Correlations between neutral and ionized solar wind

We report results of a statistical study correlating ionized solar wind (ISW) fluxes observed by ACE during late 2000 and throughout 2001 with neutral solar wind (NSW) fluxes observed by IMAGE/LENA over the same period. The average correlation coefficient between the neutral and ionized solar wind is 0.66 with correlations greater than 0.80 occurring about 29% of the time. Correlations appear to be driven by high solar wind flux variability, similar to results obtained by in situ multi-spacecraft correlation studies. In this study, however, IMAGE remains inside the magnetosphere on over 95% of its orbits. As a function of day of year, or equivalently ecliptic longitude, the slope of the relationship between the neutral solar wind flux and the ionized solar wind flux shows an enhancement near the upstream direction, but the symmetry point appears shifted toward higher ecliptic longitudes than the interstellar neutral (ISN) flow direction by about 20°. The estimated peak interstellar neutral upstream density inside of 1 AU is about 7 × 10⁻³ cm⁻³.     

Noise in wireless systems from solar radio bursts

Solar radio bursts were first discovered as result of their interference in early defensive radar systems during the Second World War (1942). Such bursts can still affect radar systems, as well as new wireless technologies. We have investigated a forty-year record of solar radio burst data (1960–1999) as well as several individual radio events in the 23rd solar cycle. This paper reviews the results of a portion of this research. Statistically, for frequencies f  1 GHz (near current wireless bands), there can be a burst with amplitudes >10³ solar flux units (SFU; 1 SFU = 10⁻²² W/m²) every few days during solar maximum conditions, and such burst levels can produce problems in contemporary wireless systems.     

New flare model using recent measurements of the solar ultraviolet irradiance

The solar photon output from the Sun, which was once thought to be constant, varies considerably over time scales from seconds during solar flares to years due to the solar cycle. This is especially true in the wavelengths shorter than 190 nm. These variations cause significant deviations in the Earth and space environment on similar time scales, which then affects many things including satellite drag, radio communications, atmospheric densities and composition of particular atoms, molecules, and ions of Earth and other planets, as well as the accuracy in the Global Positioning System (GPS). The Flare Irradiance Spectral Model (FISM) is an empirical model that estimates the solar irradiance at wavelengths from 0.1 to 190 nm at 1 nm resolution with a time cadence of 60 s. This is a high enough temporal resolution to model variations due to solar flares, for which few accurate measurements at these wavelengths exist. This model also captures variations on the longer time scales of solar rotation (days) and solar cycle (years). Daily average proxies used are the 0–4 nm irradiance, the Mg II c/w, F10.7, as well as the 1 nm bins centered at 30.5 nm, 121.5 (Lyman Alpha), and 36.5 nm. The GOES 0.1–0.8 nm irradiance is used as the flare proxy. The FISM algorithms are given, and results and comparisons are shown that demonstrate the FISM estimations agree within the stated uncertainties to the various measurements of the solar Vacuum Ultraviolet (VUV) irradiance.     

Comparison of solar soft X-ray irradiance from broadband photometers to a high spectral resolution rocket observation

The solar soft X-ray (XUV; 1–30 nm) radiation is highly variable on all time scales and strongly affects the ionosphere and upper atmosphere of Earth, Mars, as well as the atmospheres and surfaces of other planets and moons in the solar system; consequently, the solar XUV irradiance is important for atmospheric studies and for space weather applications. While there have been several recent measurements of the solar XUV irradiance, detailed understanding of the solar XUV irradiance, especially its variability during flares, has been hampered by the lack of high spectral resolution measurements in this wavelength range. The conversion of the XUV photometer signal into irradiance requires the use of a solar spectral model, but there has not been direct validation of these spectral models for the XUV range. For example, the irradiance algorithm for the XUV Photometer System (XPS) measurements uses multiple CHIANTI spectral models, but validation has been limited to other solar broadband measurements or with comparisons of the atmospheric response to solar variations. A new rocket observation of the solar XUV irradiance with 0.1 nm resolution above 6 nm was obtained on 14 April 2008, and these new results provide a first direct validation of the spectral models used in the XPS data processing. The rocket observation indicates very large differences for the spectral model for many individual emission features, but the differences are significantly smaller at lower resolution, as expected since the spectral models are scaled to match the broadband measurements. While this rocket measurement can help improve a spectral model for quiet Sun conditions, many additional measurements over a wide range of solar activity are needed to fully address the spectral model variations. Such measurements are planned with a similar instrument included on NASA’s Solar Dynamics Observatory (SDO), whose launch is expected in 2009.     

The potential of Meudon spectroheliograph for investigating long term solar activity and variability

Observations of the chromosphere with Deslandres’s spectroheliograph started at Paris Observatory in 1893 and were followed by systematic observations at Meudon since 1908. The solar collection of H$\alpha$ and CaII K images is probably the longest available worldwide, with associated products such as synoptic maps and tables. Since 2018, Meudon spectroheliograph is the only instrument producing data-cubes of full line profiles of CaII H, CaII K and H$\alpha$, for each pixel of the solar disk. Slices of the cubes provide monochromatic images. We summarize in this paper the capabilities of the successive generations of the instrument, and explore the potential of the collection and products for analysis of rare events, investigations of past solar activity and studies of long term variability.     

VHF radio response of the near Earth space during solar activity growth in October, 2003

The analysis of observations of very high frequency radio noise intensity at the middle latitude on a frequency f = 500 MHz from 14th till 26th of October, 2003 is presented. These data are compared with the solar radio bursts in the range of frequencies 1–14 MHz registered by RAD2 receiver of the WAVES device installed on board the WIND spacecraft.     

Influence of Fast Global Variations of Solar Magnetic Fields on Space Weather in Cycle 23

It is established that the large-scale and global magnetic fields in the Sun's atmosphere do not change smoothly, and long-lasting periods of gradual variations are superseded by fast structural changes of the global magnetic field. Periods of fast global changes on the Sun are accompanied by anomalous manifestations in the interplanetary space and in the geomagnetic field. There is a regular recurrence of these periods in each cycle of solar activity, and the periods are characterized by enhanced flaring activity that reflects fast changes in magnetic structures. Is demonstrated, that the fast changes have essential influencing on a condition of space weather, as most strong geophysical disturbances are connected to sporadic phenomena on the Sun. An explanation has been offered for the origin of anomalous geomagnetic disturbances that are unidentifiable in traditionally used solar activity indices. Is shown, main physical mechanism that leads to fast variations of the magnetic fields in the Sun's atmosphere is the reconnection process.     

On the correlation of the solar wind observed at the L5 point and at the Earth

The L5 point is a promising location for forecasting co-rotating high-speed streams in the solar wind arriving at the Earth. We correlated the solar wind data obtained by the Nozomi spacecraft in interplanetary space and by the Advanced Composition Explorer (ACE) at the L1 point, and found that the correlation is significantly improved from that of the 27-day recurrence of ACE data. Based on the correlation between the two spacecraft observations, we estimated the correlation of the solar wind velocity between the L5 point and at the Earth, and found that the correlation coefficient was about 0.78 in late 1999, while that of the 27-day recurrence was 0.51. Eighty-eight percent of the velocity difference falls within 100 km/s between the L5 point and the Earth. This demonstrates the potential capability of solar wind monitoring at the L5 point to forecast the geomagnetic disturbances 4.5 days in advance.     

One-up on L1: Can X-rays provide longer advanced warning of solar wind flux enhancements than upstream monitors?

Observations of strong solar wind proton flux correlations with ROSAT X-ray rates along with high spectral resolution Chandra observations of X-rays from the dark Moon show that soft X-ray emission mirrors the behavior of the solar wind. In this paper, based on an analysis of an X-ray event observed by XMM-Newton resulting from charge exchange of high charge state solar wind ions and contemporaneous neutral solar wind data, we argue that X-ray observations may be able to provide reliable advance warning, perhaps by as much as half a day, of dramatic increases in solar wind flux at Earth. Like neutral atom imaging, this provides the capability to monitor the solar wind remotely rather than in situ.     

Flight safety implications of the extreme solar proton event of 23 February 1956

There is considerable speculation about the effects at aircraft altitudes resulting from extreme solar proton events. The ground level event (GLE) of 23 February 1956 (GLE 5), remains the largest solar proton event of the neutron monitor era in terms of its influence on count rates at monitors near sea level. During this GLE the count rate was increased by as much as 4760% (15-min average) at the Leeds monitor relative to the count rate from galactic cosmic radiation (GCR). Two modern models of the event cumulative solar proton spectrum for this event, a 6-parameter fit in energy and a 4-parameter Band fit in rigidity, are compared with 1-h of GCR at solar minimum. While effective doses calculated with CARI-7A for both models at low geomagnetic cutoff rigidities are indeed high when compared with GCR and can exceed recommended exposure limits, both GLE spectra exhibit a much stronger dependence on cutoff rigidity than GCR, and a larger fraction of the dose from neutrons. At locations with cutoff rigidities above 4.2 and 6.4?GV, respectively, the GLE effective doses are smaller than the GCR hourly dose. At locations with cutoff rigidities above about 4?GV, GCR was the dominant source of exposure in 10?h or less at all altitudes examined. This suggests that if a similar event occurs in the future, low- and mid-latitude flights at modern jet flight altitudes could be well-protected by Earth’s magnetic field.     

Cosmic radiation exposure of aircraft occupants on simulated high-latitude flights during solar proton events from 1 January 1986 through 1 January 2008

From 1 January 1986 through 1 January 2008, GOES satellites recorded 170 solar proton events. For 169 of these events, we estimated effective and equivalent dose rates and doses of galactic cosmic radiation (GCR) and solar cosmic radiation (SCR), received by aircraft occupants on simulated high-latitude flights. Dose rate and dose estimates that follow are for altitudes 30, 40, 50, and 60 kft, in that order.     

High-cadence Hα imaging of solar flares

The Hα observation is a powerful tool to study the high-energy aspect of solar flares. Spiky brightenings of flare kernels at the Hα center reflect the rapid fluctuation in particle acceleration; linear polarization of Hα emission might be evidence of accelerated protons; red-shifts of the Hα line are caused by the chromospheric evaporation. To study the spiky brightenings of flare kernels with high-cadence imaging at the Hα center, a high-speed Hα camera for the Solar Flare Telescope at Mitaka, NAOJ, had been developed and it started the regular observation in 2001 July. However, the polarimetry and the Dopplermetry are also important and they are required to be carried out in parallel with the high-cadence imaging at the Hα center. Then, we upgraded the original high-speed Hα camera to a new Hα camera system for the multi-aspect Hα observations, which performs all of the high-cadence imaging, the linear polarization measurements, and the off-band imaging for velocity measurements. The new system started the observation in 2002 July. In this paper, the multi-aspect Hα imaging system is described and sample Hα images are presented.     

Comparison of the transport codes HZETRN,HETC and FLUKA for a solar particle event

The protection of astronauts and instrumentation from galactic cosmic rays and solar particle events is one of the primary constraints associated with mission planning in low earth orbit or deep space. To help satisfy this constraint, several computational tools have been developed to analyze the effectiveness of various shielding materials and structures exposed to space radiation. These tools are now being carefully scrutinized through a systematic effort of verification, validation, and uncertainty quantification. In this benchmark study, the deterministic transport code HZETRN is compared to the Monte Carlo transport codes HETC-HEDS and FLUKA for a 30 g/cm² water target protected by a 20 g/cm² aluminum shield exposed to a parameterization of the February 1956 solar particle event. Neutron and proton fluences as well as dose and dose equivalent are compared at various depths in the water target. The regions of agreement and disagreement between the three codes are quantified and discussed, and recommendations for future work are given.     

轴类零件三维尺寸自动标注算法

针对尺寸自动标注仅限于表达产品的几何信息而未关注其功能特性,从而导致所标注的尺寸无法恰当地描述产品设计意图的问题,提出一种基于产品功能特性的三维尺寸自动标注算法.首先,根据零件的功能构造了尺寸标注基准集;其次,建立了轴向尺寸标注优先级确定准则,构造轴向尺寸集,并采用图论法消除了尺寸冗余;然后,构建径向尺寸集,并采用尺寸冗余度法删除其中的冗余尺寸;最后,通过实例测试,验证了所提算法的可行性和有效性.     

Seasonal and solar cycle dependence of F3-layer near the southern crest of the equatorial ionospheric anomaly

The occurrence of an additional F3-layer has been reported at Brazilian, Indian and Asian sectors by several investigators. In this paper, we report for the first time the seasonal variations of F3-layer carried out near the southern crest of the equatorial ionospheric anomaly (EIA) at São José dos Campos (23.2°S, 45.0°W; dip latitude 17.6°S – Brazil) as a function of solar cycle. The period from September 2000 to August 2001 is used as representative of high solar activity (HSA) and the period from January 2006 to December 2006 as representative of low solar activity (LSA). This investigation shows that during HSA there is a maximum occurrence of F3-layer during summer time and a minimum during winter time. However, during LSA, there is no seasonal variation in the F3-layer occurrence. Also, the frequency of occurrence of the F3-layer during HSA is 11 times more than during LSA.     

The hydroxyl radical as an indicator of SEP fluxes in the high-latitude terrestrial atmosphere

The low background values at nighttime of the mesospheric hydroxyl (OH) radical make it easier to single out the atmospheric response to the external solar forcing in Polar Regions. Because of the short lifetime of HO_x, it is possible to follow the trails of Solar Energetic Particle (SEP) events in the terrestrial atmosphere, as shown by Storini and Damiani (2008). The sensitivity of this indicator makes discernible not only extreme particle events with a flux peak of several thousand pfu [1 pfu = 1 particle/(cm² s sr)] at energies >10 MeV, but also those with lower flux up to about 300 pfu. Using data from the Microwave Limb Sounder (MLS) on board the EOS AURA satellite, we examined the correlation of OH abundance vs. solar proton flux for almost all the identified SEP events spanning from November 2004 to December 2006 (later on no more SEP events occurred during Solar Cycle no. 23). The channels at energies greater than 5 MeV and 10 MeV showed the best correlation values (r ∼ 0.90–0.95) at altitudes around 65–75 km whereas, as expected, the most energetic channels were most highly correlated at lower altitudes. Therefore, it is reasonably possible to estimate the solar proton flux from values of mesospheric OH (and viceversa) and it could be useful in studying periods with gaps in the records of solar particles.     

Using high-energy proton fluence to improve risk prediction for consequences of solar particle events

The potential for exposure to large solar particle events (SPEs) with high energy levels is a major concern during interplanetary transfer and extra-vehicular activities (EVAs) on the lunar and Mars surface. Previously, we have used data from the last 5 solar cycles to estimate percentiles of dose to a typical blood-forming organ (BFO) for a hypothetical astronaut in a nominally shielded spacecraft during a 120-d lunar mission. As part of this process, we made use of complete energy spectra for 34 large historical SPEs to calculate what the BFO mGy-Eq dose would have been in the above lunar scenario for each SPE. From these calculated doses, we then developed a prediction model for BFO dose based solely on an assumed value of integrated fluence above 30 MeV (Φ₃₀) for an otherwise unspecified future SPE. In this study, we reasoned that since BFO dose is determined more by protons with higher energies than by those with lower energies, more accurate BFO dose prediction models could be developed using integrated fluence above 60 (Φ₆₀) and above 100 MeV (Φ₁₀₀) as predictors instead of Φ₃₀. However to calculate the unconditional probability of a BFO dose exceeding a pre-specified limit (“BFO dose risk”), one must also take into account the distribution of the predictor (Φ_30,Φ₆₀, or Φ₁₀₀), as estimated from historical SPEs. But Φ₆₀ and Φ₁₀₀ have more variability, and less available historical information on which to estimate their distributions over many SPE occurrences, than does Φ₃₀. Therefore, when estimating BFO dose risk there is a tradeoff between increased BFO dose prediction at a given energy threshold and decreased accuracy of models for describing the distribution of that threshold over future SPEs as the threshold increases. Even when taking the second of these two factors into account, we still arrived at the conclusion that overall prediction improves as the energy level threshold increases from 30 to 60 to 100 MeV. These results can be applied to the development of approaches to improve radiation protection of astronauts and the optimization of mission planning for future space missions.     

双经纬仪三维测量最佳布局

用四个参数描述双经纬仪三维测量的布局,把测量不确定度表示为测量区域坐标点的函数,并以四个布局参数为优化变量,以测量区域中最大测量不确定度为目标函数进行优化,得到最佳测量布局。     

3D information from 2D images recorded in the European Modular Cultivation System on the ISS

The European Modular Cultivation System (EMCS) on the ISS allows long-term biological experiments, e.g. on plants. Video cameras provide near real-time 2D images from these experiments. A method to obtain 3D coordinates and stereoscopic images from these 2D images has been developed and is described in this paper. The procedure was developed to enhance the data output of the MULTIGEN-1 experiment in 2007. One of the main objectives of the experiment was to study growth movements of the Arabidopsis plants and the effect of gravity on these. 3D data were important during parts of the experiment and the paper presents the method developed to acquire 3D data, the accuracy of the data, limitations to the technique and ways to improve the accuracy. Sequences of 3D data obtained from the MULTIGEN-1 experiment are used to illustrate the potential of this newfound capability of the EMCS. In the experiment setup, a positional depth accuracy of about ±0.4 mm for relative object distances and an absolute depth accuracy of about ±1.4 mm for time dependent phenomena was reached. The ability to both view biological specimens in 3D as well as obtaining quantitative 3D data added greatly to the scientific output of the MULTIGEN-1 experiment. The uses of the technique to other researchers and their experiments are discussed.