The Gate Voltage Control of Long DNA Coherent Transport on Insulator Surface

We investigate the coherent transport properties of a DNA chain on a substrate which is subjected to a uniform electric field perpendicular to the surface. On the basis of the effective tight-binding model which simulates charge transport through DNA, the transmission coefficient, Lyapunov exponent, and localization length are numerically calculated by using the transfer-matrix method. It is found that an isolated extended state may appear at the Fermi level for a certain gate voltage when the interaction strength between the chain and the substrate is position dependent but independent of the base-pair sequence, leading to the gate voltage induced Metal-insulator transition (MIT). Moreover, conductance and current-voltage characteristics are also calculated. The relationship of Lyapunov exponent distribution to the current-voltage characteristics is discussed. Two different conduction mechanisms are proposed depending on effectively delocalized states and isolated extended states, respectively. These results may provide perspectives for experimental work aimed at controlling charge transport through DNA-based nanodevices.Comment: 7 pages, 6 figure

Large solar energetic particle event that occurred on 2012 March 7 and its VDA analysis

On 2012 March 7, the STEREO Ahead and Behind spacecraft, along with the near-earth spacecraft (e.g. SOHO, Wind) situated between the two STEREO spacecraft, observed an extremely large global solar energetic particle (SEP) event in Solar Cycle 24. Two successive coronal mass ejections (CMEs) have been detected close in time. From the multi-point in-situ observations, it can be found that this SEP event was caused by the first CME, and the second one was not involved. Using the velocity dispersion analysis (VDA), we find that for well magnetically connected point, the energetic protons and electrons are released nearly at the same time. The path lengths to STEREO-B(STB) of protons and electrons have distinct difference and deviate remarkably from the nominal Parker spiral path length, which is likely due to the presence of interplanetary magnetic structures situated between the source and the STB. Also the VDA method seems only to obtain reasonable results at well-connected locations and the inferred energetic particles release times in different energy channels are similar. We suggest that good-connection is crucial for obtaining both accurate release time and path length simultaneously, agreeing with the modeling result of Wang & Qin (2015)

Dependence of Intensities of Major Geomagnetic Storms (Dst ≤\le -100 nT) on Associated Solar Wind Parameters

A geomagnetic storm is the result of sustained interaction between solar wind with a southward magnetic field and the magnetosphere. To investigate the influence of various solar wind parameters on the intensity of major geomagnetic storm, 67 major geomagnetic storms that occurred between 1998 and 2006 were used to calculate the correlation coefficients (CCs) between the intensities of major geomagnetic storms and the time integrals of southward interplanetary magnetic field $B_s$, solar wind electric field ($E_y$) and injection function (Q) during the main phase of the associated geomagnetic storms. SYM-H$_{min}$ was used to indicate the intensity of the associated major geomagnetic storm, while I($B_z$), I($E_y$) and I(Q) were used to indicate the time integrals of $B_z$, $E_y$ and Q during the main phase of associated major geomagnetic storm respectively. The derived CC between I($B_z$) and SYM-H$_{min}$ is 0.33, while the CC between I($E_y$) and SYM-H$_{min}$ is 0.57 and the CC between I(Q) and SYM-H$_{min}$ is 0.86. The results provide statistical evidence that solar wind dynamic pressure or solar wind density plays a significant role in transferring solar wind energy into the magnetosphere, in addition to the southward magnetic field and solar wind speed. Solar wind that has a strong geoeffectiveness requires solar wind dynamic pressure $>$3 nPa or solar wind density $>3$ nPa$/V_{sw}^2$. Large and long duration $B_s$ alone cannot ensure a major geomagnetic storm, especially if the solar wind dynamic pressure is very low, as large and long duration Bs is not a full condition, only a necessary condition to trigger a major geomagnetic storm

Seed population in large Solar Energetic Particle events and the twin-CME scenario

It has been recently suggested that large solar energetic particle (SEP) events are often caused by twin CMEs. In the twin-CME scenario, the preceding CME is to provide both an enhanced turbulence level and enhanced seed population at the main CME-driven shock. In this work, we study the effect of the preceding CMEs on the seed population. We examine event-integrated abundance of iron to oxygen ratio (Fe/O) at energies above 25 MeV/nuc for large SEP events in solar cycle 23. We find that the Fe/O ratio (normalized to the reference coronal value of $0.134$) $\leq2.0$ for almost all single-CME events and these events tend to have smaller peak intensities. In comparison, the Fe/O ratio of twin-CME events scatters in a larger range, reaching as high as $8$, suggesting the presence of flare material from perhaps preceding flares. For extremely large SEP events with peak intensity above $1000$ pfu, the Fe/O drop below $2$, indicating that in these extreme events the seed particles are dominated by coronal material than flare material. The Fe/O ratios of Ground level enhancement (GLE) events, all being twin-CME events, scatter in a broad range. For a given Fe/O ratio, GLE events tend to have larger peak intensities than non-GLE events. Using velocity dispersion analysis (VDA), we find that GLE events have lower solar particle release (SPR) heights than non-GLE events, \red{agreeing with earlier results by Reames 2009b

A study on the dynamic spectral indices for SEP events on 2000 July 14 and 2005 January 20

We have studied the dynamic proton spectra for the two solar energetic particle (SEP) events on 2000 July 14 (hereafter GLE59) and 2005 January 20 (hereafter GLE69). The source locations of GLE59 and GLE69 are N22W07 and N12W58 respectively. Proton fluxes >30 MeV have been used to compute the dynamic spectral indices of the two SEP events. The results show that spectral indices of the two SEP events increased more swiftly at early times, suggesting that the proton fluxes >30 MeV might be accelerated particularly by the concurrent flares at early times for the two SEP events. For the GLE69 with source location at N12W58, both flare site and shock nose are well connected with the Earth at the earliest time. However, only the particles accelerated by the shock driven by eastern flank of the CME can propagate along the interplanetary magnetic field line to the Earth after the flare. For the GLE59 with source location at N22W07, only the particles accelerated by the shock driven by western flank of the associated CME can reach the Earth after the flare. Results show that there was slightly more than one hour during which the proton spectra for GLE69 are softer than that for GLE59 after the flares, suggesting that the shock driven by eastern flank of the CME associated with GLE69 is weaker than the shock driven by the western flank of the CME associated with GLE59. The results support that quasi-perpendicular shock has stronger potential in accelerating particles than the quasi-parallel shock. The results also suggest that only a small part of the shock driven by western flank of the CME associated with the GLE59 is quasi-perpendicular.Comment: Accepted by RA

Production of genuine entangled states of four atomic qubits

We propose an optical scheme to generate genuine entangled states of four atomic qubits in optical cavities using a single-photon source, beam splitters and single photon detectors. We show how to generate deterministically sixteen orthonormal and independent genuine entangled states of four atomic qubits. It is found that the sixteen genuine entangled states form a new type of representation of the four-atomic-qubit system, i.e., the genuine entangled-state representation. This representation brings new interesting insight onto better understanding multipartite entanglement.Comment: 1 figur

Dependence of great geomagnetic storm intensity (Δ\DeltaSYM-H≤\le-200 nT) on associated solar wind parameters

We use $\Delta$SYM-H to capture the variation in the SYM-H index during the main phase of a geomagnetic storm. We define great geomagnetic storms as those with $\Delta$SYM-H $\le$ -200 nT. After analyzing the data that were not obscured by solar winds, we determined that 11 such storms occurred during solar cycle 23. We calculated time integrals for the southward interplanetary magnetic field component I(B$_s$), the solar wind electric field I(E$_y$), and a combination of E$_y$ and the solar wind dynamic pressure I(Q) during the main phase of a great geomagnetic storm. The strength of the correlation coefficient (CC) between $\Delta$SYM-H and each of the three integrals I(B$_s$) (CC = 0.74), I(E$_y$) (CC = 0.85), and I(Q) (CC = 0.94) suggests that Q, which encompasses both the solar wind electric field and the solar wind dynamic pressure, is the main driving factor that determines the intensity of a great geomagnetic storm. The results also suggest that the impact of B$_s$ on the great geomagnetic storm intensity is much more significant than that of the solar wind speed and the dynamic pressure during the main phase of associated great geomagnetic storm. How to estimate the intensity of an extreme geomagnetic storm based on solar wind parameters is also discussed.Comment: 3 figure

Extreme space weather events caused by super active regions during solar cycles 21-24

Extreme space weather events including $\ge$X5.0 flares, ground level enhancement (GLE) events and super geomagnetic storms (Dst $\le$ -250 nT) caused by super active regions (SARs) during solar cycles 21-24 were studied. The total number of $\ge$X5.0 solar flares was 62, 41 of them were X5.0-X9.9 flares and 21 of them were $\ge$X10.0 flares. We found that 83.9\% of the $\ge$X5.0 flares were produced by SARs. 78.05\% of the X5.0-X9.9 and 95.24\% of the $\ge$X10.0 solar flares were produced by SARs. 46 GLEs registered during solar cycles 21-24, and 25 GLEs were caused by SARs, indicating that 54.3\% of the GLEs were caused by SARs. 24 super geomagnetic storms were recorded during solar cycles 21-24, and 12 of them were caused by SARs, namely 50\% of the super geomagnetic storms are caused by SARs. It is found that only 29 SARs can produce $\ge$X5.0 flares, 15 SARs can produce GLEs and 10 SARs can produce super geomagnetic storms. Of the 51 SARs, only 33 SARs can produce at least one extreme space weather event, while none of the rest 18 SARs can produce an extreme space weather event. There were only 4 SARs, each of them can produce not only a $\ge$X5.0 flare, but also a GLE event and a super geomagnetic storm. Most of the extreme space weather events caused by the SARs appeared during solar cycles 22 and 23, especially for GLE events and super geomagnetic storms. The longitudinal distributions of source locations for the extreme space weather events caused by SARs were also studied

Can we estimate the intensities of great geomagnetic storms(Δ\DeltaSYM-H≤−\le -200 nT) by Burton equation or by O'Brien and McPherron equation?

We input solar wind parameters responsible for the main phases of 15 great geomagnetic storms (GGSs: $\Delta$SYM-H$\le-$200 nT) into the empirical formulae created by \cite{Burton1975}(hereafter Burton equation), and by \cite{OBrien2000}(hereafter OM equation) to evaluate whether \textbf{two equations} can correctly estimate the intensities of GGSs. The results show that the intensities of most GGSs estimated by OM equation are much smaller than the observed intensities. The RMS error between the intensities estimated by OM equation and the observed intensities is \textbf{203} nT, implying that the estimated storm intensity deviates significantly from the observed one. The RMS error between the intensities estimated by Burton equation and the observed intensities is 130.8 nT. The relative error caused by Burton equation for the storms with intensities $\Delta$SYM-H$<$-400 nT is larger than 27\%, implying that the absolute error will be large for the storms with $\Delta$SYM-H$<$-400 nT. The results indicate that the two equations cannot work effectively in the estimation of GGSs. On the contrary, the intensity of a GGS estimated by the empirical formula created by \cite{WangCB2003} can always be very close to the observed one if we select the right weight for solar wind dynamic pressure, proving that solar wind dynamic pressure is an important factor for GGS intensity, but it is overlooked in the ring current injection terms of Burton equation or OM equation. This is the reason why the two equations cannot work effectively in the estimation of GGSs

Sun-Earth connection Event of Super Geomagnetic Storm on March 31, 2001: the Importance of Solar Wind Density

An X1.7 flare at 10:15 UT and a halo CME with a projected speed of 942 km/s erupted from NOAA solar active region 9393 located at N20W19, were observed on 2001 March 29. When the CME reached the Earth, it triggered a super geomagnetic storm (hereafter super storm). We find that the CME always moved towards the Earth according to the intensity-time profiles of protons with different energies. The solar wind parameters responsible for the main phase of the super storm occurred on March 31, 2001 is analyzed taking into account the delayed geomagnetic effect of solar wind at the L1 point and using the SYM-H index. According to the variation properties of SYM-H index during the main phase of the super storm, the main phase of the super storm is divided into two parts. A comparative study of solar wind parameters responsible for the two parts shows the evidence that the solar wind density plays a significant role in transferring solar wind energy into the magnetosphere, besides the southward magnetic field and solar wind speed