-SEP-associated events. 93% of SEP-associated events originate from the western hemisphere and 65% of SEP-associated events are associated with interacting CMEs. The obtained results indicate that, at least for the set of CMEs associated with m-to-DH type II bursts, SEP-associated CMEs are more energetic than those not associated with SEPs, thus suggesting that they are effective particle accelerators.Comment: 19 pages, 10 figures, 3 tables, accepted for publication by ApS

Statistical Analysis of Periodic Oscillations in LASCO Coronal Mass Ejection Speeds

A large set of coronal mass ejections (CMEs, 3463) has been selected to study their periodic oscillations in speed in the Solar and Heliospheric Observatory (SOHO) missions Large Angle and Spectrometric Coronagraph (LASCO) field of view. These events, reported in the SOHOLASCO catalog in the period of time 19962004, were selected based on having at least 11 height-time measurements. This selection criterion allows us to construct at least ten-point speed distance profiles and evaluate kinematic properties of CMEs with a reasonable accuracy. To identify quasi-periodic oscillations in the speed of the CMEs a sinusoidal function was fitted to speed distance profiles and the speed time profiles. Of the considered events 22 revealed periodic velocity fluctuations. These speed oscillations have on average amplitude equal to 87 kms(exp -1) and period 7.8R /241 min (in distance-time). The study shows that speed oscillations are a common phenomenon associated with CME propagation implying that all the CMEs have a similar magnetic flux-rope structure. The nature of oscillations can be explained in terms of magnetohydrodynamic (MHD) waves excited during the eruption process. More accurate detection of these modes could, in the future, enable us to characterize magnetic structures in space (space seismology)

Glycosylated naphthalimides and naphthalimide Tröger's bases as fluorescent aggregation probes for Con A.

Herein we report the synthesis of fluorescent, glycosylated 4-amino-1,8-naphthalimide (Nap) 1, and the related 1,8-naphthalimides Tröger's bases (TBNap) 2 and 3, from 1,8-naphthalic anhydride precursors, the α-mannosides being introduced through the use of CuAAC mediated 'click' chemistry. We investigate the photophysical properties of these probes in buffered solution and demonstrate their ability to function as fluorescent probes for Concanavalin A (Con A) lectin. We show that both the Nap and TBNap structures self-assemble in solution. The formation of the resulting supramolecular structures is driven by head-to-tail π-π stacking and extended hydrogen bonding interactions of the Nap and the triazole moieties. These interactions give rise to spherical nano-structures (ca. 260 nm and 100 nm, for 1 and 3, respectively), which interact with the Con-A protein, the interaction being probed by using both luminescent and Scanning Electron Microscopy imaging as well as dynamic light scattering measurements. Finally, we show that these supramolecular assembles can be used as luminescent imaging agents, through confocal fluorescence imaging of HeLa cells of the per-acetylated version 2

Unambiguous detection of nitrated explosive vapours by fluorescence quenching of dendrimer films

Unambiguous and selective standoff (non-contact) infield detection of nitro-containingexplosives and taggants is an important goal but difficult to achieve with standard analyticaltechniques. Oxidative fluorescence quenching is emerging as a high sensitivity method fordetecting such materials but is prone to false positives—everyday items such as perfumeselicit similar responses. Here we report thin films of light-emitting dendrimers that detectvapours of explosives and taggants selectively—fluorescence quenching is not observed for arange of common interferents. Using a combination of neutron reflectometry, quartz crystalmicrobalance and photophysical measurements we show that the origin of the selectivity isprimarily electronic and not the diffusion kinetics of the analyte or its distribution in the film.The results are a major advance in the development of sensing materials for the standoffdetection of nitro-based explosive vapours, and deliver significant insights into the physicalprocesses that govern the sensing efficacy

The Origin, Early Evolution and Predictability of Solar Eruptions

Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from the Sun. Today, it is known that the Sun produces eruptive flares, filament eruptions, coronal mass ejections and failed eruptions; all thought to be due to a release of energy stored in the coronal magnetic field during its drastic reconfiguration. This review discusses the observations and physical mechanisms behind this eruptive activity, with a view to making an assessment of the current capability of forecasting these events for space weather risk and impact mitigation. Whilst a wealth of observations exist, and detailed models have been developed, there still exists a need to draw these approaches together. In particular more realistic models are encouraged in order to asses the full range of complexity of the solar atmosphere and the criteria for which an eruption is formed. From the observational side, a more detailed understanding of the role of photospheric flows and reconnection is needed in order to identify the evolutionary path that ultimately means a magnetic structure will erupt

The Physical Processes of CME/ICME Evolution

As observed in Thomson-scattered white light, coronal mass ejections (CMEs) are manifest as large-scale expulsions of plasma magnetically driven from the corona in the most energetic eruptions from the Sun. It remains a tantalizing mystery as to how these erupting magnetic fields evolve to form the complex structures we observe in the solar wind at Earth. Here, we strive to provide a fresh perspective on the post-eruption and interplanetary evolution of CMEs, focusing on the physical processes that define the many complex interactions of the ejected plasma with its surroundings as it departs the corona and propagates through the heliosphere. We summarize the ways CMEs and their interplanetary CMEs (ICMEs) are rotated, reconfigured, deformed, deflected, decelerated and disguised during their journey through the solar wind. This study then leads to consideration of how structures originating in coronal eruptions can be connected to their far removed interplanetary counterparts. Given that ICMEs are the drivers of most geomagnetic storms (and the sole driver of extreme storms), this work provides a guide to the processes that must be considered in making space weather forecasts from remote observations of the corona.Peer reviewe

Design, constructional aspects and first results of a solar radio spectrograph

53-60A solar radio spectrograph (SRS), constructed at our School of Physics to study the dynamic activities of the sun, is described. It consists of the following four parts: (i) antenna system, (ii) analog receiver system, (iii) control system, and (iv) data acquisition and recording system. The antenna system is a log periodic array with 8 dB gain and bandwidth of 50 MHz. The receiver system is a double stage superheterodyne receiver with a overall gain and bandwidth of 50 MHz. The receiver system is a double stage superheterodyne receiver with a overall gain of 80 dB. The control system consists of IEEE 488 GPIB card and a PC to control the sweeping frequency synthesizer which is acting as one of the local oscillator in the receiver. The data acquisition and recording system include a hi-speed data acquisition card and a PC for acquiring the observed data and recording the same for the reproduction of the spectra. The spectrograph is acquiring observational data on solar radio bursts in the bandwidth of 30-80 MHz, which is quite important for understanding the physics of flares and bursts. Its calibration and reproduction of the observed results using it are also described