SH22A-0835
Coronal Heating by Small Scale Eruptive Events on Quiet sun Investigated By Coaligned Observations From Soho and Hinode
Co-ordinated observations with Soho and Hinode were made of all layers of the quiet Sun atmosphere. Observations were made from photospheric to lower corona lines. The region covered quiet Sun and soft X-ray bright points. Magnetic data and Doppler maps are provided by high resolution MDI-SUMER/Soho and SP- SOT/Hinode. In the meantime XRT-EIS/Hinode could track the whole evolution of microflares showing up on some bright points. In many aspects they look like coronal jets. These observations provide evidence of acceleration and heating of plasma in quiet Sun expelled in the lower corona.
SH22A-0836
The Dynamics and Magnteic enviroments of Solar X-ray Jets observed with Hinode
An X-ray jet is a phenomena discovered by SXT/Yohkoh and the observed properties of the X-ray jets are well explained by the X-ray jet model based on magnetic reconnection (Shibata et al. 1992). The model proposed that the X-ray jet is produced by the magnetic reconnection between pre-exist coronal magnetic field (a part of open field or large loops) and the emerging flux. The configuration is very simple and we can easily predict the position of the reconnection site. Hence, we think that an X-ray jet is a useful phenomenon for investigating the detail properties of reconnection process in the corona. In the study, we study the dynamics of fine structures and temperature structures of X-ray jets using X-ray images observed with the XRT/Hinode and investigate the detail properties of magnetic reconnection in corona. We also use the data of magnetic distribution taken by the SOT/Hinode and study the relationship of magnetic connectivity and reconnection process. At first, we found that two fine structure dynamics from the X-ray images observed with the XRT. One of the fine structures observed by XRT is an expanding loop. The loop appears near the footpoint of the jet when the footpoint brightening is observed. Additionally, we have found that the X-ray jets begin just after the expanding loop 'breaks'. Other fine structures discovered by XRT are thread-like features along the axis of the jets. XRT has shown that these thread structures compose the cross-section of jets. The fine structures and their motions strongly support the X-ray jet model based on magnetic reconnection, and also suggest that we must consider the three-dimensional configuration of magnetic field to understand jet phenomenon.@In the paper, we also discuss the magnetic environment at X-ray jets sites and the temperature structure of X-ray jets.
SH22A-0837
Search for Solar Neutrons Using the MESSENGER Neutron Spectrometer Between 0.7 and 0.32 AU
The MESSENGER Neutron Spectrometer is composed of three separate sensors that span the neutron energy range between 0 and about 8 MeV. It has been operating continuously since about 1 February 2007. After the spacecraft's second Venus flyby on 5 June 2007, this detector will be sensitive to solar neutrons in the heliospheric distance range between 0.32 AU and 0.7 AU. The time period between the Venus flyby and orbit insertion in March 2011 spans the solar activity cycle between solar minimum and solar maximum. The first perihelion of MESSENGER's new orbit occurred on 1 September 2007. Counting rates of neutrons in the thermal and epithermal energy range (up to about 0.5 MeV) are sensibly zero. Observed rates for neutron energies between about 0.5 MeV and 8 MeV, signifying cosmic-ray interactions with spacecraft material, average about 1.9/s. As of the time of writing of this abstract, no solar flares have occurred and it is too early to place either actual rates for, or lower limits on, detection of background solar neutrons that result from the quiet-time heating of the corona. These rates will be reported at the meeting.
SH22A-0838
Alfven Waves observed in Polar Jets
Data collected on X-ray jets during a polar coronal hole observation campaign has revealed that some events have two distinct velocity components, one near the Alfv\rm\acute{e}n speed (~ 800 km sec-1) and the other near the sound speed (200 km sec-1). Previous reports indicate the incidence of jet formation to be only a few per day, with average radial speeds of 200 km sec-1. With the X-Ray Telescope (XRT) we detect an average of 10 events per hour. These jets are approximately 2 × 103 - 2 × 104 km wide and than 1 × 105 km long. The jet lifetimes range from 100 - 2500 secs. A large percentage of these jets are associated with small footpoint flares (1). The large number of events, coupled with the high velocities of the apparent outflows, indicate that these jets may contribute significantly to the high-speed solar wind from coronal holes. These observations provide unique and important evidence for the generation of Alfvén waves during reconnection and are possibly the first evidence of Alfv´n wave observations driving the high speed solar wind.
SH22A-0839
Polar Jet Observations by Hinode/XRT
We have observed 232 X-ray Jets during a polar coronal observation campaign 8 January - 21 January 2007. Previous articles have reported on these events, but the incidence of these events was only known to be a few events per day. We have found that there are in fact several per hour. These jets are approximately 2 × 104? ?2 × 105 km wide and routinely 1 × 106 km long. The durations of these evnts range from 100 secs 2500 secs. A large percentage of the jets are associated with a small footpoint flare as reported by Shimojo et al. (1996).
SH22A-0840
Three Dimensional Structure and Time Evolution of a Transition Region Explosive Event Observed in He II
Transition Region Explosive Events (TREEs) have been observed with slit spectrographs since at least 1975, most commonly in lines of C IV (1548A,1550A) and Si IV (1393A, 1402A). We report what we believe to be the first observation of a TREE in He II 304A. With the MOSES sounding rocket, a novel type of imaging spectrograph, we are able to see the spatial and spectral structure of the event. It consists of a bright core expelling two jets, oppositely directed but not collinear, which curve away from the axis of the core. The jets have both line-of-sight and sky-plane motion. The core is a region of high non-thermal doppler broadening, characteristic of TREEs. It is possible to resolve the core broadening into red and blue line-of-sight components. MOSES captured approximately 150 sec of time evolution before the rocket flight ended. We see the beginning (core activation) and middle (jet ejection), but not the end. It is clear from our data-set that TREEs in He II 304A are much less common than observed in other wavelengths.
SH22A-0841
The Differential Emission Measure and Analysis of X-Ray Bright Points using Hinode's X-Ray Telescope (XRT)
The X-Ray telescope aboard Hinode utilizes up to thirteen filter combinations with one arc second resolution to provide unprecedented temperature coverage. In this study, we have used eleven X-Ray filters to examine the statistical properties of X-ray bright points including temperature, emission, and size distributions. We have analyzed what appears to be a population of XRBs that are hotter than the main group in order to identify any distinguishing properties.We discuss the results of our analysis and their implications on XBP classification.
SH22A-0842
Transient Phenomena in Multi-thread Arcades of Coronal Loops
The post-flare coronal loops having well defined filamentary structure, often appear as an arcades of thin magnetic threads resembling winding in a curved solenoid or a funnel. Compared to flare timescales, post-flare arcades are long living, well organized structures. Elemental filaments in arcades are, however, in highly dynamic state, showing oscillations, and harboring frequent microflares. These microflares often appear simultaneously in different places. Besides, many individual filaments produce homologous, repetitive microflares. Microflares are often accompanied by short living jets. We present the observations of these events using the data taken with SOT and XRT instruments on Hinode combined with the TRACE 195 ~Å coronal line. The object of the observation is AR 10930 which exhibited several flare events in December, 2006. After a major flare on 13 December, a typical "solenoidal" system of coronal threads was formed that lasted over 6 hours. The observed spatial and temporal regularities in appearence of the EUV transients can be well understood on basis of a spatio-temporal echoes resulted from nonlinear response of a system ("coupled oscillators") to impulsive disturbences associated with the changes in the photospheric magnetic fields. Observations in the SOT chromospheric lines show appearence of precursors of coronal jets and microflares.
SH22A-0843
On the Chromospheric Micro-jets Associated with the Penumbral Filaments
We present observations of sunspot penumbrae obtained during the disk passage of AR 10923 (November 10--20, 2006) with the Solar Optical Telescope (SOT) on the Hinode satellite. Co-aligned multi-hour movies taken simultaneously in several wavelengths show fine-scale dynamics at the sub-arcsecond level. The dynamics include helical flows along penumbral filaments, branching of filaments, and penumbral "micro-jets" recently described by Katsukawa et al. (AAS 210, 94.13). We present quantitative analyzes of the penumbral jets and interpret them relative to our recent model of penumbral filaments (Ryutova, Berger and Title, 2007, in "Collective phenomena in macroscopic systems", Ed. G. Bertin, et al., World Scientific) to show that the jets are the result of magnetic reconnection of the helical field lines in neighboring non-collinear filaments.
SH22A-0844
Intensity and Velocity Structure of a Light Bridge in a Pore Seen by IBIS at NSO/DST: Analysis and Interpretation
Light bridges are bright structures separating umbral areas of pores or sunspots in two or more sub-regions. We analyze intensity and velocity small scale properties of a light bridge, observed in the pore AR10812, using both broad-band and monochromatic images acquired with the Interferometric BI-dimensional Spectrometer (IBIS) at the adaptive optics channel of the NSO/Dunn Solar Telescope. The observed pore shows a mean downward velocity of about -200 m/s and an external annulus with average downward velocity of -350 m/s. Besides, an elongated dark structure along light bridge axis matches a feeble upward plasma structure of about +100 m/s. We interpret this sort of reversed convective feature as a consequence of the higher gas pressure in a photospheric field-free cusp, above the light bridge, located between two magnetic walls. To reproduce this configuration, we developed a simple light bridge thermal model in which we consider a quiet field free region below a partially emptied of plasma magnetic region. http://www.fisica.uniroma2.it/~solare/index.htm
SH22A-0845
MHD Simulations of Small Active Regions Interacting with Coronal Holes
We use our 3D MHD algorithm in spherical coordinates to study the interaction of the magnetic field of two small bipoles with that of a coronal hole. To prescribe the magnetic flux distribution at the lower boundary, we add two bipolar active regions to a smoothed Kitt Peak magnetogram for Carrington Rotation 1913 (late August 1996). Starting from a potential field extrapolation and a 1D solar wind solution, we relax the configuration until coronal holes, streamers, and the heliospheric current sheet are formed. At this point we introduce surface flows, which evolve the magnetic flux distribution at the boundary. We study the reconnection events and the changes in the distribution of closed and open magnetic flux associated with the bipolar active regions.
SH22A-0846
Development in the SONNE Instrument, a Solar Neutron Spectrometer for Solar Orbiter and Solar Sentinels
We report on the technical development of SONNE (Solar Neutron Experiment), a solar neutron spectrometer intended for use on the ESA Solar Orbiter and/or the NASA Solar Sentinels Missions. Development has taken place on three fronts, (1) simulations of a flight instrument, including the spacecraft radiation environment, (2) calibrating a prototype instrument in a monoenergetic neutron beam and (3) mechanical and electrical design of a deep space mission instrument. SONNE will be sensitive to fast neutrons up to 20 MeV, using double scatter imaging techniques to dramatically reduce background. Preliminary beam measurement analysis, conducted just before this abstract, supports advertised design goals in terms of sensitivity and energy resolution, meaning that time stamping neutron emission from the Sun will be possible. Combined with gamma ray measurements, new insight into particle acceleration will emerge when deployed on an inner heliospheric mission. Progress will be reported on simulations and physical design as well as calibrations.
SH22A-0847
Interplanetary Magnetic Field Folds in High Speed Streams Observed with Ulysses and ACE
Large rotations observed in the interplanetary magnetic field (IMF) can be due to true field polarity reversals, i.e. crossings of the heliospheric current sheet. But very often they are instead encounters with fields that are locally folded back upon themselves. Within coronal hole-related high-speed streams, we find that folds can be readily distinguished from true polarity reversals by using the property of differential streaming between alpha particles and protons. The vector difference between the alpha particle velocity and the proton velocity lies parallel (or anti- parallel) to the magnetic field, but always points in the field-aligned direction away from the sun. Previously we presented a survey of folds within the uniform coronal hole-related high-speed solar wind sampled by Ulysses at solar minimum during the first Northern Polar pass. We found that all the folds examined showed correlation between the field turnings and variations in the solar wind velocity vector, indicative of propagating Alfvenic features. Here we present an extension of that survey to solar wind from isolated polar coronal holes seen by ACE and Ulysses at solar maximum. We report on the occurence of folded fields and polarity reversals near solar maximum, including how the observed frequency and duration of folded field intervals differ between flow from larger solar minimum polar coronal holes and smaller isolated solar maximum coronal holes.
SH22A-0848
Alfven Wave Evolution in an Interaction System of the Fast and Slow Solar Wind
Large-amplitude Alfven waves (AWs) are often embedded in a high-speed stream of the solar wind. As the high- speed streams overtake the low-speed streams ahead, corotating interaction regions (CIRs) are produced in low heliographic latitudes. In this study, the nonlinear evolution of AWs swept into CIRs is numerically investigated by one-dimensional MHD simulations. Ulysses observations suggest that not only AWs amplified through the reverse shock but also magnetic depression structures (MDs) are found in the trailing portions of CIRs (e.g., Tsurutani et al., 1995). Our interest is the generation mechanism of MDs in the context of AWs-CIRs interaction system. While MDs are supposed to be remnants of the mirror instability (e.g., Winterhalter et al., 1994), we give alternative processes from a macroscopic view as follows. A large pressure gradient developed in CIRs results in intensifying the diamagnetic current, which reflects a portion of the incident AW energy in the opposite direction (from a plasma-rest frame) as AWs penetrate into CIRs. Since the reflected AWs also carry the current, the reduction of the background field intensity (i.e. MD formation) is simultaneously taken place in the area sandwiched between the forward-reverse pair of AWs. Further analysis will be given via hybrid simulations to show how these MHD processes are manifested in particle behaviors, such as an acceleration due to a ponderomotive force.
SH22A-0849
RHESSI Hard X-ray Microflare Statistics
We present the first in-depth statistical survey of all X-ray microflares observed by RHESSI between March 2002 and March 2007, a total of 25,705 events. These microflares were found using a new flare-finding algorithm designed to search the 6--12~keV count rate when RHESSIs full sensitivity was available in order to find the smallest events. These microflares are small flares, from low GOES C Class to below A Class (background subtracted) and associated with active regions. Each microflare is automatically analyzed at the peak time of the 6--12~keV emission. Spectral parameters are determined both by considering ratios between energy channels and by forward fitting a thermal plus non-thermal model. Flare images are created using back-projection and centroids and by forward fitting the complex visibilities. The combination of imaging and spectral parameters allow for the first time analysis of the thermal and non-thermal energy at the peak time of these microflares.
SH22A-0850
Numerical Simulations of Nanoflares: PDFs of Released Energy, Waiting Times and Quiet- Sun Magnetic Field Elements
A numerical model for nanoflares is proposed to describe probability density functions (PDF) and waiting time statistics of the emitted magnetic energy and to guess PDF of quiet-Sun magnetic field strength. In the simulation, footpoints of reconnecting magnetic loops are advected by photospheric flows computed via a n-body algorithm. The model simulates a system whose behavior is characterized by small scale (i.e., granulation) flows that interact to develop large organization scales (i.e., mesogranulation). Such spatio-temporal correlated flows, incessantly supply , remove and convey the passive magnetic footpoints onto the photospheric surface, triggering reconnections and magnetic field reconfigurations. http://www.fisica.uniroma2.it/~solare/index.htm
SH22A-0851
Ulysses 2007 Fast Latitude Scan : Radio Observations of High-Speed Solar Wind Electron Parameters Near Solar Minimum
Ulysses spacecraft gives a unique opportunity to study continuously the stationary and steady-state high-speed wind out of the ecliptic plane and its large-scale variations during a whole solar cycle. The fast pole-to-pole transit in 1994-1995 has allowed us to make an accurate in situ diagnostics of the electron plasma parameters at high-latitude near solar minimum, using the quasi-thermal noise spectroscopy method on the URAP radio receiver. In particular, we have accurately obtained the radial profile of the electron density and temperature in the fast wind without data selection in contrast to ecliptic observations where different types of winds have to be sorted out. The electron thermal temperature profile behaves between adiabatic and isothermal, in qualitative agreement with a simple kinetic collisionless model. Since February 2007, Ulysses is performing its second high latitude exploration at solar activity minimum, the magnetic field of the Sun being reversed compared to the previous solar minimum. We will present electron measurements acquired in the southern polar coronal hole in 2007 using the quasi-thermal noise method. We will compare these results to high latitude observations performed during the previous solar activity minimum, which may constraint models on the 3-D structure of the solar wind over the solar cycle.
SH22A-0852
Reconstruction of Interplanetary Magnetic Field and Solar Wind Speed for the Last 135 Years Revisited
We reconstruct the magnitude of the interplanetary magnetic field B and solar wind speed v at 1 AU using 1) yearly values of sunspot numbers and geomagnetic index aa; 2) available spacecraft measurements of v and B since 1964. We compare our results with the reconstruction done by Stamper et al. (1999) and also with the reconstruction by Svalgaard et al. (2003). References Stamper, R., M. Lockwood and M.N. Wild, Solar causes of the long-term increase in geomagnetic activity, J. Geophys. Res., Vol.104 (A12), 24325, 1999. Svalgaard, Leif, E. W. Cliver and P. Lesager, In; Solar variability as an input to the Earth's environment. International Solar Cycle Studies (ISCS) Symposium, 23 - 28 June 2003, Tatranska Lomnica, Slovak Republic. Ed.:A. Wilson. ESA SP-535, Noorwijk: ESA Publications Division, IBSN 92-9092-845-X, 2003, p. 15 - 23
SH22A-0853
Planar Orientation of Co-Rotating Interactions Regions as Observed by Ulysses.
We present here an investigation into the orientation of co-rotating interaction regions (CIRs) observed by the ESA/NASA Ulysses spacecraft. Ulysses is uniquely suited to this investigation as it is the only spacecraft to observe CIRs out of the ecliptic plane. Launched in 1990, Ulysses now has a little over 17 years of continual solar wind observations. As such, with the tendency for CIRs to form during the declining phase of solar activity, Ulysses has now observed two separate periods of CIR activity. Using the Planar Magnetic Structure technique to determine the normal to the planes formed by the CIRs: we show that there is a trend between the normal orientation and helio-latitude. At higher helio-latitudes (~30 degrees) the normal tends to become more aligned with the radial direction. We also present range (Sun- Spacecraft) and solar cycle trends. These results are then compared to global CIR models.